Verifying the Message

The program can now verify the validity of the message it sent. It knows that the server returns the MIC for the message it sent, so it retrieves it with its recv_token() function and then uses gss_verify_mic() to verify its “signature” (the MIC).

     maj_stat = gss_verify_mic(&min_stat, context, &in_buf,
                               &out_buf, &qop_state);
     if (maj_stat != GSS_S_COMPLETE) {
          display_status("verifying signature", maj_stat, min_stat);
          (void) close(s);
          (void) gss_delete_sec_context(&min_stat, &context, 
                                        GSS_C_NO_BUFFER);
          return -1;
     }

gss_verify_mic() compares the MIC received with the server's token (in out_buf) with one it produces from the original, unwrapped message, held in in_buf. If the two MICs match, the message is verified. The client releases the buffer for the received token, out_buf.

To finish, call_server() deletes the context and returns to main().