RFC 1416 (rfc1416) - Page 3 of 7

Telnet Authentication Option

RFC 1416              Telnet Authentication Option         February 1993


   IAC SB AUTHENTICATION REPLY authentication-type-pair  IAC
   SE

      The sender of this command (the server) is sending a reply to the
      the authentication information received in a previous IS command.
      Only the server side (DO AUTHENTICATION) is allowed to send this.

   IAC SB AUTHENTICATION NAME remote-user IAC SE

      This optional command is sent to specify the account name on the
      remote host that the user wishes to be authorized to use.  Note
      that authentication may succeed, and the authorization to use a
      particular account may still fail.  Some authentication mechanisms
      may ignore this command.

   The "authentication-type-pair" is two octets, the first is the
   authentication type (as listed in Section 1, additions to this list
   must be registered with the Internet Assigned Numbers Authority
   (IANA)), and the second is a modifier to the type.  There are
   currently two one bit fields defined in the modifier, the
   AUTH_WHO_MASK bit and the AUTH_HOW_MASK bit, so there are four
   possible combinations:

      AUTH_CLIENT_TO_SERVER
      AUTH_HOW_ONE_WAY

         The client will send authentication information about the local
         user to the server.  If the negotiation is successful, the
         server will have authenticated the user on the client side of
         the connection.

      AUTH_SERVER_TO_CLIENT
      AUTH_HOW_ONE_WAY

         The server will authenticate itself to the client.  If the
         negotiation is successful, the client will know that it is
         connected to the server that it wants to be connected to.

      AUTH_CLIENT_TO_SERVER
      AUTH_HOW_MUTUAL

         The client will send authentication information about the local
         user to the server, and then the server will authenticate
         itself to the client.  If the negotiation is successful, the
         server will have authenticated the user on the client side of
         the connection, and the client will know that it is connected
         to the server that it wants to be connected to.




Telnet Working Group