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GcrSecretExchange

GcrSecretExchange — Exchange secrets between processes in an unexposed way.

Object Hierarchy

    GObject
    ╰── GcrSecretExchange

Description

Allows exchange of secrets between two processes on the same system without exposing those secrets to things like loggers, non-pageable memory etc.

This does not protect against active attacks like MITM attacks.

Each side creates a GcrSecretExchange object, and one of the sides calls gcr_secret_exchange_begin(). This creates a string, which should be passed to the other side. Each side passes the strings it receives into gcr_secret_exchange_receive().

In order to send a reply (either with or without a secret) use gcr_secret_exchange_send(). A side must have had gcr_secret_exchange_receive() successfully called before it can use gcr_secret_exchange_send().

The GcrSecretExchange objects can be used for multiple iterations of the conversation, or for just one request/reply. The only limitation being that the initial request cannot contain a secret.

Caveat: Information about the approximate length (rounded up to the nearest 16 bytes) may be leaked. If this is considered inacceptable, do not use GcrSecretExchange.

Functions

gcr_secret_exchange_new ()

GcrSecretExchange *
gcr_secret_exchange_new (const gchar *protocol);

Create a new secret exchange object.

Specify a protocol of NULL to allow any protocol. This is especially relevant on the side of the exchange that does not call gcr_secret_exchange_begin(), that is the originator. Currently the only protocol supported is GCR_SECRET_EXCHANGE_PROTOCOL_1.

Parameters

protocol

the exchange protocol to use.

[allow-none]

Returns

A new GcrSecretExchange object.

[transfer full]


gcr_secret_exchange_begin ()

gchar *
gcr_secret_exchange_begin (GcrSecretExchange *self);

Begin the secret exchange. The resulting string should be sent to the other side of the exchange. The other side should use gcr_secret_exchange_receive() to process the string.

Parameters

self

a GcrSecretExchange object

 

Returns

A newly allocated string to be sent to the other side of the secret exchange.

[transfer full]


gcr_secret_exchange_receive ()

gboolean
gcr_secret_exchange_receive (GcrSecretExchange *self,
                             const gchar *exchange);

Receive a string from the other side of secret exchange. This string will have been created by gcr_secret_exchange_begin() or gcr_secret_exchange_send().

After this call completes successfully the value returned from gcr_secret_exchange_get_secret() will have changed.

Parameters

self

a GcrSecretExchange object

 

exchange

the string received

 

Returns

whether the string was successfully parsed and received


gcr_secret_exchange_get_protocol ()

const gchar *
gcr_secret_exchange_get_protocol (GcrSecretExchange *self);

Will return NULL if no protocol was specified, and either gcr_secret_exchange_begin() or gcr_secret_exchange_receive() have not been called successfully.

Parameters

self

a GcrSecretExchange object Get the secret exchange protocol.

 

Returns

the protocol or NULL


gcr_secret_exchange_get_secret ()

const gchar *
gcr_secret_exchange_get_secret (GcrSecretExchange *self,
                                gsize *secret_len);

Returns the last secret received. If no secret has yet been received this will return NULL. The string is owned by the GcrSecretExchange object and will be valid until the next time that gcr_secret_exchange_receive() is called on this object, or the object is destroyed.

Depending on the secret passed into the other side of the secret exchange, the result may be a binary string. It does however have a null terminator, so if you're certain that it is does not contain arbitrary binary data, it can be used as a string.

Parameters

self

a GcrSecretExchange object

 

secret_len

optionally, a location to store the length of returned secret.

[allow-none]

Returns

the last secret received.

[transfer none][array length=secret_len]


gcr_secret_exchange_send ()

gchar *
gcr_secret_exchange_send (GcrSecretExchange *self,
                          const gchar *secret,
                          gssize secret_len);

Send a reply to the other side of the secret exchange, optionally sending a secret.

gcr_secret_exchange_receive() must have been successfully called at least once on this object. In other words this object must have received data from the other side of the secret exchange, before we can send a secret.

Parameters

self

a GcrSecretExchange object

 

secret

optionally, a secret to send to the other side.

[allow-none]

secret_len

length of secret , or -1 if null terminated

 

Returns

a newly allocated string to be sent to the other side of the secret exchange.

[transfer full]

Types and Values

struct GcrSecretExchange

struct GcrSecretExchange;

An object representing one side of a secret exchange.


struct GcrSecretExchangeClass

struct GcrSecretExchangeClass {
};

The class for GcrSecretExchange


GCR_SECRET_EXCHANGE_PROTOCOL_1

#define GCR_SECRET_EXCHANGE_PROTOCOL_1 "sx-aes-1"

The current secret exchange protocol. Key agreement is done using DH with the 1536 bit IKE parameter group. Keys are derived using SHA256 with HKDF. The transport encryption is done with 128 bit AES.

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