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Add protection against out-of-bounds read in ttconv #20629

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Merged
merged 2 commits into from
Jul 13, 2021
Merged

Add protection against out-of-bounds read in ttconv #20629

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635f67a
Add protection against out-of-bounds read in ttconv
sauerburger Jul 11, 2021
deefcba
Test EPS with Type 42 font without prep table
sauerburger Jul 13, 2021
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57 changes: 30 additions & 27 deletions extern/ttconv/pprdrv_tt.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -757,33 +757,36 @@ void ttfont_sfnts(TTStreamWriter& stream, struct TTFONT *font)
** Find the tables we want and store there vital
** statistics in tables[].
*/
for (x=0; x < 9; x++ )
{
do
{
diff = strncmp( (char*)ptr, table_names[x], 4 );

if ( diff > 0 ) /* If we are past it. */
{
tables[x].length = 0;
diff = 0;
}
else if ( diff < 0 ) /* If we haven't hit it yet. */
{
ptr += 16;
}
else if ( diff == 0 ) /* Here it is! */
{
tables[x].newoffset = nextoffset;
tables[x].checksum = getULONG( ptr + 4 );
tables[x].oldoffset = getULONG( ptr + 8 );
tables[x].length = getULONG( ptr + 12 );
nextoffset += ( ((tables[x].length + 3) / 4) * 4 );
count++;
ptr += 16;
}
}
while (diff != 0);
ULONG num_tables_read = 0; /* Number of tables read from the directory */
for (x = 0; x < 9; x++) {
do {
if (num_tables_read < font->numTables) {
/* There are still tables to read from ptr */
diff = strncmp((char*)ptr, table_names[x], 4);

if (diff > 0) { /* If we are past it. */
tables[x].length = 0;
diff = 0;
} else if (diff < 0) { /* If we haven't hit it yet. */
ptr += 16;
num_tables_read++;
} else if (diff == 0) { /* Here it is! */
tables[x].newoffset = nextoffset;
tables[x].checksum = getULONG( ptr + 4 );
tables[x].oldoffset = getULONG( ptr + 8 );
tables[x].length = getULONG( ptr + 12 );
nextoffset += ( ((tables[x].length + 3) / 4) * 4 );
count++;
ptr += 16;
num_tables_read++;
}
} else {
/* We've read the whole table directory already */
/* Some tables couldn't be found */
tables[x].length = 0;
break; /* Proceed to next tables[x] */
}
} while (diff != 0);

} /* end of for loop which passes over the table directory */

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