[woff2] Fix memory leak.

Reported as

  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=28148

* src/sfnt/sfwoff2.c (woff2_open_font): Reject fonts that have
multiple tables with the same tag.  While not explicitly forbidden
in the OpenType specification, it is implicitly forbidden by
describing a binary search algorithm for tables that only works
reliably if table tags are unique.

ChangeLog

@@ -1,3 +1,17 @@
+2021-02-25  Werner Lemberg  <wl@gnu.org>
+
+	[woff2] Fix memory leak.
+
+	Reported as
+
+	  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=28148
+
+	* src/sfnt/sfwoff2.c (woff2_open_font): Reject fonts that have
+	multiple tables with the same tag.  While not explicitly forbidden
+	in the OpenType specification, it is implicitly forbidden by
+	describing a binary search algorithm for tables that only works
+	reliably if table tags are unique.
+
 2021-02-22  Werner Lemberg  <wl@gnu.org>
 
 	* CMakeLists.txt: Update location of `LICENSE.TXT`.

src/sfnt/sfwoff2.c

@@ -2208,6 +2208,25 @@
               sizeof ( WOFF2_Table ),
               compare_tags );
 
+    /* reject fonts that have multiple tables with the same tag */
+    for ( nn = 1; nn < woff2.num_tables; nn++ )
+    {
+      FT_ULong  tag = indices[nn]->Tag;
+
+
+      if ( tag == indices[nn - 1]->Tag )
+      {
+        FT_ERROR(( "woff2_open_font:"
+                   " multiple tables with tag `%c%c%c%c'.\n",
+                   (FT_Char)( tag >> 24 ),
+                   (FT_Char)( tag >> 16 ),
+                   (FT_Char)( tag >> 8  ),
+                   (FT_Char)( tag       ) ));
+        error = FT_THROW( Invalid_Table );
+        goto Exit;
+      }
+    }
+
     if ( woff2.uncompressed_size < 1 )
     {
       error = FT_THROW( Invalid_Table );