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Date: Sat, 1 Apr 2017 14:16:28 +0000
From: "Agostino Sarubbo" <ago@...too.org>
To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com>
Subject: podofo: heap-based buffer overflow in PoDoFo::PdfPainter::ExpandTabs (PdfPainter.cpp)

Description:
podofo is a C++ library to work with the PDF file format.

A fuzz on it through the podofotxt2pdf command line tool reavealed an heap overflow. This post will be forwarded on the upstream mailing list.

The complete ASan output:

# podofotxt2pdf $FILE out.pdf
==12524==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x607000001178 at pc 0x7f44ebaa5c89 bp 0x7ffce55aac90 sp 0x7ffce55aac88
READ of size 2 at 0x607000001178 thread T0
    #0 0x7f44ebaa5c88 in PoDoFo::PdfPainter::ExpandTabs(PoDoFo::PdfString const&, long) const /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/src/doc/PdfPainter.cpp:1945:26
    #1 0x7f44eba95942 in PoDoFo::PdfPainter::DrawText(double, double, PoDoFo::PdfString const&, long) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/src/doc/PdfPainter.cpp:755:31
    #2 0x519755 in draw(char*, PoDoFo::PdfDocument*, bool, char const*) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofotxt2pdf/podofotxt2pdf.cpp:94:25
    #3 0x51aa52 in init(char const*, char const*, bool, char const*) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofotxt2pdf/podofotxt2pdf.cpp:165:5
    #4 0x51c253 in main /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofotxt2pdf/podofotxt2pdf.cpp:212:7
    #5 0x7f44e9a3878f in __libc_start_main /tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/csu/../csu/libc-start.c:289
    #6 0x41ccb8 in _start (/usr/bin/podofotxt2pdf+0x41ccb8)

0x607000001178 is located 0 bytes to the right of 72-byte region [0x607000001130,0x607000001178)
allocated by thread T0 here:
    #0 0x514870 in operator new(unsigned long) /tmp/portage/sys-libs/compiler-rt-sanitizers-4.0.0/work/compiler-rt-4.0.0.src/lib/asan/asan_new_delete.cc:82
    #1 0x7f44eb460304 in PoDoFo::PdfRefCountedBuffer::ReallyResize(unsigned long) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/src/base/PdfRefCountedBuffer.cpp:161:21
    #2 0x7f44eb21212d in PoDoFo::PdfRefCountedBuffer::Resize(unsigned long) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/src/base/PdfRefCountedBuffer.h:307:9
    #3 0x7f44eb47a466 in PoDoFo::PdfRefCountedBuffer::PdfRefCountedBuffer(unsigned long) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/src/base/PdfRefCountedBuffer.h:227:11
    #4 0x7f44eb47a466 in PoDoFo::PdfString::Init(char const*, long) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/src/base/PdfString.cpp:570
    #5 0x7f44eb47c24c in PoDoFo::PdfString::PdfString(char const*, PoDoFo::PdfEncoding const*) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/src/base/PdfString.cpp:109:9
    #6 0x519718 in draw(char*, PoDoFo::PdfDocument*, bool, char const*) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofotxt2pdf/podofotxt2pdf.cpp:94:43
    #7 0x51aa52 in init(char const*, char const*, bool, char const*) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofotxt2pdf/podofotxt2pdf.cpp:165:5
    #8 0x51c253 in main /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofotxt2pdf/podofotxt2pdf.cpp:212:7
    #9 0x7f44e9a3878f in __libc_start_main /tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/csu/../csu/libc-start.c:289

SUMMARY: AddressSanitizer: heap-buffer-overflow /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/src/doc/PdfPainter.cpp:1945:26 in PoDoFo::PdfPainter::ExpandTabs(PoDoFo::PdfString 
const&, long) const
Shadow bytes around the buggy address:
  0x0c0e7fff81d0: fa fa 00 00 00 00 00 00 00 00 00 00 fa fa fa fa
  0x0c0e7fff81e0: 00 00 00 00 00 00 00 00 00 fa fa fa fa fa fd fd
  0x0c0e7fff81f0: fd fd fd fd fd fd fd fa fa fa fa fa 00 00 00 00
  0x0c0e7fff8200: 00 00 00 00 00 fa fa fa fa fa 00 00 00 00 00 00
  0x0c0e7fff8210: 00 00 00 fa fa fa fa fa fd fd fd fd fd fd fd fd
=>0x0c0e7fff8220: fd fa fa fa fa fa 00 00 00 00 00 00 00 00 00[fa]
  0x0c0e7fff8230: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0e7fff8240: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0e7fff8250: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0e7fff8260: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0e7fff8270: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==12524==ABORTING

Affected version:
0.9.5

Fixed version:
N/A

Commit fix:
N/A

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

CVE:
CVE-2017-7378

Reproducer:
https://github.com/asarubbo/poc/blob/master/00248-podofo-heapoverflow-PdfPainter_cpp

Timeline:
2017-03-31: bug discovered and reported to upstream
2017-03-31: blog post about the issue
2017-03-31: CVE assigned

Note:
This bug was found with American Fuzzy Lop.

Permalink:
https://blogs.gentoo.org/ago/2017/03/31/podofo-heap-based-buffer-overflow-in-podofopdfpainterexpandtabs-pdfpainter-cpp

--
Agostino Sarubbo
Gentoo Linux Developer


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