Network Working Group                                       Mike StJohns
Request for Comments: 931                                           TPSC
Supersedes: RFC 912                                         January 1985

                         Authentication Server


STATUS OF THIS MEMO

   This RFC suggests a proposed protocol for the ARPA-Internet
   community, and requests discussion and suggestions for improvements.
   This is the second draft of this proposal (superseding RFC 912) and
   incorporates a more formal description of the syntax for the request
   and response dialog, as well as a change to specify the type of user
   identification returned.  Distribution of this memo is unlimited.

INTRODUCTION

   The Authentication Server Protocol provides a means to determine the
   identity of a user of a particular TCP connection.  Given a TCP port
   number pair, it returns a character string which identifies the owner
   of that connection on the server's system.  Suggested uses include
   automatic identification and verification of a user during an FTP
   session, additional verification of a TAC dial up user, and access
   verification for a generalized network file server.

OVERVIEW

   This is a connection based application on TCP.  A server listens for
   TCP connections on TCP port 113 (decimal).  Once a connection is
   established, the server reads one line of data which specifies the
   connection of interest.  If it exists, the system dependent user
   identifier of the connection of interest is sent out the connection.
   The service closes the connection after sending the user identifier.

RESTRICTIONS

   Queries are permitted only for fully specified connections. The
   local/foreign host pair used to fully specify the connection are
   taken from the query connection.  This means a user on Host A may
   only query the server on Host B about connections between A and B.















RFC 931                                                     January 1985
Authentication Server


QUERY/RESPONSE FORMAT

   The server accepts simple text query requests of the form

      , <foreign-port>

   where  is the TCP port (decimal) on the target (server)
   system, and <foreign-port> is the TCP port (decimal) on the source
   (user) system.

      For example:

         23, 6191

   The response is of the form

      , <foreign-port> : <response-type> : <additional-info>

   where ,<foreign-port> are the same pair as the query,
   <response-type> is a keyword identifying the type of response, and
   <additional info> is context dependent.

      For example:

         23, 6191 : USERID : MULTICS : StJohns.DODCSC.a
         23, 6193 : USERID : TAC : MCSJ-MITMUL
         23, 6195 : ERROR : NO-USER

RESPONSE TYPES

   A response can be one of two types:

   USERID

      In this case, <additional-info> is a string consisting of an
      operating system name, followed by a ":", followed by user
      identification string in a format peculiar to the operating system
      indicated.  Permitted operating system names are specified in
      RFC-923, "Assigned Numbers" or its successors.  The only other
      names permitted are "TAC" to specify a BBN Terminal Access