podofo: NULL pointer dereference in PoDoFo::PdfVariant::DelayedLoad (PdfVariant.h)

["Agostino Sarubbo" <ago () gentoo org>]

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

A fuzz on it discovered a null pointer dereference. The upstream project denies me to open a new ticket. So, I just 
will forward this on the -users mailing list.

The complete ASan output:

# podofocolor dummy $FILE foo
==5768==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000018 (pc 0x7f6504f1742c bp 0x7fffc41a0df0 sp 
0x7fffc41a0d00 T0)
==5768==The signal is caused by a READ memory access.
==5768==Hint: address points to the zero page.
    #0 0x7f6504f1742b in PoDoFo::PdfVariant::DelayedLoad() const 
/tmp/portage/app-text/podofo-0.9.4/work/podofo-0.9.4/src/base/PdfVariant.h:545:10
    #1 0x7f6504f1742b in PoDoFo::PdfVariant::GetArray() 
/tmp/portage/app-text/podofo-0.9.4/work/podofo-0.9.4/src/base/PdfVariant.h:795
    #2 0x7f6504f1742b in PoDoFo::PdfXObject::PdfXObject(PoDoFo::PdfObject*) 
/tmp/portage/app-text/podofo-0.9.4/work/podofo-0.9.4/src/doc/PdfXObject.cpp:264
    #3 0x51ff55 in ColorChanger::start() 
/tmp/portage/app-text/podofo-0.9.4/work/podofo-0.9.4/tools/podofocolor/colorchanger.cpp:137:28
    #4 0x51c06d in main /tmp/portage/app-text/podofo-0.9.4/work/podofo-0.9.4/tools/podofocolor/podofocolor.cpp:116:12
    #5 0x7f650358c61f in __libc_start_main /var/tmp/portage/sys-libs/glibc-2.22-r4/work/glibc-2.22/csu/libc-start.c:289
    #6 0x428718 in _start (/usr/bin/podofocolor+0x428718)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /tmp/portage/app-text/podofo-0.9.4/work/podofo-0.9.4/src/base/PdfVariant.h:545:10 in 
PoDoFo::PdfVariant::DelayedLoad() const
==5768==ABORTING

Affected version:
0.9.4

Fixed version:
N/A

Commit fix:
N/A

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

CVE:
N/A

Reproducer:
https://github.com/asarubbo/poc/blob/master/00174-podofo-nullptr-PoDoFo-PdfVariant-DelayedLoad

Timeline:
2017-02-13: bug discovered
2017-03-02: bug reported to upstream
2017-03-02: blog post about the issue

Note:
This bug was found with American Fuzzy Lop.

Permalink:
https://blogs.gentoo.org/ago/2017/03/02/podofo-null-pointer-dereference-in-podofopdfvariantdelayedload-pdfvariant-h

--
Agostino Sarubbo
Gentoo Linux Developer