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michaelrsweet / htmldoc

HTML Conversion Software
https://www.msweet.org/htmldoc
GNU General Public License v2.0
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AddressSanitizer: heap-buffer-overflow in function parse_table at ps-pdf.cxx:7198 #483

Closed hdthky closed 2 years ago

hdthky commented 2 years ago

Description

Whilst experimenting with htmldoc, built from commit 0bef12c, we are able to induce a vulnerability at htmldoc/htmldoc/ps-pdf.cxx:7198 in function parse_table , using a harness compiled from htmldoc/htmldoc.cxx.

Because there is no bounds checking, a heap-based out-of-bound read will be triggered when the software encounters a malformed file, result in information disclosure or denial of service.

Environment

Ubuntu 20.04

gcc 10.3.0 with ASAN

Proof of Concept

The POC is: poc_heap_overflow6

The command is: ./htmldoc --webpage -t pdf -f /dev/null poc_heap_overflow6

The ASAN report is:

=================================================================
==105819==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x621000003910 at pc 0x5555555eec34 bp 0x7fffffff3a60 sp 0x7fffffff3a50
READ of size 8 at 0x621000003910 thread T0
    #0 0x5555555eec33 in parse_table /work/htmldoc/htmldoc/ps-pdf.cxx:7198
    #1 0x5555555f066a in parse_doc /work/htmldoc/htmldoc/ps-pdf.cxx:4191
    #2 0x5555555f63f3 in render_table_row /work/htmldoc/htmldoc/ps-pdf.cxx:5860
    #3 0x5555555ee769 in parse_table /work/htmldoc/htmldoc/ps-pdf.cxx:7146
    #4 0x5555555f066a in parse_doc /work/htmldoc/htmldoc/ps-pdf.cxx:4191
    #5 0x5555555f4f23 in parse_doc /work/htmldoc/htmldoc/ps-pdf.cxx:4537
    #6 0x555555604d71 in pspdf_export /work/htmldoc/htmldoc/ps-pdf.cxx:803
    #7 0x55555559f764 in main /work/htmldoc/htmldoc/htmldoc.cxx:1291
    #8 0x7ffff6b620b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #9 0x55555559fbcd in _start (/work/htmldoc/htmldoc/htmldoc+0x4bbcd)

0x621000003910 is located 32 bytes to the right of 4080-byte region [0x621000002900,0x6210000038f0)
allocated by thread T0 here:
    #0 0x7ffff769bc47 in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:145
    #1 0x5555555cf500 in check_pages /work/htmldoc/htmldoc/ps-pdf.cxx:8867

SUMMARY: AddressSanitizer: heap-buffer-overflow /work/htmldoc/htmldoc/ps-pdf.cxx:7198 in parse_table
Shadow bytes around the buggy address:
  0x0c427fff86d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fff86e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fff86f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fff8700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fff8710: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fa fa
=>0x0c427fff8720: fa fa[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff8730: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff8740: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff8750: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff8760: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff8770: 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
  Shadow gap:              cc
==105819==ABORTING

Impact

This vulnerability is capable of inducing information disclosure or denial of service.

michaelrsweet commented 2 years ago

[master 3b44975] Fix another potential use of pages array without checking (Issue #483)