[woff2] Check whether known tag is in array bounds.GSoC-2019-nikhil

If table tag is not 0x3f, we expect a value between 0 and 62. If this is
not the case, exit with errors.

* src/sfnt/sfwoff2/c: Check whether table tag makes sense.

* src/sfnt/woff2tags.c: Return 0 if tag is out of bounds.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/sfnt/woff2tags.c b/src/sfnt/woff2tags.c
index 5b274d520..45ef3fa32 100644
--- a/src/sfnt/woff2tags.c
+++ b/src/sfnt/woff2tags.c
@@ -91,6 +91,9 @@
     };
 
 
+    if ( index < 0 || index > 62 )
+      return 0;
+
     return known_tags[index];
   }