7.3.3 Obtaining session information

Most of the times it is desirable to know the security properties of the current established session. This includes the underlying ciphers and the protocols involved. That is the purpose of the following function. Note that this function will print meaningful values only if called after a successful gnutls_handshake.

#if HAVE_CONFIG_H
# include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>

extern void print_x509_certificate_info (gnutls_session_t);

/* This function will print some details of the
 * given session.
 */
int
print_info (gnutls_session_t session)
{
  const char *tmp;
  gnutls_credentials_type_t cred;
  gnutls_kx_algorithm_t kx;

  /* print the key exchange's algorithm name
   */
  kx = gnutls_kx_get (session);
  tmp = gnutls_kx_get_name (kx);
  printf ("- Key Exchange: %s\n", tmp);

  /* Check the authentication type used and switch
   * to the appropriate.
   */
  cred = gnutls_auth_get_type (session);
  switch (cred)
    {
    case GNUTLS_CRD_SRP:
      printf ("- SRP session with username %s\n",
	      gnutls_srp_server_get_username (session));
      break;

    case GNUTLS_CRD_ANON:	/* anonymous authentication */

      printf ("- Anonymous DH using prime of %d bits\n",
	      gnutls_dh_get_prime_bits (session));
      break;

    case GNUTLS_CRD_CERTIFICATE:	/* certificate authentication */

      /* Check if we have been using ephemeral Diffie Hellman.
       */
      if (kx == GNUTLS_KX_DHE_RSA || kx == GNUTLS_KX_DHE_DSS)
	{
	  printf ("\n- Ephemeral DH using prime of %d bits\n",
		  gnutls_dh_get_prime_bits (session));
	}

      /* if the certificate list is available, then
       * print some information about it.
       */
      print_x509_certificate_info (session);

    }				/* switch */

  /* print the protocol's name (ie TLS 1.0) 
   */
  tmp = gnutls_protocol_get_name (gnutls_protocol_get_version (session));
  printf ("- Protocol: %s\n", tmp);

  /* print the certificate type of the peer.
   * ie X.509
   */
  tmp =
    gnutls_certificate_type_get_name (gnutls_certificate_type_get (session));

  printf ("- Certificate Type: %s\n", tmp);

  /* print the compression algorithm (if any)
   */
  tmp = gnutls_compression_get_name (gnutls_compression_get (session));
  printf ("- Compression: %s\n", tmp);

  /* print the name of the cipher used.
   * ie 3DES.
   */
  tmp = gnutls_cipher_get_name (gnutls_cipher_get (session));
  printf ("- Cipher: %s\n", tmp);

  /* Print the MAC algorithms name.
   * ie SHA1
   */
  tmp = gnutls_mac_get_name (gnutls_mac_get (session));
  printf ("- MAC: %s\n", tmp);

  return 0;
}