From ac3d0d365b1f01a6782565feda0c7432a5795671 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= Date: Thu, 14 Feb 2019 14:12:22 +0100 Subject: [PATCH] CVE-2019-7577: Fix a buffer overread in MS_ADPCM_decode MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Písař --- src/audio/SDL_wave.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/src/audio/SDL_wave.c b/src/audio/SDL_wave.c index b4ad6c7..e42d01c 100644 --- a/src/audio/SDL_wave.c +++ b/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 { -- 2.20.1