Network Working Group Internet Engineering Task Force
Internet-Draft Telnet Working Group
Kannan Alagappan
Digital Equipment Corporation
July 1992
Telnet Authentication : SPX
Status of this Memo
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1. Command Names and Codes
Authentication Types
SPX 3
Suboption Commands
AUTH 0
REJECT 1
ACCEPT 2
2. Command Meanings
IAC SB AUTHENTICATION IS <authentication-type-pair> AUTH <SPX authen-
tication token> IAC SE
This is used to pass the SPX authentication token to the remote
side of the connection. (A document which describes the authenti-
cation token syntax is forthcoming.) The first octet of the
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<authentication-type-pair> value is SPX. The second octet is a
modifier to the SPX authentication type.
IAC SB AUTHENTICATION REPLY <authentication-type-pair> ACCEPT <mutual
response> IAC SE
This command indicates that the authentication was successful.
After an SPX authentication exchange, both sides have securely es-
tablished a random 8-byte key to be used as the default key for
the ENCRYPTION option. If the AUTH_HOW_MUTUAL bit is set in the
second octet of the authentication-type-pair, the sender includes
the mutual response bytes. The receiver of the ACCEPT command
compares the "mutual response" with its expected mutual response.
(A document which describes the mutual response syntax is forth-
coming.) If the AUTH_HOW_ONE_WAY bit is set in the second octet
of the authentication-type-pair, the sender includes zero bytes of
mutual response.
IAC SB AUTHENTICATION REPLY <authentication-type-pair> REJECT <op-
tional reason for rejection> IAC SE
This command indicates that the authentication was not successful,
and if there is any more data in the sub-option, it is an ASCII
text message of the reason for the rejection.
3. Implementation Rules
Every command after the first AUTHENTICATION IS must carry the same
set of modifiers (e.g., CLIENT|MUTUAL) for subsequent AUTHENTICATION
IS and AUTHENTICATION REPLY commands.
If the second octet of the authentication-type-pair has the AUTH_WHO
bit set to AUTH_WHO_CLIENT, then the client sends the initial AUTH
command, and the server responds with either ACCEPT or REJECT.
If the second octet of the authentication-type-pair has the AUTH_WHO
bit set to AUTH_WHO_SERVER, then the server sends the initial AUTH
command, and the client responds with either ACCEPT or REJECT.
4. Examples
User "joe" may wish to log in as user "pete" on machine "foo". If
"pete" has set things up on "foo" to allow "joe" access to his ac-
count, then the client would send IAC SB AUTHENTICATION NAME "pete"
IAC SE IAC SB AUTHENTICATION IS SPX AUTH <joe's spx authentication
token> IAC SE. The server would then authenticate the user as "joe"
from the token information, and the server would send back either AC-
CEPT or REJECT. If mutual authentication is being used, the server
would include in the ACCEPT message, a mutual response. The authori-
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zation check to see if "pete" is allowing "joe" to use his account is
made after the authentication exchange is complete. Therefore, it is
possible for the client to receive an ACCEPT response (based on the
authentication token), but for joe to be denied access to log in to
pete's account.
Client Server
IAC DO AUTHENTICATION
IAC WILL AUTHENTICATION
[ The server is now free to request authentication information.
]
IAC SB AUTHENTICATION SEND SPX
CLIENT|MUTUAL SPX CLIENT|ONE_WAY
IAC SE
[ The server has requested mutual SPX authentication. If mutual
authentication is not supported, then the server is willing to
do one-way SPX authentication. ]
[ The client will now respond with the name of the user that it
wants to log in as, and the SPX authentication token. ]
IAC SB AUTHENTICATION NAME
"pete" IAC SE
IAC SB AUTHENTICATION IS SPX
CLIENT|MUTUAL AUTH <spx
authentication token
information> IAC SE
[ The server responds with an ACCEPT command to state that the
authentication was successful. ]
[ If AUTH_HOW_MUTUAL, the server responds with the mutual
response so the client can verify that it is really talking to
the right server. ]
[ If AUTH_HOW_ONE_WAY, the server responds with a NULL mutual
response, since the client is willing to trust the server
already. ]
IAC SB AUTHENTICATION REPLY SPX
CLIENT|MUTUAL ACCEPT <mutual
response> IAC SE
Author's Address
Kannan Alagappan
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Internet-Draft SPX for Telnet July 1992
Digital Equipment Corporation
550 King Street, LKG1-2/A19
Littleton, MA 01460
Mailing List: telnet-ietf@CRAY.COM
EMail: kannan@sejour.lkg.dec.com
The working group can be contacted via the current chair:
Steve Alexander
INTERACTIVE Systems Corporation
1901 North Naper Boulevard
Naperville, IL 60563-8895
Phone: (708) 505-9100 x256
EMail: stevea@isc.com
Telnet Working Group Expires January 1993 [Page 4]
