[FFmpeg-devel] [PATCH]Auto-detection for concat demuxer

[Carl Eugen Hoyos]

On Sunday 03 February 2013 09:21:31 am Nicolas George wrote:
> > Attached patch adds auto-detection for the concat demuxer.
> >
> > Please review, Carl Eugen
>
> Thanks, but I am afraid this may be a security concern: 
> allowing a foreign file to redirect to any file in the system 
> may expose sensitive information, or worse.

Maybe a configure switch?

I honestly have no opinion here, I just wanted to post the patch.

[...]

> I find that SCORE_MAX for just a line that starts with "file" 
> and a space  is a bit too much.

Improved patch attached.

Thank you, Carl Eugen
-------------- next part --------------
diff --git a/libavformat/concatdec.c b/libavformat/concatdec.c
index 0514755..32d57c3 100644
--- a/libavformat/concatdec.c
+++ b/libavformat/concatdec.c
@@ -37,6 +37,22 @@ typedef struct {
 
 static int concat_probe(AVProbeData *probe)
 {
+    const char *buf = probe->buf;
+    const char *end = buf + probe->buf_size;
+    int found = 0;
+
+    while (buf + 6 < end) {
+        if (!strncmp(buf, "file ", 5)) {
+            found++;
+            buf += 5;
+        } else if (*buf != '#') {
+            return 0;
+        }
+        while (buf < end && *buf++ != '\n')
+            ;
+    }
+    if (found >= 2) return AVPROBE_SCORE_MAX;
+    if (found == 1) return AVPROBE_SCORE_MAX / 4;
     return 0;
 }