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Bug 473674 (CVE-2013-2175) - <net-proxy/haproxy-1.4.24: may crash when using header occurrences relative to the tail (CVE-2013-2175)
Summary: <net-proxy/haproxy-1.4.24: may crash when using header occurrences relative t...
Alias: CVE-2013-2175
Product: Gentoo Security
Classification: Unclassified
Component: Vulnerabilities (show other bugs)
Hardware: All Linux
: Normal minor (vote)
Assignee: Gentoo Security
Whiteboard: B3 [glsa]
Depends on:
Reported: 2013-06-18 08:45 UTC by Agostino Sarubbo
Modified: 2013-08-29 01:20 UTC (History)
3 users (show)

See Also:
Package list:
Runtime testing required: ---


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Description Agostino Sarubbo gentoo-dev 2013-06-18 08:45:30 UTC
From ${URL} :

David Torgerson reported an haproxy crash with enough traces to diagnose
the cause as being related to the use of a negative occurrence number in
a header extraction, which is used to extract an entry starting from the
last occurrence.

--- summary ---

Configurations at risk are those which make use of "hdr_ip(name,-1)" (in
1.4) or any hdr_* variant with a negative occurrence count in 1.5, or
the "usesrc hdr_ip(name)" statement in both 1.4 and 1.5. These
configurations may be crashed when run with haproxy 1.4.4 to 1.4.23 or
development versions up to and including 1.5-dev18. Versions 1.4.24 and
1.5-dev19 are safe.

--- quick workaround ---

A workaround consists in rejecting dangerous requests early using
hdr_cnt(<name>), which is available both in 1.4 and 1.5 :
       block if { hdr_cnt(<name>) ge 10 }

--- details ---

When a config makes use of hdr_ip(x-forwarded-for,-1) or any such thing
involving a negative occurrence count, the header is still parsed in the
order it appears, and an array of up to MAX_HDR_HISTORY entries is created.
When more entries are used, the entries simply wrap and continue this way.
A problem happens when the incoming header field count exactly divides
MAX_HDR_HISTORY, because the computation removes the number of requested
occurrences from the count, but does not care about the risk of wrapping
with a negative number. Thus we can dereference the array with a negative
number and randomly crash the process.
The bug is located in http_get_hdr() in haproxy 1.5, and get_ip_from_hdr2()
in haproxy 1.4. It affects configurations making use of one of the following
functions with a negative <value> occurence number :
   - hdr_ip(<name>, <value>)  (in 1.4)
   - hdr_*(<name>, <value>)   (in 1.5)
It also affects "source" statements involving "hdr_ip(<name>)" since that
statement implicitly uses -1 for <value> :
   - source usesrc hdr_ip(<name>)
This bug has been present since the introduction of the negative offset
count in 1.4.4 via commit bce70882.

CVE-2013-2175 was assigned to this bug.

Special thanks to David Torgerson who provided a significant number of
traces, and to Ryan O'Hara from Red Hat for providing a CVE id.
--- links ---
 1.4-stable patch for version <= 1.4.23 :;a=commitdiff;h=f534af74ed
 1.4.24 source code:
 1.5-dev patch for versions <= 1.5-dev18 :;a=commitdiff;h=67dad2715b
 1.5-dev19 source code:

@maintainer(s): after the bump, in case we need to stabilize the package, please say explicitly if it is ready for the stabilization or not.
Comment 1 Christian Ruppert (idl0r) gentoo-dev 2013-06-29 16:35:20 UTC
haproxy-1.4.24 has just been commited. Feel free to stabilize =net-proxy/haproxy-1.4.24.
Comment 2 Sean Amoss (RETIRED) gentoo-dev Security 2013-06-30 17:51:56 UTC
(In reply to Christian Ruppert (idl0r) from comment #1)
> haproxy-1.4.24 has just been commited. Feel free to stabilize
> =net-proxy/haproxy-1.4.24.

Thanks, Christian.

Arches, please test and mark stable.
Comment 3 Agostino Sarubbo gentoo-dev 2013-06-30 18:17:14 UTC
amd64 stable
Comment 4 Agostino Sarubbo gentoo-dev 2013-06-30 18:17:43 UTC
x86 stable
Comment 5 Agostino Sarubbo gentoo-dev 2013-06-30 21:14:16 UTC
ppc stable
Comment 6 Tobias Heinlein (RETIRED) gentoo-dev 2013-07-07 15:08:48 UTC
Ready for vote, I vote YES.
Comment 7 Alex Legler (RETIRED) archtester gentoo-dev Security 2013-07-07 15:09:33 UTC
Comment 8 GLSAMaker/CVETool Bot gentoo-dev 2013-07-11 23:33:31 UTC
This issue was resolved and addressed in
 GLSA 201307-01 at
by GLSA coordinator Sean Amoss (ackle).
Comment 9 GLSAMaker/CVETool Bot gentoo-dev 2013-08-29 01:20:07 UTC
CVE-2013-2175 (
  HAProxy 1.4 before 1.4.24 and 1.5 before 1.5-dev19, when configured to use
  hdr_ip or other "hdr_*" functions with a negative occurrence count, allows
  remote attackers to cause a denial of service (negative array index usage
  and crash) via an HTTP header with a certain number of values, related to
  the MAX_HDR_HISTORY variable.