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9.1 Invoking gnutls-cli
Simple client program to set up a TLS connection to some other computer. It sets up a TLS connection and forwards data from the standard input to the secured socket and vice versa.
This section was generated by AutoGen,
using the agtexi-cmd template and the option descriptions for the gnutls-cli program.
This software is released under the GNU General Public License, version 3 or later.
gnutls-cli help/usage (‘--help’)
This is the automatically generated usage text for gnutls-cli.
The text printed is the same whether selected with the help option
(‘--help’) or the more-help option (‘--more-help’). more-help will print
the usage text by passing it through a pager program.
more-help is disabled on platforms without a working
fork(2) function. The PAGER environment variable is
used to select the program, defaulting to ‘more’. Both will exit
with a status code of 0.
gnutls-cli is unavailable - no --help
debug option (-d)
This is the “enable debugging” option. This option takes a number argument. Specifies the debug level.
tofu option
This is the “enable trust on first use authentication” option.
This option has some usage constraints. It:
- can be disabled with –no-tofu.
This option will, in addition to certificate authentication, perform authentication based on previously seen public keys, a model similar to SSH authentication. Note that when tofu is specified (PKI) and DANE authentication will become advisory to assist the public key acceptance process.
strict-tofu option
This is the “fail to connect if a known certificate has changed” option.
This option has some usage constraints. It:
- can be disabled with –no-strict-tofu.
This option will perform authentication as with option –tofu; however, while –tofu asks whether to trust a changed public key, this option will fail in case of public key changes.
dane option
This is the “enable dane certificate verification (dnssec)” option.
This option has some usage constraints. It:
- can be disabled with –no-dane.
This option will, in addition to certificate authentication using the trusted CAs, verify the server certificates using on the DANE information available via DNSSEC.
local-dns option
This is the “use the local dns server for dnssec resolving” option.
This option has some usage constraints. It:
- can be disabled with –no-local-dns.
This option will use the local DNS server for DNSSEC. This is disabled by default due to many servers not allowing DNSSEC.
ca-verification option
This is the “disable ca certificate verification” option.
This option has some usage constraints. It:
- can be disabled with –no-ca-verification.
- It is enabled by default.
This option will disable CA certificate verification. It is to be used with the –dane or –tofu options.
ocsp option
This is the “enable ocsp certificate verification” option.
This option has some usage constraints. It:
- can be disabled with –no-ocsp.
This option will enable verification of the peer’s certificate using ocsp
resume option (-r)
This is the “establish a session and resume” option. Connect, establish a session, reconnect and resume.
rehandshake option (-e)
This is the “establish a session and rehandshake” option. Connect, establish a session and rehandshake immediately.
starttls option (-s)
This is the “connect, establish a plain session and start tls” option. The TLS session will be initiated when EOF or a SIGALRM is received.
dh-bits option
This is the “the minimum number of bits allowed for dh” option. This option takes a number argument. This option sets the minimum number of bits allowed for a Diffie-Hellman key exchange. You may want to lower the default value if the peer sends a weak prime and you get an connection error with unacceptable prime.
priority option
This is the “priorities string” option. This option takes a string argument. TLS algorithms and protocols to enable. You can use predefined sets of ciphersuites such as PERFORMANCE, NORMAL, PFS, SECURE128, SECURE256. The default is NORMAL.
Check the GnuTLS manual on section “Priority strings” for more information on the allowed keywords
ranges option
This is the “use length-hiding padding to prevent traffic analysis” option. When possible (e.g., when using CBC ciphersuites), use length-hiding padding to prevent traffic analysis.
list option (-l)
This is the “print a list of the supported algorithms and modes” option. Print a list of the supported algorithms and modes. If a priority string is given then only the enabled ciphersuites are shown.
alpn option
This is the “application layer protocol” option. This option takes a string argument.
This option has some usage constraints. It:
- may appear an unlimited number of times.
This option will set and enable the Application Layer Protocol Negotiation (ALPN) in the TLS protocol.
disable-extensions option
This is the “disable all the tls extensions” option. This option disables all TLS extensions. Deprecated option. Use the priority string.
inline-commands option
This is the “inline commands of the form ^<cmd>^” option. Enable inline commands of the form ^<cmd>^. The inline commands are expected to be in a line by themselves. The available commands are: resume and renegotiate.
inline-commands-prefix option
This is the “change the default (^) used as a delimiter for inline commands. the value is a single us-ascii character (octets 0 - 127).” option. This option takes a string argument. Change the default (^) delimiter used for inline commands. The delimiter is expected to be a single US-ASCII character (octets 0 - 127). This option is only relevant if inline commands are enabled via the inline-commands option
provider option
This is the “specify the pkcs #11 provider library” option. This option takes a file argument. This will override the default options in /etc/gnutls/pkcs11.conf
gnutls-cli exit status
One of the following exit values will be returned:
- ‘0 (EXIT_SUCCESS)’
Successful program execution.
- ‘1 (EXIT_FAILURE)’
The operation failed or the command syntax was not valid.
gnutls-cli See Also
gnutls-cli-debug(1), gnutls-serv(1)
gnutls-cli Examples
Connecting using PSK authentication
To connect to a server using PSK authentication, you need to enable the choice of PSK by using a cipher priority parameter such as in the example below.
$ ./gnutls-cli -p 5556 localhost --pskusername psk_identity \
--pskkey 88f3824b3e5659f52d00e959bacab954b6540344 \
--priority NORMAL:-KX-ALL:+ECDHE-PSK:+DHE-PSK:+PSK
Resolving 'localhost'...
Connecting to '127.0.0.1:5556'...
- PSK authentication.
- Version: TLS1.1
- Key Exchange: PSK
- Cipher: AES-128-CBC
- MAC: SHA1
- Compression: NULL
- Handshake was completed
- Simple Client Mode:
By keeping the –pskusername parameter and removing the –pskkey parameter, it will query only for the password during the handshake.
Listing ciphersuites in a priority string
To list the ciphersuites in a priority string:
$ ./gnutls-cli --priority SECURE192 -l Cipher suites for SECURE192 TLS_ECDHE_ECDSA_AES_256_CBC_SHA384 0xc0, 0x24 TLS1.2 TLS_ECDHE_ECDSA_AES_256_GCM_SHA384 0xc0, 0x2e TLS1.2 TLS_ECDHE_RSA_AES_256_GCM_SHA384 0xc0, 0x30 TLS1.2 TLS_DHE_RSA_AES_256_CBC_SHA256 0x00, 0x6b TLS1.2 TLS_DHE_DSS_AES_256_CBC_SHA256 0x00, 0x6a TLS1.2 TLS_RSA_AES_256_CBC_SHA256 0x00, 0x3d TLS1.2 Certificate types: CTYPE-X.509 Protocols: VERS-TLS1.2, VERS-TLS1.1, VERS-TLS1.0, VERS-SSL3.0, VERS-DTLS1.0 Compression: COMP-NULL Elliptic curves: CURVE-SECP384R1, CURVE-SECP521R1 PK-signatures: SIGN-RSA-SHA384, SIGN-ECDSA-SHA384, SIGN-RSA-SHA512, SIGN-ECDSA-SHA512
Connecting using a PKCS #11 token
To connect to a server using a certificate and a private key present in a PKCS #11 token you need to substitute the PKCS 11 URLs in the x509certfile and x509keyfile parameters.
Those can be found using "p11tool –list-tokens" and then listing all the objects in the needed token, and using the appropriate.
$ p11tool --list-tokens Token 0: URL: pkcs11:model=PKCS15;manufacturer=MyMan;serial=1234;token=Test Label: Test Manufacturer: EnterSafe Model: PKCS15 Serial: 1234 $ p11tool --login --list-certs "pkcs11:model=PKCS15;manufacturer=MyMan;serial=1234;token=Test" Object 0: URL: pkcs11:model=PKCS15;manufacturer=MyMan;serial=1234;token=Test;object=client;object-type=cert Type: X.509 Certificate Label: client ID: 2a:97:0d:58:d1:51:3c:23:07:ae:4e:0d:72:26:03:7d:99:06:02:6a $ export MYCERT="pkcs11:model=PKCS15;manufacturer=MyMan;serial=1234;token=Test;object=client;object-type=cert" $ export MYKEY="pkcs11:model=PKCS15;manufacturer=MyMan;serial=1234;token=Test;object=client;object-type=private" $ gnutls-cli www.example.com --x509keyfile $MYKEY --x509certfile MYCERT
Notice that the private key only differs from the certificate in the object-type.
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