gnutls_srp_set_server_fake_salt_seed man page

gnutls_srp_set_server_fake_salt_seed — API function

Synopsis

#include <gnutls/gnutls.h>

void gnutls_srp_set_server_fake_salt_seed(gnutls_srp_server_credentials_t cred, const gnutls_datum_t * seed, unsigned int salt_length);

Arguments

gnutls_srp_server_credentials_t cred

is a gnutls_srp_server_credentials_t type

const gnutls_datum_t * seed

is the seed data, only needs to be valid until the function returns; size of the seed must be greater than zero

unsigned int salt_length

is the length of the generated fake salts

Description

This function sets the seed that is used to generate salts for invalid (non-existent) usernames.

In order to prevent attackers from guessing valid usernames, when a user does not exist gnutls generates a salt and a verifier and proceeds with the protocol as usual. The authentication will ultimately fail, but the client cannot tell whether the username is valid (exists) or invalid.

If an attacker learns the seed, given a salt (which is part of the handshake) which was generated when the seed was in use, it can tell whether or not the authentication failed because of an unknown username. This seed cannot be used to reveal application data or passwords.

salt_length should represent the salt length your application uses. Generating fake salts longer than 20 bytes is not supported.

By default the seed is a random value, different each time a gnutls_srp_server_credentials_t is allocated and fake salts are 16 bytes long.

Since

3.3.0

Reporting Bugs

Report bugs to <bugs@gnutls.org>.
Home page: http://www.gnutls.org

See Also

The full documentation for gnutls is maintained as a Texinfo manual. If the /usr/share/doc/gnutls/ directory does not contain the HTML form visit

http://www.gnutls.org/manual/

Info

3.6.1 gnutls