[vlc-devel] [PATCH] demux/playlist: ProcessMRL: fallback to original if valid scheme

[Filip Roséen]

The changes introduced in 36bee77 had the unfortunate side-effect that
location-data that could not be parsed as a URL would be discarded,
for example an xspf playlist containing the line below would simply
ignore it (due to ProcessMRL rejecting it):

> dvb-t://frequency=674000000:inversion=-1:bandwidth=8:code-rate-hp=2/3:code-rate-lp=1/2:modulation=64QAM:transmission=8:guard=1/32:

In order to fix the issue while still allowing uri-resolving for
URI-valid entities, the following changes make sure that we retain the
original string if it contains "://" and all prior characters are
valid in a scheme.

fixes: #18155
---
 modules/demux/playlist/playlist.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/modules/demux/playlist/playlist.c b/modules/demux/playlist/playlist.c
index ef80a55a33..b2b7b7cfb9 100644
--- a/modules/demux/playlist/playlist.c
+++ b/modules/demux/playlist/playlist.c
@@ -230,6 +230,8 @@ char *FindPrefix(demux_t *p_demux)
  */
 char *ProcessMRL(const char *str, const char *base)
 {
+    char const* orig = str;
+
     if (str == NULL)
         return NULL;
 
@@ -267,6 +269,25 @@ char *ProcessMRL(const char *str, const char *base)
 
     char *abs = vlc_uri_resolve(base, str);
     free(rel);
+
+    if (abs == NULL)
+    {
+        /** If the input is not a valid URL, see if there is a scheme:// where
+         * the scheme itself consists solely of valid scheme-characters
+         * (including the VLC's scheme-extension). If it does, fall back to
+         * allowing the URI in order to not break back-compatibility.
+         */
+        char const* scheme_end = strstr( orig, "://" );
+        char const* valid_chars = "abcdefghijklmnopqrstuvwxyz"
+                                  "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+                                  "0123456789" "+-./";
+        if (scheme_end &&
+            strspn (orig, valid_chars) == (size_t)(scheme_end - orig))
+        {
+            abs = strdup (orig);
+        }
+    }
+
     return abs;
 }
 
-- 
2.12.0