Red Hat Bugzilla – Bug 4648
linuxconf and "special domain routing" creates an open SMTP relay
Last modified: 2008-05-01 11:37:51 EDT
If you use the "special domain routing" feature in Linuxconf it replaces the version 8.9.3 sendmail.cf with a version 8.8.7 sendmail.cf (bug id #2480). This is bad as the anti-relay rules in 8.8.7 are weaker. This also means that exposed RH6 machines with special domain routing now fail anti-relay tests (eg ORBS, MAPS etc) and can become black listed. Here's a sample of defeating the 8.8.7 relay rules: 220 ns2.xxx.com.au ESMTP Sendmail 8.9.3/8.8.7; Sun, 22 Aug 1999 15:38:58 +1000 mail from: <tom@oz.tm> 250 <tom@oz.tm>... Sender ok rcpt to: <"tom@interact.net.au"@xxx.com.au> 250 <"tom@interact.net.au"@xxx.com.au>... Recipient ok data 354 Enter mail, end with "." on a line by itself testing 123 . 250 PAA06431 Message accepted for delivery quit Here's the stock RH6 8.9.3 cf running which defeats this attempt: 220 ns2.xxx.com.au ESMTP Sendmail 8.9.3/8.9.3; Sun, 22 Aug 1999 15:59:50 +1000 mail from: <tom@oz.tm> 250 <tom@oz.tm>... Sender ok rcpt to: <"tom@interact.net.au"@xxx.com.au> 550 <"tom@interact.net.au"@xxx.com.au>... Relaying denied
This is actually a bug in the linuxconf component, not the sendmail one. This also happens even with the updated linuxconf RPM: linuxconf-1.16r1.3-1
Added Jacques to CC list
*** Bug 4719 has been marked as a duplicate of this bug. *** The following alert appeared on the Oz-ISP mailing list. It appears that Linuxconf over-writes the Sendmail-8.9 conf files with Sendmail 8.8.x config. It appears that Sendmail-8.8 still has some serious bugs in prevent spam as indicated in the following mail message extract. Is anyone looking at this problem ? ------------------------------------------------------------ --------------- For those people still using sendmail 8.8.x in hostile environments, note that your anti-relaying is very likely to be compromised. ORBS and RRS are listing 8.8.x as open relays (as they are relaying) because of this. Here's an example of poor.victim.com.au relaying spam to tom@oz.tm: 220 poor.victim.com.au ESMTP Sendmail 8.8.5/8.8.5; Wed, 25 Aug 1999 09:55:39 +1000 (EST) mail from: <lkjfe@netscape.net> 250 <lkjfe@netscape.net>... Sender ok rcpt to: <"tom@oz.tm"@victim.com.au> 250 <"tom@oz.tm"@victim.com.au>... Recipient ok data [... insert porn spam here ..] ------------------------------------------------------------ --------------- Given the popularity of RedHat 6 and Linuxconf with ISPs who are a little short on Unix, inparticular Sendmail skills. This could be a major problem. Regards Terry O'Connor
linuxconf has defaulted to allowing relaying but that is being changed now. We will release linuxconf-1.16r10-1 or later after some testing and that will have relaying turned off by default.
1.16r10-2 released