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heap-buffer-overflow read in flushline() #64

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kcwu opened this issue Dec 2, 2016 · 2 comments
Closed

heap-buffer-overflow read in flushline() #64

kcwu opened this issue Dec 2, 2016 · 2 comments

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@kcwu
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kcwu commented Dec 2, 2016 •
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input (xxd cases/tats-w3m-64)

00000000: 3c74 6162 6c65 3e3c 4361 7074 696f 6e3e  <table><Caption>
00000010: 3c69 6d67 2073 7263 3d22 2277 6964 7468  <img src=""width
00000020: 3d33 3030 3030 3020 6865 6967 6874 3d30  =300000 height=0
00000030: 3e3c 693e                                ><i>

how to reproduce:

ASAN_OPTIONS=abort_on_error=1:detect_leaks=0 LD_LIBRARY_PATH=./notgc ./w3m-tats.asan -T text/html -dump cases/tats-w3m-64

stderr:

=================================================================
==3694705==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x62e0000116c4 at pc 0x00000044ba68 bp 0x7ffee2207790 sp 0x7ffee2206f40
READ of size 1 at 0x62e0000116c4 thread T0
    #0 0x44ba67 in strlen (/w3m-tats.asan+0x44ba67)
    #1 0x6e355d in Strnew_charp /targets/w3m-tats/Str.c:67:9
    #2 0x56129c in flushline /targets/w3m-tats/file.c:2789:9
    #3 0x58a28a in HTMLtagproc1 /targets/w3m-tats/file.c:5069:6
    #4 0x5927e3 in HTMLlineproc0 /targets/w3m-tats/file.c:6477:10
    #5 0x60c63a in make_caption /targets/w3m-tats/table.c:1691:5
    #6 0x606cab in renderTable /targets/w3m-tats/table.c:1724:2
    #7 0x59240b in HTMLlineproc0 /targets/w3m-tats/file.c:6452:3
    #8 0x5a7d14 in completeHTMLstream /targets/w3m-tats/file.c:7022:2
    #9 0x5a5b21 in loadHTMLstream /targets/w3m-tats/file.c:7258:5
    #10 0x55bbf8 in loadHTMLBuffer /targets/w3m-tats/file.c:6781:5
    #11 0x55ee64 in loadSomething /targets/w3m-tats/file.c:224:16
    #12 0x5535ac in loadGeneralFile /targets/w3m-tats/file.c:2241:6
    #13 0x4f9202 in main /targets/w3m-tats/main.c:1017:12
    #14 0x7f220e53ff44 in __libc_start_main /build/eglibc-oGUzwX/eglibc-2.19/csu/libc-start.c:287
    #15 0x41bf25 in _start (/w3m-tats.asan+0x41bf25)

AddressSanitizer can not describe address in more detail (wild memory access suspected).
SUMMARY: AddressSanitizer: heap-buffer-overflow (/w3m-tats.asan+0x44ba67) in strlen
Shadow bytes around the buggy address:
  0x0c5c7fffa280: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c5c7fffa290: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c5c7fffa2a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c5c7fffa2b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c5c7fffa2c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c5c7fffa2d0: fa fa fa fa fa fa fa fa[fa]fa fa fa fa fa fa fa
  0x0c5c7fffa2e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c5c7fffa2f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c5c7fffa300: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c5c7fffa310: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c5c7fffa320: 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
==3694705==ABORTING

This is detected with help of dummy libgc wrapper. See http://github.com/kcwu/fuzzing-w3m/notgc for detail.
More detail to reproduce please see http://github.com/kcwu/fuzzing-w3m

For your convenience,
gdbline:
LD_LIBRARY_PATH=./notgc ASAN_OPTIONS=abort_on_error=1:detect_leaks=0 gdb --args ./w3m-tats.asan -T text/html -dump cases/tats-w3m-64

This is found by afl-fuzz.
@kcwu kcwu changed the title heap-buffer-overflow read in Strnew_charp() heap-buffer-overflow read in flushline() Dec 2, 2016
@kcwu
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kcwu commented Dec 6, 2016

The string pointer is got from has_hidden_link()

2303          return line->ptr + p->offset;

where p->offset=-27964.

So, I think issue #66 is the same issue. Just because p->offset is out of boundary too much, ASan is unable to know they are actually identical. BTW, following test case is yet another and ASan say it is heap-use-after-free

00000000: 3c74 6162 6c65 3e3c 696e 7075 7420 7479  <table><input ty                                                                                                                                                                                                                                                 │·····················································
00000010: 7065 3d22 696d 6167 6522 6865 6967 6874  pe="image"height                                                                                                                                                                                                                                                 │·····················································
00000020: 3d30 2073 7263 3d30 2077 6964 7468 3d33  =0 src=0 width=3                                                                                                                                                                                                                                                 │·····················································
00000030: 3330 3030 303e 3c69 3e3c 703e 3c74 6162  30000><i><p><tab                                                                                                                                                                                                                                                 │·····················································
00000040: 6c65 3e3c 696e 7075 7420 7479 7065 3d22  le><input type="                                                                                                                                                                                                                                                 │·····················································
00000050: 696d 6167 6522 6865 6967 6874 3d30 2073  image"height=0 s                                                                                                                                                                                                                                                 │·····················································
00000060: 7263 3d30 2077 6964 7468 3d33 3030 3030  rc=0 width=30000                                                                                                                                                                                                                                                 │·····················································
00000070: 303e                                     0>

This case, p->offset=-24113.

@kcwu kcwu mentioned this issue Dec 6, 2016
Closed
tats added a commit that referenced this issue Dec 7, 2016
@tats
Prevent negative values for offset and pos in push_link()
ecf5771 
Bug-Debian: #64
@tats
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tats commented Dec 7, 2016

Fixed, thank you.

@tats tats closed this as completed Dec 7, 2016
tats added a commit that referenced this issue May 5, 2017
@tats
Fix multiple vulnerabilities (closes: #850432)
d73f74e 
- New patch 934_menu.patch to fix buffer overflow (#49)
- New patch 935_shiftanchor.patch to fix buffer overflow (#62)
- New patch 936_metarefresh.patch to fix buffer overflow (#63)
- New patch 937_lineproc0.patch to fix buffer overflow (#67)
- New patch 938_lineproc2body.patch to fix buffer overflow (#61)
- New patch 939_textarea.patch to fix buffer overflow (#58)
- New patch 940_tabattr.patch to fix buffer overflow (#60)
- New patch 941_integeredwidth.patch to fix buffer overflow (#70)
- New patch 942_tridvalue.patch to fix buffer overflow (#71)
- New patch 943_pushlink.patch to fix buffer overflow (#64, #66)
- New patch 944_lineproc0.patch to fix use after free (#65)
- New patch 945_wtfstrwidth.patch to fix buffer overflow (#57)
- New patch 946_strnewsize.patch to fix buffer overflow (#72)
- New patch 947_realcolumn.patch to fix buffer overflow (#69)
- New patch 948_getmclen.patch to fix buffer overflow
  (#59, #73, #74, #75, #76, #78, #79, #80, #83, #84)
- New patch 949_wtftowcs.patch to fix buffer overflow (#77)
- New patch 950_textarea.patch to fix infinite loop (#85)
- New patch 951_lineproc0.patch to fix use after free (#81)
- New patch 952_formupdatebuffer.patch to fix buffer overflow (#82)
- New patch 953_formupdateline.patch to fix buffer overflow
  (#68#issuecomment-266214643)
- New patch 954_wtfparse1.patch to fix buffer overflow (#68)
tats added a commit that referenced this issue May 5, 2017
@tats
Prevent negative values for offset and pos in push_link()
0e0c678 
Bug-Debian: #64
Bug-Debian: #66
Origin: https://anonscm.debian.org/cgit/collab-maint/w3m.git/commit/?id=ecf57714191b77142da74035b748262cdc80dfb7
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