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global buffer overflow in strnmatch (char.c) #3096

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fatal0 opened this issue Jun 14, 2017 · 0 comments
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global buffer overflow in strnmatch (char.c) #3096

fatal0 opened this issue Jun 14, 2017 · 0 comments

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@fatal0
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fatal0 commented Jun 14, 2017

# fontforge -lang=ff -c 'Open($1)' ./poc/strnmatch-in-char.c-global-buffer-overflow.otf
Copyright (c) 2000-2014 by George Williams. See AUTHORS for Contributors.
 License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
 with many parts BSD <http://fontforge.org/license.html>. Please read LICENSE.
 Based on sources from 09:14 UTC 13-Jun-2017-D.
 Based on source from git with hash: b8e5ff8f24955f4d7d59ac73c903cc088b21bdb6
Table 'hmtx' extends beyond end of file and must be ignored.
The PostScript font name "ˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇ" is invalid.
It should be printable ASCII,
must not contain (){}[]<>%/ or space
and must be shorter than 63 characters
=================================================================
==21426==ERROR: AddressSanitizer: global-buffer-overflow on address 0x000000ff18d8 at pc 0x000000cf4f38 bp 0x7ffda943fc40 sp 0x7ffda943fc30
READ of size 2 at 0x000000ff18d8 thread T0
    #0 0xcf4f37 in strnmatch /root/afl_fuzz/project/test/fontforge/Unicode/char.c:73
    #1 0x51e847 in readttfcopyrights /root/afl_fuzz/project/test/fontforge/fontforge/parsettf.c:1770
    #2 0x51ee2a in readttfpreglyph /root/afl_fuzz/project/test/fontforge/fontforge/parsettf.c:1804
    #3 0x545d74 in readttf /root/afl_fuzz/project/test/fontforge/fontforge/parsettf.c:5487
    #4 0x552652 in _SFReadTTF /root/afl_fuzz/project/test/fontforge/fontforge/parsettf.c:6266
    #5 0x7e8756 in _ReadSplineFont /root/afl_fuzz/project/test/fontforge/fontforge/splinefont.c:1114
    #6 0x7ea217 in ReadSplineFont /root/afl_fuzz/project/test/fontforge/fontforge/splinefont.c:1285
    #7 0x7ea675 in LoadSplineFont /root/afl_fuzz/project/test/fontforge/fontforge/splinefont.c:1343
    #8 0x660df3 in bOpen /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:1854
    #9 0x6b967e in docall /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:9352
    #10 0x6b9f99 in handlename /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:9463
    #11 0x6be15f in term /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:9707
    #12 0x6bf96f in mul /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:9852
    #13 0x6bffcf in add /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:9897
    #14 0x6c0b1b in comp /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:9972
    #15 0x6c1338 in _and /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:10015
    #16 0x6c1871 in _or /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:10046
    #17 0x6c1e41 in assign /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:10078
    #18 0x6c2ff9 in expr /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:10156
    #19 0x6c4ab3 in ff_statement /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:10365
    #20 0x6c5b4f in ProcessNativeScript /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:10513
    #21 0x6c6536 in _CheckIsScript /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:10605
    #22 0x6c675b in CheckIsScript /root/afl_fuzz/project/test/fontforge/fontforge/scripting.c:10642
    #23 0x41fa8f in fontforge_main /root/afl_fuzz/project/test/fontforge/fontforgeexe/startnoui.c:113
    #24 0x41f705 in main /root/afl_fuzz/project/test/fontforge/fontforgeexe/main.c:39
    #25 0x7fd46350282f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
    #26 0x41f618 in _start (/root/afl_fuzz/project/test/fontforge/fontforgeexe/fontforge+0x41f618)

0x000000ff18d8 is located 21 bytes to the right of global variable '*.LC4' defined in 'ustring.c' (0xff18c0) of size 3
  '*.LC4' is ascii string '%d'
SUMMARY: AddressSanitizer: global-buffer-overflow /root/afl_fuzz/project/test/fontforge/Unicode/char.c:73 strnmatch
Shadow bytes around the buggy address:
  0x0000801f62c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801f62d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801f62e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801f62f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801f6300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0000801f6310: 04 f9 f9 f9 f9 f9 f9 f9 03 f9 f9[f9]f9 f9 f9 f9
  0x0000801f6320: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801f6330: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801f6340: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801f6350: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801f6360: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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
==21426==ABORTING

Testcase:
https://github.com/gnehsoah/poc/blob/master/fontforge/strnmatch-in-char.c-global-buffer-overflow.otf

Omnikron13 pushed a commit to Omnikron13/fontforge that referenced this issue May 31, 2022
* parsettf.c: Reading past the end of the fontnames array
* psread.c: Reading more data than is available in type1
* tottf.c: Use snprintf instead of sprintf

Closes fontforge#3096
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