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avformat/id3v2: support buggy id3v2.3 tag length in id3v2.4

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Some encoders do not use syncsafe sizes in v2.4 id3 tags. Check the next
tag to try to choose between the two.

Fixes ticket #4003

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Benoit Fouet 2014-10-17 10:56:59 +02:00 committed by Michael Niedermayer
parent ac1594bc17
commit 242f8bb3a8
1 changed files with 62 additions and 2 deletions
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64
libavformat/id3v2.c
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@ -170,6 +170,48 @@ static unsigned int get_size(AVIOContext *s, int len)
return v;
}
static unsigned int size_to_syncsafe(unsigned int size)
{
return (((size) & (0x7f << 0)) >> 0) +
(((size) & (0x7f << 8)) >> 1) +
(((size) & (0x7f << 16)) >> 2) +
(((size) & (0x7f << 24)) >> 3);
}
/* No real verification, only check that the tag consists of
* a combination of capital alpha-numerical characters */
static int is_tag(const char *buf, unsigned int len)
{
if (!len)
return 0;
while (len--)
if ((buf[len] < 'A' ||
buf[len] > 'Z') &&
(buf[len] < '0' ||
buf[len] > '9'))
return 0;
return 1;
}
/**
* Return 1 if the tag of length len at the given offset is valid, 0 if not, -1 on error
*/
static int check_tag(AVIOContext *s, int offset, unsigned int len)
{
char tag[4];
if (len > 4 ||
avio_seek(s, offset, SEEK_SET) < 0 ||
avio_read(s, tag, len) < len)
return -1;
else if (!AV_RB32(tag) || is_tag(tag, len))
return 1;
return 0;
}
/**
* Free GEOB type extra metadata.
*/
@ -734,8 +776,26 @@ static void id3v2_parse(AVIOContext *pb, AVDictionary **metadata,
tag[4] = 0;
if (version == 3) {
tlen = avio_rb32(pb);
} else
tlen = get_size(pb, 4);
} else {
/* some encoders incorrectly uses v3 sizes instead of syncsafe ones
* so check the next tag to see which one to use */
tlen = avio_rb32(pb);
if (tlen > 0x7f) {
if (tlen < len) {
int64_t cur = avio_tell(pb);
if (ffio_ensure_seekback(pb, 2 /* tflags */ + tlen + 4 /* next tag */))
break;
if (check_tag(pb, cur + 2 + size_to_syncsafe(tlen), 4) == 1)
tlen = size_to_syncsafe(tlen);
else if (check_tag(pb, cur + 2 + tlen, 4) != 1)
break;
avio_seek(pb, cur, SEEK_SET);
} else
tlen = size_to_syncsafe(tlen);
}
}
tflags = avio_rb16(pb);
tunsync = tflags & ID3v2_FLAG_UNSYNCH;
} else {