[cobalt-users] If you use ClamAV read this

[desa15@xxxxxxxx]

   Para: bugs@xxxxxxxxxx           
                                   
     cc: bugtraq@xxxxxxxxxxxxxxxxx 
                                   
 Asunto: clamav 0.65 remote DOS    
         exploit                   
                                   



>Description:

It is trivial to crash clamd using a malformed uuencoded message, resulting
in a
denial of service for all programs (e.g. SMTP daemons) relying on clamd
running.
The message must only contain one uuencoded line with an illegal line
lenght, i.e.
starting with a small letter.

libclamav calculates the line lenght of an uuencoded line by taking the
ASCII value
of the first character minus 64 and does an `assert' if the length is not
in the
allowed range, effectively terminating the calling program.

>How-To-Repeat:

Save the following file to ~/clamtest.mbox, removing the leading 'X':

XFrom -
X
Xbegin 644 byebye
Xbyebye
Xend

Then do:

# clamscan --mbox -v ~/clamtest.mbox
assertion "(len >= 0) && (len <= 63)" failed: file "message.c", line 887
Abort (core dumped)

or

# clamdscan -v ~/clamtest.mbox; ps ax | grep clam

>Fix:

Apply the following patch to libclamav/message.c:

--- libclamav/message.c.orig         Wed Nov  5 11:59:53 2003
+++ libclamav/message.c        Mon Feb  9 15:17:13 2004
@@ -878,13 +878,16 @@
                                     if(strcasecmp(line, "end") == 0)
                                                 break;

-                                    assert(strlen(line) <= 62);
+                                    if(strlen(line) > 62)
+                                                break;
+
                                     if((line[0] & 0x3F) == ' ')
                                                 break;

                                     len = *line++ - ' ';

-                                    assert((len >= 0) && (len <= 63));
+                                    if(len < 0 || len > 63)
+                                                break;

                                     ptr = decode(line, ptr, uudecode, (len
& 3) == 0);
                                     break;

>References:

FreeBSD PR 62586:
  <http://www.freebsd.org/cgi/query-pr.cgi?pr=62586>


Un saludo, Danny