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From d5ec943db7d51fccd7230c9df0c7a2e46d611f50 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
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Date: Mon, 10 Jun 2019 08:54:11 -0700
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Subject: [PATCH 04/11] CVE-2019-7577: Fix a buffer overread in MS_ADPCM_decode
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If RIFF/WAV data chunk length is shorter then expected for an audio format
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defined in preceeding RIFF/WAV format headers, a buffer overread can happen.
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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This patch fixes it by checking a MS ADPCM data to be decoded are not
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past the initialized buffer.
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CVE-2019-7577
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Reproducer: https://bugzilla.libsdl.org/show_bug.cgi?id=4492
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Signed-off-by: Petr Písař <ppisar@redhat.com>
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--HG--
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branch : SDL-1.2
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---
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src/audio/SDL_wave.c | 10 +++++++++-
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1 file changed, 9 insertions(+), 1 deletion(-)
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diff --git a/src/audio/SDL_wave.c b/src/audio/SDL_wave.c
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index 66f804421..6c6eb14eb 100644
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--- a/src/audio/SDL_wave.c
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+++ b/src/audio/SDL_wave.c
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@@ -115,7 +115,7 @@ static Sint32 MS_ADPCM_nibble(struct MS_ADPCM_decodestate *state,
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static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
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{
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struct MS_ADPCM_decodestate *state[2];
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- Uint8 *freeable, *encoded, *decoded;
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+ Uint8 *freeable, *encoded, *encoded_end, *decoded;
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Sint32 encoded_len, samplesleft;
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Sint8 nybble, stereo;
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Sint16 *coeff[2];
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@@ -124,6 +124,7 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
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/* Allocate the proper sized output buffer */
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encoded_len = *audio_len;
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encoded = *audio_buf;
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+ encoded_end = encoded + encoded_len;
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freeable = *audio_buf;
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*audio_len = (encoded_len/MS_ADPCM_state.wavefmt.blockalign) *
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MS_ADPCM_state.wSamplesPerBlock*
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@@ -141,6 +142,7 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
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state[1] = &MS_ADPCM_state.state[stereo];
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while ( encoded_len >= MS_ADPCM_state.wavefmt.blockalign ) {
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/* Grab the initial information for this block */
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+ if (encoded + 7 + (stereo ? 7 : 0) > encoded_end) goto too_short;
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state[0]->hPredictor = *encoded++;
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if ( stereo ) {
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state[1]->hPredictor = *encoded++;
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@@ -188,6 +190,8 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
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samplesleft = (MS_ADPCM_state.wSamplesPerBlock-2)*
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MS_ADPCM_state.wavefmt.channels;
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while ( samplesleft > 0 ) {
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+ if (encoded + 1 > encoded_end) goto too_short;
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+
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nybble = (*encoded)>>4;
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new_sample = MS_ADPCM_nibble(state[0],nybble,coeff[0]);
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decoded[0] = new_sample&0xFF;
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@@ -209,6 +213,10 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
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}
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SDL_free(freeable);
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return(0);
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+too_short:
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+ SDL_SetError("Too short chunk for a MS ADPCM decoder");
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+ SDL_free(freeable);
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+ return(-1);
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}
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struct IMA_ADPCM_decodestate {
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--
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2.21.0
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