Martin Strand writes:

On Fri, 12 Dec 2008 00:51:23 +0100, Sam Varshavchik <[email protected]> 
wrote:

Martin Strand writes:

Using courier-pop3d, is there any way to disable simple USER/PASS login so that 
only AUTH login with CRAM-SHA1 works?
I tried setting POP3DAUTH="CRAM-SHA1" but USER/PASS still works...

USER/PASS is always permitted. There is no toggle to turn it off.

Thanks.
Does anyone have any good tips on how to work around this at the moment?
Is there perhaps a way to configure a set of "banned" commands?
Maybe I could write a small pop3 proxy in Perl and intercept any USER/PASS 
commands?

As someone pointed out, SSL would make more sense but unfortunately that's not 
an option in this case.

POP3 is actually a very simple protocol. Writing a POP3 proxy would actually be a fairly trivial excersize, especially for something like this.

Actually, one just option that occured to me. You can use the authuserdb module which optionally uses a separate field for pre-hashed CRAM passwords. Those fields are not used for user/pass authentication.

userdbpw -hmac-sha1 | userdb {username} set hmac-sha1pw

This would set the CRAM-SHA1 password for {username}. So, you would proceed to set CRAM-SHA1 passwords for all accounts, and set a dummy, invalid password (and NOT a blank password) otherwise, so that USER/PASS authentication would not work, but CRAM-SHA1 authentication would work just fine. This process is documented further in the man pages and the associated INSTALL files. This only works when using the userdb module, it's one of its quirks, in the way that it was written, originally.


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