ref: 7d4e55c329e5e70873fd8d660716c27f9cf55202
parent: 3a278381ae1d11841ac4c2986eaa66bd644ebe35
author: Dominik Röttsches <[email protected]>
date: Mon Jun 28 12:29:49 EDT 2021
[sfnt] Improve paint limit checks Paint tables can appear before the `base_glyphs_v1` offset if the font is produced with the layer list before the base glyph list. In this case paint tables can occur after the layer list but before the base glyph list. Checks in the 'COLR' v1 code were rejecting fonts with this layout. Improve these checks by calculating a minimum offset after which paint tables can occur and use that in safety checks. * src/sfnt/ttcolr.c (Colr, tt_face_load_colr): Declare `paint_start_v1` and calculate that as the minimum of the end of layer list and base glyph list. (get_child_table_pointer, read_paint, tt_face_get_paint_layers): Use that in safety checks.
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,21 @@
+2021-06-28 Dominik Röttsches <[email protected]>
+
+ [sfnt] Improve paint limit checks
+
+ Paint tables can appear before the `base_glyphs_v1` offset if the
+ font is produced with the layer list before the base glyph list. In
+ this case paint tables can occur after the layer list but before the
+ base glyph list. Checks in the 'COLR' v1 code were rejecting fonts
+ with this layout. Improve these checks by calculating a minimum
+ offset after which paint tables can occur and use that in safety
+ checks.
+
+ * src/sfnt/ttcolr.c (Colr, tt_face_load_colr): Declare
+ `paint_start_v1` and calculate that as the minimum of the end of
+ layer list and base glyph list.
+ (get_child_table_pointer, read_paint, tt_face_get_paint_layers):
+ Use that in safety checks.
+
2021-06-28 Alexei Podtelezhnikov <[email protected]>
[raster] Clean up vertical sweep.
@@ -202,7 +220,7 @@
2021-06-09 Alexei Podtelezhnikov <[email protected]>
- * src/truetype/ttinterp.c (TT_RunIns): Optimize tracing.
+ * src/truetype/ttinterp.c (TT_RunIns): Optimize tracing.
2021-06-09 Alexei Podtelezhnikov <[email protected]>
--- a/src/sfnt/ttcolr.c
+++ b/src/sfnt/ttcolr.c
@@ -41,7 +41,7 @@
/* NOTE: These are the table sizes calculated through the specs. */
#define BASE_GLYPH_SIZE 6U
-#define BASE_GLYPH_V1_RECORD_SIZE 6U
+#define BASE_GLYPH_PAINT_RECORD_SIZE 6U
#define LAYER_V1_LIST_PAINT_OFFSET_SIZE 4U
#define LAYER_V1_LIST_NUM_LAYERS_SIZE 4U
#define COLOR_STOP_SIZE 6U
@@ -83,6 +83,13 @@
FT_ULong num_layers_v1;
FT_Byte* layers_v1;
+ /*
+ * Paint tables start at the minimum of the end of the LayerList and the
+ * end of the BaseGlyphList. Record this location in a field here for
+ * safety checks when accessing paint tables.
+ */
+ FT_Byte* paints_start_v1;
+
/* The memory that backs up the `COLR' table. */
void* table;
FT_ULong table_size;
@@ -170,7 +177,7 @@
p1 = (FT_Byte*)( table + base_glyphs_offset_v1 );
num_base_glyphs_v1 = FT_PEEK_ULONG( p1 );
- if ( num_base_glyphs_v1 * BASE_GLYPH_V1_RECORD_SIZE >
+ if ( num_base_glyphs_v1 * BASE_GLYPH_PAINT_RECORD_SIZE >
table_size - base_glyphs_offset_v1 )
goto InvalidTable;
@@ -185,8 +192,18 @@
p1 = (FT_Byte*)( table + layer_offset_v1 );
num_layers_v1 = FT_PEEK_ULONG( p1 );
+ if ( num_layers_v1 * LAYER_V1_LIST_PAINT_OFFSET_SIZE >
+ table_size - layer_offset_v1 )
+ goto InvalidTable;
+
colr->num_layers_v1 = num_layers_v1;
colr->layers_v1 = p1;
+
+ colr->paints_start_v1 =
+ FT_MIN( colr->base_glyphs_v1 +
+ colr->num_base_glyphs_v1 * BASE_GLYPH_PAINT_RECORD_SIZE,
+ colr->layers_v1 +
+ colr->num_layers_v1 * LAYER_V1_LIST_PAINT_OFFSET_SIZE );
}
colr->base_glyphs = (FT_Byte*)( table + base_glyph_offset );
@@ -367,7 +384,7 @@
child_table_p = (FT_Byte*)( paint_base + paint_offset );
- if ( child_table_p < colr->base_glyphs_v1 ||
+ if ( child_table_p < colr->paints_start_v1 ||
child_table_p >= ( (FT_Byte*)colr->table + colr->table_size ) )
return 0;
@@ -388,7 +405,7 @@
if ( !p || !colr || !colr->table )
return 0;
- if ( p < colr->base_glyphs_v1 ||
+ if ( p < colr->paints_start_v1 ||
p >= ( (FT_Byte*)colr->table + colr->table_size ) )
return 0;
@@ -608,7 +625,7 @@
* skip `numBaseGlyphV1Records` by adding 4 to start binary search
* in the array of `BaseGlyphV1Record`.
*/
- FT_Byte *p = base_glyph_begin + 4 + mid * BASE_GLYPH_V1_RECORD_SIZE;
+ FT_Byte *p = base_glyph_begin + 4 + mid * BASE_GLYPH_PAINT_RECORD_SIZE;
FT_UShort gid = FT_NEXT_USHORT( p );
@@ -704,7 +721,7 @@
/*
* First ensure that p is within COLRv1.
*/
- if ( p < colr->base_glyphs_v1 ||
+ if ( p < colr->layers_v1 ||
p >= ( (FT_Byte*)colr->table + colr->table_size ) )
return 0;
@@ -731,7 +748,7 @@
p_paint = (FT_Byte*)( colr->layers_v1 + paint_offset );
- if ( p_paint < colr->base_glyphs_v1 ||
+ if ( p_paint < colr->paints_start_v1 ||
p_paint >= ( (FT_Byte*)colr->table + colr->table_size ) )
return 0;