Closed Bug 157989 Opened 18 years ago Closed 18 years ago
Possible heap corruption with 0-width GIF
Submitter name: zen-parse Submitter email address: firstname.lastname@example.org Acknowledgement checkbox: on Product: Netscape 6.x Operating system: Unix: x86 Linux OS version: redhat 7.0 Issue summary: a "0 width" GIF image: exploitable heap overwrite. Issue details: A specially formed gif image with width 0 can be used to overwrite 'chunk' information and other heap based information. By overwriting a function pointer with an address containing user supplied data, it is possible to execute arbitary code. http://lxr.mozilla.org/mozilla/source/modules/libimg/gifcom/gif.cpp#1274 down to line 1310 and then line 1351 and 1354 This form was submitted from http://help.netscape.com/forms/bug-security.html?cp=bbpctr with Opera/6.0 (Linux 2.2.19-7.0.16 i686; U) [en].
We need to know if this is really exploitable.
Paper? Can you take a look at this?
Removing adt1.0.1 until there is a patch with reviews attached.
Firstly, gifcom is dead :) It's been moved to /modules/libpr0n/decoders/gif/ which still contains a lot of the old gifcom code. I talked it over with tor, and stopping the 0 width before the memory allocation seemed to be the best solution. And this is the patch. The memory overwrite actually happens later on during do_lzw, which first writes one byte, incrememnts the pointer, then checks whether it hit the end of the buffer. I looked into fixing the problem there, but it just caused problems in other areas (namely in BeginGIF(), which will never initialize mImageContainer if the width or height is 0.. which trickles down to assertion errors) I've also plugged the memory overwrite hole in do_lzw. In theory, the width check part of the patch should stop do_lzw from ever being called when the buffer is 0 in length, but it's better to check anyway.
This doesn't do anything malicious, however, it does crash Mozilla. I took a 14x14 GIF with one frame, and edited the image header and frame header so that it says 0x0.
Severity: normal → major
Priority: -- → P1
Target Milestone: --- → mozilla1.0.1
seems like we have a patch from Arron M. dan/mitch: can you review and super-review the patch, so we can try and get it landed asap. thanks!
Whiteboard: [adt1 RTM] [ETA Needed] → [adt1 RTM] [ETA 07/22]
Comment on attachment 91974 [details] [diff] [review] stop memory overwrite r=pavlov
Attachment #91974 - Flags: review+
Comment on attachment 91974 [details] [diff] [review] stop memory overwrite sr=tor
Attachment #91974 - Flags: superreview+
looks like we have the reviews. pav: are you in a position to land this patch for aaron m?
who's in a position to apply this patch to the trunk, so we can get some bake time on this change?
Comment on attachment 91974 [details] [diff] [review] stop memory overwrite Mixed indentation (2 vs. 4 space), but that seems to pervade the file already. email@example.com for 1.1beta trunk checkin. /be
Attachment #91974 - Flags: approval+
Whiteboard: [adt1 RTM] [ETA 07/22] → [adt1 RTM] [ETA 07/24]
Adding adt1.0.1+ on behalf of the adt. Please get Drivers approval for the branch and check the fix into the branch.
a=chofmann for 1.0.1. add the fixed1.0.1 keyword after getting this on the branch.
landed on trunk and branch.
Status: NEW → RESOLVED
Closed: 18 years ago
Resolution: --- → FIXED
thanks pav. tpreston: teri, can you verify this fix on the branch, then replace "fixed1.0.1" with "verified1.0.1"? thanks!
Verified fix checked into bonsai.mozilla.org and lxr.mozilla.org
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