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avformat/aadec: Don't unnecessarily reinitialize AVTEA context

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We use ECB, not CBC mode here, so one does not need to reinitialize
the context; for the same reason, one can also just let av_tea_crypt()
loop over the blocks, avoiding a loop here.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2021-12-05 21:08:06 +01:00
parent a0900a318a
commit c9b3099210
1 changed files with 4 additions and 11 deletions
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15
libavformat/aadec.c
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@ -173,6 +173,7 @@ static int aa_read_header(AVFormatContext *s)
for (i = 0; i < 16; i++)
av_log(s, AV_LOG_DEBUG, "%02x", c->file_key[i]);
av_log(s, AV_LOG_DEBUG, "\n");
av_tea_init(c->tea_ctx, c->file_key, 16);
/* decoder setup */
st = avformat_new_stream(s, NULL);
@ -246,9 +247,6 @@ static int aa_read_header(AVFormatContext *s)
static int aa_read_packet(AVFormatContext *s, AVPacket *pkt)
{
int i;
int blocks;
uint8_t *buf;
int ret;
AADemuxContext *c = s->priv_data;
uint64_t pos = avio_tell(s->pb);
@ -279,15 +277,10 @@ static int aa_read_packet(AVFormatContext *s, AVPacket *pkt)
if (ret != c->current_codec_second_size)
return AVERROR_EOF;
buf = pkt->data;
// decrypt c->current_codec_second_size bytes
// decrypt c->current_codec_second_size bytes in blocks of TEA_BLOCK_SIZE
// trailing bytes are left unencrypted!
blocks = c->current_codec_second_size / TEA_BLOCK_SIZE;
for (i = 0; i < blocks; i++) {
av_tea_init(c->tea_ctx, c->file_key, 16);
av_tea_crypt(c->tea_ctx, buf, buf, 1, NULL, 1);
buf += TEA_BLOCK_SIZE;
}
av_tea_crypt(c->tea_ctx, pkt->data, pkt->data,
c->current_codec_second_size / TEA_BLOCK_SIZE, NULL, 1);
// update state
c->current_chapter_size = c->current_chapter_size - c->current_codec_second_size;