129001 – [vuxml] [patch] print/cups-base: fix NULL-pointer dereference

It was discovered [1] that CUPS up to 1.3.9 has code path that will
dereference NULL pointer and it is trivially reproducible when user hits
the subscription limit, for example via repeated commands 'lpr -m
<somefile>'.

[1] http://www.openwall.com/lists/oss-security/2008/11/19/4/ and
    the rest of the thread.

Fix: There is no official fix yet -- I had just informed CUPS developer and
posted the simple patch to the oss-security mailing list.  Here is the
patch that will introduce checks for the values returned by
cupsdAddSubscription() and bump port version:



The preliminary VuXML entry follows:
  <vuln vid="unknown">
    <topic>cups -- Denial of Service by authenticated client</topic>
    <affects>
      <package>
	<name>cups-base</name>
	<range><lt>1.3.9_1</lt></range>
      </package>
    </affects>
    <description>
      <body xmlns="http://www.w3.org/1999/xhtml">
	<p>Josh Bressers discovered that CUPS daemon can be crashed
	via trivial NULL-pointer dereference:</p>
	<blockquote cite="http://www.openwall.com/lists/oss-security/2008/11/19/4/">
	<p>The upstream fix could still obviously let a local
	authenticated user crash the server.</p>
	</blockquote>
      </body>
    </description>
    <references>
      <mlist>http://www.openwall.com/lists/oss-security/2008/11/19/4/</mlist>
    </references>
    <dates>
      <discovery>2008-11-19</discovery>
    </dates>
  </vuln>

--- vuln.xml ends here ---

Please, note that this vulnerability was already disclosed in the
oss-security mailing list, so there is no much sense in hiding this
discussion.--Bt6MZmTlqT1FYuYB5tCxiG3xDkwBTObRlsr48eoUEfzajFye
Content-Type: text/plain; name="1.3.9-to-1.3.9_1-fix-null-deference.patch"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="1.3.9-to-1.3.9_1-fix-null-deference.patch"

diff -urN ./Makefile ../cups-base/Makefile
--- ./Makefile	2008-11-20 02:48:10.000000000 +0300
+++ ../cups-base/Makefile	2008-11-20 03:07:03.000000000 +0300
@@ -7,6 +7,7 @@
 
 PORTNAME=	cups
 PORTVERSION=	1.3.9
+PORTREVISION=	1
 DISTVERSIONSUFFIX=	-source
 CATEGORIES=	print
 MASTER_SITES=	EASYSW/${PORTNAME}/${DISTVERSION}
diff -urN ./files/patch-fix-subscriptions-null-dereference ../cups-base/files/patch-fix-subscriptions-null-dereference
--- ./files/patch-fix-subscriptions-null-dereference	1970-01-01 03:00:00.000000000 +0300
+++ ../cups-base/files/patch-fix-subscriptions-null-dereference	2008-11-20 03:11:26.000000000 +0300
@@ -0,0 +1,48 @@
+--- scheduler/subscriptions.c.orig	2008-11-20 02:57:17.000000000 +0300
++++ scheduler/subscriptions.c	2008-11-20 03:02:06.000000000 +0300
+@@ -728,6 +728,13 @@
+       {
+         sub = cupsdAddSubscription(CUPSD_EVENT_NONE, NULL, NULL, NULL,
+ 	                           atoi(value));
++	if (!sub)
++	{
++          cupsdLogMessage(CUPSD_LOG_ERROR,
++	                  "Unable to add new subscription.  Was parsing line %d of subscriptions.conf.",
++	                  linenum);
++          break;
++	}
+       }
+       else
+       {
+--- scheduler/ipp.c.orig	2008-11-20 02:55:59.000000000 +0300
++++ scheduler/ipp.c	2008-11-20 02:56:03.000000000 +0300
+@@ -2121,6 +2121,14 @@
+ 
+     sub = cupsdAddSubscription(mask, cupsdFindDest(job->dest), job, recipient,
+                                0);
++    if (!sub)
++    {
++      cupsdLogMessage(CUPSD_LOG_ERROR,
++		      "Failed to create subscription for job %d", job->id);
++      send_ipp_status(con, IPP_TOO_MANY_SUBSCRIPTIONS,
++                      _("Unable to add new subscription"));
++      return;
++    }
+ 
+     sub->interval = interval;
+ 
+@@ -5591,6 +5599,14 @@
+       job = NULL;
+ 
+     sub = cupsdAddSubscription(mask, printer, job, recipient, 0);
++    if (!sub)
++    {
++      cupsdLogMessage(CUPSD_LOG_ERROR,
++		      "Failed to create subscription for job %d", job->id);
++      send_ipp_status(con, IPP_TOO_MANY_SUBSCRIPTIONS,
++                      _("Unable to add new subscription"));
++      return;
++    }
+ 
+     if (job)
+       cupsdLogMessage(CUPSD_LOG_DEBUG, "Added subscription %d for job %d",
How-To-Repeat: 
Set 'MaxSubscriptions' in the cupsd.conf to some small value and invoke
'lpr -m <somefile>' multiple times.  You'll see that after some attempt
server will be unreachable due to its crash.  Default value of 100 for
MaxSubscription does not prevent the DoS, because many big files could
be feeded to CUPS daemon.