How to Reject Anonymous Identity

Alan DeKok aland at
Fri Nov 2 18:02:50 CET 2018

On Nov 2, 2018, at 12:49 PM, Selahattin Cilek <selahattin_cilek at> wrote:
> "Anonymous" users those who use another user name in the outer EAP request. The option to use an anonymous (or "outer" or "secret" or "hidden") identity is enabled default on SecureW2 and  Windows 10's Microsoft EAP-TLS implementation and almost all devices can be configured to use it. This is a measure designed to prevent an attacker from getting a user's true user name by sniffing the packets that go between the NAS and the RADIUS server. Of course, when the request enters the the TLS tunnel, the server gets the user's true user name. I think these two lines from the log should make it clear:

  OK.  I understand all that.  Given the vagueness of the message, I wasn't sure what *you* meant by it.

> ... But the problem is that the user can hide his true user name in the outer request.

  That's sort of the point of the anonymous outer identity.

> Yes, but a user can choose to supply another false user name in the outer request, can't he?

  Which is why you only authenticate the user via the *inner* identity.

> I want to check if a user is using anonymous identity and reject access to him in the FreeRADIUS configuration, that is, without the help of MySQL. Something like: If he is using anonymous identity, do not let him in.

  Just look for the anonymous identity in the outer session.  This is why we tell people to read the debug output.  It *tells you* what's going on.

  In sites-enabled/default, do:

authorize {
	if (User-Name =~ /^anom/) {


  Though the user can just change the outer identity to anything else.

  The question here is why do you care what the outer identity is?  All of the default configuration uses the inner identity for authenticating users.

  Again, the default configuration *works*.  If you've done something to allow weird things, then it's due to your local changes.  Don't do that...

  Alan DeKok.

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