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- - Orange Bat advisory -

Name           : VLC 0.8.6i
Class          : Heap overflow
Published     : 2008-08-16
Credit    : g_ (g_ # orange-bat # com)

- - Details -


\modules\demux\tta.c
 
    #define TTA_FRAMETIME 1.04489795918367346939
  .
  .
  .
    int         i_seektable_size = 0, i;
  .
  .
  .
    /* Read the metadata */
    es_format_Init( &fmt, AUDIO_ES, VLC_FOURCC( 'T', 'T', 'A', '1' ) );
    fmt.audio.i_channels = GetWLE( &p_header[6] );
    fmt.audio.i_bitspersample = GetWLE( &p_header[8] );
[1] fmt.audio.i_rate = GetDWLE( &p_header[10] );

    p_sys->i_datalength = GetDWLE( &p_header[14] );
    p_sys->i_framelength = TTA_FRAMETIME * fmt.audio.i_rate;

[2] p_sys->i_totalframes = p_sys->i_datalength / p_sys->i_framelength +
                       ((p_sys->i_datalength % p_sys->i_framelength) ? 1 : 0);
    p_sys->i_currentframe = 0;

[3] i_seektable_size = sizeof(uint32_t)*p_sys->i_totalframes;
    p_seektable = (uint8_t *)malloc( i_seektable_size );
    stream_Read( p_demux->s, p_seektable, i_seektable_size ); 
    p_sys->pi_seektable = (uint32_t *)malloc(i_seektable_size);

    for( i = 0; i < p_sys->i_totalframes; i++ )
[4]      p_sys->pi_seektable[i] = GetDWLE( &p_seektable[i*4] );


[1] - we can set i_rate to 1
[2] - i_framelength = 1 (look for constant definition, it's ~1), 
  so i_totalframes = i_datalength
[3] - because we can set i_datalength to 2^30 and bacause 
  i_totalframes = i_datalength, multiplication will overflow
[4] - i_totalframes is positive (highest bit not set), so this loop will 
  spin 2^30 times, overwriting everything with data from the heap. 
  unfortunate thing is we have little control over what is written. 

- - Proof of concept -


http://www.orange-bat.com/adv/2008/vlc.dos.tta
backup: http://milw0rm.com/sploits/2008-vlc.dos.tta

- - PGP -

All advisories from Orange Bat are signed. You can find our public
key here: http://www.orange-bat.com/g_.asc

- - Disclaimer -

This document and all the information it contains is provided "as is",
without any warranty. Orange Bat is not responsible for the
misuse of the information provided in this advisory. The advisory is
provided for educational purposes only.

Permission is hereby granted to redistribute this advisory, providing
that no changes are made and that the copyright notices and
disclaimers remain intact.

(c) 2008 www.orange-bat.com 


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