Graphite2 – TtfUtil::CmapSubtable4NextCodepoint Heap Overread
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=755 The following crash due to a heap-based buffer overread can be observed in an ASAN build of the standard Graphite2 gr2FontTest utility (git trunk), triggered with the following command: $ ./gr2fonttest /path/to/file -auto --- cut --- ==19167==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60e00000dff1 at pc 0x000000553c7d bp 0x7ffc6c2c7100 sp 0x7ffc6c2c70f8 READ of size 1 at 0x60e00000dff1 thread T0 #0 0x553c7c in unsigned long be::_peek<1>(unsigned char const*) graphite/src/./inc/Endian.h:77:73 #1 0x553be8 in unsigned long be::_peek<2>(unsigned char const*) graphite/src/./inc/Endian.h:50:43 #2 0x56d7e3 in unsigned short be::peek<unsigned short>(void const*) graphite/src/./inc/Endian.h:55:18 #3 0x5f2bad in graphite2::TtfUtil::CmapSubtable4NextCodepoint(void const*, unsigned int, int*) graphite/src/TtfUtil.cpp:1042:16 #4 0x4fce35 in bool cache_subtable<&graphite2::TtfUtil::CmapSubtable4NextCodepoint, &graphite2::TtfUtil::CmapSubtable4Lookup>(unsigned short**, void const*, unsigned int) graphite/src/CmapCache.cpp:65:33 #5 0x4fb097 in graphite2::CachedCmap::CachedCmap(graphite2::Face const&) graphite/src/CmapCache.cpp:107:14 #6 0x54b6d2 in graphite2::Face::readGlyphs(unsigned int) graphite/src/Face.cpp:108:22 #7 0x56f5d4 in (anonymous namespace)::load_face(graphite2::Face&, unsigned int) graphite/src/gr_face.cpp:54:14 #8 0x56f0e4 in gr_make_face_with_ops graphite/src/gr_face.cpp:89:16 #9 0x571420 in gr_make_file_face graphite/src/gr_face.cpp:242:23 #10 0x4ed0b3 in Parameters::testFileFont() const (graphite/gr2fonttest/gr2fonttest+0x4ed0b3) #11 0x4f06c9 in main (graphite/gr2fonttest/gr2fonttest+0x4f06c9) 0x60e00000dff1 is located 0 bytes to the right of 145-byte region [0x60e00000df60,0x60e00000dff1) allocated by thread T0 here: #0 0x4b85b8 in malloc llvm/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:40 #1 0x55d42b in graphite2::FileFace::get_table_fn(void const*, unsigned int, unsigned long*) graphite/src/FileFace.cpp:94:11 #2 0x54f0d1 in graphite2::Face::Table::Table(graphite2::Face const&, graphite2::TtfUtil::Tag, unsigned int) graphite/src/Face.cpp:281:36 #3 0x4faad3 in graphite2::CachedCmap::CachedCmap(graphite2::Face const&) graphite/src/CmapCache.cpp:91:23 #4 0x54b6d2 in graphite2::Face::readGlyphs(unsigned int) graphite/src/Face.cpp:108:22 #5 0x56f5d4 in (anonymous namespace)::load_face(graphite2::Face&, unsigned int) graphite/src/gr_face.cpp:54:14 #6 0x56f0e4 in gr_make_face_with_ops graphite/src/gr_face.cpp:89:16 #7 0x571420 in gr_make_file_face graphite/src/gr_face.cpp:242:23 #8 0x4ed0b3 in Parameters::testFileFont() const (graphite/gr2fonttest/gr2fonttest+0x4ed0b3) #9 0x4f06c9 in main (graphite/gr2fonttest/gr2fonttest+0x4f06c9) SUMMARY: AddressSanitizer: heap-buffer-overflow graphite/src/./inc/Endian.h:77:73 in unsigned long be::_peek<1>(unsigned char const*) Shadow bytes around the buggy address: 0x0c1c7fff9ba0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c1c7fff9bb0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c1c7fff9bc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c1c7fff9bd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c1c7fff9be0: fa fa fa fa fa fa fa fa fa fa fa fa 00 00 00 00 =>0x0c1c7fff9bf0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00[01]fa 0x0c1c7fff9c00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c1c7fff9c10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c1c7fff9c20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c1c7fff9c30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c1c7fff9c40: 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 Heap right redzone: fb Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack partial redzone: f4 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 ==19167==ABORTING --- cut --- The bug was reported at https://bugzilla.mozilla.org/show_bug.cgi?id=1254487. Attached are three font files which reproduce the crash. Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/39862.zip |