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[woff2] Disallow zero table font entries 

The existing code already disallows zero table woff2 overall, but still
allows for individual CollectionFontEntry to create font instances with
zero tables. Such fonts are not useful so error early.

This also fixes an MSAN discovered issue where if a CollectionFontEntry
numTables is zero then the sfnt_header was not fully initialized.

* src/sfnt/sfwoff2.c (woff2_open_font): error on zero tables, always
initalize sfnt_header

Fixes: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=68384
This commit is contained in:
Ben Wanger 2024-05-02 13:16:46 -04:00
parent 4d50468478
commit 13d1180f45
1 changed files with 10 additions and 7 deletions
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17
src/sfnt/sfwoff2.c
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@ -1791,7 +1791,6 @@
FT_Byte* sfnt = NULL;
FT_Stream sfnt_stream = NULL;
FT_Byte* sfnt_header;
FT_ULong sfnt_size;
FT_Byte* uncompressed_buf = NULL;
@ -2135,6 +2134,13 @@
WOFF2_TtcFont ttc_font = woff2.ttc_fonts + face_index;
if ( ttc_font->num_tables == 0 )
{
FT_ERROR(( "woff2_open_font: invalid WOFF2 CollectionFontEntry\n" ));
error = FT_THROW( Invalid_Table );
goto Exit;
}
/* Create a temporary array. */
if ( FT_QNEW_ARRAY( temp_indices,
ttc_font->num_tables ) )
@ -2190,13 +2196,9 @@
FT_NEW( sfnt_stream ) )
goto Exit;
sfnt_header = sfnt;
WRITE_ULONG( sfnt_header, woff2.flavor );
if ( woff2.num_tables )
{
FT_UInt searchRange, entrySelector, rangeShift, x;
FT_UInt searchRange, entrySelector, rangeShift, x;
FT_Byte* sfnt_header = sfnt;
x = woff2.num_tables;
@ -2211,6 +2213,7 @@
searchRange = ( 1 << entrySelector ) * 16;
rangeShift = ( woff2.num_tables * 16 ) - searchRange;
WRITE_ULONG( sfnt_header, woff2.flavor );
WRITE_USHORT( sfnt_header, woff2.num_tables );
WRITE_USHORT( sfnt_header, searchRange );
WRITE_USHORT( sfnt_header, entrySelector );