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Network Working Group Mike StJohns
Request for Comments: 912 TPSC
September 1984
Authentication Service
STATUS OF THIS MEMO
This RFC suggests a proposed protocol for the ARPA-Internet
community, and requests discussion and suggestions for improvements.
Distribution of this memo is unlimited.
INTRODUCTION
The Authentication Server 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.
QUERY/RESPONSE FORMAT
The server accepts simple text query requests of the form
<local-port>, <foreign-port>
where <local-port>, 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:
StJohns [Page 1]
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RFC 912 September 1984
Authentication Service
23, 6191
The response is of the form
<local-port>, <foreign-port> : <response-type> : <additional-info>
where <local-port>, <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 : StJohns
RESPONSE TYPES
A response can be one of two types:
USERID
In this case, <additional-info> is the printable representation of
the user identifier of the owner of the connection. The format of
the returned user identifier is completely system dependent.
ERROR
For some reason the owner of the TCP port could not be determined,
<additional-info> tells why. The following are suggested values
of <additional-info> and their meanings.
INVALID PORT
Either the local or foreign port was improperly specified.
NO USER
The connection specified by the port pair is not currently
in use.
UNKNOWN ERROR
Can't determine connection owner; reason unknown.
Other values may be specified as necessary.
StJohns [Page 2]
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RFC 912 September 1984
Authentication Service
CAVEATS
Unfortunately, the trustworthiness of the various host systems that
might implement an authentication server will vary quite a bit. It
is up to the various applications that will use the server to
determine the amount of trust they will place in the returned
information. It may be appropriate in some cases restrict the use of
the server to within a locally controlled subnet.
APPLICATIONS
1) Automatic user authentication for FTP.
2) Verification for privileged network operations. For example,
having the server start or stop special purpose servers.
DISCLAIMER
I designed this protocol to allow me to eliminate the bother of
having to identify myself before continuing an FTP session.
Since I started work on it, other applications appeared. I have
tried to consider all of our applications while still making this as
general as possible.
StJohns [Page 3]
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