I can't see this as having hit the list yet, so I'll forward it. It's a
SpamAssassin bug which particularly affects Exim users. See below.
----- Forwarded message from Timo Sirainen <tss@???> -----
From: Timo Sirainen <tss@???>
Subject: SpamAssassin / spamc+BSMTP remote buffer overflow
To: bugtraq@???
Date: 24 Jan 2003 00:21:32 +0200
Message-Id: <1043360492.29567.59.camel@hurina>
Organization:
Well, I was going to wait until 2.50 release, but it seems to be taking and
this likely affects only few installations. Besides, it's been in their
public bugzilla for over a month. So:
Attacker may be able to execute arbitrary code by sending a specially
crafted e-mail to a system using SpamAssassin's spamc program in BSMTP mode
(-B option). Versions from 2.40 to 2.43 are affected.
Exim users especially should check if they're affected, the -B option is
used in several Exim+SpamAssassin HOWTOs.
The problem is with escaping '.' characters at the beginning of lines.
Off-by-one bounds checking error allows writing '.' character past a
buffer, overwriting the stack frame address. Depending on system this may
be exploitable. Pre-built Debian unstable/x86 package wasn't vulnerable, my
self compiled was.
Patch:
diff -ru spamassassin-2.43-old/spamd/libspamc.c spamassassin-2.43/spamd/libspamc.c
--- spamassassin-2.43-old/spamd/libspamc.c 2002-10-15 18:22:49.000000000 +0300
+++ spamassassin-2.43/spamd/libspamc.c 2002-12-27 20:19:36.000000000 +0200
@@ -309,7 +309,7 @@
case MESSAGE_BSMTP:
total=full_write(fd, m->pre, m->pre_len);
for(i=0; i<m->out_len; ){
- for(j=0; i<m->out_len && j<sizeof(buffer)/sizeof(*buffer)-1; ){
+ for(j=0; i<m->out_len && j<sizeof(buffer)/sizeof(*buffer)-2; ){
if(i+1<m->out_len && m->out[i]=='\n' && m->out[i+1]=='.'){
buffer[j++]=m->out[i++];
buffer[j++]=m->out[i++];
----- End forwarded message -----
