[freetype2] master 57c4252ab: [sfnt] Guard access in 'COLR' v1 glyph binary search.

[Werner Lemberg]

branch: master
commit 57c4252ab5f435c52e66b619bd514068f7a683b0
Author: Werner Lemberg <wl@gnu.org>
Commit: Werner Lemberg <wl@gnu.org>

    [sfnt] Guard access in 'COLR' v1 glyph binary search.
    
    Reported as
    
      https://bugs.chromium.org/p/chromium/issues/detail?id=1505216
    
    * src/sfnt/ttcolr.c (find_base_glyph_v1_record): Guard access of the search
    pointer during binary search.  The pointer needs to be checked as we go as
    the test that compares number of v1 glyphs with table size at the time of
    loading the table is not sufficient on its own.
    
    A scenario is possible in which the `BaseGlyphRecord` list extends into
    non-`BaseGlyphRecord` parts of the 'COLR' v1 table (but passed the size
    comparison check).  Then, at those locations, invalid glyph ID values are
    read and may provoke an invalid read due to reassigning min and max values
    during the binary search.
---
 src/sfnt/ttcolr.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/sfnt/ttcolr.c b/src/sfnt/ttcolr.c
index 281e7135e..0601d2661 100644
--- a/src/sfnt/ttcolr.c
+++ b/src/sfnt/ttcolr.c
@@ -1269,6 +1269,7 @@
   static FT_Bool
   find_base_glyph_v1_record( FT_Byte *           base_glyph_begin,
                              FT_UInt             num_base_glyph,
+                             FT_Byte *           end_colr,
                              FT_UInt             glyph_id,
                              BaseGlyphV1Record  *record )
   {
@@ -1287,6 +1288,14 @@
        */
       FT_Byte  *p = base_glyph_begin + 4 + mid * BASE_GLYPH_PAINT_RECORD_SIZE;
 
+
+      /* We need to be able to read 2 bytes (FT_NEXT_USHORT) for the glyph */
+      /* ID, then 4 bytes (FT_NEXT_ULONG) for the paint offset.  If that's */
+      /* not available before the end of the table, something's wrong with */
+      /* the font and we can't find a COLRv1 glyph.                        */
+      if ( p > end_colr - 2 - 4 )
+        return 0;
+
       FT_UShort  gid = FT_NEXT_USHORT( p );
 
 
@@ -1328,6 +1337,7 @@
 
     if ( !find_base_glyph_v1_record( colr->base_glyphs_v1,
                                      colr->num_base_glyphs_v1,
+                                     (FT_Byte*)colr->table + colr->table_size,
                                      base_glyph,
                                      &base_glyph_v1_record ) )
       return 0;