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[type42] Track how much type42 ttf data is available. 

Currently `T42_Open_Face` eagerly allocates 12 bytes for the ttf header
data which it expects `t42_parse_sfnts` to fill out from /sfnts data.
However, there is no guarantee that `t42_parse_sfnts` will actually be
called while parsing the type42 data as the /sfnts array may be missing
or very short. This is also confusing behavior as it means
`T42_Open_Face` is tightly coupled to the implementation of the very
distant `t42_parse_sfnts` code which requires at least 12 bytes to
already be reserved in `face->ttf_data`.

`t42_parse_sfnts` itself eagerly updates `face->ttf_size` to track how
much space is reserved for ttf data instead of traking how much data has
actually been written into `face->ttf_data`. It will also act strangely
in the presense of multiple /sfnts arrays.

* src/type42/t42objs.c (T42_Open_Face): ensure `ttf_data` is initialized
to NULL. Free `ttf_data` on error.

* src/type42/t42parse.c (t42_parse_sfnts): delay setting `ttf_size` and
set it to the actual number of bytes read. Ensure `ttf_data` is freed
if there are multiple /sfnts arrays or there are any errors.
This commit is contained in:
Ben Wagner 2022-01-11 11:14:32 -05:00
parent 3876846e26
commit e838c37c2c
2 changed files with 45 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
src/type42/t42objs.c
View File

@ -44,15 +44,8 @@
parser = &loader.parser;
/* To handle buggy fonts we don't use `FT_QALLOC` here. */
if ( FT_ALLOC( face->ttf_data, 12 ) )
goto Exit;
/* while parsing the font we always update `face->ttf_size' so that */
/* even in case of buggy data (which might lead to premature end of */
/* scanning without causing an error) the call to `FT_Open_Face' in */
/* `T42_Face_Init' passes the correct size */
face->ttf_size = 12;
face->ttf_data = NULL;
face->ttf_size = 0;
error = t42_parser_init( parser,
face->root.stream,
@ -153,6 +146,11 @@
Exit:
t42_loader_done( &loader );
if ( error )
{
FT_FREE(face->ttf_data);
face->ttf_size = 0;
}
return error;
}

64
src/type42/t42parse.c
View File

@ -538,7 +538,8 @@
FT_Byte* limit = parser->root.limit;
FT_Error error;
FT_Int num_tables = 0;
FT_Long count;
FT_Long ttf_count;
FT_Long ttf_reserved;
FT_ULong n, string_size, old_string_size, real_size;
FT_Byte* string_buf = NULL;
@ -546,6 +547,9 @@
T42_Load_Status status;
/** There should only be one sfnts array, but free any previous. */
FT_FREE( face->ttf_data );
face->ttf_size = 0;
/* The format is */
/* */
@ -574,7 +578,10 @@
status = BEFORE_START;
string_size = 0;
old_string_size = 0;
count = 0;
ttf_count = 0;
ttf_reserved = 12;
if ( FT_QALLOC( face->ttf_data, ttf_reserved ) )
goto Fail;
FT_TRACE2(( "\n" ));
FT_TRACE2(( "t42_parse_sfnts:\n" ));
@ -589,6 +596,7 @@
if ( *cur == ']' )
{
parser->root.cursor++;
face->ttf_size = ttf_count;
goto Exit;
}
@ -684,7 +692,7 @@
}
FT_TRACE2(( " PS string size %5lu bytes, offset 0x%08lx (%lu)\n",
string_size, count, count ));
string_size, ttf_count, ttf_count ));
/* The whole TTF is now loaded into `string_buf'. We are */
/* checking its contents while copying it to `ttf_data'. */
@ -697,45 +705,48 @@
{
case BEFORE_START:
/* load offset table, 12 bytes */
if ( count < 12 )
if ( ttf_count < 12 )
{
face->ttf_data[count++] = string_buf[n];
face->ttf_data[ttf_count++] = string_buf[n];
continue;
}
else
{
num_tables = 16 * face->ttf_data[4] + face->ttf_data[5];
status = BEFORE_TABLE_DIR;
face->ttf_size = 12 + 16 * num_tables;
FT_Long ttf_reserved_prev = ttf_reserved;
num_tables = 16 * face->ttf_data[4] + face->ttf_data[5];
status = BEFORE_TABLE_DIR;
ttf_reserved = 12 + 16 * num_tables;
FT_TRACE2(( " SFNT directory contains %d tables\n",
num_tables ));
if ( (FT_Long)size < face->ttf_size )
if ( (FT_Long)size < ttf_reserved )
{
FT_ERROR(( "t42_parse_sfnts: invalid data in sfnts array\n" ));
error = FT_THROW( Invalid_File_Format );
goto Fail;
}
/* To handle bad fonts with an invalid table directory */
/* we don't use `FT_QREALLOC` here. */
if ( FT_REALLOC( face->ttf_data, 12, face->ttf_size ) )
if ( FT_QREALLOC( face->ttf_data, ttf_reserved_prev,
ttf_reserved ) )
goto Fail;
}
/* fall through */
case BEFORE_TABLE_DIR:
/* the offset table is read; read the table directory */
if ( count < face->ttf_size )
if ( ttf_count < ttf_reserved )
{
face->ttf_data[count++] = string_buf[n];
face->ttf_data[ttf_count++] = string_buf[n];
continue;
}
else
{
int i;
FT_ULong len;
FT_Long ttf_reserved_prev = ttf_reserved;
FT_TRACE2(( "\n" ));
@ -751,7 +762,7 @@
FT_TRACE2(( " %4i 0x%08lx (%lu)\n", i, len, len ));
if ( len > size ||
face->ttf_size > (FT_Long)( size - len ) )
ttf_reserved > (FT_Long)( size - len ) )
{
FT_ERROR(( "t42_parse_sfnts:"
" invalid data in sfnts array\n" ));
@ -760,35 +771,31 @@
}
/* Pad to a 4-byte boundary length */
face->ttf_size += (FT_Long)( ( len + 3 ) & ~3U );
ttf_reserved += (FT_Long)( ( len + 3 ) & ~3U );
}
ttf_reserved += 1;
status = OTHER_TABLES;
FT_TRACE2(( "\n" ));
FT_TRACE2(( " allocating %ld bytes\n", face->ttf_size + 1 ));
FT_TRACE2(( " allocating %ld bytes\n", ttf_reserved ));
FT_TRACE2(( "\n" ));
/* To handle bad fonts we don't use `FT_QREALLOC` here: */
/* chances are high that due to incorrect values in the */
/* table directory the computation of `ttf_size` would be */
/* incorrect otherwise, causing run-time errors because of */
/* accessing uninitialized memory. */
if ( FT_REALLOC( face->ttf_data, 12 + 16 * num_tables,
face->ttf_size + 1 ) )
if ( FT_QREALLOC( face->ttf_data, ttf_reserved_prev,
ttf_reserved ) )
goto Fail;
}
/* fall through */
case OTHER_TABLES:
/* all other tables are just copied */
if ( count >= face->ttf_size )
if ( ttf_count >= ttf_reserved )
{
FT_ERROR(( "t42_parse_sfnts: too much binary data\n" ));
error = FT_THROW( Invalid_File_Format );
goto Fail;
}
face->ttf_data[count++] = string_buf[n];
face->ttf_data[ttf_count++] = string_buf[n];
}
}
@ -802,6 +809,11 @@
parser->root.error = error;
Exit:
if ( parser->root.error )
{
FT_FREE( face->ttf_data );
face->ttf_size = 0;
}
if ( allocated )
FT_FREE( string_buf );
}