PEAP auth rejected due to different inner and outer user-id

Alan DeKok aland at
Sat Feb 15 20:50:01 CET 2014

douglas eseng wrote:
> Trying to find a configuration that allow accurate accounting when PEAP
> / TTLS having anonymous outer user-id.
> Using FR 2.2.3 with default configuration.
> - add a testing user
> - enable eap.conf use_tunneled_reply for both PEAP & TTLS
> Observed that,
> - PEAP sent inner user-id in the Access-Accept
> - TTLS-PAP sent outer user-id in the Access-Accept instead. (debug
> output attached)

  OK, I see the same.

> Additionally enable 'update outer.reply' in post-auth section for the
> inner-tunnel virtual server.

  Don't do that.  If you have "use_tunneled_reply" set, then what will
happen is this:

- you update outer.reply with the User-Name
- when TTLS / PEAP finishes, it will toss the outer reply
- and replace it with the reply from the inner tunnel

> Observed that,
> - PEAP failed due to identity mismatch. (debug output attached)

  Your NAS is broken.  And arguably your FreeRADIUS configuration.

  The server is sending User-Name = "testing" back in an
Access-Challenge.  The NAS is using this User-Name in the next

  There are two things wrong here.  One, you can filter Access-Challenge
packets in FreeRADIUS.  See raddb/sites-available/default.  Look for

  Two, the NAS shouldn't be changing the User-Name in the middle of a
session.  This is ridiculous behavior.

  My $0.02 would be to file a bug with the NAS vendor, asking them to
fix their software, so that it ignores User-Name in the Access-Challenge.

> - TTLS-PAP sent inner user-id in the Access-Accept.
> Seem like both use_tunneled_reply option and update outer.reply in
> post-auth section have inconsistent behavior.

  Patches are welcome.

> What would be the correct configuration to allow accurate accounting?

  Set use_tunneled_reply = yes

  In the inner-tunnel post_auth section, do:

	update reply {
		User-Name := "%{User-Name}"

  That works for me.

  Also, enable filtering of Access-Challenge packets as described above.
 And file a bug with the NAS vendor.

  Alan DeKok.

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