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CVE-2019-7577: Fix a buffer overread in MS_ADPCM_decode

If RIFF/WAV data chunk length is shorter then expected for an audio
format defined in preceeding RIFF/WAV format headers, a buffer
overread can happen.

This patch fixes it by checking a MS ADPCM data to be decoded are not
past the initialized buffer.

CVE-2019-7577
Reproducer: https://bugzilla.libsdl.org/show_bug.cgi?id=4492

Signed-off-by: Petr P?sa? <ppisar@redhat.com>
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ppisar committed Jun 10, 2019
1 parent 76871a1 commit 82e503c2e026a8eee64e199c2648c296d924a5ab
Showing with 9 additions and 1 deletion.
  1. +9 −1 src/audio/SDL_wave.c
@@ -115,7 +115,7 @@ static Sint32 MS_ADPCM_nibble(struct MS_ADPCM_decodestate *state,
static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
{
struct MS_ADPCM_decodestate *state[2];
Uint8 *freeable, *encoded, *decoded;
Uint8 *freeable, *encoded, *encoded_end, *decoded;
Sint32 encoded_len, samplesleft;
Sint8 nybble, stereo;
Sint16 *coeff[2];
@@ -124,6 +124,7 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
/* Allocate the proper sized output buffer */
encoded_len = *audio_len;
encoded = *audio_buf;
encoded_end = encoded + encoded_len;
freeable = *audio_buf;
*audio_len = (encoded_len/MS_ADPCM_state.wavefmt.blockalign) *
MS_ADPCM_state.wSamplesPerBlock*
@@ -141,6 +142,7 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
state[1] = &MS_ADPCM_state.state[stereo];
while ( encoded_len >= MS_ADPCM_state.wavefmt.blockalign ) {
/* Grab the initial information for this block */
if (encoded + 7 + (stereo ? 7 : 0) > encoded_end) goto too_short;
state[0]->hPredictor = *encoded++;
if ( stereo ) {
state[1]->hPredictor = *encoded++;
@@ -188,6 +190,8 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
samplesleft = (MS_ADPCM_state.wSamplesPerBlock-2)*
MS_ADPCM_state.wavefmt.channels;
while ( samplesleft > 0 ) {
if (encoded + 1 > encoded_end) goto too_short;

nybble = (*encoded)>>4;
new_sample = MS_ADPCM_nibble(state[0],nybble,coeff[0]);
decoded[0] = new_sample&0xFF;
@@ -209,6 +213,10 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
}
SDL_free(freeable);
return(0);
too_short:
SDL_SetError("Too short chunk for a MS ADPCM decoder");
SDL_free(freeable);
return(-1);
}

struct IMA_ADPCM_decodestate {

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