gnutls_anti_replay_enable - Linux


gnutls_anti_replay_enable is a command used to manage anti-replay protection in the GNU TLS (GnuTLS) library. Anti-replay protection helps prevent attackers from replaying old messages to trick a server into performing an action multiple times.


gnutls_anti_replay_enable(session, enable)


| Option | Description | Default |
| — | — | — |
| session | The GnuTLS session to modify | N/A |
| enable | Boolean value indicating whether to enable or disable anti-replay protection | False |


Enable anti-replay protection for a session:

session = gnutls_init(GNUTLS_CLIENT, GNUTLS_TLS1_2)
gnutls_anti_replay_enable(session, true)

Disable anti-replay protection for a session:

session = gnutls_init(GNUTLS_SERVER, GNUTLS_TLS1_2)
gnutls_anti_replay_enable(session, false)

Common Issues

If anti-replay protection is enabled, the server may reject messages that it has already processed. This can occur if the server’s clock is out of sync with the client’s clock. To resolve this issue, ensure that both the server and client have accurate clocks.


gnutls_anti_replay_enable can be used with other GnuTLS commands to enhance security. For example, it can be used with gnutls_session_set_verify_flags to require certificate verification.

Related Commands

  • gnutls_session_set_verify_flags
  • gnutls_init

Additional Resources: