mov: Add an option to toggle dref opening

This feature is mostly only used by NLE software, and is
both of dubious value being enabled by default, and a
possible security risk.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/isom.h

@@ -227,6 +227,7 @@ typedef struct MOVContext {
     struct AVAES *aes_decrypt;
     uint8_t *decryption_key;
     int decryption_key_len;
+    int enable_drefs;
 } MOVContext;
 
 int ff_mp4_read_descr_len(AVIOContext *pb);

libavformat/mov.c

@@ -3051,6 +3051,7 @@ static int mov_read_trak(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
     if (sc->dref_id-1 < sc->drefs_count && sc->drefs[sc->dref_id-1].path) {
         MOVDref *dref = &sc->drefs[sc->dref_id - 1];
+        if (c->enable_drefs) {
             if (mov_open_dref(c, &sc->pb, c->fc->filename, dref,
                               &c->fc->interrupt_callback) < 0)
                 av_log(c->fc, AV_LOG_ERROR,
@@ -3058,6 +3059,15 @@ static int mov_read_trak(MOVContext *c, AVIOContext *pb, MOVAtom atom)
                        "filename='%s', volume='%s', nlvl_from=%d, nlvl_to=%d\n",
                        st->index, dref->path, dref->dir, dref->filename,
                        dref->volume, dref->nlvl_from, dref->nlvl_to);
+        } else {
+            av_log(c->fc, AV_LOG_WARNING,
+                   "Skipped opening external track: "
+                   "stream %d, alias: path='%s', dir='%s', "
+                   "filename='%s', volume='%s', nlvl_from=%d, nlvl_to=%d."
+                   "Set enable_drefs to allow this.\n",
+                   st->index, dref->path, dref->dir, dref->filename,
+                   dref->volume, dref->nlvl_from, dref->nlvl_to);
+        }
     } else {
         sc->pb = c->fc->pb;
         sc->pb_is_copied = 1;
@@ -5219,6 +5229,8 @@ static const AVOption mov_options[] = {
         AV_OPT_TYPE_BINARY, {.str="77214d4b196a87cd520045fd20a51d67"},
         .flags = AV_OPT_FLAG_DECODING_PARAM },
     { "decryption_key", "The media decryption key (hex)", OFFSET(decryption_key), AV_OPT_TYPE_BINARY, .flags = AV_OPT_FLAG_DECODING_PARAM },
+    { "enable_drefs", "Enable external track support.", OFFSET(enable_drefs), AV_OPT_TYPE_BOOL,
+        {.i64 = 0}, 0, 1, FLAGS },
 
     { NULL },
 };

libavformat/version.h

@@ -30,8 +30,8 @@
 #include "libavutil/version.h"
 
 #define LIBAVFORMAT_VERSION_MAJOR  57
-#define LIBAVFORMAT_VERSION_MINOR  21
-#define LIBAVFORMAT_VERSION_MICRO 101
+#define LIBAVFORMAT_VERSION_MINOR  22
+#define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
                                                LIBAVFORMAT_VERSION_MINOR, \