RFC 2759 (rfc2759) - Page 5 of 20

Microsoft PPP CHAP Extensions, Version 2

RFC 2759                  Microsoft MS-CHAP-V2              January 2000


   The  quantity is a 20 octet number encoded in ASCII as
   40 hexadecimal digits.  The hexadecimal digits A-F (if present) MUST
   be uppercase.  This number is derived from the challenge from the
   Challenge packet, the Peer-Challenge and NT-Response fields from the
   Response packet, and the peer password as output by the routine
   GenerateAuthenticatorResponse() (see section 8.7, below).  The
   authenticating peer MUST verify the authenticator response when a
   Success packet is received.  The method for verifying the
   authenticator is described in section 8.8, below.  If the
   authenticator response is either missing or incorrect, the peer MUST
   end the session.

   The  quantity is human-readable text in the appropriate
   charset and language [12].

6.  Failure Packet

   The Failure packet is identical in format to the standard CHAP
   Failure packet.  There is, however, formatted text stored in the
   Message field which, contrary to the standard CHAP rules, does affect
   the operation of the protocol.  The Message field format is:

      "E=eeeeeeeeee R=r C=cccccccccccccccccccccccccccccccc V=vvvvvvvvvv
M="

      where

      The "eeeeeeeeee" is the ASCII representation of a decimal error
      code (need not be 10 digits) corresponding to one of those listed
      below, though implementations should deal with codes not on this
      list gracefully.

         646 ERROR_RESTRICTED_LOGON_HOURS
         647 ERROR_ACCT_DISABLED
         648 ERROR_PASSWD_EXPIRED
         649 ERROR_NO_DIALIN_PERMISSION
         691 ERROR_AUTHENTICATION_FAILURE
         709 ERROR_CHANGING_PASSWORD

      The "r" is an ASCII flag set to '1' if a retry is allowed, and '0'
      if not.  When the authenticator sets this flag to '1' it disables
      short timeouts, expecting the peer to prompt the user for new
      credentials and resubmit the response.

      The "cccccccccccccccccccccccccccccccc" is the ASCII representation
      of a hexadecimal challenge value.  This field MUST be exactly 32
      octets long and MUST be present.




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