Sourceware Bugzilla – Full Text Bug Listing
|Summary:||tzfile.c heap overrun/corruption|
|Product:||glibc||Reporter:||Paul Eggert <eggert>|
|Component:||libc||Assignee:||Ulrich Drepper <drepper.fsp>|
|Severity:||normal||CC:||allan, law, polacek, rguenth, toolchain, vapier|
Jeff Law work-in-progress patch
catch multiplication as well as addition overflows
Description Paul Eggert 2011-12-15 20:44:55 UTC
Created attachment 6113 [details] Jeff Law work-in-progress patch In <http://cygwin.com/ml/libc-alpha/2011-12/msg00037.html> Jeff Law writes: -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 As y'all may be aware, there's an integer overflow which can be used to trigger a heap overrun/corruption in time/tzfile.c http://dividead.wordpress.com/2009/06/01/glibc-timezone-integer-overflow/ http://rcvalle.com/post/14169476482/exploiting-glibc-tzfile-read-integer-overflow-to I'm not terribly familiar with the code in question, but ISTM we have to verify the intermediate computations to determine the amount of memory to malloc don't overflow/wrap. Here's a WIP. It catches the cases I've been made aware of (overflowing total_size to 0 by creating a tzfile with a very large tzh_charcnt). But there may be further overflows I've missed. Obviously it's not commented and it's unclear to me if we also want to put in some kind of sanity checks on total_size to prevent it from trying to malloc unreasoanble amounts of memory. Your feedback would be greatly appreciated. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJO6k6gAAoJEBRtltQi2kC7ASQH/0UmQm0wqk3NRmlsVr5M1r3f fUelY55y8OQssaFCLDZ9LX1vybam9j85gmvGtRJUU4MJ3134hn/v73k8TYCd3rHJ /QIQY10zPBHkmEwp8G56+3l9QRl418C+ajTq0W4NAzM1rIHtPUgrqZ3AkNJgFVYU OAF+2afFDGE5vJ3HR7LSL62tuxjDf7m66r4tHHkbhkSSZgkyW/YxfFUPDupZnlz8 Wl87JU/RWHdMJ+RR+fB1ofgFKrNZnGpIsD3sAc07KWTp63S358DSRpZ1IaF2o3vh N93z28eCQQKIVciOKgAE5q/qYr1KmcyU/6M4xPk+Pqv5YFdKOz8uNiw5NQu2rv0= =RKgA -----END PGP SIGNATURE-----
Comment 1 Paul Eggert 2011-12-15 21:00:49 UTC
Created attachment 6114 [details] catch multiplication as well as addition overflows Jeff Law's work-in-progress patch misses some problematic overflows. This is because the integer multiplications may overflow too. Attached is an untested patch that catches the problematic overflows that I found by inspection. This patch does not attempt to catch all overflows, only those that might corrupt memory.
Comment 2 Ulrich Drepper 2011-12-18 01:19:35 UTC
I added a patch.
Comment 3 Mike Frysinger 2011-12-19 05:35:35 UTC
Comment 4 Allan McRae 2011-12-19 05:50:57 UTC
Note that there is a typo in that patch. The "tzspec == 0" should be "tzspec_len == 0". I sent the trivial patch to the mailing list (awaiting moderation).
Comment 5 law 2011-12-19 07:57:44 UTC
Also looks like s390 won't build because SIZE_MAX is not defined. Guessing stdint.h needs to be included in tzfile.c