Network Working Group K. Alagappan
Request for Comments:
1412 Digital Equipment Corporation
January 1993
Telnet Authentication: SPX
Status of this Memo
This memo defines an Experimental Protocol for the Internet
community. Discussion and suggestions for improvement are requested.
Please refer to the current edition of the "IAB Official Protocol
Standards" for the standardization state and status of this protocol.
Distribution of this memo is unlimited.
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 authentication token> IAC SE
This is used to pass the SPX authentication token to the remote
side of the connection. (A document which describes the
authentication token syntax is forthcoming.) The first octet of
the <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
established 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
<optional 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
account, 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
ACCEPT or REJECT. If mutual authentication is being used, the server
would include in the ACCEPT message, a mutual response. The
authorization 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.