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Date: Sat, 29 Jan 2011 22:21:08 -0700
From: Sam Trenholme <>
Subject: MaraDNS 1.4.06 and released

In 2002, when I rewrote the compression code for MaraDNS for the first
time, I made a mistake in allocating an array of integers, allocating
it in bytes instead of sizeof(int) units.  The resulted in a buffer
being too small, allowing it to be overwritten.

The impact of this programming error is that MaraDNS can be crashed by
sending MaraDNS a single "packet of death".  Since the data placed in
the overwritten array can not be remotely controlled (it is a list of
increasing integers), there is no way to increase privileges
exploiting this bug.

The attached patch resolves this issue by allocating in sizeof(int)
units instead of byte-sized units for an integer array.  In addition,
it uses a smaller array because a DNS name can only have, at most, 128

I would like to thank Mr. Witold Baryluk for pointing out this issue,
taking the time to backtrace the bug, and for bringing it to my
attention by posting to the MaraDNS mailing list.  However, I need to
let him know that making this public by filing a public Debian bug
without first trying to contact me is not the appropriate way to
handle a security problem with MaraDNS.  The appropriate way to do so
is via private email.  My email address is here:

( was an account created so I could make entries in
an older MaraDNS blog, and is not presently actively looked at)

As it turns out, I only occasionally look at the Debian bug database
and people with issues with MaraDNS would be better off joining the
MaraDNS mailing list instead of filing a Debian bug (unless the issue
is Debian-specific).

In response to this bug, I have released MaraDNS 1.4.06 and
 These releases are available here:

Since has recently suffered a security breach, their
file uploading feature is currently undergoing maintenance and new
files currently can not be uploaded there.

I have not made a new release of MaraDNS 2.0 yet.  Yarin has
contributed a number of patches, and I would like to integrate his
patches before making a new MaraDNS 2.0 release; MaraDNS 2.0 users can
use the supplied patch.

As an aside, I have become a better programmer since making this
mistake back in 2002.  Deadwood, which is a complete rewrite of
MaraDNS' recursive code, does not have this issue in its
compression/decompression code.  Instead of using different data types
in structures, Deadwood, by and large, uses special overflow-resistant
strings to store most data.

Also, I would like to take the time to make a public service
announcement for djbdns users: DjbDNS 1.05 does have known security
issues, and needs to be patched.  More details are here:

(I am making this announcement because I have seen people, as recently
as last year, claiming djbdns-1.05 is perfectly secure on public

- Sam

--- maradns-1.4.05/dns/Compress.c       2010-07-31 01:17:08.000000000 -0600
+++ maradns-1.4.06/dns/Compress.c       2011-01-28 18:28:46.000000000 -0700
@@ -22,7 +22,7 @@
 #include "functions_dns.h"

 /* Maximum allowed number of dlabel points */
-#define MAX_DLABEL_POINTS 512
+#define MAX_DLABEL_POINTS 160

 /* Maximum allowed length of compressed string; this is 4096 for TCP
  * packets */
@@ -87,7 +87,8 @@
         return 0;
-    if((new->dlabel_points = js_alloc(MAX_DLABEL_POINTS + 3,1)) == 0) {
+    if((new->dlabel_points = js_alloc(MAX_DLABEL_POINTS + 3,sizeof(int)))
+               == 0) {
         return 0;

Download attachment "maradns-1.4.05-CVE-2011-0520.patch" of type "application/octet-stream" (701 bytes)

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