avformat/utils: be even more strict about stream specifiers

After this change we always parse the full specifier even if we know the result
in the middle of the parsing. Sligtly slower, but this is needed to
consistently reject incorrect specifiers in both matching and non-matching
cases.
Signed-off-by: Marton Balint <cus@passwd.hu>

libavformat/utils.c

@@ -5109,11 +5109,12 @@ AVRational av_guess_frame_rate(AVFormatContext *format, AVStream *st, AVFrame *f
 static int match_stream_specifier(AVFormatContext *s, AVStream *st,
                                   const char *spec, const char **indexptr)
 {
+    int match = 1;                      /* Stores if the specifier matches so far. */
     while (*spec) {
     if (*spec <= '9' && *spec >= '0') { /* opt:index */
         if (indexptr)
             *indexptr = spec;
-        return 1;
+        return match;
     } else if (*spec == 'v' || *spec == 'a' || *spec == 's' || *spec == 'd' ||
                *spec == 't' || *spec == 'V') { /* opt:[vasdtV] */
         enum AVMediaType type;
@@ -5135,14 +5136,14 @@ static int match_stream_specifier(AVFormatContext *s, AVStream *st,
 FF_DISABLE_DEPRECATION_WARNINGS
         if (type != st->codecpar->codec_type
            && (st->codecpar->codec_type != AVMEDIA_TYPE_UNKNOWN || st->codec->codec_type != type))
-            return 0;
+            match = 0;
 FF_ENABLE_DEPRECATION_WARNINGS
 #else
         if (type != st->codecpar->codec_type)
-            return 0;
+            match = 0;
 #endif
         if (nopic && (st->disposition & AV_DISPOSITION_ATTACHED_PIC))
-            return 0;
+            match = 0;
     } else if (*spec == 'p' && *(spec + 1) == ':') {
         int prog_id, i, j;
         int found = 0;
@@ -5153,6 +5154,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
         if (spec == endptr || (*endptr && *endptr++ != ':'))
             return AVERROR(EINVAL);
         spec = endptr;
+        if (match) {
         for (i = 0; i < s->nb_programs; i++) {
             if (s->programs[i]->id != prog_id)
                 continue;
@@ -5165,8 +5167,9 @@ FF_ENABLE_DEPRECATION_WARNINGS
                 }
             }
         }
+        }
         if (!found)
-            return 0;
+            match = 0;
     } else if (*spec == '#' ||
                (*spec == 'i' && *(spec + 1) == ':')) {
         int stream_id;
@@ -5175,12 +5178,13 @@ FF_ENABLE_DEPRECATION_WARNINGS
         stream_id = strtol(spec, &endptr, 0);
         if (spec == endptr || *endptr)                /* Disallow empty id and make sure we are at the end. */
             return AVERROR(EINVAL);
-        return stream_id == st->id;
+        return match && (stream_id == st->id);
     } else if (*spec == 'm' && *(spec + 1) == ':') {
         AVDictionaryEntry *tag;
         char *key, *val;
         int ret;
 
+        if (match) {
         spec += 2;
         val = strchr(spec, ':');
 
@@ -5198,7 +5202,8 @@ FF_ENABLE_DEPRECATION_WARNINGS
             ret = 0;
 
         av_freep(&key);
-        return ret;
+        }
+        return match && ret;
     } else if (*spec == 'u' && *(spec + 1) == '\0') {
         AVCodecParameters *par = st->codecpar;
 #if FF_API_LAVF_AVCTX
@@ -5240,17 +5245,16 @@ FF_ENABLE_DEPRECATION_WARNINGS
             break;
         }
 #if FF_API_LAVF_AVCTX
-        return (par->codec_id != AV_CODEC_ID_NONE || codec->codec_id != AV_CODEC_ID_NONE) && val != 0;
+        return match && ((par->codec_id != AV_CODEC_ID_NONE || codec->codec_id != AV_CODEC_ID_NONE) && val != 0);
 #else
-        return par->codec_id != AV_CODEC_ID_NONE && val != 0;
+        return match && (par->codec_id != AV_CODEC_ID_NONE && val != 0);
 #endif
     } else {
         return AVERROR(EINVAL);
     }
     }
 
-    /* empty specifier, matches everything */
-    return 1;
+    return match;
 }