Bug 438146 (CVE-2012-4504) – <net-libs/libproxy-0.4.10 : buffer overflow vulnerability (CVE-2012-4504)

• Product: Gentoo Security
• Status: RESOLVED FIXED

[Description Agostino Sarubbo 2012-10-12 16:24:58 UTC]

https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2012-4505

An insufficient input validation flaw, leading to a heap-based buffer overflow was found in libproxy 0.3.x in the px_pac_reload() function.  libproxy allocates a memory to store downloaded proxy.pac proxy auto-configuration file content using the Content-Length size from the remote server's HTTP response header.  Allocation size is content length + 1.  A malicious host hosting proxy.pac, or a man in the middle attacker, could use this flaw to make libproxy allocate insufficient amount of memory and subsequently overflow a heap-based buffer.

http://code.google.com/p/libproxy/source/browse/tags/libproxy-0.3.1/src/lib/pac.c#165

165      self->cache = px_malloc0(content_length+1);
166      for (int recvd=0 ; recvd != content_length ; )
167              recvd += recv(sock, self->cache + recvd, content_length - recvd, 0);

This issue was confirmed with libproxy 0.3.x.  Earlier 0.2.x versions seems to be affected too.  It does not affect 0.4.x versions, where fixed size buffer is used.




https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2012-4504

A buffer overflow flaw was discovered in the libproxy's url::get_pac() used to download proxy.pac proxy auto-configuration file.  A malicious host hosting proxy.pac, or a man in the middle attacker, could use this flaw to trigger a stack-based buffer overflow in an application using libproxy, if proxy configuration instructed it to download proxy.pac file from a remote HTTP server.

url::get_pac() uses a fixed size buffer buffer[] to store content of the proxy.pac file downloaded from a remote server.  When filling the buffer, it uses server-supplied content length value, rather than size buffer, as a limit for the size of the input copied into the buffer.  Overflow occurs when server provides sufficiently large file and does not use chunked content encoding.  The buffer size is checked when using chunked encoding.

http://code.google.com/p/libproxy/source/browse/trunk/libproxy/url.cpp?r=846#462

This issue was introduced upstream with the addition of the chunked encoding support, which first appears in version 0.4.

http://code.google.com/p/libproxy/source/detail?r=489
http://code.google.com/p/libproxy/issues/detail?id=77

[Comment 1 Alexandre Rostovtsev (RETIRED) 2012-10-16 04:45:34 UTC]

> (In reply to comment #0)
> https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2012-4505
[...]
> This issue was confirmed with libproxy 0.3.x.  Earlier 0.2.x versions seems
> to be affected too.  It does not affect 0.4.x versions, where fixed size
> buffer is used.

This one doesn't affect us, libproxy-0.4.6 is the earliest we have in the tree.

[Comment 2 Alexandre Rostovtsev (RETIRED) 2012-10-16 08:05:01 UTC]

(In reply to comment #0)
> https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2012-4504

Thanks, fixed in libproxy-0.4.10

>*libproxy-0.4.10 (16 Oct 2012)
>
>  16 Oct 2012; Alexandre Rostovtsev <[e-mail]>
>  libproxy-0.4.6-r3.ebuild, libproxy-0.4.7.ebuild, +libproxy-0.4.10.ebuild,
>  +files/libproxy-0.4.10-disable-pac-test.patch,
>  +files/libproxy-0.4.10-mozjs185.pc.patch, metadata.xml:
>  Version bump; fixes buffer overflow (bug #438146, CVE-2012-4504, thanks to
>  Agostino Sarubbo). Re-add USE=webkit since it now works correctly (bug
>  #412573, thanks to Lucian Muresan) and it enable by default to provide PAC
>  and WPAD support. Alternatively, spidermonkey could be used for PAC instead
>  (but might lead to firefox crashes, see bug #373397). Update license.

[Comment 3 Agostino Sarubbo 2012-10-16 14:37:30 UTC]

(In reply to comment #1)
> This one doesn't affect us, libproxy-0.4.6 is the earliest we have in the
> tree.

Right!

Arches, please test and mark stable:
=net-libs/libproxy-0.4.10
Target keywords : "alpha amd64 arm hppa ia64 ppc ppc64 sh sparc x86"

[Comment 4 Anthony Basile 2012-10-17 02:08:45 UTC]

stable ppc ppc64

[Comment 5 Agostino Sarubbo 2012-10-17 11:07:01 UTC]

amd64 stable

[Comment 6 Jeroen Roovers (RETIRED) 2012-10-17 12:58:37 UTC]

Stable for HPPA.

[Comment 7 Markus Meier 2012-10-17 19:07:34 UTC]

arm stable

[Comment 8 Andreas Schürch 2012-10-19 06:36:03 UTC]

x86 done.

[Comment 9 Chris Reffett (RETIRED) 2012-10-21 02:55:59 UTC]

Would it be possible to switch to stabilizing 0.4.10-r1? Just added it, it fixes a DEPEND problem (bug 438714). If not, no problem, just wanted to ask.

[Comment 10 Alexandre Rostovtsev (RETIRED) 2012-10-21 03:47:42 UTC]

(In reply to comment #9)
> Would it be possible to switch to stabilizing 0.4.10-r1? Just added it, it
> fixes a DEPEND problem (bug 438714). If not, no problem, just wanted to ask.

Chris, thanks for fixing 438714. I've merged your change into the 0.4.10 ebuild and removed 0.4.10-r1; there is no need to make a revision bump when you are only adding a necessary dependency to an ebuild and that new dependency does not break any of the ebuild's keywords.

[Comment 11 Alexandre Rostovtsev (RETIRED) 2012-10-21 04:11:23 UTC]

(In reply to comment #10)

As pointed out by Chris on IRC, adding the automoc build dependency can change the set of installed files, since the kde plugin will no longer silently fail to build/install. So the 0.4.10-r1 revision bump was indeed correct.

Please reset the stabilization target to =net-libs/libproxy-0.4.10-r1

I have opened a separate bug #439122 for stabilization of 0.4.10-r1 on those arches who had already finished stabilizing 0.4.10.

[Comment 12 Tobias Klausmann (RETIRED) 2012-10-27 14:22:44 UTC]

Stable on alpha. (took =dev-lang/spidermonkey-1.8.5-r1 along for the ride).

[Comment 13 GLSAMaker/CVETool Bot 2012-11-11 16:19:28 UTC]

CVE-2012-4504 (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2012-4504):
  Stack-based buffer overflow in the url::get_pac function in url.cpp in
  libproxy 0.4.x before 0.4.9 allows remote servers to have an unspecified
  impact via a large proxy.pac file.

[Comment 14 Raúl Porcel (RETIRED) 2012-11-25 18:57:11 UTC]

ia64/sh/sparc stable

[Comment 15 Sean Amoss (RETIRED) 2012-11-26 01:37:11 UTC]

Thanks, everyone.

New GLSA request filed.

[Comment 16 GLSAMaker/CVETool Bot 2014-04-07 19:11:21 UTC]

This issue was resolved and addressed in
 GLSA 201404-02 at http://security.gentoo.org/glsa/glsa-201404-02.xml
by GLSA coordinator Mikle Kolyada (Zlogene).