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[sfnt] Better checks for invalid cmaps (2/2) (#46019). 

While the current code in `FT_Get_Next_Char' correctly rejects
out-of-bounds glyph indices, it can be extremely slow for malformed
cmaps that use 32bit values.  This commit tries to improve that.

* src/sfnt/ttcmap.c (tt_cmap8_char_next, tt_cmap12_next,
tt_cmap12_char_map_binary, tt_cmap13_next,
tt_cmap13_char_map_binary): Reject glyph indices larger than or
equal to the number of glyphs.
This commit is contained in:
Werner Lemberg 2015-09-24 13:39:44 +02:00
parent c409eb18ae
commit 5339c75ee6
4 changed files with 45 additions and 3 deletions
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13
ChangeLog
View File

@ -1,3 +1,16 @@
2015-09-23 Werner Lemberg <wl@gnu.org>
[sfnt] Better checks for invalid cmaps (2/2) (#46019).
While the current code in `FT_Get_Next_Char' correctly rejects
out-of-bounds glyph indices, it can be extremely slow for malformed
cmaps that use 32bit values. This commit tries to improve that.
* src/sfnt/ttcmap.c (tt_cmap8_char_next, tt_cmap12_next,
tt_cmap12_char_map_binary, tt_cmap13_next,
tt_cmap13_char_map_binary): Reject glyph indices larger than or
equal to the number of glyphs.
2015-09-23 Werner Lemberg <wl@gnu.org>
[base, sfnt] Better checks for invalid cmaps (1/2).

7
include/freetype/freetype.h
View File

@ -3372,6 +3372,13 @@ FT_BEGIN_HEADER
/* } */
/* } */
/* */
/* Be aware that character codes can have values up to 0xFFFFFFFF; */
/* this might happen for non-Unicode or malformed cmaps. However, */
/* even with regular Unicode encoding, so-called `last resort fonts' */
/* (using SFNT cmap format 13, see function @FT_Get_CMap_Format) */
/* normally have entries for all Unicode characters up to 0x1FFFFF, */
/* which can cause *a lot* of iterations. */
/* */
/* Note that `*agindex' is set to~0 if the charmap is empty. The */
/* result itself can be~0 in two cases: if the charmap is empty or */
/* if the value~0 is the first valid character code. */

5
include/freetype/internal/services/svttcmap.h
View File

@ -48,11 +48,12 @@ FT_BEGIN_HEADER
/* `ttnameid.h'. */
/* */
/* format :: */
/* The cmap format. OpenType 1.5 defines the formats 0 (byte */
/* The cmap format. OpenType 1.6 defines the formats 0 (byte */
/* encoding table), 2~(high-byte mapping through table), 4~(segment */
/* mapping to delta values), 6~(trimmed table mapping), 8~(mixed */
/* 16-bit and 32-bit coverage), 10~(trimmed array), 12~(segmented */
/* coverage), and 14 (Unicode Variation Sequences). */
/* coverage), 13~(last resort font), and 14 (Unicode Variation */
/* Sequences). */
/* */
typedef struct TT_CMapInfo_
{

23
src/sfnt/ttcmap.c
View File

@ -1797,6 +1797,7 @@
tt_cmap8_char_next( TT_CMap cmap,
FT_UInt32 *pchar_code )
{
FT_Face face = cmap->cmap.charmap.face;
FT_UInt32 result = 0;
FT_UInt32 char_code;
FT_UInt gindex = 0;
@ -1841,6 +1842,11 @@
goto Again;
}
/* if `gindex' is invalid, the remaining values */
/* in this group are invalid, too */
if ( gindex >= (FT_UInt)face->num_glyphs )
continue;
result = char_code;
break;
}
@ -2181,6 +2187,7 @@
static void
tt_cmap12_next( TT_CMap12 cmap )
{
FT_Face face = cmap->cmap.cmap.charmap.face;
FT_Byte* p;
FT_ULong start, end, start_id, char_code;
FT_ULong n;
@ -2221,6 +2228,11 @@
goto Again;
}
/* if `gindex' is invalid, the remaining values */
/* in this group are invalid, too */
if ( gindex >= (FT_UInt)face->num_glyphs )
continue;
cmap->cur_charcode = char_code;
cmap->cur_gindex = gindex;
cmap->cur_group = n;
@ -2293,6 +2305,7 @@
if ( next )
{
FT_Face face = cmap->cmap.charmap.face;
TT_CMap12 cmap12 = (TT_CMap12)cmap;
@ -2310,6 +2323,9 @@
cmap12->cur_charcode = char_code;
cmap12->cur_group = mid;
if ( gindex >= (FT_UInt)face->num_glyphs )
gindex = 0;
if ( !gindex )
{
tt_cmap12_next( cmap12 );
@ -2517,6 +2533,7 @@
static void
tt_cmap13_next( TT_CMap13 cmap )
{
FT_Face face = cmap->cmap.cmap.charmap.face;
FT_Byte* p;
FT_ULong start, end, glyph_id, char_code;
FT_ULong n;
@ -2542,7 +2559,7 @@
{
gindex = (FT_UInt)glyph_id;
if ( gindex )
if ( gindex && gindex < (FT_UInt)face->num_glyphs )
{
cmap->cur_charcode = char_code;
cmap->cur_gindex = gindex;
@ -2612,6 +2629,7 @@
if ( next )
{
FT_Face face = cmap->cmap.charmap.face;
TT_CMap13 cmap13 = (TT_CMap13)cmap;
@ -2629,6 +2647,9 @@
cmap13->cur_charcode = char_code;
cmap13->cur_group = mid;
if ( gindex >= (FT_UInt)face->num_glyphs )
gindex = 0;
if ( !gindex )
{
tt_cmap13_next( cmap13 );