P B <[EMAIL PROTECTED]> wrote:
> I am using freeradius-0.5 on RH7.2. My NAS is sending
> an Access Request with User_Name, Chap_Password, 
> chap_id and Chap_Challenge as attributes.
> 
> The NAS calculates the Chap_Password as:
>  MD5(chap_id + password + chap_challenge) 
> where, "+" denotes concatenation.

  As per the RFC's, that's what it's supposed to do.
 
> The Chap_Challenge is sent as a separate attribute 
> (not as the authenticator).

  That should be fine.

> If I use a chap_challenge of 16 octets then everything
> is OK, but if I use any other size (24 for instance)
> then the authentication always fails and "Incorrect 
> Password" is logged in the radius log-file.

  My question is why and how are you changing the length of the
CHAP-Challenge?

  If I use 'radclient', I can send a packet like:

  User-Name = "bob"
  CHAP-Challenge = "afffffffffffffffffffffffffffffffffffffffa"
  CHAP-Password = "bob"              # encrypted, of course

  And it authenticates fine.

> Does freeradius accept CHAP challenge of only 16
> octets? Is this some configurable parameter?

  FreeRADIUS has *no* code in it which depends on the length of the
CHAP-Challenge.  If there isn't a CHAP-Challenge in the packet, then
it's taken from the request authenticator, and MUST be 16 octets.

  The CHAP-Challenge attribute can be almost any length, and that's
the way the 'verify challenge' code works.

  Alan DeKok.

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