uri: Fix parsing issues

Make host IPs in square brackets store only the IP, i.e. strip the brackets.
Strip leading whitespace characters in URIs.
Fail parsing when host part does not match any valid formats from RFC3986.

https://bugzilla.gnome.org/show_bug.cgi?id=743195

gst/gsturi.c

@@ -1256,6 +1256,13 @@ _gst_uri_escape_host (const gchar * host)
       G_URI_RESERVED_CHARS_SUBCOMPONENT_DELIMITERS, FALSE);
 }
 
+static gchar *
+_gst_uri_escape_host_colon (const gchar * host)
+{
+  return g_uri_escape_string (host,
+      G_URI_RESERVED_CHARS_SUBCOMPONENT_DELIMITERS ":", FALSE);
+}
+
 static gchar *
 _gst_uri_escape_path_segment (const gchar * segment)
 {
@@ -1504,21 +1511,27 @@ gst_uri_new_with_base (GstUri * base, const gchar * scheme,
  * gst_uri_from_string:
  * @uri: The URI string to parse.
  *
- * Parses a URI string into a new #GstUri object.
+ * Parses a URI string into a new #GstUri object. Will return NULL if the URI
+ * cannot be parsed.
  *
- * Returns: (transfer full): A new #GstUri object.
+ * Returns: (transfer full)(nullable): A new #GstUri object, or NULL.
  *
  * Since: 1.6
  */
 GstUri *
 gst_uri_from_string (const gchar * uri)
 {
+  const gchar *orig_uri = uri;
   GstUri *uri_obj;
 
   uri_obj = _gst_uri_new ();
 
   if (uri_obj && uri != NULL) {
     int i = 0;
+
+    /* be helpful and skip initial white space */
+    while (*uri == '\v' || g_ascii_isspace (*uri)) uri++;
+
     if (g_ascii_isalpha (uri[i])) {
       /* find end of scheme name */
       i++;
@@ -1532,13 +1545,12 @@ gst_uri_from_string (const gchar * uri)
       uri += i + 1;
     }
     if (uri[0] == '/' && uri[1] == '/') {
-      const gchar *eoa, *eoui, *eoh;
+      const gchar *eoa, *eoui, *eoh, *reoh;
       /* get authority [userinfo@]host[:port] */
       uri += 2;
       /* find end of authority */
-      eoa = strchr (uri, '/');
+      eoa = uri + strcspn (uri, "/?#");
-      if (eoa == NULL)
+
-        eoa = uri + strlen (uri);
       /* find end of userinfo */
       eoui = strchr (uri, '@');
       if (eoui != NULL && eoui < eoa) {
@@ -1548,25 +1560,32 @@ gst_uri_from_string (const gchar * uri)
       /* find end of host */
       if (uri[0] == '[') {
         eoh = strchr (uri, ']');
-        if (eoh == NULL || eoh >= eoa)
+        if (eoh == NULL || eoh > eoa) {
-          eoh = eoa - 1;
+          GST_DEBUG ("Unable to parse the host part of the URI '%s'.",
-      } else {
+                  orig_uri);
-        eoh = strchr (uri, ':');
+	  _gst_uri_free (uri_obj);
-        if (eoh == NULL || eoh >= eoa)
+          return NULL;
-          eoh = eoa - 1;
-        else
-          eoh--;
         }
-      uri_obj->host = g_uri_unescape_segment (uri, eoh + 1, NULL);
+        reoh = eoh + 1;
-      uri = eoh + 1;
+        uri++;
-      if (uri < eoa) {
-        /* if port number is malformed, do best effort and concat string */
-        if (uri[0] != ':' || strspn (uri + 1, "0123456789") != eoa - uri - 1) {
-          gchar *tmp = uri_obj->host;
-          uri_obj->host = g_malloc (strlen (uri_obj->host) + eoa - uri + 1);
-          g_strlcpy (g_stpcpy (uri_obj->host, tmp), uri, eoa - uri + 1);
-          g_free (tmp);
       } else {
+        reoh = eoh = strchr (uri, ':');
+        if (eoh == NULL || eoh > eoa)
+          reoh = eoh = eoa;
+      }
+      /* don't capture empty host strings */
+      if (eoh != uri)
+        uri_obj->host = g_uri_unescape_segment (uri, eoh, NULL);
+
+      uri = reoh;
+      if (uri < eoa) {
+        /* if port number is malformed then we can't parse this */
+        if (uri[0] != ':' || strspn (uri + 1, "0123456789") != eoa - uri - 1) {
+          GST_DEBUG ("Unable to parse host/port part of the URI '%s'.",
+                  orig_uri);
+          _gst_uri_free (uri_obj);
+          return NULL;
+        }
         /* otherwise treat port as unsigned decimal number */
         uri++;
         while (uri < eoa) {
@@ -1574,7 +1593,6 @@ gst_uri_from_string (const gchar * uri)
           uri++;
         }
       }
-      }
       uri = eoa;
     }
     if (uri != NULL && uri[0] != '\0') {
@@ -1956,10 +1974,16 @@ gst_uri_to_string (const GstUri * uri)
   }
 
   if (uri->host != NULL) {
+    if (strchr (uri->host, ':') != NULL) {
+      escaped = _gst_uri_escape_host_colon (uri->host);
+      g_string_append_printf (uri_str, "[%s]", escaped);
+      g_free (escaped);
+    } else {
       escaped = _gst_uri_escape_host (uri->host);
       g_string_append (uri_str, escaped);
       g_free (escaped);
     }
+  }
 
   if (uri->port != GST_URI_NO_PORT)
     g_string_append_printf (uri_str, ":%u", uri->port);