[exim] Abused as spam relay with A=login:0 ??

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Auteur: Heiko Schlittermann
Date:  
À: exim-users
Sujet: [exim] Abused as spam relay with A=login:0 ??
Hello,


I just found some strange lines in my logs:

    2006-04-28 16:50:52 1FZUJ0-0001pq-6S <= pouch@??? H=(ii) [222.183.147.213] P=esmtpa A=login:0 S=3376
                                                                                              ~~~~~~~~~
    2006-04-28 16:50:54 1FZUJ0-0001pq-6S => qtom@??? R=amavis T=amavis H=eth1.tigger.schlittermann.de [212.80.235.129]
    2006-04-28 16:50:54 1FZUJ0-0001pq-6S Completed


User '0' does not exist here.

I just wanted to ask you help me finding the bug. But I found it
myself. Now I'm just posting it because I hope that I'm not the only
stupid one ;-) and at the end you'll find a question.

Here's my login authenticator (part of it, in reality there's a longer
condition). I've to have a clear text password file.

    # login authentication using a clear text password file
    login:
      driver = plaintext
      public_name = LOGIN
      server_prompts = Username:: : Password::
      server_condition = ${if eq{$2}{${lookup{$1}lsearch{/etc/exim4/passwd}}}{yes}{no}}
      server_set_id = $1


If there's an unknown user and an empty password this authenticator
*will* succeed! Now I changed it a little bit:

      server_condition = ${if eq{PLAIN\:$2}{${lookup{$1}lsearch{/etc/exim4/passwd}}}{yes}{no}}


(and of course my password file as well containing lines like 'user:PLAIN:xxx'


My question: Is there a more elegant solution? In this case here it
would be enough if failing lseach could about the complete condition.
Which chapter in TFM I'm missing?


    Best regards from Dresden
    Viele Grüße aus Dresden
    Heiko Schlittermann
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