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avformat/mp3dec: Require probing data to be 50% mp3 frames for low score probing to succeed

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This massively reduces the detection of random data as low score mp3
It may improve security by making it harder to read non multimedia data

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2018-05-12 18:33:27 +02:00
parent 2b86472a65
commit 60d1792779
1 changed files with 7 additions and 3 deletions
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10
libavformat/mp3dec.c
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@ -71,6 +71,7 @@ static int mp3_read_probe(AVProbeData *p)
int max_frames, first_frames = 0;
int whole_used = 0;
int frames, ret;
int framesizes, max_framesizes;
uint32_t header;
const uint8_t *buf, *buf0, *buf2, *end;
@ -80,11 +81,12 @@ static int mp3_read_probe(AVProbeData *p)
buf0++;
max_frames = 0;
max_framesizes = 0;
buf = buf0;
for(; buf < end; buf= buf2+1) {
buf2 = buf;
for(frames = 0; buf2 < end; frames++) {
for(framesizes = frames = 0; buf2 < end; frames++) {
MPADecodeHeader h;
header = AV_RB32(buf2);
@ -92,8 +94,10 @@ static int mp3_read_probe(AVProbeData *p)
if (ret != 0)
break;
buf2 += h.frame_size;
framesizes += h.frame_size;
}
max_frames = FFMAX(max_frames, frames);
max_framesizes = FFMAX(max_framesizes, framesizes);
if(buf == buf0) {
first_frames= frames;
if (buf2 == end + sizeof(uint32_t))
@ -104,11 +108,11 @@ static int mp3_read_probe(AVProbeData *p)
// issues with MPEG-files!
if (first_frames>=7) return AVPROBE_SCORE_EXTENSION + 1;
else if(max_frames>200)return AVPROBE_SCORE_EXTENSION;
else if(max_frames>=4 && max_frames >= p->buf_size/10000) return AVPROBE_SCORE_EXTENSION / 2;
else if(max_frames>=4 && p->buf_size < 2*max_framesizes) return AVPROBE_SCORE_EXTENSION / 2;
else if(ff_id3v2_match(buf0, ID3v2_DEFAULT_MAGIC) && 2*ff_id3v2_tag_len(buf0) >= p->buf_size)
return p->buf_size < PROBE_BUF_MAX ? AVPROBE_SCORE_EXTENSION / 4 : AVPROBE_SCORE_EXTENSION - 2;
else if(first_frames > 1 && whole_used) return 5;
else if(max_frames>=1 && max_frames >= p->buf_size/10000) return 1;
else if(max_frames>=1 && p->buf_size < 2*max_framesizes) return 1;
else return 0;
//mpegps_mp3_unrecognized_format.mpg has max_frames=3
}