Project: libredwg (libredwg/libredwg), language: c++
Vulnerability instance: libredwg.cve-2020-21830
Sanitizer: address

================= Bug Report (1/1) ==================
## Source: GitHub Issue
## URL: https://github.com/LibreDWG/libredwg/issues/188#issuecomment-574493134
## Description:
Issue: LibreDWG/libredwg#188
Title: Several bugs found by fuzzing
Referenced comment by linhlhq on 2020-01-15 04:41:39+00:00:

**8.heap-buffer-overflow in bit_calc_CRC ../../src/bits.c:2213**
POC: https://github.com/linhlhq/research/blob/master/PoCs/libreDWG_4c26d37/id:000034%2Csig:06%2Csrc:003269%2B004108%2Cop:splice%2Crep:4

```
=================================================================
==18234==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x62b000006a00 at pc 0x55d633177a35 bp 0x7ffdcca65160 sp 0x7ffdcca65150
READ of size 1 at 0x62b000006a00 thread T0
    #0 0x55d633177a34 in bit_calc_CRC ../../src/bits.c:2213
    #1 0x55d633177a34 in bit_check_CRC ../../src/bits.c:1279
    #2 0x55d63374e8b7 in dwg_decode_add_object ../../src/decode.c:5555
    #3 0x55d6337816a4 in read_2004_section_handles ../../src/decode.c:2719
    #4 0x55d6337816a4 in decode_R2004 ../../src/decode.c:3354
    #5 0x55d63379308d in dwg_decode ../../src/decode.c:246
    #6 0x55d633125fae in dwg_read_file ../../src/dwg.c:211
    #7 0x55d6331249d0 in get_bmp ../../programs/dwgbmp.c:111
    #8 0x55d633124066 in main ../../programs/dwgbmp.c:280
    #9 0x7f3fdd3f6b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
    #10 0x55d6331246c9 in _start (/home/user/linhlhq/libredwg/asan_build/programs/dwgbmp+0x28f6c9)

0x62b000006a00 is located 0 bytes to the right of 26624-byte region [0x62b000000200,0x62b000006a00)
allocated by thread T0 here:
    #0 0x7f3fddc42d38 in __interceptor_calloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xded38)
    #1 0x55d6331bcf25 in read_2004_compressed_section ../../src/decode.c:2321
    #2 0x55d633c674b2  (/home/user/linhlhq/libredwg/asan_build/programs/dwgbmp+0xdd24b2)

SUMMARY: AddressSanitizer: heap-buffer-overflow ../../src/bits.c:2213 in bit_calc_CRC
Shadow bytes around the buggy address:
  0x0c567fff8cf0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c567fff8d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c567fff8d10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c567fff8d20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c567fff8d30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c567fff8d40:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c567fff8d50: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c567fff8d60: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c567fff8d70: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c567fff8d80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c567fff8d90: 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
==18234==ABORTING
```

Build script:
#!/bin/bash -eu
# Minimized build script with only core build commands
set -eu
sh ./autogen.sh
./configure --disable-shared
make -j$(nproc)

Dockerfile:
FROM hwiwonlee/secb.base:latest
RUN apt-get update && apt-get install -y autoconf libtool texinfo
RUN git clone https://github.com/libredwg/libredwg libredwg
RUN git -C libredwg checkout d5a51c01023d5585ddf3dd17c83dbb3c81efc97e
WORKDIR $SRC/libredwg
COPY build.sh $SRC/

Additional files:
filename: fuzz_dwg_decode.options
content: [libfuzzer]
detect_leaks=0