oss-security - libpcre: invalid memory read in phar (pcretest.c)

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Message-ID: <890963.317451195-sendEmail@localhost>
Date: Mon, 20 Mar 2017 10:22:38 +0000
From: "Agostino Sarubbo" <ago@...too.org>
To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com>
Subject: libpcre: invalid memory read in phar (pcretest.c)

Description:
libpcre is a perl-compatible regular expression library.

A fuzz on libpcre1 through the pcretest utility revealed an invalid read in the utility itself. For the nature of the crash, it is not security relevant because the library is not affected but if you 
have a web application that calls directly the pcretest utility to parse untrusted data, then you are affected.
Also, it is important share the details because some distros/packagers may want to take the patch in their repository.

The complete ASan output:

# pcretest -16 -d $FILE
==28444==ERROR: AddressSanitizer: SEGV on unknown address 0x7f3c2de3e2dd (pc 0x0000005409dd bp 0x7fff0423db40 sp 0x7fff0423dac0 T0)
==28444==The signal is caused by a READ memory access.
    #0 0x5409dc in pchar /tmp/portage/dev-libs/libpcre-8.40/work/pcre-8.40/pcretest.c:1986:5
    #1 0x54006f in pchars16 /tmp/portage/dev-libs/libpcre-8.40/work/pcre-8.40/pcretest.c:2115:12
    #2 0x52e3e1 in main /tmp/portage/dev-libs/libpcre-8.40/work/pcre-8.40/pcretest.c:5092:15
    #3 0x7f3c2dc3878f in __libc_start_main /tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/csu/../csu/libc-start.c:289
    #4 0x41b438 in _init (/usr/bin/pcretest+0x41b438)

Affected version:
8.40

Fixed version:
8.41 (not released atm)

Commit fix:
https://vcs.pcre.org/pcre/code/trunk/pcretest.c?r1=1665&r2=1685&sortby=date

Credit:
This bug was discovered by Agostino Sarubbo of Gentoo.

CVE:
N/A

Reproducer:
https://github.com/asarubbo/poc/blob/master/00194-pcre-invalidread-phar

Timeline:
2017-02-22: bug discovered and reported to upstream
2017-02-22: upstream released a patch
2017-03-14: blog post about the issue

Note:
This bug was found with American Fuzzy Lop.

Permalink:
https://blogs.gentoo.org/ago/2017/03/14/libpcre-invalid-memory-read-in-phar-pcretest-c

--
Agostino Sarubbo
Gentoo Linux Developer

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