[UNIX] qwik-smtpd Format String Vulnerability

From: SecuriTeam (support_at_securiteam.com)
Date: 11/03/04

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Date: 3 Nov 2004 17:58:08 +0200

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      qwik-smtpd Format String Vulnerability
    ------------------------------------------------------------------------

    SUMMARY

    The <http://qwikmail.sourceforge.net/smtpd/> QwikMail SMTP server
    (qwik-smtpd) is "a fast, secure, and efficient mail server (MTA). It is
    written in C and many security precautions have been taken to ensure that
    the code is safe".

    A format string vulnerability exists in the product's logging routine that
    allows a remote attacker to cause the product to execute arbitrary code.

    DETAILS

    Vulnerable Systems:
     * qwik-smtpd version 0.3

    Vulnerable code:
    In the file qwik-smtpd.c the following can be found:

    sprintf(Received,"Received: from %s (HELO %s) (%s) by %s with SMTP; %s\n",
    clientHost, clientHelo, clientIP, localHost, timebuf);
    ..
              else
              {
                fprintf(fpout,Received);
    ..

    As you can see, bug found in main() function.

    Vendor patch:
    A vendor patch is available from:
    <http://qwikmail.sourceforge.net/smtpd/qwik-smtpd-0.3.patch>
    http://qwikmail.sourceforge.net/smtpd/qwik-smtpd-0.3.patch

    --- qwik-smtpd-0.3.orig/qwik-smtpd.c 2002-06-27 22:35:24.000000000
    -0700
    +++ qwik-smtpd.c 2004-10-30 19:56:14.579287608 -0700
    @@ -208,7 +208,7 @@
                   for(x = 0; x < max_recipients; x++)
                   {
                     if(clientRcptTo[x] == NULL) break;
    - fprintf(fpout,clientRcptTo[x]);
    + fprintf(fpout,"%s", clientRcptTo[x]);
                     (void) fflush(fpout);
                     fprintf(fpout,"\n");
                     (void) fflush(fpout);
    @@ -431,9 +431,9 @@
               }
               else
               {
    - fprintf(fpout,Received);
    + fprintf(fpout,"%s", Received);
                 (void) fflush(fpout);
    - fprintf(fpout,messageID);
    + fprintf(fpout,"%s", messageID);
                 (void) fflush(fpout);
                 out(354, "type away!");
                 alarm(data_timeout);

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:darkeagle@list.ru> Dark
    Eagle.
    The original article can be found at:
    <http://unl0ck.info/advisories/qwik-smtpd.txt>
    http://unl0ck.info/advisories/qwik-smtpd.txt

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