Bug 840822 - Crash in __pmDecodeCreds decoding crafted PDUs
Summary: Crash in __pmDecodeCreds decoding crafted PDUs
Status: CLOSED ERRATA
Alias: None
Product: Fedora
Classification: Fedora
Component: pcp
Version: 16
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: ---
Assignee: Nathan Scott
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Keywords: Security
Depends On:
Blocks: 840765 CVE-2012-3418
TreeView+ depends on / blocked
 
Reported: 2012-07-17 09:59 UTC by Florian Weimer
Modified: 2012-08-20 03:52 UTC (History)
6 users (show)

(edit)
Clone Of:
(edit)
Last Closed: 2012-08-20 03:52:18 UTC


Attachments (Terms of Use)
preliminary patch to __pmDecodeCreds to fix this (854 bytes, patch)
2012-07-18 00:30 UTC, Mark Goodwin
no flags Details | Diff
Updated patch to address pcp credentials pdu buffer overflow exploit (1.45 KB, patch)
2012-07-19 10:18 UTC, Nathan Scott
no flags Details | Diff

Description Florian Weimer 2012-07-17 09:59:48 UTC
pmcd (and probably others) in pcp-3.6.3 crash when decoding crafted PDUs where the numcreds field exceeds the number of elements actually contained in the PDU.

On 32-bit architectures, the size passed to malloc can be too small, leading to a heap-based buffer overflow.  On 64-bit architectures, the multiplication is performed with 64 bits, so no overflow occurs, and the crash happens because __pmDecodeCreds reads beyond the end of an allocated buffer.

pmcd runs with root privileges and starts automatically when the pcp package is installed.  It listens on 0.0.0.0 and does not require authentication.

Comment 8 Mark Goodwin 2012-07-18 00:30:25 UTC
Created attachment 598767 [details]
preliminary patch to __pmDecodeCreds to fix this


Attached preliminary patch from Nathan Scott (upstream). Has been tested
against the reproducer script.

Comment 9 Florian Weimer 2012-07-18 06:54:43 UTC
(In reply to comment #8)
> Created attachment 598767 [details]
> preliminary patch to __pmDecodeCreds to fix this
> 
> 
> Attached preliminary patch from Nathan Scott (upstream). Has been tested
> against the reproducer script.

This calculation can overflow:

  need = sizeof(creds_t) + ((numcred-1) * sizeof(__pmCred));

There should be a check *before* the calculation that this cannot happen, something like numcred < (INT_MAX - sizeof(creds_t))/sizeof(__pmCred).

Comment 10 Nathan Scott 2012-07-19 10:18:37 UTC
Created attachment 599108 [details]
Updated patch to address pcp credentials pdu buffer overflow exploit

Incorporates an additional check to guard against malloc size overflow.  Uses a tighter restriction than the MAXINT-based suggestion, based on current uses and likely future uses of this PDU.

Comment 11 Mark Goodwin 2012-07-19 10:23:23 UTC
Ressign to Nathan since he is following thru and this seems to be the way
to go for these bugs.

Comment 12 Nathan Scott 2012-07-19 10:25:03 UTC
I have a pcpqa test (513) which uses Florian's initial test case to exercise this change.  I'll hang onto it privately until we get a/ confirmation on permission to make use of this, and b/ public knowledge of the issue.

thanks!

Comment 13 Florian Weimer 2012-07-19 11:33:00 UTC
(In reply to comment #10)
> Created attachment 599108 [details]
> Updated patch to address pcp credentials pdu buffer overflow exploit
> 
> Incorporates an additional check to guard against malloc size overflow. 
> Uses a tighter restriction than the MAXINT-based suggestion, based on
> current uses and likely future uses of this PDU.

This looks good, thanks.

Comment 14 Huzaifa S. Sidhpurwala 2012-08-16 03:41:32 UTC
Upstream patch:

http://oss.sgi.com/cgi-bin/gitweb.cgi?p=pcp/pcp.git;a=commit;h=cced6012b4b93bfb640a9678589ced5416743910

This issue has been addressed in pcp-3.6.5


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