info gnutls

9.1 Core Functions

The prototypes for the following functions lie in ‘gnutls/gnutls.h’.

gnutls_alert_get_name

Function: const char * gnutls_alert_get_name (gnutls_alert_description_t alert)

alert: is an alert number gnutls_session_t structure.

This function will return a string that describes the given alert number, or NULL. See gnutls_alert_get().

Returns: string corresponding to gnutls_alert_description_t value.

gnutls_alert_get

Function: gnutls_alert_description_t gnutls_alert_get (gnutls_session_t session)

session: is a gnutls_session_t structure.

This function will return the last alert number received. This function should be called if GNUTLS_E_WARNING_ALERT_RECEIVED or GNUTLS_E_FATAL_ALERT_RECEIVED has been returned by a gnutls function. The peer may send alerts if he thinks some things were not right. Check gnutls.h for the available alert descriptions.

If no alert has been received the returned value is undefined.

Returns: returns the last alert received, a gnutls_alert_description_t value.

gnutls_alert_send_appropriate

Function: int gnutls_alert_send_appropriate (gnutls_session_t session, int err)

session: is a gnutls_session_t structure.

err: is an integer

Sends an alert to the peer depending on the error code returned by a gnutls function. This function will call gnutls_error_to_alert() to determine the appropriate alert to send.

This function may also return GNUTLS_E_AGAIN, or GNUTLS_E_INTERRUPTED.

If the return value is GNUTLS_E_INVALID_REQUEST, then no alert has been sent to the peer.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_alert_send

Function: int gnutls_alert_send (gnutls_session_t session, gnutls_alert_level_t level, gnutls_alert_description_t desc)

session: is a gnutls_session_t structure.

level: is the level of the alert

desc: is the alert description

This function will send an alert to the peer in order to inform him of something important (eg. his Certificate could not be verified). If the alert level is Fatal then the peer is expected to close the connection, otherwise he may ignore the alert and continue.

The error code of the underlying record send function will be returned, so you may also receive GNUTLS_E_INTERRUPTED or GNUTLS_E_AGAIN as well.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_anon_allocate_client_credentials

Function: int gnutls_anon_allocate_client_credentials (gnutls_anon_client_credentials_t * sc)

sc: is a pointer to a gnutls_anon_client_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_anon_allocate_server_credentials

Function: int gnutls_anon_allocate_server_credentials (gnutls_anon_server_credentials_t * sc)

sc: is a pointer to a gnutls_anon_server_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_anon_free_client_credentials

Function: void gnutls_anon_free_client_credentials (gnutls_anon_client_credentials_t sc)

sc: is a gnutls_anon_client_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.

gnutls_anon_free_server_credentials

Function: void gnutls_anon_free_server_credentials (gnutls_anon_server_credentials_t sc)

sc: is a gnutls_anon_server_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.

gnutls_anon_set_params_function

Function: void gnutls_anon_set_params_function (gnutls_anon_server_credentials_t res, gnutls_params_function * func)

res: is a gnutls_anon_server_credentials_t structure

func: is the function to be called

This function will set a callback in order for the server to get the Diffie-Hellman or RSA parameters for anonymous authentication. The callback should return zero on success.

gnutls_anon_set_server_dh_params

Function: void gnutls_anon_set_server_dh_params (gnutls_anon_server_credentials_t res, gnutls_dh_params_t dh_params)

res: is a gnutls_anon_server_credentials_t structure

dh_params: is a structure that holds Diffie-Hellman parameters.

This function will set the Diffie-Hellman parameters for an anonymous server to use. These parameters will be used in Anonymous Diffie-Hellman cipher suites.

gnutls_anon_set_server_params_function

Function: void gnutls_anon_set_server_params_function (gnutls_anon_server_credentials_t res, gnutls_params_function * func)

res: is a gnutls_certificate_credentials_t structure

func: is the function to be called

This function will set a callback in order for the server to get the Diffie-Hellman parameters for anonymous authentication. The callback should return zero on success.

gnutls_auth_client_get_type

Function: gnutls_credentials_type_t gnutls_auth_client_get_type (gnutls_session_t session)

session: is a gnutls_session_t structure.

Returns the type of credentials that were used for client authentication. The returned information is to be used to distinguish the function used to access authentication data.

Returns: The type of credentials for the client authentication schema, a gnutls_credentials_type_t type.

gnutls_auth_get_type

Function: gnutls_credentials_type_t gnutls_auth_get_type (gnutls_session_t session)

session: is a gnutls_session_t structure.

Returns type of credentials for the current authentication schema. The returned information is to be used to distinguish the function used to access authentication data.

Eg. for CERTIFICATE ciphersuites (key exchange algorithms: GNUTLS_KX_RSA, GNUTLS_KX_DHE_RSA), the same function are to be used to access the authentication data.

Returns: The type of credentials for the current authentication schema, a gnutls_credentials_type_t type.

gnutls_auth_server_get_type

Function: gnutls_credentials_type_t gnutls_auth_server_get_type (gnutls_session_t session)

session: is a gnutls_session_t structure.

Returns the type of credentials that were used for server authentication. The returned information is to be used to distinguish the function used to access authentication data.

Returns: The type of credentials for the server authentication schema, a gnutls_credentials_type_t type.

gnutls_bye

Function: int gnutls_bye (gnutls_session_t session, gnutls_close_request_t how)

session: is a gnutls_session_t structure.

how: is an integer

Terminates the current TLS/SSL connection. The connection should have been initiated using gnutls_handshake(). how should be one of GNUTLS_SHUT_RDWR, GNUTLS_SHUT_WR.

In case of GNUTLS_SHUT_RDWR then the TLS connection gets terminated and further receives and sends will be disallowed. If the return value is zero you may continue using the connection. GNUTLS_SHUT_RDWR actually sends an alert containing a close request and waits for the peer to reply with the same message.

In case of GNUTLS_SHUT_WR then the TLS connection gets terminated and further sends will be disallowed. In order to reuse the connection you should wait for an EOF from the peer. GNUTLS_SHUT_WR sends an alert containing a close request.

Note that not all implementations will properly terminate a TLS connection. Some of them, usually for performance reasons, will terminate only the underlying transport layer, thus causing a transmission error to the peer. This error cannot be distinguished from a malicious party prematurely terminating the session, thus this behavior is not recommended.

This function may also return GNUTLS_E_AGAIN or GNUTLS_E_INTERRUPTED; cf. gnutls_record_get_direction().

Returns: GNUTLS_E_SUCCESS on success, or an error code, see function documentation for entire semantics.

gnutls_certificate_activation_time_peers

Function: time_t gnutls_certificate_activation_time_peers (gnutls_session_t session)

session: is a gnutls session

This function will return the peer’s certificate activation time. This is the creation time for openpgp keys.

Returns: (time_t)-1 on error.

Deprecated: gnutls_certificate_verify_peers2() now verifies activation times.

gnutls_certificate_allocate_credentials

Function: int gnutls_certificate_allocate_credentials (gnutls_certificate_credentials_t * res)

res: is a pointer to a gnutls_certificate_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_certificate_client_get_request_status

Function: int gnutls_certificate_client_get_request_status (gnutls_session_t session)

session: is a gnutls session

Get whether client certificate is requested or not.

Returns: 0 if the peer (server) did not request client authentication or 1 otherwise, or a negative value in case of error.

gnutls_certificate_client_set_retrieve_function

Function: void gnutls_certificate_client_set_retrieve_function (gnutls_certificate_credentials_t cred, gnutls_certificate_client_retrieve_function * func)

cred: is a gnutls_certificate_credentials_t structure.

func: is the callback function

This function sets a callback to be called in order to retrieve the certificate to be used in the handshake.

The callback’s function prototype is: int (*callback)(gnutls_session_t, const gnutls_datum_t* req_ca_dn, int nreqs, const gnutls_pk_algorithm_t* pk_algos, int pk_algos_length, gnutls_retr_st* st);

req_ca_cert is only used in X.509 certificates. Contains a list with the CA names that the server considers trusted. Normally we should send a certificate that is signed by one of these CAs. These names are DER encoded. To get a more meaningful value use the function gnutls_x509_rdn_get().

pk_algos contains a list with server’s acceptable signature algorithms. The certificate returned should support the server’s given algorithms.

st should contain the certificates and private keys.

If the callback function is provided then gnutls will call it, in the handshake, after the certificate request message has been received.

The callback function should set the certificate list to be sent, and return 0 on success. If no certificate was selected then the number of certificates should be set to zero. The value (-1) indicates error and the handshake will be terminated.

gnutls_certificate_expiration_time_peers

Function: time_t gnutls_certificate_expiration_time_peers (gnutls_session_t session)

session: is a gnutls session

This function will return the peer’s certificate expiration time.

Returns: (time_t)-1 on error.

Deprecated: gnutls_certificate_verify_peers2() now verifies expiration times.

gnutls_certificate_free_ca_names

Function: void gnutls_certificate_free_ca_names (gnutls_certificate_credentials_t sc)

sc: is a gnutls_certificate_credentials_t structure.

This function will delete all the CA name in the given credentials. Clients may call this to save some memory since in client side the CA names are not used.

CA names are used by servers to advertize the CAs they support to clients.

gnutls_certificate_free_cas

Function: void gnutls_certificate_free_cas (gnutls_certificate_credentials_t sc)

sc: is a gnutls_certificate_credentials_t structure.

This function will delete all the CAs associated with the given credentials. Servers that do not use gnutls_certificate_verify_peers2() may call this to save some memory.

gnutls_certificate_free_credentials

Function: void gnutls_certificate_free_credentials (gnutls_certificate_credentials_t sc)

sc: is a gnutls_certificate_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.

This function does not free any temporary parameters associated with this structure (ie RSA and DH parameters are not freed by this function).

gnutls_certificate_free_crls

Function: void gnutls_certificate_free_crls (gnutls_certificate_credentials_t sc)

sc: is a gnutls_certificate_credentials_t structure.

This function will delete all the CRLs associated with the given credentials.

gnutls_certificate_free_keys

Function: void gnutls_certificate_free_keys (gnutls_certificate_credentials_t sc)

sc: is a gnutls_certificate_credentials_t structure.

This function will delete all the keys and the certificates associated with the given credentials. This function must not be called when a TLS negotiation that uses the credentials is in progress.

gnutls_certificate_get_openpgp_keyring

Function: void gnutls_certificate_get_openpgp_keyring (gnutls_certificate_credentials_t sc, gnutls_openpgp_keyring_t * keyring)

sc: is a gnutls_certificate_credentials_t structure.

keyring: the exported keyring. Should be treated as constant

This function will export the OpenPGP keyring associated with the given credentials.

Since: 2.4.0

gnutls_certificate_get_ours

Function: const gnutls_datum_t * gnutls_certificate_get_ours (gnutls_session_t session)

session: is a gnutls session

Get the certificate as sent to the peer, in the last handshake. These certificates are in raw format. In X.509 this is a certificate list. In OpenPGP this is a single certificate.

Returns: return a pointer to a gnutls_datum_t containing our certificates, or NULL in case of an error or if no certificate was used.

gnutls_certificate_get_peers

Function: const gnutls_datum_t * gnutls_certificate_get_peers (gnutls_session_t session, unsigned int * list_size)

session: is a gnutls session

list_size: is the length of the certificate list

Get the peer’s raw certificate (chain) as sent by the peer. These certificates are in raw format (DER encoded for X.509). In case of a X.509 then a certificate list may be present. The first certificate in the list is the peer’s certificate, following the issuer’s certificate, then the issuer’s issuer etc.

In case of OpenPGP keys a single key will be returned in raw format.

Returns: return a pointer to a gnutls_datum_t containing our certificates, or NULL in case of an error or if no certificate was used.

gnutls_certificate_get_x509_cas

Function: void gnutls_certificate_get_x509_cas (gnutls_certificate_credentials_t sc, gnutls_x509_crt_t ** x509_ca_list, unsigned int * ncas)

sc: is a gnutls_certificate_credentials_t structure.

x509_ca_list: will point to the CA list. Should be treated as constant

ncas: the number of CAs

This function will export all the CAs associated with the given credentials.

Since: 2.4.0

gnutls_certificate_get_x509_crls

Function: void gnutls_certificate_get_x509_crls (gnutls_certificate_credentials_t sc, gnutls_x509_crl_t ** x509_crl_list, unsigned int * ncrls)

sc: is a gnutls_certificate_credentials_t structure.

x509_crl_list: the exported CRL list. Should be treated as constant

ncrls: the number of exported CRLs

This function will export all the CRLs associated with the given credentials.

Since: 2.4.0

gnutls_certificate_send_x509_rdn_sequence

Function: void gnutls_certificate_send_x509_rdn_sequence (gnutls_session_t session, int status)

session: is a pointer to a gnutls_session_t structure.

status: is 0 or 1

If status is non zero, this function will order gnutls not to send the rdnSequence in the certificate request message. That is the server will not advertize it’s trusted CAs to the peer. If status is zero then the default behaviour will take effect, which is to advertize the server’s trusted CAs.

This function has no effect in clients, and in authentication methods other than certificate with X.509 certificates.

gnutls_certificate_server_set_request

Function: void gnutls_certificate_server_set_request (gnutls_session_t session, gnutls_certificate_request_t req)

session: is a gnutls_session_t structure.

req: is one of GNUTLS_CERT_REQUEST, GNUTLS_CERT_REQUIRE

This function specifies if we (in case of a server) are going to send a certificate request message to the client. If req is GNUTLS_CERT_REQUIRE then the server will return an error if the peer does not provide a certificate. If you do not call this function then the client will not be asked to send a certificate.

gnutls_certificate_server_set_retrieve_function

Function: void gnutls_certificate_server_set_retrieve_function (gnutls_certificate_credentials_t cred, gnutls_certificate_server_retrieve_function * func)

cred: is a gnutls_certificate_credentials_t structure.

func: is the callback function

This function sets a callback to be called in order to retrieve the certificate to be used in the handshake.

The callback’s function prototype is: int (*callback)(gnutls_session_t, gnutls_retr_st* st);

st should contain the certificates and private keys.

If the callback function is provided then gnutls will call it, in the handshake, after the certificate request message has been received.

The callback function should set the certificate list to be sent, and return 0 on success. The value (-1) indicates error and the handshake will be terminated.

gnutls_certificate_set_dh_params

Function: void gnutls_certificate_set_dh_params (gnutls_certificate_credentials_t res, gnutls_dh_params_t dh_params)

res: is a gnutls_certificate_credentials_t structure

dh_params: is a structure that holds Diffie-Hellman parameters.

This function will set the Diffie-Hellman parameters for a certificate server to use. These parameters will be used in Ephemeral Diffie-Hellman cipher suites. Note that only a pointer to the parameters are stored in the certificate handle, so if you deallocate the parameters before the certificate is deallocated, you must change the parameters stored in the certificate first.

gnutls_certificate_set_params_function

Function: void gnutls_certificate_set_params_function (gnutls_certificate_credentials_t res, gnutls_params_function * func)

res: is a gnutls_certificate_credentials_t structure

func: is the function to be called

This function will set a callback in order for the server to get the Diffie-Hellman or RSA parameters for certificate authentication. The callback should return zero on success.

gnutls_certificate_set_rsa_export_params

Function: void gnutls_certificate_set_rsa_export_params (gnutls_certificate_credentials_t res, gnutls_rsa_params_t rsa_params)

res: is a gnutls_certificate_credentials_t structure

rsa_params: is a structure that holds temporary RSA parameters.

This function will set the temporary RSA parameters for a certificate server to use. These parameters will be used in RSA-EXPORT cipher suites.

gnutls_certificate_set_verify_flags

Function: void gnutls_certificate_set_verify_flags (gnutls_certificate_credentials_t res, unsigned int flags)

res: is a gnutls_certificate_credentials_t structure

flags: are the flags

This function will set the flags to be used at verification of the certificates. Flags must be OR of the gnutls_certificate_verify_flags enumerations.

gnutls_certificate_set_verify_function

Function: void gnutls_certificate_set_verify_function (gnutls_certificate_credentials_t cred, gnutls_certificate_verify_function * func)

cred: is a gnutls_certificate_credentials_t structure.

func: is the callback function

This function sets a callback to be called when peer’s certificate has been received in order to verify it on receipt rather than doing after the handshake is completed.

The callback’s function prototype is: int (*callback)(gnutls_session_t);

If the callback function is provided then gnutls will call it, in the handshake, just after the certificate message has been received. To verify or obtain the certificate the gnutls_certificate_verify_peers2(), gnutls_certificate_type_get(), gnutls_certificate_get_peers() functions can be used.

The callback function should return 0 for the handshake to continue or non-zero to terminate.

Since: 2.10.0

gnutls_certificate_set_verify_limits

Function: void gnutls_certificate_set_verify_limits (gnutls_certificate_credentials_t res, unsigned int max_bits, unsigned int max_depth)

res: is a gnutls_certificate_credentials structure

max_bits: is the number of bits of an acceptable certificate (default 8200)

max_depth: is maximum depth of the verification of a certificate chain (default 5)

This function will set some upper limits for the default verification function, gnutls_certificate_verify_peers2(), to avoid denial of service attacks. You can set them to zero to disable limits.

gnutls_certificate_set_x509_crl_file

Function: int gnutls_certificate_set_x509_crl_file (gnutls_certificate_credentials_t res, const char * crlfile, gnutls_x509_crt_fmt_t type)

res: is a gnutls_certificate_credentials_t structure.

crlfile: is a file containing the list of verified CRLs (DER or PEM list)

type: is PEM or DER

This function adds the trusted CRLs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using gnutls_certificate_verify_peers2(). This function may be called multiple times.

Returns: number of CRLs processed or a negative value on error.

gnutls_certificate_set_x509_crl_mem

Function: int gnutls_certificate_set_x509_crl_mem (gnutls_certificate_credentials_t res, const gnutls_datum_t * CRL, gnutls_x509_crt_fmt_t type)

res: is a gnutls_certificate_credentials_t structure.

CRL: is a list of trusted CRLs. They should have been verified before.

type: is DER or PEM

Returns: number of CRLs processed, or a negative value on error.

gnutls_certificate_set_x509_crl

Function: int gnutls_certificate_set_x509_crl (gnutls_certificate_credentials_t res, gnutls_x509_crl_t * crl_list, int crl_list_size)

res: is a gnutls_certificate_credentials_t structure.

crl_list: is a list of trusted CRLs. They should have been verified before.

crl_list_size: holds the size of the crl_list

Returns: GNUTLS_E_SUCCESS on success, or an error code.

Since: 2.4.0

gnutls_certificate_set_x509_key_file

Function: int gnutls_certificate_set_x509_key_file (gnutls_certificate_credentials_t res, const char * certfile, const char * keyfile, gnutls_x509_crt_fmt_t type)

res: is a gnutls_certificate_credentials_t structure.

certfile: is a file that containing the certificate list (path) for the specified private key, in PKCS7 format, or a list of certificates

keyfile: is a file that contains the private key

type: is PEM or DER

This function sets a certificate/private key pair in the gnutls_certificate_credentials_t structure. This function may be called more than once (in case multiple keys/certificates exist for the server). For clients that wants to send more than its own end entity certificate (e.g., also an intermediate CA cert) then put the certificate chain in certfile.

Currently only PKCS-1 encoded RSA and DSA private keys are accepted by this function.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_certificate_set_x509_key_mem

Function: int gnutls_certificate_set_x509_key_mem (gnutls_certificate_credentials_t res, const gnutls_datum_t * cert, const gnutls_datum_t * key, gnutls_x509_crt_fmt_t type)

res: is a gnutls_certificate_credentials_t structure.

cert: contains a certificate list (path) for the specified private key

key: is the private key, or NULL

type: is PEM or DER

Currently are supported: RSA PKCS-1 encoded private keys, DSA private keys.

DSA private keys are encoded the OpenSSL way, which is an ASN.1 DER sequence of 6 INTEGERs - version, p, q, g, pub, priv.

Note that the keyUsage (2.5.29.15) PKIX extension in X.509 certificates is supported. This means that certificates intended for signing cannot be used for ciphersuites that require encryption.

If the certificate and the private key are given in PEM encoding then the strings that hold their values must be null terminated.

The key may be NULL if you are using a sign callback, see gnutls_sign_callback_set().

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_certificate_set_x509_key

Function: int gnutls_certificate_set_x509_key (gnutls_certificate_credentials_t res, gnutls_x509_crt_t * cert_list, int cert_list_size, gnutls_x509_privkey_t key)

res: is a gnutls_certificate_credentials_t structure.

cert_list: contains a certificate list (path) for the specified private key

cert_list_size: holds the size of the certificate list

key: is a gnutls_x509_privkey_t key

Returns: GNUTLS_E_SUCCESS on success, or an error code.

Since: 2.4.0

gnutls_certificate_set_x509_simple_pkcs12_file

Function: int gnutls_certificate_set_x509_simple_pkcs12_file (gnutls_certificate_credentials_t res, const char * pkcs12file, gnutls_x509_crt_fmt_t type, const char * password)

res: is a gnutls_certificate_credentials_t structure.

pkcs12file: filename of file containing PKCS12 blob.

type: is PEM or DER of the pkcs12file.

password: optional password used to decrypt PKCS12 file, bags and keys.

This function sets a certificate/private key pair and/or a CRL in the gnutls_certificate_credentials_t structure. This function may be called more than once (in case multiple keys/certificates exist for the server).

MAC: ed PKCS12 files are supported. Encrypted PKCS12 bags are supported. Encrypted PKCS8 private keys are supported. However, only password based security, and the same password for all operations, are supported.

The private keys may be RSA PKCS1 or DSA private keys encoded in the OpenSSL way.

PKCS12 file may contain many keys and/or certificates, and there is no way to identify which key/certificate pair you want. You should make sure the PKCS12 file only contain one key/certificate pair and/or one CRL.

It is believed that the limitations of this function is acceptable for most usage, and that any more flexibility would introduce complexity that would make it harder to use this functionality at all.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_certificate_set_x509_simple_pkcs12_mem

Function: int gnutls_certificate_set_x509_simple_pkcs12_mem (gnutls_certificate_credentials_t res, const gnutls_datum_t * p12blob, gnutls_x509_crt_fmt_t type, const char * password)

res: is a gnutls_certificate_credentials_t structure.

p12blob: the PKCS12 blob.

type: is PEM or DER of the pkcs12file.

password: optional password used to decrypt PKCS12 file, bags and keys.

The private keys may be RSA PKCS1 or DSA private keys encoded in the OpenSSL way.

It is believed that the limitations of this function is acceptable for most usage, and that any more flexibility would introduce complexity that would make it harder to use this functionality at all.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

Since: 2.8.0

gnutls_certificate_set_x509_trust_file

Function: int gnutls_certificate_set_x509_trust_file (gnutls_certificate_credentials_t res, const char * cafile, gnutls_x509_crt_fmt_t type)

res: is a gnutls_certificate_credentials_t structure.

cafile: is a file containing the list of trusted CAs (DER or PEM list)

type: is PEM or DER

This function adds the trusted CAs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using gnutls_certificate_verify_peers2(). This function may be called multiple times.

In case of a server the names of the CAs set here will be sent to the client if a certificate request is sent. This can be disabled using gnutls_certificate_send_x509_rdn_sequence().

Returns: number of certificates processed, or a negative value on error.

gnutls_certificate_set_x509_trust_mem

Function: int gnutls_certificate_set_x509_trust_mem (gnutls_certificate_credentials_t res, const gnutls_datum_t * ca, gnutls_x509_crt_fmt_t type)

res: is a gnutls_certificate_credentials_t structure.

ca: is a list of trusted CAs or a DER certificate

type: is DER or PEM

In case of a server the CAs set here will be sent to the client if a certificate request is sent. This can be disabled using gnutls_certificate_send_x509_rdn_sequence().

Returns: the number of certificates processed or a negative value on error.

gnutls_certificate_set_x509_trust

Function: int gnutls_certificate_set_x509_trust (gnutls_certificate_credentials_t res, gnutls_x509_crt_t * ca_list, int ca_list_size)

res: is a gnutls_certificate_credentials_t structure.

ca_list: is a list of trusted CAs

ca_list_size: holds the size of the CA list

In case of a server the CAs set here will be sent to the client if a certificate request is sent. This can be disabled using gnutls_certificate_send_x509_rdn_sequence().

Returns: GNUTLS_E_SUCCESS on success, or an error code.

Since: 2.4.0

gnutls_certificate_type_get_id

Function: gnutls_certificate_type_t gnutls_certificate_type_get_id (const char * name)

name: is a certificate type name

The names are compared in a case insensitive way.

Returns: a gnutls_certificate_type_t for the specified in a string certificate type, or GNUTLS_CRT_UNKNOWN on error.

gnutls_certificate_type_get_name

Function: const char * gnutls_certificate_type_get_name (gnutls_certificate_type_t type)

type: is a certificate type

Convert a gnutls_certificate_type_t type to a string.

Returns: a string that contains the name of the specified certificate type, or NULL in case of unknown types.

gnutls_certificate_type_get

Function: gnutls_certificate_type_t gnutls_certificate_type_get (gnutls_session_t session)

session: is a gnutls_session_t structure.

The certificate type is by default X.509, unless it is negotiated as a TLS extension.

Returns: the currently used gnutls_certificate_type_t certificate type.

gnutls_certificate_type_list

Function: const gnutls_certificate_type_t * gnutls_certificate_type_list ( void)

Get a list of certificate types. Note that to be able to use OpenPGP certificates, you must link to libgnutls-extra and call gnutls_global_init_extra().

Returns: a zero-terminated list of gnutls_certificate_type_t integers indicating the available certificate types.

gnutls_certificate_type_set_priority

Function: int gnutls_certificate_type_set_priority (gnutls_session_t session, const int * list)

session: is a gnutls_session_t structure.

list: is a 0 terminated list of gnutls_certificate_type_t elements.

Sets the priority on the certificate types supported by gnutls. Priority is higher for elements specified before others. After specifying the types you want, you must append a 0. Note that the certificate type priority is set on the client. The server does not use the cert type priority except for disabling types that were not specified.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_certificate_verify_peers2

Function: int gnutls_certificate_verify_peers2 (gnutls_session_t session, unsigned int * status)

session: is a gnutls session

status: is the output of the verification

This function will try to verify the peer’s certificate and return its status (trusted, invalid etc.). The value of status should be one or more of the gnutls_certificate_status_t enumerated elements bitwise or’d. To avoid denial of service attacks some default upper limits regarding the certificate key size and chain size are set. To override them use gnutls_certificate_set_verify_limits().

Note that you must also check the peer’s name in order to check if the verified certificate belongs to the actual peer.

This function uses gnutls_x509_crt_list_verify() with the CAs in the credentials as trusted CAs.

Returns: a negative error code on error and zero on success.

gnutls_certificate_verify_peers

Function: int gnutls_certificate_verify_peers (gnutls_session_t session)

session: is a gnutls session

This function will try to verify the peer’s certificate and return its status (trusted, invalid etc.). However you must also check the peer’s name in order to check if the verified certificate belongs to the actual peer.

This function uses gnutls_x509_crt_list_verify().

Returns: one or more of the gnutls_certificate_status_t enumerated elements bitwise or’d, or a negative value on error.

Deprecated: Use gnutls_certificate_verify_peers2() instead.

gnutls_check_version

Function: const char * gnutls_check_version (const char * req_version)

req_version: version string to compare with, or NULL.

Check GnuTLS Library version.

See GNUTLS_VERSION for a suitable req_version string.

Return value: Check that the version of the library is at minimum the one given as a string in req_version and return the actual version string of the library; return NULL if the condition is not met. If NULL is passed to this function no check is done and only the version string is returned.

gnutls_cipher_decrypt

Function: int gnutls_cipher_decrypt (gnutls_cipher_hd_t handle, void * ciphertext, size_t ciphertextlen)

handle: is a gnutls_cipher_hd_t structure.

ciphertext: the data to encrypt

ciphertextlen: The length of data to encrypt

This function will decrypt the given data using the algorithm specified by the context.

Returns: Zero or a negative value on error.

Since: 2.10.0

gnutls_cipher_deinit

Function: void gnutls_cipher_deinit (gnutls_cipher_hd_t handle)

handle: is a gnutls_cipher_hd_t structure.

This function will deinitialize all resources occupied by the given encryption context.

Since: 2.10.0

gnutls_cipher_encrypt

Function: int gnutls_cipher_encrypt (gnutls_cipher_hd_t handle, void * text, size_t textlen)

handle: is a gnutls_cipher_hd_t structure.

text: the data to encrypt

textlen: The length of data to encrypt

This function will encrypt the given data using the algorithm specified by the context.

Returns: Zero or a negative value on error.

Since: 2.10.0

gnutls_cipher_get_block_size

Function: int gnutls_cipher_get_block_size (gnutls_cipher_algorithm_t algorithm)

algorithm: is an encryption algorithm

Get block size for encryption algorithm.

Returns: block size for encryption algorithm.

Since: 2.10.0

gnutls_cipher_get_id

Function: gnutls_cipher_algorithm_t gnutls_cipher_get_id (const char * name)

name: is a MAC algorithm name

The names are compared in a case insensitive way.

Returns: return a gnutls_cipher_algorithm_t value corresponding to the specified cipher, or GNUTLS_CIPHER_UNKNOWN on error.

gnutls_cipher_get_key_size

Function: size_t gnutls_cipher_get_key_size (gnutls_cipher_algorithm_t algorithm)

algorithm: is an encryption algorithm

Get key size for cipher.

Returns: length (in bytes) of the given cipher’s key size, or 0 if the given cipher is invalid.

gnutls_cipher_get_name

Function: const char * gnutls_cipher_get_name (gnutls_cipher_algorithm_t algorithm)

algorithm: is an encryption algorithm

Convert a gnutls_cipher_algorithm_t type to a string.

Returns: a pointer to a string that contains the name of the specified cipher, or NULL.

gnutls_cipher_get

Function: gnutls_cipher_algorithm_t gnutls_cipher_get (gnutls_session_t session)

session: is a gnutls_session_t structure.

Get currently used cipher.

Returns: the currently used cipher, a gnutls_cipher_algorithm_t type.

gnutls_cipher_init

Function: int gnutls_cipher_init (gnutls_cipher_hd_t * handle, gnutls_cipher_algorithm_t cipher, const gnutls_datum_t * key, const gnutls_datum_t * iv)

handle: is a gnutls_cipher_hd_t structure.

cipher: the encryption algorithm to use

key: The key to be used for encryption

iv: The IV to use (if not applicable set NULL)

This function will initialize an context that can be used for encryption/decryption of data. This will effectively use the current crypto backend in use by gnutls or the cryptographic accelerator in use.

Returns: Zero or a negative value on error.

Since: 2.10.0

gnutls_cipher_list

Function: const gnutls_cipher_algorithm_t * gnutls_cipher_list ( void)

Get a list of supported cipher algorithms. Note that not necessarily all ciphers are supported as TLS cipher suites. For example, DES is not supported as a cipher suite, but is supported for other purposes (e.g., PKCS8 or similar).

Returns: a zero-terminated list of gnutls_cipher_algorithm_t integers indicating the available ciphers.

gnutls_cipher_set_priority

Function: int gnutls_cipher_set_priority (gnutls_session_t session, const int * list)

session: is a gnutls_session_t structure.

list: is a 0 terminated list of gnutls_cipher_algorithm_t elements.

Sets the priority on the ciphers supported by gnutls. Priority is higher for elements specified before others. After specifying the ciphers you want, you must append a 0. Note that the priority is set on the client. The server does not use the algorithm’s priority except for disabling algorithms that were not specified.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_cipher_suite_get_name

Function: const char * gnutls_cipher_suite_get_name (gnutls_kx_algorithm_t kx_algorithm, gnutls_cipher_algorithm_t cipher_algorithm, gnutls_mac_algorithm_t mac_algorithm)

kx_algorithm: is a Key exchange algorithm

cipher_algorithm: is a cipher algorithm

mac_algorithm: is a MAC algorithm

Note that the full cipher suite name must be prepended by TLS or SSL depending of the protocol in use.

Returns: a string that contains the name of a TLS cipher suite, specified by the given algorithms, or NULL.

gnutls_cipher_suite_info

Function: const char * gnutls_cipher_suite_info (size_t idx, char * cs_id, gnutls_kx_algorithm_t * kx, gnutls_cipher_algorithm_t * cipher, gnutls_mac_algorithm_t * mac, gnutls_protocol_t * min_version)

idx: index of cipher suite to get information about, starts on 0.

cs_id: output buffer with room for 2 bytes, indicating cipher suite value

kx: output variable indicating key exchange algorithm, or NULL.

cipher: output variable indicating cipher, or NULL.

mac: output variable indicating MAC algorithm, or NULL.

Get information about supported cipher suites. Use the function iteratively to get information about all supported cipher suites. Call with idx=0 to get information about first cipher suite, then idx=1 and so on until the function returns NULL.

Returns: the name of idx cipher suite, and set the information about the cipher suite in the output variables. If idx is out of bounds, NULL is returned.

gnutls_compression_get_id

Function: gnutls_compression_method_t gnutls_compression_get_id (const char * name)

name: is a compression method name

The names are compared in a case insensitive way.

Returns: an id of the specified in a string compression method, or GNUTLS_COMP_UNKNOWN on error.

gnutls_compression_get_name

Function: const char * gnutls_compression_get_name (gnutls_compression_method_t algorithm)

algorithm: is a Compression algorithm

Convert a gnutls_compression_method_t value to a string.

Returns: a pointer to a string that contains the name of the specified compression algorithm, or NULL.

gnutls_compression_get

Function: gnutls_compression_method_t gnutls_compression_get (gnutls_session_t session)

session: is a gnutls_session_t structure.

Get currently used compression algorithm.

Returns: the currently used compression method, a gnutls_compression_method_t value.

gnutls_compression_list

Function: const gnutls_compression_method_t * gnutls_compression_list ( void)

Get a list of compression methods. Note that to be able to use LZO compression, you must link to libgnutls-extra and call gnutls_global_init_extra().

Returns: a zero-terminated list of gnutls_compression_method_t integers indicating the available compression methods.

gnutls_compression_set_priority

Function: int gnutls_compression_set_priority (gnutls_session_t session, const int * list)

session: is a gnutls_session_t structure.

list: is a 0 terminated list of gnutls_compression_method_t elements.

Sets the priority on the compression algorithms supported by gnutls. Priority is higher for elements specified before others. After specifying the algorithms you want, you must append a 0. Note that the priority is set on the client. The server does not use the algorithm’s priority except for disabling algorithms that were not specified.

TLS 1.0 does not define any compression algorithms except NULL. Other compression algorithms are to be considered as gnutls extensions.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_credentials_clear

Function: void gnutls_credentials_clear (gnutls_session_t session)

session: is a gnutls_session_t structure.

Clears all the credentials previously set in this session.

gnutls_credentials_set

Function: int gnutls_credentials_set (gnutls_session_t session, gnutls_credentials_type_t type, void * cred)

session: is a gnutls_session_t structure.

type: is the type of the credentials

cred: is a pointer to a structure.

Sets the needed credentials for the specified type. Eg username, password - or public and private keys etc. The cred parameter is a structure that depends on the specified type and on the current session (client or server).

In order to minimize memory usage, and share credentials between several threads gnutls keeps a pointer to cred, and not the whole cred structure. Thus you will have to keep the structure allocated until you call gnutls_deinit().

For GNUTLS_CRD_ANON, cred should be gnutls_anon_client_credentials_t in case of a client. In case of a server it should be gnutls_anon_server_credentials_t.

For GNUTLS_CRD_SRP, cred should be gnutls_srp_client_credentials_t in case of a client, and gnutls_srp_server_credentials_t, in case of a server.

For GNUTLS_CRD_CERTIFICATE, cred should be gnutls_certificate_credentials_t.

Returns: On success, GNUTLS_E_SUCCESS (zero) is returned, otherwise an error code is returned.

gnutls_crypto_bigint_register2

Function: int gnutls_crypto_bigint_register2 (int priority, int version, const gnutls_crypto_bigint_st * s)

priority: is the priority of the interface

version: should be set to GNUTLS_CRYPTO_API_VERSION

s: is a structure holding new interface’s data

This function will register an interface for gnutls to operate on big integers. Any interface registered will override the included interface. The interface with the lowest priority will be used by gnutls.

Note that the bigint interface must interoperate with the public key interface. Thus if this interface is updated the gnutls_crypto_pk_register() should also be used.

This function should be called before gnutls_global_init().

For simplicity you can use the convenience gnutls_crypto_bigint_register() macro.

Returns: GNUTLS_E_SUCCESS on success, otherwise an error.

Since: 2.6.0

gnutls_crypto_cipher_register2

Function: int gnutls_crypto_cipher_register2 (int priority, int version, const gnutls_crypto_cipher_st * s)

priority: is the priority of the cipher interface

version: should be set to GNUTLS_CRYPTO_API_VERSION

s: is a structure holding new interface’s data

This function will register a cipher interface to be used by gnutls. Any interface registered will override the included engine and by convention kernel implemented interfaces should have priority of 90. The interface with the lowest priority will be used by gnutls.

This function should be called before gnutls_global_init().

For simplicity you can use the convenience gnutls_crypto_cipher_register() macro.

Returns: GNUTLS_E_SUCCESS on success, otherwise an error.

Since: 2.6.0

gnutls_crypto_digest_register2

Function: int gnutls_crypto_digest_register2 (int priority, int version, const gnutls_crypto_digest_st * s)

priority: is the priority of the digest interface

version: should be set to GNUTLS_CRYPTO_API_VERSION

s: is a structure holding new interface’s data

This function will register a digest interface to be used by gnutls. Any interface registered will override the included engine and by convention kernel implemented interfaces should have priority of 90. The interface with the lowest priority will be used by gnutls.

This function should be called before gnutls_global_init().

For simplicity you can use the convenience gnutls_crypto_digest_register() macro.

Returns: GNUTLS_E_SUCCESS on success, otherwise an error.

Since: 2.6.0

gnutls_crypto_mac_register2

Function: int gnutls_crypto_mac_register2 (int priority, int version, const gnutls_crypto_mac_st * s)

priority: is the priority of the mac interface

version: should be set to GNUTLS_CRYPTO_API_VERSION

s: is a structure holding new interface’s data

This function will register a mac interface to be used by gnutls. Any interface registered will override the included engine and by convention kernel implemented interfaces should have priority of 90. The interface with the lowest priority will be used by gnutls.

This function should be called before gnutls_global_init().

For simplicity you can use the convenience gnutls_crypto_digest_register() macro.

Returns: GNUTLS_E_SUCCESS on success, otherwise an error.

Since: 2.6.0

gnutls_crypto_pk_register2

Function: int gnutls_crypto_pk_register2 (int priority, int version, const gnutls_crypto_pk_st * s)

priority: is the priority of the interface

version: should be set to GNUTLS_CRYPTO_API_VERSION

s: is a structure holding new interface’s data

This function will register an interface for gnutls to operate on public key operations. Any interface registered will override the included interface. The interface with the lowest priority will be used by gnutls.

Note that the bigint interface must interoperate with the bigint interface. Thus if this interface is updated the gnutls_crypto_bigint_register() should also be used.

This function should be called before gnutls_global_init().

For simplicity you can use the convenience gnutls_crypto_pk_register() macro.

Returns: GNUTLS_E_SUCCESS on success, otherwise an error.

Since: 2.6.0

gnutls_crypto_rnd_register2

Function: int gnutls_crypto_rnd_register2 (int priority, int version, const gnutls_crypto_rnd_st * s)

priority: is the priority of the generator

version: should be set to GNUTLS_CRYPTO_API_VERSION

s: is a structure holding new generator’s data

This function will register a random generator to be used by gnutls. Any generator registered will override the included generator and by convention kernel implemented generators have priority of 90. The generator with the lowest priority will be used by gnutls.

This function should be called before gnutls_global_init().

For simplicity you can use the convenience gnutls_crypto_rnd_register() macro.

Returns: GNUTLS_E_SUCCESS on success, otherwise an error.

Since: 2.6.0

gnutls_crypto_single_cipher_register2

Function: int gnutls_crypto_single_cipher_register2 (gnutls_cipher_algorithm_t algorithm, int priority, int version, const gnutls_crypto_cipher_st * s)

algorithm: is the gnutls algorithm identifier

priority: is the priority of the algorithm

version: should be set to GNUTLS_CRYPTO_API_VERSION

s: is a structure holding new cipher’s data

This function will register a cipher algorithm to be used by gnutls. Any algorithm registered will override the included algorithms and by convention kernel implemented algorithms have priority of 90. The algorithm with the lowest priority will be used by gnutls.

This function should be called before gnutls_global_init().

For simplicity you can use the convenience gnutls_crypto_single_cipher_register() macro.

Returns: GNUTLS_E_SUCCESS on success, otherwise an error.

Since: 2.6.0

gnutls_crypto_single_digest_register2

Function: int gnutls_crypto_single_digest_register2 (gnutls_digest_algorithm_t algorithm, int priority, int version, const gnutls_crypto_digest_st * s)

algorithm: is the gnutls algorithm identifier

priority: is the priority of the algorithm

version: should be set to GNUTLS_CRYPTO_API_VERSION

s: is a structure holding new algorithms’s data

This function will register a digest (hash) algorithm to be used by gnutls. Any algorithm registered will override the included algorithms and by convention kernel implemented algorithms have priority of 90. The algorithm with the lowest priority will be used by gnutls.

This function should be called before gnutls_global_init().

For simplicity you can use the convenience gnutls_crypto_single_digest_register() macro.

Returns: GNUTLS_E_SUCCESS on success, otherwise an error.

Since: 2.6.0

gnutls_crypto_single_mac_register2

Function: int gnutls_crypto_single_mac_register2 (gnutls_mac_algorithm_t algorithm, int priority, int version, const gnutls_crypto_mac_st * s)

algorithm: is the gnutls algorithm identifier

priority: is the priority of the algorithm

version: should be set to GNUTLS_CRYPTO_API_VERSION

s: is a structure holding new algorithms’s data

This function will register a MAC algorithm to be used by gnutls. Any algorithm registered will override the included algorithms and by convention kernel implemented algorithms have priority of 90. The algorithm with the lowest priority will be used by gnutls.

This function should be called before gnutls_global_init().

For simplicity you can use the convenience gnutls_crypto_single_mac_register() macro.

Returns: GNUTLS_E_SUCCESS on success, otherwise an error.

Since: 2.6.0

gnutls_db_check_entry

Function: int gnutls_db_check_entry (gnutls_session_t session, gnutls_datum_t session_entry)

session: is a gnutls_session_t structure.

session_entry: is the session data (not key)

Check if database entry has expired. This function is to be used when you want to clear unnesessary session which occupy space in your backend.

Returns: Returns GNUTLS_E_EXPIRED, if the database entry has expired or 0 otherwise.

gnutls_db_get_ptr

Function: void * gnutls_db_get_ptr (gnutls_session_t session)

session: is a gnutls_session_t structure.

Get db function pointer.

Returns: the pointer that will be sent to db store, retrieve and delete functions, as the first argument.

gnutls_db_remove_session

Function: void gnutls_db_remove_session (gnutls_session_t session)

session: is a gnutls_session_t structure.

This function will remove the current session data from the session database. This will prevent future handshakes reusing these session data. This function should be called if a session was terminated abnormally, and before gnutls_deinit() is called.

Normally gnutls_deinit() will remove abnormally terminated sessions.

gnutls_db_set_cache_expiration

Function: void gnutls_db_set_cache_expiration (gnutls_session_t session, int seconds)

session: is a gnutls_session_t structure.

seconds: is the number of seconds.

Set the expiration time for resumed sessions. The default is 3600 (one hour) at the time writing this.

gnutls_db_set_ptr

Function: void gnutls_db_set_ptr (gnutls_session_t session, void * ptr)

session: is a gnutls_session_t structure.

ptr: is the pointer

Sets the pointer that will be provided to db store, retrieve and delete functions, as the first argument.

gnutls_db_set_remove_function

Function: void gnutls_db_set_remove_function (gnutls_session_t session, gnutls_db_remove_func rem_func)

session: is a gnutls_session_t structure.

rem_func: is the function.

Sets the function that will be used to remove data from the resumed sessions database. This function must return 0 on success.

The first argument to rem_func will be null unless gnutls_db_set_ptr() has been called.

gnutls_db_set_retrieve_function

Function: void gnutls_db_set_retrieve_function (gnutls_session_t session, gnutls_db_retr_func retr_func)

session: is a gnutls_session_t structure.

retr_func: is the function.

Sets the function that will be used to retrieve data from the resumed sessions database. This function must return a gnutls_datum_t containing the data on success, or a gnutls_datum_t containing null and 0 on failure.

The datum’s data must be allocated using the function gnutls_malloc().

The first argument to retr_func will be null unless gnutls_db_set_ptr() has been called.

gnutls_db_set_store_function

Function: void gnutls_db_set_store_function (gnutls_session_t session, gnutls_db_store_func store_func)

session: is a gnutls_session_t structure.

store_func: is the function

Sets the function that will be used to store data from the resumed sessions database. This function must remove 0 on success.

The first argument to store_func() will be null unless gnutls_db_set_ptr() has been called.

gnutls_deinit

Function: void gnutls_deinit (gnutls_session_t session)

session: is a gnutls_session_t structure.

This function clears all buffers associated with the session. This function will also remove session data from the session database if the session was terminated abnormally.

gnutls_dh_get_group

Function: int gnutls_dh_get_group (gnutls_session_t session, gnutls_datum_t * raw_gen, gnutls_datum_t * raw_prime)

session: is a gnutls session

raw_gen: will hold the generator.

raw_prime: will hold the prime.

This function will return the group parameters used in the last Diffie-Hellman key exchange with the peer. These are the prime and the generator used. This function should be used for both anonymous and ephemeral Diffie-Hellman. The output parameters must be freed with gnutls_free().

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_dh_get_peers_public_bits

Function: int gnutls_dh_get_peers_public_bits (gnutls_session_t session)

session: is a gnutls session

Get the Diffie-Hellman public key bit size. Can be used for both anonymous and ephemeral Diffie-Hellman.

Returns: the public key bit size used in the last Diffie-Hellman key exchange with the peer, or a negative value in case of error.

gnutls_dh_get_prime_bits

Function: int gnutls_dh_get_prime_bits (gnutls_session_t session)

session: is a gnutls session

This function will return the bits of the prime used in the last Diffie-Hellman key exchange with the peer. Should be used for both anonymous and ephemeral Diffie-Hellman. Note that some ciphers, like RSA and DSA without DHE, does not use a Diffie-Hellman key exchange, and then this function will return 0.

Returns: The Diffie-Hellman bit strength is returned, or 0 if no Diffie-Hellman key exchange was done, or a negative error code on failure.

gnutls_dh_get_pubkey

Function: int gnutls_dh_get_pubkey (gnutls_session_t session, gnutls_datum_t * raw_key)

session: is a gnutls session

raw_key: will hold the public key.

This function will return the peer’s public key used in the last Diffie-Hellman key exchange. This function should be used for both anonymous and ephemeral Diffie-Hellman. The output parameters must be freed with gnutls_free().

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_dh_get_secret_bits

Function: int gnutls_dh_get_secret_bits (gnutls_session_t session)

session: is a gnutls session

This function will return the bits used in the last Diffie-Hellman key exchange with the peer. Should be used for both anonymous and ephemeral Diffie-Hellman.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_dh_params_cpy

Function: int gnutls_dh_params_cpy (gnutls_dh_params_t dst, gnutls_dh_params_t src)

dst: Is the destination structure, which should be initialized.

src: Is the source structure

This function will copy the DH parameters structure from source to destination.

Returns: On success, GNUTLS_E_SUCCESS (zero) is returned, otherwise an error code is returned.

gnutls_dh_params_deinit

Function: void gnutls_dh_params_deinit (gnutls_dh_params_t dh_params)

dh_params: Is a structure that holds the prime numbers

This function will deinitialize the DH parameters structure.

gnutls_dh_params_export_pkcs3

Function: int gnutls_dh_params_export_pkcs3 (gnutls_dh_params_t params, gnutls_x509_crt_fmt_t format, unsigned char * params_data, size_t * params_data_size)

params: Holds the DH parameters

format: the format of output params. One of PEM or DER.

params_data: will contain a PKCS3 DHParams structure PEM or DER encoded

params_data_size: holds the size of params_data (and will be replaced by the actual size of parameters)

This function will export the given dh parameters to a PKCS3 DHParams structure. This is the format generated by "openssl dhparam" tool. If the buffer provided is not long enough to hold the output, then GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.

If the structure is PEM encoded, it will have a header of "BEGIN DH PARAMETERS".

Returns: On success, GNUTLS_E_SUCCESS (zero) is returned, otherwise an error code is returned.

gnutls_dh_params_export_raw

Function: int gnutls_dh_params_export_raw (gnutls_dh_params_t params, gnutls_datum_t * prime, gnutls_datum_t * generator, unsigned int * bits)

params: Holds the DH parameters

prime: will hold the new prime

generator: will hold the new generator

bits: if non null will hold is the prime’s number of bits

This function will export the pair of prime and generator for use in the Diffie-Hellman key exchange. The new parameters will be allocated using gnutls_malloc() and will be stored in the appropriate datum.

Returns: On success, GNUTLS_E_SUCCESS (zero) is returned, otherwise an error code is returned.

gnutls_dh_params_generate2

Function: int gnutls_dh_params_generate2 (gnutls_dh_params_t params, unsigned int bits)

params: Is the structure that the DH parameters will be stored

bits: is the prime’s number of bits

This function will generate a new pair of prime and generator for use in the Diffie-Hellman key exchange. The new parameters will be allocated using gnutls_malloc() and will be stored in the appropriate datum. This function is normally slow.

Note that the bits value should be one of 768, 1024, 2048, 3072 or 4096. Also note that the DH parameters are only useful to servers. Since clients use the parameters sent by the server, it’s of no use to call this in client side.

Returns: On success, GNUTLS_E_SUCCESS (zero) is returned, otherwise an error code is returned.

gnutls_dh_params_import_pkcs3

Function: int gnutls_dh_params_import_pkcs3 (gnutls_dh_params_t params, const gnutls_datum_t * pkcs3_params, gnutls_x509_crt_fmt_t format)

params: A structure where the parameters will be copied to

pkcs3_params: should contain a PKCS3 DHParams structure PEM or DER encoded

format: the format of params. PEM or DER.

This function will extract the DHParams found in a PKCS3 formatted structure. This is the format generated by "openssl dhparam" tool.

If the structure is PEM encoded, it should have a header of "BEGIN DH PARAMETERS".

Returns: On success, GNUTLS_E_SUCCESS (zero) is returned, otherwise an error code is returned.

gnutls_dh_params_import_raw

Function: int gnutls_dh_params_import_raw (gnutls_dh_params_t dh_params, const gnutls_datum_t * prime, const gnutls_datum_t * generator)

dh_params: Is a structure that will hold the prime numbers

prime: holds the new prime

generator: holds the new generator

This function will replace the pair of prime and generator for use in the Diffie-Hellman key exchange. The new parameters should be stored in the appropriate gnutls_datum.

Returns: On success, GNUTLS_E_SUCCESS (zero) is returned, otherwise an error code is returned.

gnutls_dh_params_init

Function: int gnutls_dh_params_init (gnutls_dh_params_t * dh_params)

dh_params: Is a structure that will hold the prime numbers

This function will initialize the DH parameters structure.

Returns: On success, GNUTLS_E_SUCCESS (zero) is returned, otherwise an error code is returned.

gnutls_dh_set_prime_bits

Function: void gnutls_dh_set_prime_bits (gnutls_session_t session, unsigned int bits)

session: is a gnutls_session_t structure.

bits: is the number of bits

This function sets the number of bits, for use in an Diffie-Hellman key exchange. This is used both in DH ephemeral and DH anonymous cipher suites. This will set the minimum size of the prime that will be used for the handshake.

In the client side it sets the minimum accepted number of bits. If a server sends a prime with less bits than that GNUTLS_E_DH_PRIME_UNACCEPTABLE will be returned by the handshake.

This function has no effect in server side.

gnutls_error_is_fatal

Function: int gnutls_error_is_fatal (int error)

error: is a GnuTLS error code, a negative value

If a GnuTLS function returns a negative value you may feed that value to this function to see if the error condition is fatal.

Note that you may want to check the error code manually, since some non-fatal errors to the protocol may be fatal for you program.

This function is only useful if you are dealing with errors from the record layer or the handshake layer.

Returns: 1 if the error code is fatal, for positive error values, 0 is returned. For unknown error values, -1 is returned.

gnutls_error_to_alert

Function: int gnutls_error_to_alert (int err, int * level)

err: is a negative integer

level: the alert level will be stored there

Get an alert depending on the error code returned by a gnutls function. All alerts sent by this function should be considered fatal. The only exception is when err is GNUTLS_E_REHANDSHAKE, where a warning alert should be sent to the peer indicating that no renegotiation will be performed.

If there is no mapping to a valid alert the alert to indicate internal error is returned.

Returns: the alert code to use for a particular error code.

gnutls_ext_register

Function: int gnutls_ext_register (int type, const char * name, gnutls_ext_parse_type_t parse_type, gnutls_ext_recv_func recv_func, gnutls_ext_send_func send_func)

type: the 16-bit integer referring to the extension type

name: human printable name of the extension used for debugging

parse_type: either GNUTLS_EXT_TLS or GNUTLS_EXT_APPLICATION.

recv_func: a function to receive extension data

send_func: a function to send extension data

This function is used to register a new TLS extension handler.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

Since: 2.6.0

gnutls_fingerprint

Function: int gnutls_fingerprint (gnutls_digest_algorithm_t algo, const gnutls_datum_t * data, void * result, size_t * result_size)

algo: is a digest algorithm

data: is the data

result: is the place where the result will be copied (may be null).

result_size: should hold the size of the result. The actual size of the returned result will also be copied there.

This function will calculate a fingerprint (actually a hash), of the given data. The result is not printable data. You should convert it to hex, or to something else printable.

This is the usual way to calculate a fingerprint of an X.509 DER encoded certificate. Note however that the fingerprint of an OpenPGP is not just a hash and cannot be calculated with this function.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_free

Function: void gnutls_free (void * ptr)

This function will free data pointed by ptr.

The deallocation function used is the one set by gnutls_global_set_mem_functions().

gnutls_global_deinit

Function: void gnutls_global_deinit ( void)

This function deinitializes the global data, that were initialized using gnutls_global_init().

Note! This function is not thread safe. See the discussion for gnutls_global_init() for more information.

gnutls_global_init

Function: int gnutls_global_init ( void)

This function initializes the global data to defaults. Every gnutls application has a global data which holds common parameters shared by gnutls session structures. You should call gnutls_global_deinit() when gnutls usage is no longer needed

Note that this function will also initialize libgcrypt, if it has not been initialized before. Thus if you want to manually initialize libgcrypt you must do it before calling this function. This is useful in cases you want to disable libgcrypt’s internal lockings etc.

This function increment a global counter, so that gnutls_global_deinit() only releases resources when it has been called as many times as gnutls_global_init(). This is useful when GnuTLS is used by more than one library in an application. This function can be called many times, but will only do something the first time.

Note! This function is not thread safe. If two threads call this function simultaneously, they can cause a race between checking the global counter and incrementing it, causing both threads to execute the library initialization code. That would lead to a memory leak. To handle this, your application could invoke this function after aquiring a thread mutex. To ignore the potential memory leak is also an option.

Returns: On success, GNUTLS_E_SUCCESS (zero) is returned, otherwise an error code is returned.

gnutls_global_set_log_function

Function: void gnutls_global_set_log_function (gnutls_log_func log_func)

log_func: it’s a log function

This is the function where you set the logging function gnutls is going to use. This function only accepts a character array. Normally you may not use this function since it is only used for debugging purposes.

gnutls_log_func is of the form, void (*gnutls_log_func)( int level, const char*);

gnutls_global_set_log_level

Function: void gnutls_global_set_log_level (int level)

level: it’s an integer from 0 to 9.

This is the function that allows you to set the log level. The level is an integer between 0 and 9. Higher values mean more verbosity. The default value is 0. Larger values should only be used with care, since they may reveal sensitive information.

Use a log level over 10 to enable all debugging options.

gnutls_global_set_mem_functions

Function: void gnutls_global_set_mem_functions (gnutls_alloc_function alloc_func, gnutls_alloc_function secure_alloc_func, gnutls_is_secure_function is_secure_func, gnutls_realloc_function realloc_func, gnutls_free_function free_func)

alloc_func: it’s the default memory allocation function. Like malloc().

secure_alloc_func: This is the memory allocation function that will be used for sensitive data.

is_secure_func: a function that returns 0 if the memory given is not secure. May be NULL.

realloc_func: A realloc function

free_func: The function that frees allocated data. Must accept a NULL pointer.

This is the function were you set the memory allocation functions gnutls is going to use. By default the libc’s allocation functions (malloc(), free()), are used by gnutls, to allocate both sensitive and not sensitive data. This function is provided to set the memory allocation functions to something other than the defaults (ie the gcrypt allocation functions).

This function must be called before gnutls_global_init() is called. This function is not thread safe.

gnutls_handshake_get_last_in

Function: gnutls_handshake_description_t gnutls_handshake_get_last_in (gnutls_session_t session)

session: is a gnutls_session_t structure.

This function is only useful to check where the last performed handshake failed. If the previous handshake succeed or was not performed at all then no meaningful value will be returned.

Check gnutls_handshake_description_t in gnutls.h for the available handshake descriptions.

Returns: the last handshake message type received, a gnutls_handshake_description_t.

gnutls_handshake_get_last_out

Function: gnutls_handshake_description_t gnutls_handshake_get_last_out (gnutls_session_t session)

session: is a gnutls_session_t structure.

This function is only useful to check where the last performed handshake failed. If the previous handshake succeed or was not performed at all then no meaningful value will be returned.

Check gnutls_handshake_description_t in gnutls.h for the available handshake descriptions.

Returns: the last handshake message type sent, a gnutls_handshake_description_t.

gnutls_handshake_set_max_packet_length

Function: void gnutls_handshake_set_max_packet_length (gnutls_session_t session, size_t max)

session: is a gnutls_session_t structure.

max: is the maximum number.

This function will set the maximum size of all handshake messages. Handshakes over this size are rejected with GNUTLS_E_HANDSHAKE_TOO_LARGE error code. The default value is 48kb which is typically large enough. Set this to 0 if you do not want to set an upper limit.

The reason for restricting the handshake message sizes are to limit Denial of Service attacks.

gnutls_handshake_set_post_client_hello_function

Function: void gnutls_handshake_set_post_client_hello_function (gnutls_session_t session, gnutls_handshake_post_client_hello_func func)

session: is a gnutls_session_t structure.

func: is the function to be called

This function will set a callback to be called after the client hello has been received (callback valid in server side only). This allows the server to adjust settings based on received extensions.

Those settings could be ciphersuites, requesting certificate, or anything else except for version negotiation (this is done before the hello message is parsed).

This callback must return 0 on success or a gnutls error code to terminate the handshake.

Warning: You should not use this function to terminate the handshake based on client input unless you know what you are doing. Before the handshake is finished there is no way to know if there is a man-in-the-middle attack being performed.

gnutls_handshake_set_private_extensions

Function: void gnutls_handshake_set_private_extensions (gnutls_session_t session, int allow)

session: is a gnutls_session_t structure.

allow: is an integer (0 or 1)

This function will enable or disable the use of private cipher suites (the ones that start with 0xFF). By default or if allow is 0 then these cipher suites will not be advertized nor used.

Unless this function is called with the option to allow (1), then no compression algorithms, like LZO. That is because these algorithms are not yet defined in any RFC or even internet draft.

Enabling the private ciphersuites when talking to other than gnutls servers and clients may cause interoperability problems.

gnutls_handshake

Function: int gnutls_handshake (gnutls_session_t session)

session: is a gnutls_session_t structure.

This function does the handshake of the TLS/SSL protocol, and initializes the TLS connection.

This function will fail if any problem is encountered, and will return a negative error code. In case of a client, if the client has asked to resume a session, but the server couldn’t, then a full handshake will be performed.

The non-fatal errors such as GNUTLS_E_AGAIN and GNUTLS_E_INTERRUPTED interrupt the handshake procedure, which should be later be resumed. Call this function again, until it returns 0; cf. gnutls_record_get_direction() and gnutls_error_is_fatal().

If this function is called by a server after a rehandshake request then GNUTLS_E_GOT_APPLICATION_DATA or GNUTLS_E_WARNING_ALERT_RECEIVED may be returned. Note that these are non fatal errors, only in the specific case of a rehandshake. Their meaning is that the client rejected the rehandshake request or in the case of GNUTLS_E_GOT_APPLICATION_DATA it might also mean that some data were pending.

Returns: GNUTLS_E_SUCCESS on success, otherwise an error.

gnutls_hash_deinit

Function: void gnutls_hash_deinit (gnutls_hash_hd_t handle, void * digest)

handle: is a gnutls_hash_hd_t structure.

digest: is the output value of the hash

This function will deinitialize all resources occupied by the given hash context.

Since: 2.10.0

gnutls_hash_fast

Function: int gnutls_hash_fast (gnutls_digest_algorithm_t algorithm, const void * text, size_t textlen, void * digest)

algorithm: the hash algorithm to use

text: the data to hash

textlen: The length of data to hash

digest: is the output value of the hash

This convenience function will hash the given data and return output on a single call.

Returns: Zero or a negative value on error.

Since: 2.10.0

gnutls_hash_get_len

Function: int gnutls_hash_get_len (gnutls_digest_algorithm_t algorithm)

algorithm: the hash algorithm to use

This function will return the length of the output data of the given hash algorithm.

Returns: The length or zero on error.

Since: 2.10.0

gnutls_hash_init

Function: int gnutls_hash_init (gnutls_hash_hd_t * dig, gnutls_digest_algorithm_t algorithm)

dig: is a gnutls_hash_hd_t structure.

algorithm: the hash algorithm to use

This function will initialize an context that can be used to produce a Message Digest of data. This will effectively use the current crypto backend in use by gnutls or the cryptographic accelerator in use.

Returns: Zero or a negative value on error.

Since: 2.10.0

gnutls_hash_output

Function: void gnutls_hash_output (gnutls_hash_hd_t handle, void * digest)

handle: is a gnutls_hash_hd_t structure.

digest: is the output value of the hash

This function will output the current hash value.

Since: 2.10.0

gnutls_hash

Function: int gnutls_hash (gnutls_hash_hd_t handle, const void * text, size_t textlen)

handle: is a gnutls_cipher_hd_t structure.

text: the data to hash

textlen: The length of data to hash

This function will hash the given data using the algorithm specified by the context.

Returns: Zero or a negative value on error.

Since: 2.10.0

gnutls_hex2bin

Function: int gnutls_hex2bin (const char * hex_data, size_t hex_size, char * bin_data, size_t * bin_size)

hex_data: string with data in hex format

hex_size: size of hex data

bin_data: output array with binary data

bin_size: when calling *bin_size should hold size of bin_data, on return will hold actual size of bin_data.

Convert a buffer with hex data to binary data.

Returns: GNUTLS_E_SUCCESS on success, otherwise an error.

Since: 2.4.0

gnutls_hex_decode

Function: int gnutls_hex_decode (const gnutls_datum_t * hex_data, char * result, size_t * result_size)

hex_data: contain the encoded data

result: the place where decoded data will be copied

result_size: holds the size of the result

This function will decode the given encoded data, using the hex encoding used by PSK password files.

Note that hex_data should be null terminated.

Returns: GNUTLS_E_SHORT_MEMORY_BUFFER if the buffer given is not long enough, or 0 on success.

gnutls_hex_encode

Function: int gnutls_hex_encode (const gnutls_datum_t * data, char * result, size_t * result_size)

data: contain the raw data

result: the place where hex data will be copied

result_size: holds the size of the result

This function will convert the given data to printable data, using the hex encoding, as used in the PSK password files.

Returns: GNUTLS_E_SHORT_MEMORY_BUFFER if the buffer given is not long enough, or 0 on success.

gnutls_hmac_deinit

Function: void gnutls_hmac_deinit (gnutls_hmac_hd_t handle, void * digest)

handle: is a gnutls_hmac_hd_t structure.

digest: is the output value of the MAC

This function will deinitialize all resources occupied by the given hmac context.

Since: 2.10.0

gnutls_hmac_fast

Function: int gnutls_hmac_fast (gnutls_mac_algorithm_t algorithm, const void * key, size_t keylen, const void * text, size_t textlen, void * digest)

algorithm: the hash algorithm to use

key: the key to use

keylen: The length of the key

text: the data to hash

textlen: The length of data to hash

digest: is the output value of the hash

This convenience function will hash the given data and return output on a single call.

Returns: Zero or a negative value on error.

Since: 2.10.0

gnutls_hmac_get_len

Function: int gnutls_hmac_get_len (gnutls_mac_algorithm_t algorithm)

algorithm: the hmac algorithm to use

This function will return the length of the output data of the given hmac algorithm.

Returns: The length or zero on error.

Since: 2.10.0

gnutls_hmac_init

Function: int gnutls_hmac_init (gnutls_hmac_hd_t * dig, gnutls_digest_algorithm_t algorithm, const void * key, size_t keylen)

dig: is a gnutls_hmac_hd_t structure.

algorithm: the HMAC algorithm to use

key: The key to be used for encryption

keylen: The length of the key

This function will initialize an context that can be used to produce a Message Authentication Code (MAC) of data. This will effectively use the current crypto backend in use by gnutls or the cryptographic accelerator in use.

Returns: Zero or a negative value on error.

Since: 2.10.0

gnutls_hmac_output

Function: void gnutls_hmac_output (gnutls_hmac_hd_t handle, void * digest)

handle: is a gnutls_hmac_hd_t structure.

digest: is the output value of the MAC

This function will output the current MAC value.

Since: 2.10.0

gnutls_hmac

Function: int gnutls_hmac (gnutls_hmac_hd_t handle, const void * text, size_t textlen)

handle: is a gnutls_cipher_hd_t structure.

text: the data to hash

textlen: The length of data to hash

This function will hash the given data using the algorithm specified by the context.

Returns: Zero or a negative value on error.

Since: 2.10.0

gnutls_init

Function: int gnutls_init (gnutls_session_t * session, gnutls_connection_end_t con_end)

session: is a pointer to a gnutls_session_t structure.

con_end: indicate if this session is to be used for server or client.

This function initializes the current session to null. Every session must be initialized before use, so internal structures can be allocated. This function allocates structures which can only be free’d by calling gnutls_deinit(). Returns zero on success.

con_end can be one of GNUTLS_CLIENT and GNUTLS_SERVER.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_kx_get_id

Function: gnutls_kx_algorithm_t gnutls_kx_get_id (const char * name)

name: is a KX name

Convert a string to a gnutls_kx_algorithm_t value. The names are compared in a case insensitive way.

Returns: an id of the specified KX algorithm, or GNUTLS_KX_UNKNOWN on error.

gnutls_kx_get_name

Function: const char * gnutls_kx_get_name (gnutls_kx_algorithm_t algorithm)

algorithm: is a key exchange algorithm

Convert a gnutls_kx_algorithm_t value to a string.

Returns: a pointer to a string that contains the name of the specified key exchange algorithm, or NULL.

gnutls_kx_get

Function: gnutls_kx_algorithm_t gnutls_kx_get (gnutls_session_t session)

session: is a gnutls_session_t structure.

Get currently used key exchange algorithm.

Returns: the key exchange algorithm used in the last handshake, a gnutls_kx_algorithm_t value.

gnutls_kx_list

Function: const gnutls_kx_algorithm_t * gnutls_kx_list ( void)

Get a list of supported key exchange algorithms.

Returns: a zero-terminated list of gnutls_kx_algorithm_t integers indicating the available key exchange algorithms.

gnutls_kx_set_priority

Function: int gnutls_kx_set_priority (gnutls_session_t session, const int * list)

session: is a gnutls_session_t structure.

list: is a 0 terminated list of gnutls_kx_algorithm_t elements.

Sets the priority on the key exchange algorithms supported by gnutls. Priority is higher for elements specified before others. After specifying the algorithms you want, you must append a 0. Note that the priority is set on the client. The server does not use the algorithm’s priority except for disabling algorithms that were not specified.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_mac_get_id

Function: gnutls_mac_algorithm_t gnutls_mac_get_id (const char * name)

name: is a MAC algorithm name

Convert a string to a gnutls_mac_algorithm_t value. The names are compared in a case insensitive way.

Returns: a gnutls_mac_algorithm_t id of the specified MAC algorithm string, or GNUTLS_MAC_UNKNOWN on failures.

gnutls_mac_get_key_size

Function: size_t gnutls_mac_get_key_size (gnutls_mac_algorithm_t algorithm)

algorithm: is an encryption algorithm

Get size of MAC key.

Returns: length (in bytes) of the given MAC key size, or 0 if the given MAC algorithm is invalid.

gnutls_mac_get_name

Function: const char * gnutls_mac_get_name (gnutls_mac_algorithm_t algorithm)

algorithm: is a MAC algorithm

Convert a gnutls_mac_algorithm_t value to a string.

Returns: a string that contains the name of the specified MAC algorithm, or NULL.

gnutls_mac_get

Function: gnutls_mac_algorithm_t gnutls_mac_get (gnutls_session_t session)

session: is a gnutls_session_t structure.

Get currently used MAC algorithm.

Returns: the currently used mac algorithm, a gnutls_mac_algorithm_t value.

gnutls_mac_list

Function: const gnutls_mac_algorithm_t * gnutls_mac_list ( void)

Get a list of hash algorithms for use as MACs. Note that not necessarily all MACs are supported in TLS cipher suites. For example, MD2 is not supported as a cipher suite, but is supported for other purposes (e.g., X.509 signature verification or similar).

Returns: Return a zero-terminated list of gnutls_mac_algorithm_t integers indicating the available MACs.

gnutls_mac_set_priority

Function: int gnutls_mac_set_priority (gnutls_session_t session, const int * list)

session: is a gnutls_session_t structure.

list: is a 0 terminated list of gnutls_mac_algorithm_t elements.

Sets the priority on the mac algorithms supported by gnutls. Priority is higher for elements specified before others. After specifying the algorithms you want, you must append a 0. Note that the priority is set on the client. The server does not use the algorithm’s priority except for disabling algorithms that were not specified.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_malloc

Function: void * gnutls_malloc (size_t s)

This function will allocate ’s’ bytes data, and return a pointer to memory. This function is supposed to be used by callbacks.

The allocation function used is the one set by gnutls_global_set_mem_functions().

gnutls_openpgp_send_cert

Function: void gnutls_openpgp_send_cert (gnutls_session_t session, gnutls_openpgp_crt_status_t status)

session: is a pointer to a gnutls_session_t structure.

status: is one of GNUTLS_OPENPGP_CERT, or GNUTLS_OPENPGP_CERT_FINGERPRINT

This function will order gnutls to send the key fingerprint instead of the key in the initial handshake procedure. This should be used with care and only when there is indication or knowledge that the server can obtain the client’s key.

gnutls_oprfi_enable_client

Function: void gnutls_oprfi_enable_client (gnutls_session_t session, size_t len, unsigned char * data)

session: is a gnutls_session_t structure.

len: length of Opaque PRF data to use in client.

data: Opaque PRF data to use in client.

Request that the client should attempt to negotiate the Opaque PRF Input TLS extension, using the given data as the client’s Opaque PRF input.

The data is copied into the session context after this call, so you may de-allocate it immediately after calling this function.

gnutls_oprfi_enable_server

Function: void gnutls_oprfi_enable_server (gnutls_session_t session, gnutls_oprfi_callback_func cb, void * userdata)

session: is a gnutls_session_t structure.

cb: function pointer to Opaque PRF extension server callback.

userdata: hook passed to callback function for passing application state.

Request that the server should attempt to accept the Opaque PRF Input TLS extension. If the client requests the extension, the provided callback cb will be invoked. The callback must have the following prototype:

int callback (gnutls_session_t session, void *userdata, size_t oprfi_len, const unsigned char *in_oprfi, unsigned char *out_oprfi);

The callback can inspect the client-provided data in the input parameters, and specify its own opaque prf input data in the output variable. The function must return 0 on success, otherwise the handshake will be aborted.

gnutls_pem_base64_decode_alloc

Function: int gnutls_pem_base64_decode_alloc (const char * header, const gnutls_datum_t * b64_data, gnutls_datum_t * result)

header: The PEM header (eg. CERTIFICATE)

b64_data: contains the encoded data

result: the place where decoded data lie

This function will decode the given encoded data. The decoded data will be allocated, and stored into result. If the header given is non null this function will search for "—–BEGIN header" and decode only this part. Otherwise it will decode the first PEM packet found.

You should use gnutls_free() to free the returned data.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_pem_base64_decode

Function: int gnutls_pem_base64_decode (const char * header, const gnutls_datum_t * b64_data, unsigned char * result, size_t * result_size)

header: A null terminated string with the PEM header (eg. CERTIFICATE)

b64_data: contain the encoded data

result: the place where decoded data will be copied

result_size: holds the size of the result

This function will decode the given encoded data. If the header given is non null this function will search for "—–BEGIN header" and decode only this part. Otherwise it will decode the first PEM packet found.

Returns: On success GNUTLS_E_SUCCESS (0) is returned, GNUTLS_E_SHORT_MEMORY_BUFFER is returned if the buffer given is not long enough, or 0 on success.

gnutls_pem_base64_encode_alloc

Function: int gnutls_pem_base64_encode_alloc (const char * msg, const gnutls_datum_t * data, gnutls_datum_t * result)

msg: is a message to be put in the encoded header

data: contains the raw data

result: will hold the newly allocated encoded data

This function will convert the given data to printable data, using the base64 encoding. This is the encoding used in PEM messages. This function will allocate the required memory to hold the encoded data.

You should use gnutls_free() to free the returned data.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_pem_base64_encode

Function: int gnutls_pem_base64_encode (const char * msg, const gnutls_datum_t * data, char * result, size_t * result_size)

msg: is a message to be put in the header

data: contain the raw data

result: the place where base64 data will be copied

result_size: holds the size of the result

This function will convert the given data to printable data, using the base64 encoding. This is the encoding used in PEM messages.

The output string will be null terminated, although the size will not include the terminating null.

Returns: On success GNUTLS_E_SUCCESS (0) is returned, GNUTLS_E_SHORT_MEMORY_BUFFER is returned if the buffer given is not long enough, or 0 on success.

gnutls_perror

Function: void gnutls_perror (int error)

error: is a GnuTLS error code, a negative value

This function is like perror(). The only difference is that it accepts an error number returned by a gnutls function.

gnutls_pk_algorithm_get_name

Function: const char * gnutls_pk_algorithm_get_name (gnutls_pk_algorithm_t algorithm)

algorithm: is a pk algorithm

Convert a gnutls_pk_algorithm_t value to a string.

Returns: a string that contains the name of the specified public key algorithm, or NULL.

gnutls_pk_get_id

Function: gnutls_pk_algorithm_t gnutls_pk_get_id (const char * name)

name: is a string containing a public key algorithm name.

Convert a string to a gnutls_pk_algorithm_t value. The names are compared in a case insensitive way. For example, gnutls_pk_get_id("RSA") will return GNUTLS_PK_RSA.

Returns: a gnutls_pk_algorithm_t id of the specified public key algorithm string, or GNUTLS_PK_UNKNOWN on failures.

Since: 2.6.0

gnutls_pk_get_name

Function: const char * gnutls_pk_get_name (gnutls_pk_algorithm_t algorithm)

algorithm: is a public key algorithm

Convert a gnutls_pk_algorithm_t value to a string.

Returns: a pointer to a string that contains the name of the specified public key algorithm, or NULL.

Since: 2.6.0

gnutls_pk_list

Function: const gnutls_pk_algorithm_t * gnutls_pk_list ( void)

Get a list of supported public key algorithms.

Returns: a zero-terminated list of gnutls_pk_algorithm_t integers indicating the available ciphers.

Since: 2.6.0

gnutls_prf_raw

Function: int gnutls_prf_raw (gnutls_session_t session, size_t label_size, const char * label, size_t seed_size, const char * seed, size_t outsize, char * out)

session: is a gnutls_session_t structure.

label_size: length of the label variable.

label: label used in PRF computation, typically a short string.

seed_size: length of the seed variable.

seed: optional extra data to seed the PRF with.

outsize: size of pre-allocated output buffer to hold the output.

out: pre-allocate buffer to hold the generated data.

Apply the TLS Pseudo-Random-Function (PRF) using the master secret on some data.

The label variable usually contain a string denoting the purpose for the generated data. The seed usually contain data such as the client and server random, perhaps together with some additional data that is added to guarantee uniqueness of the output for a particular purpose.

Because the output is not guaranteed to be unique for a particular session unless seed include the client random and server random fields (the PRF would output the same data on another connection resumed from the first one), it is not recommended to use this function directly. The gnutls_prf() function seed the PRF with the client and server random fields directly, and is recommended if you want to generate pseudo random data unique for each session.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_prf

Function: int gnutls_prf (gnutls_session_t session, size_t label_size, const char * label, int server_random_first, size_t extra_size, const char * extra, size_t outsize, char * out)

session: is a gnutls_session_t structure.

label_size: length of the label variable.

label: label used in PRF computation, typically a short string.

server_random_first: non-0 if server random field should be first in seed

extra_size: length of the extra variable.

extra: optional extra data to seed the PRF with.

outsize: size of pre-allocated output buffer to hold the output.

out: pre-allocate buffer to hold the generated data.

Apply the TLS Pseudo-Random-Function (PRF) using the master secret on some data, seeded with the client and server random fields.

The label variable usually contain a string denoting the purpose for the generated data. The server_random_first indicate whether the client random field or the server random field should be first in the seed. Non-0 indicate that the server random field is first, 0 that the client random field is first.

The extra variable can be used to add more data to the seed, after the random variables. It can be used to tie make sure the generated output is strongly connected to some additional data (e.g., a string used in user authentication).

The output is placed in *OUT, which must be pre-allocated.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_priority_deinit

Function: void gnutls_priority_deinit (gnutls_priority_t priority_cache)

priority_cache: is a gnutls_prioritity_t structure.

Deinitializes the priority cache.

gnutls_priority_init

Function: int gnutls_priority_init (gnutls_priority_t * priority_cache, const char * priorities, const char ** err_pos)

priority_cache: is a gnutls_prioritity_t structure.

priorities: is a string describing priorities

err_pos: In case of an error this will have the position in the string the error occured

Sets priorities for the ciphers, key exchange methods, MACs and compression methods. This provides a more flexible interface compared to the gnutls_*_priority functions.

The priorities parameter allows you to specify a colon separated list of the cipher priorities to enable.

Unless the first keyword is "NONE" the defaults (in preference order) are for TLS protocols TLS1.1, TLS1.0, SSL3.0; for compression NULL; for certificate types X.509, OpenPGP.

For key exchange algorithms when in NORMAL or SECURE levels the perfect forward secrecy algorithms take precedence of the other protocols. In all cases all the supported key exchange algorithms are enabled (except for the RSA-EXPORT which is only enabled in EXPORT level).

Note that although one can select very long key sizes (such as 256 bits) for symmetric algorithms, to actually increase security the public key algorithms have to use longer key sizes as well.

For all the current available algorithms and protocols use "gnutls-cli -l" to get a listing.

Common keywords: Some keywords are defined to provide quick access to common preferences.

"PERFORMANCE" means all the "secure" ciphersuites are enabled, limited to 128 bit ciphers and sorted by terms of speed performance.

"NORMAL" means all "secure" ciphersuites. The 256-bit ciphers are included as a fallback only. The ciphers are sorted by security margin.

"SECURE128" means all "secure" ciphersuites with ciphers up to 128 bits, sorted by security margin.

"SECURE256" means all "secure" ciphersuites including the 256 bit ciphers, sorted by security margin.

"EXPORT" means all ciphersuites are enabled, including the low-security 40 bit ciphers.

"NONE" means nothing is enabled. This disables even protocols and compression methods.

Special keywords: "!" or "-" appended with an algorithm will remove this algorithm.

"+" appended with an algorithm will add this algorithm.

"%COMPAT" will enable compatibility features for a server.

"%DISABLE_SAFE_RENEGOTIATION" will disable safe renegotiation completely. Do not use unless you know what you are doing. Testing purposes only.

"%UNSAFE_RENEGOTIATION" will allow handshakes and rehandshakes without the safe renegotiation extension. Note that for clients this mode is insecure (you may be under attack), and for servers it will allow insecure clients to connect (which could be fooled by an attacker). Do not use unless you know what you are doing and want maximum compatibility.

"%PARTIAL_RENEGOTIATION" will allow initial handshakes to proceed, but not rehandshakes. This leaves the client vulnerable to attack, and servers will be compatible with non-upgraded clients for initial handshakes. This is currently the default for clients and servers, for compatibility reasons.

"%SAFE_RENEGOTIATION" will enforce safe renegotiation. Clients and servers will refuse to talk to an insecure peer. Currently this causes operability problems, but is required for full protection.

"%SSL3_RECORD_VERSION" will use SSL3.0 record version in client hello.

"%VERIFY_ALLOW_SIGN_RSA_MD5" will allow RSA-MD5 signatures in certificate chains.

"%VERIFY_ALLOW_X509_V1_CA_CRT" will allow V1 CAs in chains.

Namespace: To avoid collisions in order to specify a compression algorithm in this string you have to prefix it with "COMP-", protocol versions with "VERS-", signature algorithms with "SIGN-" and certificate types with "CTYPE-". Other algorithms don’t need a prefix.

Examples: "NORMAL:!AES-128-CBC" means normal ciphers except for AES-128.

"EXPORT:!VERS-TLS1.0:+COMP-DEFLATE" means that export ciphers are enabled, TLS 1.0 is disabled, and libz compression enabled.

"NONE:+VERS-TLS1.0:+AES-128-CBC:+RSA:+SHA1:+COMP-NULL", "NORMAL", "%COMPAT".

Returns: On syntax error GNUTLS_E_INVALID_REQUEST is returned, GNUTLS_E_SUCCESS on success, or an error code.

gnutls_priority_set_direct

Function: int gnutls_priority_set_direct (gnutls_session_t session, const char * priorities, const char ** err_pos)

session: is a gnutls_session_t structure.

priorities: is a string describing priorities

err_pos: In case of an error this will have the position in the string the error occured

Sets the priorities to use on the ciphers, key exchange methods, macs and compression methods. This function avoids keeping a priority cache and is used to directly set string priorities to a TLS session. For documentation check the gnutls_priority_init().

Returns: On syntax error GNUTLS_E_INVALID_REQUEST is returned, GNUTLS_E_SUCCESS on success, or an error code.

gnutls_priority_set

Function: int gnutls_priority_set (gnutls_session_t session, gnutls_priority_t priority)

session: is a gnutls_session_t structure.

priority: is a gnutls_priority_t structure.

Sets the priorities to use on the ciphers, key exchange methods, macs and compression methods.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_protocol_get_id

Function: gnutls_protocol_t gnutls_protocol_get_id (const char * name)

name: is a protocol name

The names are compared in a case insensitive way.

Returns: an id of the specified protocol, or GNUTLS_VERSION_UNKNOWN on error.

gnutls_protocol_get_name

Function: const char * gnutls_protocol_get_name (gnutls_protocol_t version)

version: is a (gnutls) version number

Convert a gnutls_protocol_t value to a string.

Returns: a string that contains the name of the specified TLS version (e.g., "TLS1.0"), or NULL.

gnutls_protocol_get_version

Function: gnutls_protocol_t gnutls_protocol_get_version (gnutls_session_t session)

session: is a gnutls_session_t structure.

Get TLS version, a gnutls_protocol_t value.

Returns: the version of the currently used protocol.

gnutls_protocol_list

Function: const gnutls_protocol_t * gnutls_protocol_list ( void)

Get a list of supported protocols, e.g. SSL 3.0, TLS 1.0 etc.

Returns: a zero-terminated list of gnutls_protocol_t integers indicating the available protocols.

gnutls_protocol_set_priority

Function: int gnutls_protocol_set_priority (gnutls_session_t session, const int * list)

session: is a gnutls_session_t structure.

list: is a 0 terminated list of gnutls_protocol_t elements.

Sets the priority on the protocol versions supported by gnutls. This function actually enables or disables protocols. Newer protocol versions always have highest priority.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_psk_allocate_client_credentials

Function: int gnutls_psk_allocate_client_credentials (gnutls_psk_client_credentials_t * sc)

sc: is a pointer to a gnutls_psk_server_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_psk_allocate_server_credentials

Function: int gnutls_psk_allocate_server_credentials (gnutls_psk_server_credentials_t * sc)

sc: is a pointer to a gnutls_psk_server_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_psk_client_get_hint

Function: const char * gnutls_psk_client_get_hint (gnutls_session_t session)

session: is a gnutls session

The PSK identity hint may give the client help in deciding which username to use. This should only be called in case of PSK authentication and in case of a client.

Returns: the identity hint of the peer, or NULL in case of an error.

Since: 2.4.0

gnutls_psk_free_client_credentials

Function: void gnutls_psk_free_client_credentials (gnutls_psk_client_credentials_t sc)

sc: is a gnutls_psk_client_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.

gnutls_psk_free_server_credentials

Function: void gnutls_psk_free_server_credentials (gnutls_psk_server_credentials_t sc)

sc: is a gnutls_psk_server_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.

gnutls_psk_netconf_derive_key

Function: int gnutls_psk_netconf_derive_key (const char * password, const char * psk_identity, const char * psk_identity_hint, gnutls_datum_t * output_key)

password: zero terminated string containing password.

psk_identity: zero terminated string with PSK identity.

psk_identity_hint: zero terminated string with PSK identity hint.

output_key: output variable, contains newly allocated *data pointer.

This function will derive a PSK key from a password, for use with the Netconf protocol.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

Since: 2.4.0

gnutls_psk_server_get_username

Function: const char * gnutls_psk_server_get_username (gnutls_session_t session)

session: is a gnutls session

This should only be called in case of PSK authentication and in case of a server.

Returns: the username of the peer, or NULL in case of an error.

gnutls_psk_set_client_credentials_function

Function: void gnutls_psk_set_client_credentials_function (gnutls_psk_client_credentials_t cred, gnutls_psk_client_credentials_function * func)

cred: is a gnutls_psk_server_credentials_t structure.

func: is the callback function

This function can be used to set a callback to retrieve the username and password for client PSK authentication. The callback’s function form is: int (*callback)(gnutls_session_t, char** username, gnutls_datum_t* key);

The username and key->data must be allocated using gnutls_malloc(). username should be ASCII strings or UTF-8 strings prepared using the "SASLprep" profile of "stringprep".

The callback function will be called once per handshake.

The callback function should return 0 on success. -1 indicates an error.

gnutls_psk_set_client_credentials

Function: int gnutls_psk_set_client_credentials (gnutls_psk_client_credentials_t res, const char * username, const gnutls_datum_t * key, gnutls_psk_key_flags flags)

res: is a gnutls_psk_client_credentials_t structure.

username: is the user’s zero-terminated userid

key: is the user’s key

This function sets the username and password, in a gnutls_psk_client_credentials_t structure. Those will be used in PSK authentication. username should be an ASCII string or UTF-8 strings prepared using the "SASLprep" profile of "stringprep". The key can be either in raw byte format or in Hex format (without the 0x prefix).

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_psk_set_params_function

Function: void gnutls_psk_set_params_function (gnutls_psk_server_credentials_t res, gnutls_params_function * func)

res: is a gnutls_psk_server_credentials_t structure

func: is the function to be called

This function will set a callback in order for the server to get the Diffie-Hellman or RSA parameters for PSK authentication. The callback should return zero on success.

gnutls_psk_set_server_credentials_file

Function: int gnutls_psk_set_server_credentials_file (gnutls_psk_server_credentials_t res, const char * password_file)

res: is a gnutls_psk_server_credentials_t structure.

password_file: is the PSK password file (passwd.psk)

This function sets the password file, in a gnutls_psk_server_credentials_t structure. This password file holds usernames and keys and will be used for PSK authentication.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_psk_set_server_credentials_function

Function: void gnutls_psk_set_server_credentials_function (gnutls_psk_server_credentials_t cred, gnutls_psk_server_credentials_function * func)

cred: is a gnutls_psk_server_credentials_t structure.

func: is the callback function

This function can be used to set a callback to retrieve the user’s PSK credentials. The callback’s function form is: int (*callback)(gnutls_session_t, const char* username, gnutls_datum_t* key);

username contains the actual username. The key must be filled in using the gnutls_malloc().

In case the callback returned a negative number then gnutls will assume that the username does not exist.

The callback function will only be called once per handshake. The callback function should return 0 on success, while -1 indicates an error.

gnutls_psk_set_server_credentials_hint

Function: int gnutls_psk_set_server_credentials_hint (gnutls_psk_server_credentials_t res, const char * hint)

res: is a gnutls_psk_server_credentials_t structure.

hint: is the PSK identity hint string

This function sets the identity hint, in a gnutls_psk_server_credentials_t structure. This hint is sent to the client to help it chose a good PSK credential (i.e., username and password).

Returns: GNUTLS_E_SUCCESS on success, or an error code.

Since: 2.4.0

gnutls_psk_set_server_dh_params

Function: void gnutls_psk_set_server_dh_params (gnutls_psk_server_credentials_t res, gnutls_dh_params_t dh_params)

res: is a gnutls_psk_server_credentials_t structure

dh_params: is a structure that holds Diffie-Hellman parameters.

This function will set the Diffie-Hellman parameters for an anonymous server to use. These parameters will be used in Diffie-Hellman exchange with PSK cipher suites.

gnutls_psk_set_server_params_function

Function: void gnutls_psk_set_server_params_function (gnutls_psk_server_credentials_t res, gnutls_params_function * func)

res: is a gnutls_certificate_credentials_t structure

func: is the function to be called

This function will set a callback in order for the server to get the Diffie-Hellman parameters for PSK authentication. The callback should return zero on success.

gnutls_record_check_pending

Function: size_t gnutls_record_check_pending (gnutls_session_t session)

session: is a gnutls_session_t structure.

This function checks if there are any data to receive in the gnutls buffers.

Notice that you may also use select() to check for data in a TCP connection, instead of this function. GnuTLS leaves some data in the tcp buffer in order for select to work.

Returns: the size of that data or 0.

gnutls_record_disable_padding

Function: void gnutls_record_disable_padding (gnutls_session_t session)

session: is a gnutls_session_t structure.

Used to disabled padding in TLS 1.0 and above. Normally you do not need to use this function, but there are buggy clients that complain if a server pads the encrypted data. This of course will disable protection against statistical attacks on the data.

Normally only servers that require maximum compatibility with everything out there, need to call this function.

gnutls_record_get_direction

Function: int gnutls_record_get_direction (gnutls_session_t session)

session: is a gnutls_session_t structure.

This function provides information about the internals of the record protocol and is only useful if a prior gnutls function call (e.g. gnutls_handshake()) was interrupted for some reason, that is, if a function returned GNUTLS_E_INTERRUPTED or GNUTLS_E_AGAIN. In such a case, you might want to call select() or poll() before calling the interrupted gnutls function again. To tell you whether a file descriptor should be selected for either reading or writing, gnutls_record_get_direction() returns 0 if the interrupted function was trying to read data, and 1 if it was trying to write data.

Returns: 0 if trying to read data, 1 if trying to write data.

gnutls_record_get_max_size

Function: size_t gnutls_record_get_max_size (gnutls_session_t session)

session: is a gnutls_session_t structure.

Get the record size. The maximum record size is negotiated by the client after the first handshake message.

Returns: The maximum record packet size in this connection.

gnutls_record_recv

Function: ssize_t gnutls_record_recv (gnutls_session_t session, void * data, size_t sizeofdata)

session: is a gnutls_session_t structure.

data: the buffer that the data will be read into

sizeofdata: the number of requested bytes

This function has the similar semantics with recv(). The only difference is that it accepts a GnuTLS session, and uses different error codes.

In the special case that a server requests a renegotiation, the client may receive an error code of GNUTLS_E_REHANDSHAKE. This message may be simply ignored, replied with an alert GNUTLS_A_NO_RENEGOTIATION, or replied with a new handshake, depending on the client’s will.

If EINTR is returned by the internal push function (the default is recv()) then GNUTLS_E_INTERRUPTED will be returned. If GNUTLS_E_INTERRUPTED or GNUTLS_E_AGAIN is returned, you must call this function again to get the data. See also gnutls_record_get_direction().

A server may also receive GNUTLS_E_REHANDSHAKE when a client has initiated a handshake. In that case the server can only initiate a handshake or terminate the connection.

Returns: the number of bytes received and zero on EOF. A negative error code is returned in case of an error. The number of bytes received might be less than sizeofdata.

gnutls_record_send

Function: ssize_t gnutls_record_send (gnutls_session_t session, const void * data, size_t sizeofdata)

session: is a gnutls_session_t structure.

data: contains the data to send

sizeofdata: is the length of the data

This function has the similar semantics with send(). The only difference is that it accepts a GnuTLS session, and uses different error codes.

Note that if the send buffer is full, send() will block this function. See the send() documentation for full information. You can replace the default push function by using gnutls_transport_set_ptr2() with a call to send() with a MSG_DONTWAIT flag if blocking is a problem.

If the EINTR is returned by the internal push function (the default is send()} then GNUTLS_E_INTERRUPTED will be returned. If GNUTLS_E_INTERRUPTED or GNUTLS_E_AGAIN is returned, you must call this function again, with the same parameters; alternatively you could provide a NULL pointer for data, and 0 for size. cf. gnutls_record_get_direction().

Returns: the number of bytes sent, or a negative error code. The number of bytes sent might be less than sizeofdata. The maximum number of bytes this function can send in a single call depends on the negotiated maximum record size.

gnutls_record_set_max_size

Function: ssize_t gnutls_record_set_max_size (gnutls_session_t session, size_t size)

session: is a gnutls_session_t structure.

size: is the new size

This function sets the maximum record packet size in this connection. This property can only be set to clients. The server may choose not to accept the requested size.

Acceptable values are 512(=2^9), 1024(=2^10), 2048(=2^11) and 4096(=2^12). The requested record size does get in effect immediately only while sending data. The receive part will take effect after a successful handshake.

This function uses a TLS extension called ’max record size’. Not all TLS implementations use or even understand this extension.

Returns: On success, GNUTLS_E_SUCCESS (zero) is returned, otherwise an error code is returned.

gnutls_rehandshake

Function: int gnutls_rehandshake (gnutls_session_t session)

session: is a gnutls_session_t structure.

This function will renegotiate security parameters with the client. This should only be called in case of a server.

This message informs the peer that we want to renegotiate parameters (perform a handshake).

If this function succeeds (returns 0), you must call the gnutls_handshake() function in order to negotiate the new parameters.

Since TLS is full duplex some application data might have been sent during peer’s processing of this message. In that case one should call gnutls_record_recv() until GNUTLS_E_REHANDSHAKE is returned to clear any pending data. Care must be taken if rehandshake is mandatory to terminate if it does not start after some threshold.

If the client does not wish to renegotiate parameters he will should with an alert message, thus the return code will be GNUTLS_E_WARNING_ALERT_RECEIVED and the alert will be GNUTLS_A_NO_RENEGOTIATION. A client may also choose to ignore this message.

Returns: GNUTLS_E_SUCCESS on success, otherwise an error.

gnutls_rsa_export_get_modulus_bits

Function: int gnutls_rsa_export_get_modulus_bits (gnutls_session_t session)

session: is a gnutls session

Get the export RSA parameter’s modulus size.

Returns: the bits used in the last RSA-EXPORT key exchange with the peer, or a negative value in case of error.

gnutls_rsa_export_get_pubkey

Function: int gnutls_rsa_export_get_pubkey (gnutls_session_t session, gnutls_datum_t * exponent, gnutls_datum_t * modulus)

session: is a gnutls session

exponent: will hold the exponent.

modulus: will hold the modulus.

This function will return the peer’s public key exponent and modulus used in the last RSA-EXPORT authentication. The output parameters must be freed with gnutls_free().

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_rsa_params_cpy

Function: int gnutls_rsa_params_cpy (gnutls_rsa_params_t dst, gnutls_rsa_params_t src)

dst: Is the destination structure, which should be initialized.

src: Is the source structure

This function will copy the RSA parameters structure from source to destination.

Returns: GNUTLS_E_SUCCESS on success, or an negative error code.

gnutls_rsa_params_deinit

Function: void gnutls_rsa_params_deinit (gnutls_rsa_params_t rsa_params)

rsa_params: Is a structure that holds the parameters

This function will deinitialize the RSA parameters structure.

gnutls_rsa_params_export_pkcs1

Function: int gnutls_rsa_params_export_pkcs1 (gnutls_rsa_params_t params, gnutls_x509_crt_fmt_t format, unsigned char * params_data, size_t * params_data_size)

params: Holds the RSA parameters

format: the format of output params. One of PEM or DER.

params_data: will contain a PKCS1 RSAPublicKey structure PEM or DER encoded

params_data_size: holds the size of params_data (and will be replaced by the actual size of parameters)

This function will export the given RSA parameters to a PKCS1 RSAPublicKey structure. If the buffer provided is not long enough to hold the output, then GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.

If the structure is PEM encoded, it will have a header of "BEGIN RSA PRIVATE KEY".

Returns: GNUTLS_E_SUCCESS on success, or an negative error code.

gnutls_rsa_params_export_raw

Function: int gnutls_rsa_params_export_raw (gnutls_rsa_params_t params, gnutls_datum_t * m, gnutls_datum_t * e, gnutls_datum_t * d, gnutls_datum_t * p, gnutls_datum_t * q, gnutls_datum_t * u, unsigned int * bits)

params: a structure that holds the rsa parameters

m: will hold the modulus

e: will hold the public exponent

d: will hold the private exponent

p: will hold the first prime (p)

q: will hold the second prime (q)

u: will hold the coefficient

bits: if non null will hold the prime’s number of bits

This function will export the RSA parameters found in the given structure. The new parameters will be allocated using gnutls_malloc() and will be stored in the appropriate datum.

Returns: GNUTLS_E_SUCCESS on success, or an negative error code.

gnutls_rsa_params_generate2

Function: int gnutls_rsa_params_generate2 (gnutls_rsa_params_t params, unsigned int bits)

params: The structure where the parameters will be stored

bits: is the prime’s number of bits

This function will generate new temporary RSA parameters for use in RSA-EXPORT ciphersuites. This function is normally slow.

Note that if the parameters are to be used in export cipher suites the bits value should be 512 or less. Also note that the generation of new RSA parameters is only useful to servers. Clients use the parameters sent by the server, thus it’s no use calling this in client side.

Returns: GNUTLS_E_SUCCESS on success, or an negative error code.

gnutls_rsa_params_import_pkcs1

Function: int gnutls_rsa_params_import_pkcs1 (gnutls_rsa_params_t params, const gnutls_datum_t * pkcs1_params, gnutls_x509_crt_fmt_t format)

params: A structure where the parameters will be copied to

pkcs1_params: should contain a PKCS1 RSAPublicKey structure PEM or DER encoded

format: the format of params. PEM or DER.

This function will extract the RSAPublicKey found in a PKCS1 formatted structure.

If the structure is PEM encoded, it should have a header of "BEGIN RSA PRIVATE KEY".

Returns: GNUTLS_E_SUCCESS on success, or an negative error code.

gnutls_rsa_params_import_raw

Function: int gnutls_rsa_params_import_raw (gnutls_rsa_params_t rsa_params, const gnutls_datum_t * m, const gnutls_datum_t * e, const gnutls_datum_t * d, const gnutls_datum_t * p, const gnutls_datum_t * q, const gnutls_datum_t * u)

rsa_params: Is a structure will hold the parameters

m: holds the modulus

e: holds the public exponent

d: holds the private exponent

p: holds the first prime (p)

q: holds the second prime (q)

u: holds the coefficient

This function will replace the parameters in the given structure. The new parameters should be stored in the appropriate gnutls_datum.

Returns: GNUTLS_E_SUCCESS on success, or an negative error code.

gnutls_rsa_params_init

Function: int gnutls_rsa_params_init (gnutls_rsa_params_t * rsa_params)

rsa_params: Is a structure that will hold the parameters

This function will initialize the temporary RSA parameters structure.

Returns: GNUTLS_E_SUCCESS on success, or an negative error code.

gnutls_safe_renegotiation_status

Function: int gnutls_safe_renegotiation_status (gnutls_session_t session)

session: is a gnutls_session_t structure.

Can be used to check whether safe renegotiation is being used in the current session.

Returns: 0 when safe renegotiation is not used and non zero when safe renegotiation is used.

Since: 2.10.0

gnutls_server_name_get

Function: int gnutls_server_name_get (gnutls_session_t session, void * data, size_t * data_length, unsigned int * type, unsigned int indx)

session: is a gnutls_session_t structure.

data: will hold the data

data_length: will hold the data length. Must hold the maximum size of data.

type: will hold the server name indicator type

indx: is the index of the server_name

This function will allow you to get the name indication (if any), a client has sent. The name indication may be any of the enumeration gnutls_server_name_type_t.

If type is GNUTLS_NAME_DNS, then this function is to be used by servers that support virtual hosting, and the data will be a null terminated UTF-8 string.

If data has not enough size to hold the server name GNUTLS_E_SHORT_MEMORY_BUFFER is returned, and data_length will hold the required size.

index is used to retrieve more than one server names (if sent by the client). The first server name has an index of 0, the second 1 and so on. If no name with the given index exists GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE is returned.

Returns: On success, GNUTLS_E_SUCCESS (zero) is returned, otherwise an error code is returned.

gnutls_server_name_set

Function: int gnutls_server_name_set (gnutls_session_t session, gnutls_server_name_type_t type, const void * name, size_t name_length)

session: is a gnutls_session_t structure.

type: specifies the indicator type

name: is a string that contains the server name.

name_length: holds the length of name

This function is to be used by clients that want to inform (via a TLS extension mechanism) the server of the name they connected to. This should be used by clients that connect to servers that do virtual hosting.

The value of name depends on the type type. In case of GNUTLS_NAME_DNS, an ASCII zero-terminated domain name string, without the trailing dot, is expected. IPv4 or IPv6 addresses are not permitted.

Returns: On success, GNUTLS_E_SUCCESS (zero) is returned, otherwise an error code is returned.

gnutls_session_enable_compatibility_mode

Function: void gnutls_session_enable_compatibility_mode (gnutls_session_t session)

session: is a gnutls_session_t structure.

This function can be used to disable certain (security) features in TLS in order to maintain maximum compatibility with buggy clients. It is equivalent to calling: gnutls_record_disable_padding()

Normally only servers that require maximum compatibility with everything out there, need to call this function.

gnutls_session_get_client_random

Function: const void * gnutls_session_get_client_random (gnutls_session_t session)

session: is a gnutls_session_t structure.

Return a pointer to the 32-byte client random field used in the session. The pointer must not be modified or deallocated.

If a client random value has not yet been established, the output will be garbage; in particular, a NULL return value should not be expected.

Returns: pointer to client random data.

gnutls_session_get_data2

Function: int gnutls_session_get_data2 (gnutls_session_t session, gnutls_datum_t * data)

session: is a gnutls_session_t structure.

data: is a pointer to a datum that will hold the session.

Returns all session parameters, in order to support resuming. The client should call this, and keep the returned session, if he wants to resume that current version later by calling gnutls_session_set_data(). This function must be called after a successful handshake. The returned datum must be freed with gnutls_free().

Resuming sessions is really useful and speedups connections after a successful one.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_session_get_data

Function: int gnutls_session_get_data (gnutls_session_t session, void * session_data, size_t * session_data_size)

session: is a gnutls_session_t structure.

session_data: is a pointer to space to hold the session.

session_data_size: is the session_data’s size, or it will be set by the function.

Returns all session parameters, in order to support resuming. The client should call this, and keep the returned session, if he wants to resume that current version later by calling gnutls_session_set_data() This function must be called after a successful handshake.

Resuming sessions is really useful and speedups connections after a successful one.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_session_get_id

Function: int gnutls_session_get_id (gnutls_session_t session, void * session_id, size_t * session_id_size)

session: is a gnutls_session_t structure.

session_id: is a pointer to space to hold the session id.

session_id_size: is the session id’s size, or it will be set by the function.

Returns the current session id. This can be used if you want to check if the next session you tried to resume was actually resumed. This is because resumed sessions have the same sessionID with the original session.

Session id is some data set by the server, that identify the current session. In TLS 1.0 and SSL 3.0 session id is always less than 32 bytes.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_session_get_master_secret

Function: const void * gnutls_session_get_master_secret (gnutls_session_t session)

session: is a gnutls_session_t structure.

Return a pointer to the 48-byte master secret in the session. The pointer must not be modified or deallocated.

If a master secret value has not yet been established, the output will be garbage; in particular, a NULL return value should not be expected.

Consider using gnutls_prf() rather than extracting the master secret and use it to derive further data.

Returns: pointer to master secret data.

gnutls_session_get_ptr

Function: void * gnutls_session_get_ptr (gnutls_session_t session)

session: is a gnutls_session_t structure.

Get user pointer for session. Useful in callbacks. This is the pointer set with gnutls_session_set_ptr().

Returns: the user given pointer from the session structure, or NULL if it was never set.

gnutls_session_get_server_random

Function: const void * gnutls_session_get_server_random (gnutls_session_t session)

session: is a gnutls_session_t structure.

Return a pointer to the 32-byte server random field used in the session. The pointer must not be modified or deallocated.

If a server random value has not yet been established, the output will be garbage; in particular, a NULL return value should not be expected.

Returns: pointer to server random data.

gnutls_session_is_resumed

Function: int gnutls_session_is_resumed (gnutls_session_t session)

session: is a gnutls_session_t structure.

Check whether session is resumed or not.

Returns: non zero if this session is resumed, or a zero if this is a new session.

gnutls_session_set_data

Function: int gnutls_session_set_data (gnutls_session_t session, const void * session_data, size_t session_data_size)

session: is a gnutls_session_t structure.

session_data: is a pointer to space to hold the session.

session_data_size: is the session’s size

Sets all session parameters, in order to resume a previously established session. The session data given must be the one returned by gnutls_session_get_data(). This function should be called before gnutls_handshake().

Keep in mind that session resuming is advisory. The server may choose not to resume the session, thus a full handshake will be performed.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_session_set_finished_function

Function: void gnutls_session_set_finished_function (gnutls_session_t session, gnutls_finished_callback_func func)

session: is a gnutls_session_t structure.

func: a gnutls_finished_callback_func callback.

Register a callback function for the session that will be called when a TLS Finished message has been generated. The function is typically used to copy away the TLS finished message for later use as a channel binding or similar purpose.

The callback should follow this prototype: void callback (gnutls_session_t session, const void *finished, size_t len);

The finished parameter will contain the binary TLS finished message, and len will contains its length. For SSLv3 connections, the len parameter will be 36 and for TLS connections it will be 12.

It is recommended that the function returns quickly in order to not delay the handshake. Use the function to store a copy of the TLS finished message for later use.

Since: 2.6.0

gnutls_session_set_ptr

Function: void gnutls_session_set_ptr (gnutls_session_t session, void * ptr)

session: is a gnutls_session_t structure.

ptr: is the user pointer

This function will set (associate) the user given pointer ptr to the session structure. This is pointer can be accessed with gnutls_session_get_ptr().

gnutls_session_ticket_enable_client

Function: int gnutls_session_ticket_enable_client (gnutls_session_t session)

session: is a gnutls_session_t structure.

Request that the client should attempt session resumption using SessionTicket.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

Since: 2.10.0

gnutls_session_ticket_enable_server

Function: int gnutls_session_ticket_enable_server (gnutls_session_t session, const gnutls_datum_t * key)

session: is a gnutls_session_t structure.

key: key to encrypt session parameters.

Request that the server should attempt session resumption using SessionTicket. key must be initialized with gnutls_session_ticket_key_generate().

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

Since: 2.10.0

gnutls_session_ticket_key_generate

Function: int gnutls_session_ticket_key_generate (gnutls_datum_t * key)

key: is a pointer to a gnutls_datum_t which will contain a newly created key.

Generate a random key to encrypt security parameters within SessionTicket.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

Since: 2.10.0

gnutls_set_default_export_priority

Function: int gnutls_set_default_export_priority (gnutls_session_t session)

session: is a gnutls_session_t structure.

Sets some default priority on the ciphers, key exchange methods, macs and compression methods. This function also includes weak algorithms.

This is the same as calling: gnutls_priority_set_direct (session, "EXPORT", NULL);

This function is kept around for backwards compatibility, but because of its wide use it is still fully supported. If you wish to allow users to provide a string that specify which ciphers to use (which is recommended), you should use gnutls_priority_set_direct() or gnutls_priority_set() instead.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_set_default_priority

Function: int gnutls_set_default_priority (gnutls_session_t session)

session: is a gnutls_session_t structure.

Sets some default priority on the ciphers, key exchange methods, macs and compression methods.

This is the same as calling: gnutls_priority_set_direct (session, "NORMAL", NULL);

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_sign_algorithm_get_name

Function: const char * gnutls_sign_algorithm_get_name (gnutls_sign_algorithm_t sign)

sign: is a sign algorithm

Convert a gnutls_sign_algorithm_t value to a string.

Returns: a string that contains the name of the specified sign algorithm, or NULL.

gnutls_sign_algorithm_get_requested

Function: int gnutls_sign_algorithm_get_requested (gnutls_session_t session, size_t indx, gnutls_sign_algorithm_t * algo)

session: is a gnutls_session_t structure.

indx: is an index of the signature algorithm to return

algo: the returned certificate type will be stored there

Returns the signature algorithm specified by index that was requested by the peer. If the specified index has no data available this function returns GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE. If the negotiated TLS version does not support signature algorithms then GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE will be returned even for the first index. The first index is 0.

This function is useful in the certificate callback functions to assist in selecting the correct certificate.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

Since: 2.10.0

gnutls_sign_callback_get

Function: gnutls_sign_func gnutls_sign_callback_get (gnutls_session_t session, void ** userdata)

session: is a gnutls session

userdata: if non-NULL, will be set to abstract callback pointer.

Retrieve the callback function, and its userdata pointer.

Returns: The function pointer set by gnutls_sign_callback_set(), or if not set, NULL.

gnutls_sign_callback_set

Function: void gnutls_sign_callback_set (gnutls_session_t session, gnutls_sign_func sign_func, void * userdata)

session: is a gnutls session

sign_func: function pointer to application’s sign callback.

userdata: void pointer that will be passed to sign callback.

Set the callback function. The function must have this prototype:

typedef int (*gnutls_sign_func) (gnutls_session_t session, void *userdata, gnutls_certificate_type_t cert_type, const gnutls_datum_t * cert, const gnutls_datum_t * hash, gnutls_datum_t * signature);

The userdata parameter is passed to the sign_func verbatim, and can be used to store application-specific data needed in the callback function. See also gnutls_sign_callback_get().

gnutls_sign_get_id

Function: gnutls_sign_algorithm_t gnutls_sign_get_id (const char * name)

name: is a MAC algorithm name

The names are compared in a case insensitive way.

Returns: return a gnutls_sign_algorithm_t value corresponding to the specified cipher, or GNUTLS_SIGN_UNKNOWN on error.

gnutls_sign_get_name

Function: const char * gnutls_sign_get_name (gnutls_sign_algorithm_t algorithm)

algorithm: is a public key signature algorithm

Convert a gnutls_sign_algorithm_t value to a string.

Returns: a pointer to a string that contains the name of the specified public key signature algorithm, or NULL.

Since: 2.6.0

gnutls_sign_list

Function: const gnutls_sign_algorithm_t * gnutls_sign_list ( void)

Get a list of supported public key signature algorithms.

Returns: a zero-terminated list of gnutls_sign_algorithm_t integers indicating the available ciphers.

gnutls_srp_allocate_client_credentials

Function: int gnutls_srp_allocate_client_credentials (gnutls_srp_client_credentials_t * sc)

sc: is a pointer to a gnutls_srp_server_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

gnutls_srp_allocate_server_credentials

Function: int gnutls_srp_allocate_server_credentials (gnutls_srp_server_credentials_t * sc)

sc: is a pointer to a gnutls_srp_server_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

gnutls_srp_base64_decode_alloc

Function: int gnutls_srp_base64_decode_alloc (const gnutls_datum_t * b64_data, gnutls_datum_t * result)

b64_data: contains the encoded data

result: the place where decoded data lie

This function will decode the given encoded data. The decoded data will be allocated, and stored into result. It will decode using the base64 algorithm as used in libsrp.

You should use gnutls_free() to free the returned data.

Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes.

Returns: 0 on success, or an error code.

gnutls_srp_base64_decode

Function: int gnutls_srp_base64_decode (const gnutls_datum_t * b64_data, char * result, size_t * result_size)

b64_data: contain the encoded data

result: the place where decoded data will be copied

result_size: holds the size of the result

This function will decode the given encoded data, using the base64 encoding found in libsrp.

Note that b64_data should be null terminated.

Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes.

Returns: GNUTLS_E_SHORT_MEMORY_BUFFER if the buffer given is not long enough, or 0 on success.

gnutls_srp_base64_encode_alloc

Function: int gnutls_srp_base64_encode_alloc (const gnutls_datum_t * data, gnutls_datum_t * result)

data: contains the raw data

result: will hold the newly allocated encoded data

This function will convert the given data to printable data, using the base64 encoding. This is the encoding used in SRP password files. This function will allocate the required memory to hold the encoded data.

You should use gnutls_free() to free the returned data.

Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes.

Returns: 0 on success, or an error code.

gnutls_srp_base64_encode

Function: int gnutls_srp_base64_encode (const gnutls_datum_t * data, char * result, size_t * result_size)

data: contain the raw data

result: the place where base64 data will be copied

result_size: holds the size of the result

This function will convert the given data to printable data, using the base64 encoding, as used in the libsrp. This is the encoding used in SRP password files. If the provided buffer is not long enough GNUTLS_E_SHORT_MEMORY_BUFFER is returned.

Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes.

Returns: GNUTLS_E_SHORT_MEMORY_BUFFER if the buffer given is not long enough, or 0 on success.

gnutls_srp_free_client_credentials

Function: void gnutls_srp_free_client_credentials (gnutls_srp_client_credentials_t sc)

sc: is a gnutls_srp_client_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.

gnutls_srp_free_server_credentials

Function: void gnutls_srp_free_server_credentials (gnutls_srp_server_credentials_t sc)

sc: is a gnutls_srp_server_credentials_t structure.

This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.

gnutls_srp_server_get_username

Function: const char * gnutls_srp_server_get_username (gnutls_session_t session)

session: is a gnutls session

This function will return the username of the peer. This should only be called in case of SRP authentication and in case of a server. Returns NULL in case of an error.

Returns: SRP username of the peer, or NULL in case of error.

gnutls_srp_set_client_credentials_function

Function: void gnutls_srp_set_client_credentials_function (gnutls_srp_client_credentials_t cred, gnutls_srp_client_credentials_function * func)

cred: is a gnutls_srp_server_credentials_t structure.

func: is the callback function

This function can be used to set a callback to retrieve the username and password for client SRP authentication. The callback’s function form is:

int (*callback)(gnutls_session_t, char** username, char**password);

The username and password must be allocated using gnutls_malloc(). username and password should be ASCII strings or UTF-8 strings prepared using the "SASLprep" profile of "stringprep".

The callback function will be called once per handshake before the initial hello message is sent.

The callback should not return a negative error code the second time called, since the handshake procedure will be aborted.

The callback function should return 0 on success. -1 indicates an error.

gnutls_srp_set_client_credentials

Function: int gnutls_srp_set_client_credentials (gnutls_srp_client_credentials_t res, const char * username, const char * password)

res: is a gnutls_srp_client_credentials_t structure.

username: is the user’s userid

password: is the user’s password

This function sets the username and password, in a gnutls_srp_client_credentials_t structure. Those will be used in SRP authentication. username and password should be ASCII strings or UTF-8 strings prepared using the "SASLprep" profile of "stringprep".

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

gnutls_srp_set_prime_bits

Function: void gnutls_srp_set_prime_bits (gnutls_session_t session, unsigned int bits)

session: is a gnutls_session_t structure.

bits: is the number of bits

This function sets the minimum accepted number of bits, for use in an SRP key exchange. If zero, the default 2048 bits will be used.

In the client side it sets the minimum accepted number of bits. If a server sends a prime with less bits than that GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER will be returned by the handshake.

This function has no effect in server side.

Since: 2.6.0

gnutls_srp_set_server_credentials_file

Function: int gnutls_srp_set_server_credentials_file (gnutls_srp_server_credentials_t res, const char * password_file, const char * password_conf_file)

res: is a gnutls_srp_server_credentials_t structure.

password_file: is the SRP password file (tpasswd)

password_conf_file: is the SRP password conf file (tpasswd.conf)

This function sets the password files, in a gnutls_srp_server_credentials_t structure. Those password files hold usernames and verifiers and will be used for SRP authentication.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

gnutls_srp_set_server_credentials_function

Function: void gnutls_srp_set_server_credentials_function (gnutls_srp_server_credentials_t cred, gnutls_srp_server_credentials_function * func)

cred: is a gnutls_srp_server_credentials_t structure.

func: is the callback function

This function can be used to set a callback to retrieve the user’s SRP credentials. The callback’s function form is:

int (*callback)(gnutls_session_t, const char* username, gnutls_datum_t* salt, gnutls_datum_t *verifier, gnutls_datum_t* g, gnutls_datum_t* n);

username contains the actual username. The salt, verifier, generator and prime must be filled in using the gnutls_malloc(). For convenience prime and generator may also be one of the static parameters defined in extra.h.

In case the callback returned a negative number then gnutls will assume that the username does not exist.

In order to prevent attackers from guessing valid usernames, if a user does not exist, g and n values should be filled in using a random user’s parameters. In that case the callback must return the special value (1).

The callback function will only be called once per handshake. The callback function should return 0 on success, while -1 indicates an error.

gnutls_srp_verifier

Function: int gnutls_srp_verifier (const char * username, const char * password, const gnutls_datum_t * salt, const gnutls_datum_t * generator, const gnutls_datum_t * prime, gnutls_datum_t * res)

username: is the user’s name

password: is the user’s password

salt: should be some randomly generated bytes

generator: is the generator of the group

prime: is the group’s prime

res: where the verifier will be stored.

This function will create an SRP verifier, as specified in RFC2945. The prime and generator should be one of the static parameters defined in gnutls/extra.h or may be generated using the libgcrypt functions gcry_prime_generate() and gcry_prime_group_generator().

The verifier will be allocated with malloc and will be stored in res using binary format.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

gnutls_strerror_name

Function: const char * gnutls_strerror_name (int error)

error: is an error returned by a gnutls function.

Return the GnuTLS error code define as a string. For example, gnutls_strerror_name (GNUTLS_E_DH_PRIME_UNACCEPTABLE) will return the string "GNUTLS_E_DH_PRIME_UNACCEPTABLE".

Returns: A string corresponding to the symbol name of the error code.

Since: 2.6.0

gnutls_strerror

Function: const char * gnutls_strerror (int error)

error: is a GnuTLS error code, a negative value

This function is similar to strerror. The difference is that it accepts an error number returned by a gnutls function; In case of an unknown error a descriptive string is sent instead of NULL.

Error codes are always a negative value.

Returns: A string explaining the GnuTLS error message.

gnutls_supplemental_get_name

Function: const char * gnutls_supplemental_get_name (gnutls_supplemental_data_format_type_t type)

type: is a supplemental data format type

Convert a gnutls_supplemental_data_format_type_t value to a string.

Returns: a string that contains the name of the specified supplemental data format type, or NULL for unknown types.

gnutls_transport_get_ptr2

Function: void gnutls_transport_get_ptr2 (gnutls_session_t session, gnutls_transport_ptr_t * recv_ptr, gnutls_transport_ptr_t * send_ptr)

session: is a gnutls_session_t structure.

recv_ptr: will hold the value for the pull function

send_ptr: will hold the value for the push function

Used to get the arguments of the transport functions (like PUSH and PULL). These should have been set using gnutls_transport_set_ptr2().

gnutls_transport_get_ptr

Function: gnutls_transport_ptr_t gnutls_transport_get_ptr (gnutls_session_t session)

session: is a gnutls_session_t structure.

Used to get the first argument of the transport function (like PUSH and PULL). This must have been set using gnutls_transport_set_ptr().

Returns: first argument of the transport function.

gnutls_transport_set_errno

Function: void gnutls_transport_set_errno (gnutls_session_t session, int err)

session: is a gnutls_session_t structure.

err: error value to store in session-specific errno variable.

Store err in the session-specific errno variable. Useful values for err is EAGAIN and EINTR, other values are treated will be treated as real errors in the push/pull function.

This function is useful in replacement push/pull functions set by gnutls_transport_set_push_function and gnutls_transport_set_pullpush_function under Windows, where the replacement push/pull may not have access to the same errno variable that is used by GnuTLS (e.g., the application is linked to msvcr71.dll and gnutls is linked to msvcrt.dll).

If you don’t have the session variable easily accessible from the push/pull function, and don’t worry about thread conflicts, you can also use gnutls_transport_set_global_errno().

gnutls_transport_set_global_errno

Function: void gnutls_transport_set_global_errno (int err)

err: error value to store in global errno variable.

Store err in the global errno variable. Useful values for err is EAGAIN and EINTR, other values are treated will be treated as real errors in the push/pull function.

Whether this function is thread safe or not depends on whether the global variable errno is thread safe, some system libraries make it a thread-local variable. When feasible, using the guaranteed thread-safe gnutls_transport_set_errno() may be better.

gnutls_transport_set_lowat

Function: void gnutls_transport_set_lowat (gnutls_session_t session, int num)

session: is a gnutls_session_t structure.

num: is the low water value.

Used to set the lowat value in order for select to check if there are pending data to socket buffer. Used only if you have changed the default low water value (default is 1). Normally you will not need that function. This function is only useful if using berkeley style sockets. Otherwise it must be called and set lowat to zero.

gnutls_transport_set_ptr2

Function: void gnutls_transport_set_ptr2 (gnutls_session_t session, gnutls_transport_ptr_t recv_ptr, gnutls_transport_ptr_t send_ptr)

session: is a gnutls_session_t structure.

recv_ptr: is the value for the pull function

send_ptr: is the value for the push function

Used to set the first argument of the transport function (like PUSH and PULL). In berkeley style sockets this function will set the connection handle. With this function you can use two different pointers for receiving and sending.

gnutls_transport_set_ptr

Function: void gnutls_transport_set_ptr (gnutls_session_t session, gnutls_transport_ptr_t ptr)

session: is a gnutls_session_t structure.

ptr: is the value.

Used to set the first argument of the transport function (like PUSH and PULL). In berkeley style sockets this function will set the connection handle.

gnutls_transport_set_pull_function

Function: void gnutls_transport_set_pull_function (gnutls_session_t session, gnutls_pull_func pull_func)

session: gnutls session

pull_func: a callback function similar to read()

This is the function where you set a function for gnutls to receive data. Normally, if you use berkeley style sockets, do not need to use this function since the default (recv(2)) will probably be ok.

PULL_FUNC is of the form, ssize_t (*gnutls_pull_func)(gnutls_transport_ptr_t, void*, size_t);

gnutls_transport_set_push_function

Function: void gnutls_transport_set_push_function (gnutls_session_t session, gnutls_push_func push_func)

session: gnutls session

push_func: a callback function similar to write()

This is the function where you set a push function for gnutls to use in order to send data. If you are going to use berkeley style sockets, you do not need to use this function since the default (send(2)) will probably be ok. Otherwise you should specify this function for gnutls to be able to send data.

PUSH_FUNC is of the form, ssize_t (*gnutls_push_func)(gnutls_transport_ptr_t, const void*, size_t);

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