On Windows, opened or locked files cannot be removed.
Since fontconfig locked an old cache file while updating the file,
fontconfig failed to replace the file with updated file on Windows.
This patch makes fontconfig does not lock the old cache file
while updating it on Windows.
Our test case relies on the outcome of the family property from freetype though,
it was changed in 2.7.1:
- PCF family names are made more `colourful'; they now include the
foundry and information whether they contain wide characters.
For example, you no longer get `Fixed' but rather `Sony Fixed'
or `Misc Fixed Wide'.
https://bugs.freedesktop.org/show_bug.cgi?id=47704
To support the one of changes in gperf 3.1:
* The 'len' parameter of the hash function and of the lookup function is now
of type 'size_t' instead of 'unsigned int'. This makes it safe to call these
functions with strings of length > 4 GB, on 64-bit machines.
Validation fails when the FcValueList contains more than font->num.
this logic was wrong because font->num contains a number of the elements
in FcPatternElt but FcValue in FcValueList.
This corrects 7a4a5bd7.
Patch from Tobias Stoeckmann
The cache files are insufficiently validated. Even though the magic
number at the beginning of the file as well as time stamps are checked,
it is not verified if contained offsets are in legal ranges or are
even pointers.
The lack of validation allows an attacker to trigger arbitrary free()
calls, which in turn allows double free attacks and therefore arbitrary
code execution. Due to the conversion from offsets into pointers through
macros, this even allows to circumvent ASLR protections.
This attack vector allows privilege escalation when used with setuid
binaries like fbterm. A user can create ~/.fonts or any other
system-defined user-private font directory, run fc-cache and adjust
cache files in ~/.cache/fontconfig. The execution of setuid binaries will
scan these files and therefore are prone to attacks.
If it's not about code execution, an endless loop can be created by
letting linked lists become circular linked lists.
This patch verifies that:
- The file is not larger than the maximum addressable space, which
basically only affects 32 bit systems. This allows out of boundary
access into unallocated memory.
- Offsets are always positive or zero
- Offsets do not point outside file boundaries
- No pointers are allowed in cache files, every "pointer or offset"
field must be an offset or NULL
- Iterating linked lists must not take longer than the amount of elements
specified. A violation of this rule can break a possible endless loop.
If one or more of these points are violated, the cache is recreated.
This is current behaviour.
Even though this patch fixes many issues, the use of mmap() shall be
forbidden in setuid binaries. It is impossible to guarantee with these
checks that a malicious user does not change cache files after
verification. This should be handled in a different patch.
Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
For Serif:
Cambria, Constantia, Elephant, MS Serif
For Sans Serif:
Arial Unicode MS, Britannic, Calibri, Candara, Century Gothic, Corbel,
Haettenschweiler, MS Sans Serif, Tahoma, Twentieth Century
For Monospace:
Consolas, Fixedsys, Terminal
Akira TAGOH
Masamichi Hosoda
Jan Alexander Steffens (heftig)
Khem Raj
Alan Coopersmith
Tobias Stoeckmann
Erik de Castro Lopo
Petr Filipsky
Behdad Esfahbod
Patrick Haller