Commit 3876846e26fdd56f4434bdabfe6722ec66a40b83
2022-01-11T13:40:20
[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.
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diff --git a/src/sfnt/ttcolr.c b/src/sfnt/ttcolr.c
index 1ff300e..50c19f7 100644
--- a/src/sfnt/ttcolr.c
+++ b/src/sfnt/ttcolr.c
@@ -857,10 +857,14 @@
p = colr->clip_list;
+ /* limit points to the first byte after the end of the color table. */
+ /* Thus, in subsequent limit checks below we need to check whether the */
+ /* read pointer is strictly greater than a position offset */
+ /* by certain field sizes to the left of that position. */
limit = (FT_Byte*)colr->table + colr->table_size;
/* Check whether we can extract one `uint8` and one `uint32`. */
- if ( p >= limit - ( 1 + 4 ) )
+ if ( p > limit - ( 1 + 4 ) )
return 0;
clip_base = p;
@@ -876,7 +880,7 @@
/* Check whether we can extract two `uint16` and one `Offset24`, */
/* `num_clip_boxes` times. */
if ( colr->table_size / ( 2 + 2 + 3 ) < num_clip_boxes ||
- p >= limit - ( 2 + 2 + 3 ) * num_clip_boxes )
+ p > limit - ( 2 + 2 + 3 ) * num_clip_boxes )
return 0;
for ( i = 0; i < num_clip_boxes; ++i )
@@ -890,7 +894,7 @@
p1 = (FT_Byte*)( clip_base + clip_box_offset );
/* Check whether we can extract one `uint8`. */
- if ( p1 >= limit - 1 )
+ if ( p1 > limit - 1 )
return 0;
format = FT_NEXT_BYTE( p1 );
@@ -899,7 +903,7 @@
return 0;
/* Check whether we can extract four `FWORD`. */
- if ( p1 >= limit - ( 2 + 2 + 2 + 2 ) )
+ if ( p1 > limit - ( 2 + 2 + 2 + 2 ) )
return 0;
/* `face->root.size->metrics.x_scale` and `y_scale` are factors */