[Git][freetype/freetype][master] [sfnt] Fix limit checks for `COLR` v1 ClipBoxes

[Werner Lemberg (@wl)]

Werner Lemberg pushed to branch master at FreeType / FreeType

Commits:

• 3876846e
  by Dominik Röttsches at 2022-01-11T13:40:20+02:00

  [sfnt] Fix limit checks for `COLR` v1 ClipBoxes
  
  * src/sfnt/ttcolr.c (tt_face_get_color_glyph_clipbox): Fix off-by-one in
  limit checks.
  

1 changed file:

• src/sfnt/ttcolr.c

Changes:

src/sfnt/ttcolr.c

---

...	...	@@ -857,10 +857,14 @@
857	857
858	858	p = colr->clip_list;
859	859
	860	+ /* limit points to the first byte after the end of the color table. */
	861	+ /* Thus, in subsequent limit checks below we need to check whether the */
	862	+ /* read pointer is strictly greater than a position offset */
	863	+ /* by certain field sizes to the left of that position. */
860	864	limit = (FT_Byte*)colr->table + colr->table_size;
861	865
862	866	/* Check whether we can extract one `uint8` and one `uint32`. */
863		- if ( p >= limit - ( 1 + 4 ) )
	867	+ if ( p > limit - ( 1 + 4 ) )
864	868	return 0;
865	869
866	870	clip_base = p;
...	...	@@ -876,7 +880,7 @@
876	880	/* Check whether we can extract two `uint16` and one `Offset24`, */
877	881	/* `num_clip_boxes` times. */
878	882	if ( colr->table_size / ( 2 + 2 + 3 ) < num_clip_boxes ||
879		- p >= limit - ( 2 + 2 + 3 ) * num_clip_boxes )
	883	+ p > limit - ( 2 + 2 + 3 ) * num_clip_boxes )
880	884	return 0;
881	885
882	886	for ( i = 0; i < num_clip_boxes; ++i )
...	...	@@ -890,7 +894,7 @@
890	894	p1 = (FT_Byte*)( clip_base + clip_box_offset );
891	895
892	896	/* Check whether we can extract one `uint8`. */
893		- if ( p1 >= limit - 1 )
	897	+ if ( p1 > limit - 1 )
894	898	return 0;
895	899
896	900	format = FT_NEXT_BYTE( p1 );
...	...	@@ -899,7 +903,7 @@
899	903	return 0;
900	904
901	905	/* Check whether we can extract four `FWORD`. */
902		- if ( p1 >= limit - ( 2 + 2 + 2 + 2 ) )
	906	+ if ( p1 > limit - ( 2 + 2 + 2 + 2 ) )
903	907	return 0;
904	908
905	909	/* `face->root.size->metrics.x_scale` and `y_scale` are factors */

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