From c68e0003d2f2b4e50bb1c4412af40c32f0b6396e Mon Sep 17 00:00:00 2001 From: Petr P?sa? Date: Mon, 10 Jun 2019 09:25:05 -0700 Subject: [PATCH] CVE-2019-7575: Fix a buffer overwrite in MS_ADPCM_decode If a WAV format defines shorter audio stream and decoded MS ADPCM data chunk is longer, decoding continued past the output audio buffer. This fix is based on a patch from . https://bugzilla.libsdl.org/show_bug.cgi?id=4493 CVE-2019-7575 Signed-off-by: Petr P?sa? --- src/audio/SDL_wave.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/src/audio/SDL_wave.c b/src/audio/SDL_wave.c index 88ac2cca6..5f9365147 100644 --- a/src/audio/SDL_wave.c +++ b/src/audio/SDL_wave.c @@ -122,7 +122,7 @@ 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, *encoded_end, *decoded; + Uint8 *freeable, *encoded, *encoded_end, *decoded, *decoded_end; Sint32 encoded_len, samplesleft; Sint8 nybble, stereo; Sint16 *coeff[2]; @@ -142,6 +142,7 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len) return(-1); } decoded = *audio_buf; + decoded_end = decoded + *audio_len; /* Get ready... Go! */ stereo = (MS_ADPCM_state.wavefmt.channels == 2); @@ -149,7 +150,7 @@ 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; + if (encoded + 7 + (stereo ? 7 : 0) > encoded_end) goto invalid_size; state[0]->hPredictor = *encoded++; if ( stereo ) { state[1]->hPredictor = *encoded++; @@ -179,6 +180,7 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len) coeff[1] = MS_ADPCM_state.aCoeff[state[1]->hPredictor]; /* Store the two initial samples we start with */ + if (decoded + 4 + (stereo ? 4 : 0) > decoded_end) goto invalid_size; decoded[0] = state[0]->iSamp2&0xFF; decoded[1] = state[0]->iSamp2>>8; decoded += 2; @@ -200,7 +202,8 @@ 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; + if (encoded + 1 > encoded_end) goto invalid_size; + if (decoded + 4 > decoded_end) goto invalid_size; nybble = (*encoded)>>4; new_sample = MS_ADPCM_nibble(state[0],nybble,coeff[0]); @@ -223,8 +226,8 @@ 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"); +invalid_size: + SDL_SetError("Unexpected chunk length for a MS ADPCM decoder"); SDL_free(freeable); return(-1); invalid_predictor: