The invalid memory dereference in
Exiv2::getULong()/Exiv2::StringValueBase::read()/Exiv2::DataValue::read()
is caused further up the call-stack, by
v->read(pData, size, byteOrder) in TiffReader::readTiffEntry()
passing an invalid pData pointer (pData points outside of the Tiff
file). pData can be set out of bounds in the (size > 4) branch where
baseOffset() and offset are added to pData_ without checking whether
the result is still in the file. As offset comes from an untrusted
source, an attacker can craft an arbitrarily large offset into the
file.
This commit adds a check into the problematic branch, whether the
result of the addition would be out of bounds of the Tiff
file. Furthermore the whole operation is checked for possible
overflows.
A heap buffer overflow could occur in memcpy when icc.size_ is larger
than data.size_ - pad, as then memcpy would read out of bounds of data.
This commit adds a sanity check to iccLength (= icc.size_): if it is
larger than data.size_ - pad (i.e. an overflow would be caused) an
exception is thrown.
This fixes#71.
Source:
https://github.com/Exiv2/exiv2/issues/57#issuecomment-333086302
tc can be a null pointer when the TIFF tag is unknown (the factory
then returns an auto_ptr(0)) => as this can happen for corrupted
files, an explicit check should be used because an assertion can be
turned of in release mode (with NDEBUG defined)
This also fixes#57
At least the musl libc on Linux has the same issue as Mac OS X: the
PTHREAD_RECURSIVE_* static initialiser does not exist. This is a
documented and purposeful omission:
http://www.openwall.com/lists/musl/2017/02/20/3
This commit uses similar logic to the Apple test on other Unixes.
=> Should fix#76 (most of the work has been done by Robin Mills in
6e3855aed7)
The problem with #76 is the contents of the 26th IFD, with the
following contents:
tag: 0x8649
type: 0x1
count: 0xffff ffff
offset: 0x4974
The issue is the size of count (uint32_t), as adding anything to it
causes an overflow. Especially the expression:
(size*count + pad+20)
results in an overflow and gives 20 as a result instead of
0x100000014, thus the condition in the if in the next line is false
and the program continues to run (until it crashes at io.read).
To properly account for the overflow, the brackets have to be removed,
as then the result is saved in the correctly sized type and not cast
after being calculated in the smaller type.
The brackets have also been removed from bigtiffimage.cpp, where the
same issue is present.
