demux_subreader: reject file if not opened by --sub

demux_subreader.c contains the old MPlayer subtitle parser, and I have
absolutely no confidence in this (very crappy) code. There might be
one or two security risks associated with running that code on
arbitrary input.

3 files changed, 5 insertions, 0 deletions

diff --git a/demux/demux.h b/demux/demux.h
index 7a663684f9..6f9437f2d3 100644
--- a/demux/demux.h
+++ b/demux/demux.h
@@ -152,6 +152,7 @@ struct demuxer_params {
     int matroska_wanted_segment;
     bool *matroska_was_valid;
     struct ass_library *ass_library;
+    bool expect_subtitle;
 };
 
 typedef struct demuxer {
diff --git a/demux/demux_subreader.c b/demux/demux_subreader.c
index 6bb39c960d..1fa449d7f0 100644
--- a/demux/demux_subreader.c
+++ b/demux/demux_subreader.c
@@ -1337,6 +1337,9 @@ static int d_open_file(struct demuxer *demuxer, enum demux_check check)
     if (check > DEMUX_CHECK_REQUEST)
         return -1;
 
+    if (!demuxer->params || !demuxer->params->expect_subtitle)
+        return -1;
+
     struct stream *ps = read_probe_stream(demuxer->stream, PROBE_SIZE);
 
     struct subreader sr;
diff --git a/player/loadfile.c b/player/loadfile.c
index 14faeb08c9..f35c63fa38 100644
--- a/player/loadfile.c
+++ b/player/loadfile.c
@@ -776,6 +776,7 @@ static struct track *open_external_file(struct MPContext *mpctx, char *filename,
                                 opts->stream_cache_seek_min_percent);
     struct demuxer_params params = {
         .ass_library = mpctx->ass_library, // demux_libass requires it
+        .expect_subtitle = filter == STREAM_SUB,
     };
     struct demuxer *demuxer =
         demux_open(stream, demuxer_name, &params, mpctx->global);