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CVE-2019-7577: Fix a buffer overread in MS_ADPCM_nibble and MS_ADPCM_…
…decode

If a chunk of RIFF/WAV file with MS ADPCM encoding contains an invalid
predictor (a valid predictor's value is between 0 and 6 inclusive),
a buffer overread can happen when the predictor is used as an index
into an array of MS ADPCM coefficients.

The overead happens when indexing MS_ADPCM_state.aCoeff[] array in
MS_ADPCM_decode() and later when dereferencing a coef pointer in
MS_ADPCM_nibble().

This patch fixes it by checking the MS ADPCM predictor values fit
into the valid range.

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 82e503c commit 68f914a78ef09a4d2db43e0c7c2848a6b7c03655
Showing with 7 additions and 0 deletions.
  1. +7 −0 src/audio/SDL_wave.c
@@ -147,6 +147,9 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
if ( stereo ) {
state[1]->hPredictor = *encoded++;
}
if (state[0]->hPredictor >= 7 || state[1]->hPredictor >= 7) {
goto invalid_predictor;
}
state[0]->iDelta = ((encoded[1]<<8)|encoded[0]);
encoded += sizeof(Sint16);
if ( stereo ) {
@@ -217,6 +220,10 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
SDL_SetError("Too short chunk for a MS ADPCM decoder");
SDL_free(freeable);
return(-1);
invalid_predictor:
SDL_SetError("Invalid predictor value for a MS ADPCM decoder");
SDL_free(freeable);
return(-1);
}

struct IMA_ADPCM_decodestate {

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