AddressSanitizer: heap-buffer-overflow in function pdf_write_links at ps-pdf.cxx:3371

[hdthky]

Description

Whilst experimenting with htmldoc, built from commit 0bef12c, we are able to induce a vulnerability at htmldoc/htmldoc/ps-pdf.cxx:3371 in function pdf_write_links , 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_overflow5

The command is: ./htmldoc --webpage -t pdf -f /dev/null poc_heap_overflow5

The ASAN report is:

=================================================================
==6776==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x607000000458 at pc 0x5555556000ad bp 0x7fffffffb030 sp 0x7fffffffb020
READ of size 4 at 0x607000000458 thread T0
    #0 0x5555556000ac in pdf_write_links /work/htmldoc/htmldoc/ps-pdf.cxx:3371
    #1 0x5555556000ac in pdf_write_document /work/htmldoc/htmldoc/ps-pdf.cxx:2299
    #2 0x555555606286 in pspdf_export /work/htmldoc/htmldoc/ps-pdf.cxx:910
    #3 0x55555559f764 in main /work/htmldoc/htmldoc/htmldoc.cxx:1291
    #4 0x7ffff6b620b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #5 0x55555559fbcd in _start (/work/htmldoc/htmldoc/htmldoc+0x4bbcd)

0x607000000458 is located 0 bytes to the right of 72-byte region [0x607000000410,0x607000000458)
allocated by thread T0 here:
    #0 0x7ffff769bc47 in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:145
    #1 0x55555560584d in pspdf_prepare_outpages /work/htmldoc/htmldoc/ps-pdf.cxx:1258
    #2 0x55555560584d in pspdf_export /work/htmldoc/htmldoc/ps-pdf.cxx:901

SUMMARY: AddressSanitizer: heap-buffer-overflow /work/htmldoc/htmldoc/ps-pdf.cxx:3371 in pdf_write_links
Shadow bytes around the buggy address:
  0x0c0e7fff8030: 00 00 00 00 00 00 00 fa fa fa fa fa 00 00 00 00
  0x0c0e7fff8040: 00 00 00 00 00 04 fa fa fa fa 00 00 00 00 00 00
  0x0c0e7fff8050: 00 00 00 01 fa fa fa fa 00 00 00 00 00 00 00 00
  0x0c0e7fff8060: 00 fa fa fa fa fa 00 00 00 00 00 00 00 00 00 fa
  0x0c0e7fff8070: fa fa fa fa 00 00 00 00 00 00 00 00 00 01 fa fa
=>0x0c0e7fff8080: fa fa 00 00 00 00 00 00 00 00 00[fa]fa fa fa fa
  0x0c0e7fff8090: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0e7fff80a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0e7fff80b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0e7fff80c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0e7fff80d0: 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
==6776==ABORTING

Impact

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

[michaelrsweet]

Reproduced, as with the others it is highly unlikely this can result in information disclosure since this is overflowing an allocated buffer for some reason but it will cause a crash of HTMLDOC without writing any output...

[michaelrsweet]

[master ffb68b6] Fix another heap overflow issue (Issue #482)