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From e1f80cadb079e35103e6eebf160a818815c823df 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: Thu, 14 Feb 2019 14:51:52 +0100
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Subject: [PATCH] CVE-2019-7575: Fix a buffer overwrite in MS_ADPCM_decode
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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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If a WAV format defines shorter audio stream and decoded MS ADPCM data chunk
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is longer, decoding continued past the output audio buffer.
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This fix is based on a patch from
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<https://bugzilla.libsdl.org/show_bug.cgi?id=4492>.
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https://bugzilla.libsdl.org/show_bug.cgi?id=4493
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CVE-2019-7575
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Signed-off-by: Petr Písař <ppisar@redhat.com>
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---
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src/audio/SDL_wave.c | 13 ++++++++-----
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1 file changed, 8 insertions(+), 5 deletions(-)
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diff --git a/src/audio/SDL_wave.c b/src/audio/SDL_wave.c
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index e42d01c..b6c49de 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, *encoded_end, *decoded;
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+ Uint8 *freeable, *encoded, *encoded_end, *decoded, *decoded_end;
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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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@@ -135,6 +135,7 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
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return(-1);
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}
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decoded = *audio_buf;
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+ decoded_end = decoded + *audio_len;
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/* Get ready... Go! */
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stereo = (MS_ADPCM_state.wavefmt.channels == 2);
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@@ -142,7 +143,7 @@ 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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+ if (encoded + 7 + (stereo ? 7 : 0) > encoded_end) goto invalid_size;
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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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@@ -169,6 +170,7 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
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coeff[1] = MS_ADPCM_state.aCoeff[state[1]->hPredictor];
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/* Store the two initial samples we start with */
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+ if (decoded + 4 + (stereo ? 4 : 0) > decoded_end) goto invalid_size;
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decoded[0] = state[0]->iSamp2&0xFF;
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decoded[1] = state[0]->iSamp2>>8;
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decoded += 2;
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@@ -190,7 +192,8 @@ 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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+ if (encoded + 1 > encoded_end) goto invalid_size;
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+ if (decoded + 4 > decoded_end) goto invalid_size;
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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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@@ -213,8 +216,8 @@ 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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+invalid_size:
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+ SDL_SetError("Unexpected chunk length 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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--
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2.20.1
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