heap-buffer-overflow exists in the function decode_preR13_section_hdr in decode_r11.c

[cxlzff]

system info

Ubuntu x86_64, clang 6.0, dwg2dxf(0.12.4.4608)

Command line

./programs/dwg2dxf -b -m @@ -o /dev/null

AddressSanitizer output

==8993==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x611000000144 at pc 0x0000007064dc bp 0x7fffffffca00 sp 0x7fffffffc9f8
WRITE of size 4 at 0x611000000144 thread T0
#0 0x7064db in decode_preR13_section_hdr /testcase/libredwg/src/decode_r11.c:136:13
#1 0x70583b in decode_preR13 /testcase/libredwg/src/decode_r11.c:737:12
#2 0x53245a in dwg_decode /testcase/libredwg/src/decode.c:209:23
#3 0x50d759 in dwg_read_file /testcase/libredwg/src/dwg.c:254:11
#4 0x50c454 in main /testcase/libredwg/programs/dwg2dxf.c:258:15
#5 0x7ffff6e22c86 in __libc_start_main /build/glibc-CVJwZb/glibc-2.27/csu/../csu/libc-start.c:310
#6 0x419ee9 in _start (/testcase/libredwg/programs/dwg2dxf+0x419ee9)

0x611000000144 is located 4 bytes to the right of 256-byte region [0x611000000040,0x611000000140)
allocated by thread T0 here:
#0 0x4d2750 in calloc /fuzzer/build/llvm_tools/llvm-4.0.0.src/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:74
#1 0x7055f0 in decode_preR13 /testcase/libredwg/src/decode_r11.c:700:40
#2 0x50d759 in dwg_read_file /testcase/libredwg/src/dwg.c:254:11
#3 0x50c454 in main /testcase/libredwg/programs/dwg2dxf.c:258:15
#4 0x7ffff6e22c86 in __libc_start_main /build/glibc-CVJwZb/glibc-2.27/csu/../csu/libc-start.c:310

SUMMARY: AddressSanitizer: heap-buffer-overflow /testcase/libredwg/src/decode_r11.c:136:13 in decode_preR13_section_hdr
Shadow bytes around the buggy address:
0x0c227fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c227fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c227fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c227fff8000: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
0x0c227fff8010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c227fff8020: 00 00 00 00 00 00 00 00[fa]fa fa fa fa fa fa fa
0x0c227fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c227fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c227fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c227fff8060: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c227fff8070: 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
==8993==ABORTING

poc

https://gitee.com/cxlzff/fuzz-poc/raw/master/libredwg/decode_preR13_section_hdr_bof

[abergmann]

CVE-2022-33032 was assigned to this issue.

[rurban]

Invalid CVE, not repro in the latest release 0.12.5.

The tested version is experimental and this preR13 DWG leads to:

Reading DWG file ../test/issues/gh488/decode_preR13_section_hdr_bof
ERROR: This version of LibreDWG is only capable of decoding version r13-r2018 (code: AC1012-AC1032) DWG files.
We don't decode many entities and no blocks yet.
ERROR: Invalid table number 1845522176 for UCS      [ 7]
ERROR: Invalid table number 6619244 for VPORT    [ 8]
ERROR: Invalid table number 2228275 for APPID    [ 9]
ERROR: Invalid table number 341118858 for VX       [11]
ERROR: Failed to decode file: ../test/issues/gh488/decode_preR13_section_hdr_bof 0x800

READ ERROR 0x800

[rurban]

Verified as fixed. the bof even parses successfully now. Without any entities though