avcodec/htmlsubtitles: Be a bit more picky on syntax
authorMichael Niedermayer <michael@niedermayer.cc>
Sat, 1 Jul 2017 22:09:42 +0000 (00:09 +0200)
committerMichael Niedermayer <michael@niedermayer.cc>
Mon, 13 May 2019 22:17:29 +0000 (00:17 +0200)
This reduces the number of strstr() calls per byte
This diasalows empty tags like '< >' as well as '<' in tags like '<ab<cd<<ef>'

Fixes timeout
Fixes: 1817/clusterfuzz-testcase-minimized-5104230530547712

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit c61715e2c505c15a5cfc9eab18b4311a6504055a)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
libavcodec/htmlsubtitles.c

index 70311c6..4c9e4f3 100644 (file)
@@ -102,13 +102,13 @@ int ff_htmlmarkup_to_ass(void *log_ctx, AVBPrint *dst, const char *in)
         case '<':
             tag_close = in[1] == '/';
             len = 0;
-            if (sscanf(in+tag_close+1, "%127[^>]>%n", buffer, &len) >= 1 && len > 0) {
+            if (sscanf(in+tag_close+1, "%127[^<>]>%n", buffer, &len) >= 1 && len > 0) {
                 const char *tagname = buffer;
                 while (*tagname == ' ')
                     tagname++;
                 if ((param = strchr(tagname, ' ')))
                     *param++ = 0;
-                if ((!tag_close && sptr < FF_ARRAY_ELEMS(stack)) ||
+                if ((!tag_close && sptr < FF_ARRAY_ELEMS(stack) && *tagname) ||
                     ( tag_close && sptr > 0 && !strcmp(stack[sptr-1].tag, tagname))) {
                     int i, j, unknown = 0;
                     in += len + tag_close;