[FFmpeg-devel] [PATCH] avformat/utils: Don't parse encrypted packets.

[Jacob Trimble]

If a packet is full-sample encrypted, then packet data can't be parsed
without decrypting it.  So this skips the packet parsing for those
packets.  If the packet has sub-sample encryption, it is assumed that
the headers are in the clear and the parser will only need that info.

Signed-off-by: Jacob Trimble <modmaker at google.com>
---
 libavformat/utils.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/libavformat/utils.c b/libavformat/utils.c
index b0b5e164a6..1107787eae 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -27,6 +27,7 @@
 #include "libavutil/avassert.h"
 #include "libavutil/avstring.h"
 #include "libavutil/dict.h"
+#include "libavutil/encryption_info.h"
 #include "libavutil/internal.h"
 #include "libavutil/mathematics.h"
 #include "libavutil/opt.h"
@@ -1576,6 +1577,9 @@ static int read_frame_internal(AVFormatContext *s, AVPacket *pkt)
     while (!got_packet && !s->internal->parse_queue) {
         AVStream *st;
         AVPacket cur_pkt;
+        uint8_t *enc_side_data;
+        int enc_side_data_size;
+        int is_full_encrypted = 0;
 
         /* read next packet */
         ret = ff_read_packet(s, &cur_pkt);
@@ -1659,7 +1663,22 @@ FF_ENABLE_DEPRECATION_WARNINGS
                 st->parser->flags |= PARSER_FLAG_USE_CODEC_TS;
         }
 
-        if (!st->need_parsing || !st->parser) {
+        /* if the packet is full-sample encrypted, we can't parse it.  If the
+         * packet uses sub-sample encryption, assume the headers are clear and
+         * can still be parsed.
+         */
+        enc_side_data = av_packet_get_side_data(
+            &cur_pkt, AV_PKT_DATA_ENCRYPTION_INFO, &enc_side_data_size);
+        if (enc_side_data) {
+            AVEncryptionInfo *enc_info =
+                av_encryption_info_get_side_data(enc_side_data, enc_side_data_size);
+            if (enc_info) {
+                is_full_encrypted = enc_info->subsample_count == 0;
+                av_encryption_info_free(enc_info);
+            }
+        }
+
+        if (!st->need_parsing || !st->parser || is_full_encrypted) {
             /* no parsing needed: we just output the packet as is */
             *pkt = cur_pkt;
             compute_pkt_fields(s, st, NULL, pkt, AV_NOPTS_VALUE, AV_NOPTS_VALUE);
-- 
2.19.0.rc0.228.g281dcd1b4d0-goog