[FFmpeg-devel] support for reading / writing encrypted MP4 files

[Eran Kornblau]

> > Please let me know if you think that is ok, and I will resubmit the patch with all fixes.
> 
> should be ok
> 
Updated patch attached, diff from previous patch is:

--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -4026,6 +4026,14 @@ static int mov_read_frma(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     case MKTAG('e','n','c','v'):        // encrypted video
     case MKTAG('e','n','c','a'):        // encrypted audio
         id = mov_codec_id(st, format);
+        if (st->codec->codec_id != AV_CODEC_ID_NONE &&
+            st->codec->codec_id != id) {
+            av_log(c->fc, AV_LOG_WARNING,
+                   "ignoring 'frma' atom of '%.4s', stream has codec id %d\n",
+                   (char*)&format, st->codec->codec_id);
+            break;
+        }
+
         st->codec->codec_id = id;
         sc->format = format;
         break;
@@ -4045,7 +4053,6 @@ static int mov_read_senc(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     AVStream *st;
     MOVStreamContext *sc;
     size_t auxiliary_info_size;
-    int ret;
 
     if (c->decryption_key_len == 0 || c->fc->nb_streams < 1)
         return 0;
@@ -4091,12 +4098,7 @@ static int mov_read_senc(MOVContext *c, AVIOContext *pb, MOVAtom atom)
         return AVERROR(ENOMEM);
     }
 
-    ret = av_aes_ctr_init(sc->cenc.aes_ctr, c->decryption_key);
-    if (ret) {
-        return ret;
-    }
-
-    return 0;
+    return av_aes_ctr_init(sc->cenc.aes_ctr, c->decryption_key);
 }
 
 static int cenc_filter(MOVContext *c, MOVStreamContext *sc, uint8_t *input, int size)
@@ -4107,7 +4109,7 @@ static int cenc_filter(MOVContext *c, MOVStreamContext *sc, uint8_t *input, int
     uint8_t* input_end = input + size;
 
     /* read the iv */
-    if (sc->cenc.auxiliary_info_pos + AES_CTR_IV_SIZE > sc->cenc.auxiliary_info_end) {
+    if (AES_CTR_IV_SIZE > sc->cenc.auxiliary_info_end - sc->cenc.auxiliary_info_pos) {
         av_log(c->fc, AV_LOG_ERROR, "failed to read iv from the auxiliary info\n");
         return AVERROR_INVALIDDATA;
     }
@@ -4123,7 +4125,7 @@ static int cenc_filter(MOVContext *c, MOVStreamContext *sc, uint8_t *input, int
     }
 
     /* read the subsample count */
-    if (sc->cenc.auxiliary_info_pos + sizeof(uint16_t) > sc->cenc.auxiliary_info_end) {
+    if (sizeof(uint16_t) > sc->cenc.auxiliary_info_end - sc->cenc.auxiliary_info_pos) {
         av_log(c->fc, AV_LOG_ERROR, "failed to read subsample count from the auxiliary info\n");
         return AVERROR_INVALIDDATA;
     }
@@ -4133,7 +4135,7 @@ static int cenc_filter(MOVContext *c, MOVStreamContext *sc, uint8_t *input, int
 
     for (; subsample_count > 0; subsample_count--)
     {
-        if (sc->cenc.auxiliary_info_pos + 6 > sc->cenc.auxiliary_info_end) {
+        if (6 > sc->cenc.auxiliary_info_end - sc->cenc.auxiliary_info_pos) {
             av_log(c->fc, AV_LOG_ERROR, "failed to read subsample from the auxiliary info\n");
             return AVERROR_INVALIDDATA;
         }
@@ -4144,7 +4146,7 @@ static int cenc_filter(MOVContext *c, MOVStreamContext *sc, uint8_t *input, int
         encrypted_bytes = AV_RB32(sc->cenc.auxiliary_info_pos);
         sc->cenc.auxiliary_info_pos += sizeof(uint32_t);
 
-        if (input + clear_bytes + encrypted_bytes > input_end) {
+        if ((uint64_t)clear_bytes + encrypted_bytes > input_end - input) {
             av_log(c->fc, AV_LOG_ERROR, "subsample size exceeds the packet size left\n");
             return AVERROR_INVALIDDATA;
         }


> [...]
> 
> -- 
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> 

Thanks, Michael !

Eran
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