fuzzer_loadfile_direct: exclude paths also for file://

Loading external files makes little sense. Might disable this completely
later, but let see how it works, The idea is the same as for direct
load. Exclude paths starting with `file://.` and `file:///`. But still
fuzz any processing that other input might have. It shouldn't be a huge
problem if we do `file://mpv` for example. Not great, but also not
terrible.

fuzzers/fuzzer_loadfile_direct.c

@@ -34,18 +34,27 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
         return -1;
 
 #ifdef MPV_PROTO
-    if (!str_startswith(data, size - 1, MPV_STRINGIFY(MPV_PROTO) "://", strlen(MPV_STRINGIFY(MPV_PROTO) "://")))
+    if (!str_startswith(data, size - 1, MPV_STRINGIFY(MPV_PROTO) "://", sizeof(MPV_STRINGIFY(MPV_PROTO) "://") - 1))
         return -1;
-#else
+#endif
+
+#if !defined(MPV_PROTO) || defined(MPV_PROTO_FILE)
+    const uint8_t *data_check = data;
+    size_t size_check = size;
+    size_t prefix_size = sizeof("file://") - 1;
+    if (str_startswith(data, size - 1, "file://", prefix_size)) {
+        data_check += prefix_size;
+        size_check -= prefix_size;
+    }
     // Exclude some common paths that are not useful for testing.
     // Exclude -
-    if (size == 2 && !strncmp(data, "-", 1))
+    if (size_check == 2 && !strncmp(data_check, "-", 1))
         return -1;
     // Exclude relative paths
-    if (str_startswith(data, size - 1, ".", 1))
+    if (str_startswith(data_check, size_check - 1, ".", 1))
         return -1;
     // Exclude absolute paths
-    if (str_startswith(data, size - 1, "/", 1))
+    if (str_startswith(data_check, size_check - 1, "/", 1))
         return -1;
 #endif
 

fuzzers/meson.build

@@ -9,7 +9,7 @@ foreach p : ['bd', 'cdda', 'dvb', 'dvd', 'edl', 'file', 'hex', 'lavf', 'memory',
              'mf', 'slice', 'smb']
   executable('fuzzer_protocol_' + p,
              'fuzzer_loadfile_direct.c',
-             c_args: ['-DMPV_PROTO=' + p],
+             c_args: ['-DMPV_PROTO=' + p, '-DMPV_PROTO_' + p.to_upper()],
              include_directories: incdir,
              link_with: libmpv)
 endforeach