[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date: Wed, 19 Nov 2008 15:14:43 -0500 (EST)
From: Josh Bressers <bressers@...hat.com>
To: oss-security@...ts.openwall.com
Cc: "Steven M. Christey" <coley@...re.org>
Subject: Re: CVE request: CUPS DoS via RSS subscriptions
----- "Kees Cook" <kees@...ntu.com> wrote:
> Hello!
>
> I'd like to get a CVE assigned for the RSS subscription DoS mentioned
> here[1]. It seems that CUPS upstream already fixed[2] the issue[3]
> in
> their 1.3.8 release. Prior to 1.3.8, the server can be made to crash
> when visiting a malicious website due to CUPS general CSRF issues.
>
> Thanks,
>
> -Kees
>
> [1] https://bugs.launchpad.net/ubuntu/+source/cups/+bug/298241
> http://www.gnucitizen.org/blog/pwning-ubuntu-via-cups/
> [2] http://www.cups.org/strfiles/2774/str2774.patch
> [3] http://www.cups.org/str.php?L2774
>
So from looking at cups 1.3.7 on Fedora 8, here is what I see:
(gdb) bt
#0 create_subscription (con=0xb88975c0, uri=0xb889ae00) at ipp.c:5858
#1 0xb7facba7 in cupsdProcessIPPRequest (con=0xb88975c0) at ipp.c:615
#2 0xb7f88bfc in cupsdReadClient (con=0xb88975c0) at client.c:2253
#3 0xb7fc0606 in cupsdDoSelect (timeout=1) at select.c:537
#4 0xb7f98710 in main (argc=1, argv=0xbfdd6194) at main.c:817
(gdb) list
5853 else if (printer)
5854 cupsdLogMessage(CUPSD_LOG_DEBUG,
5855 "Added subscription %d for printer \"%s\"",
5856 sub->id, printer->name);
5857 else
5858 cupsdLogMessage(CUPSD_LOG_DEBUG, "Added subscription %d for server",
5859 sub->id);
5860
5861 sub->interval = interval;
5862 sub->lease = lease;
(gdb) print sub
$1 = (cupsd_subscription_t *) 0x0
It would appear to be a NULL pointer dereference. It seems that this call a
few lines above the snippet shown above:
sub = cupsdAddSubscription(mask, printer, job, recipient, 0);
will return NULL when the hardcoded value of 100 subscriptions is hit. So really
the issu here is a lack of error checking which results in a NULL dereference
crash. The upstream fix could still obviously let a local authenticated user
crash the server.
I'm not sure why yet, but this doesn't crash cups 1.2.4 for me (which it should).
--
JB
Powered by blists - more mailing lists
Please check out the
Open Source Software Security Wiki, which is counterpart to this
mailing list.
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
