[internet-explorer] Make Adobe fonts work with CSS3 @font-face in IE9

If you want to do this with a PHP script instead of having to run C code (or you're on a Mac like me and you can't be arsed compiling with Xcode only to wait a year for it to open), here's a PHP function that you can use to remove the embedding permissions from the font:

function convertRestrictedFont($filename) {
    $font = fopen($filename,'r+');
    if ($font === false) {
        throw new Exception('Could not open font file.');
    }

    fseek($font, 12, 0);

    while (!feof($font)) {
        $type = '';
        for ($i = 0; $i < 4; $i++) {
            $type .= fgetc($font);
            if (feof($font)) {
                fclose($font);
                throw new Exception('Could not read the table definitions of the font.');
            }
        }
        if ($type == 'OS/2') {
            // Save the location of the table definition
            // containing the checksum and pointer to the data
            $os2TableDefinition = ftell($font);
            $checksum = 0;

            for ($i = 0; $i < 4; $i++) {
                fgetc($font);
                if (feof($font)) {
                    fclose($font);
                    throw new Exception('Could not read the OS/2 table header of the font.');
                }
            }

            // Get the pointer to the OS/2 table data
            $os2TablePointer = ord(fgetc($font)) << 24;
            $os2TablePointer |= ord(fgetc($font)) << 16;
            $os2TablePointer |= ord(fgetc($font)) << 8;
            $os2TablePointer |= ord(fgetc($font));

            $length = ord(fgetc($font)) << 24;
            $length |= ord(fgetc($font)) << 16;
            $length |= ord(fgetc($font)) << 8;
            $length |= ord(fgetc($font));

            if (fseek($font, $os2TablePointer + 8, 0) !== 0) {
                fclose($font);
                throw new Exception('Could not read the embeddable type of the font.');
            }

            // Read the fsType before overriding it
            $fsType = ord(fgetc($font)) << 8;
            $fsType |= ord(fgetc($font));

            error_log('Installable Embedding: ' . ($fsType == 0));
            error_log('Reserved: ' . ($fsType & 1));
            error_log('Restricted License: ' . ($fsType & 2));
            error_log('Preview & Print: ' . ($fsType & 4));
            error_log('Editable Embedding: ' . ($fsType & 8));
            error_log('Reserved: ' . ($fsType & 16)); 
            error_log('Reserved: ' . ($fsType & 32));
            error_log('Reserved: ' . ($fsType & 64));
            error_log('Reserved: ' . ($fsType & 128));
            error_log('No subsetting: ' . ($fsType & 256));
            error_log('Bitmap embedding only: ' . ($fsType & 512));                         
            error_log('Reserved: ' . ($fsType & 1024));
            error_log('Reserved: ' . ($fsType & 2048));
            error_log('Reserved: ' . ($fsType & 4096));
            error_log('Reserved: ' . ($fsType & 8192));
            error_log('Reserved: ' . ($fsType & 16384));
            error_log('Reserved: ' . ($fsType & 32768));

            fseek($font, ftell($font) - 2);

            // Set the two bytes of fsType to 0
            fputs($font, chr(0), 1);
            fputs($font, chr(0), 1);

            // Go to the beginning of the OS/2 table data
            fseek($font, $os2TablePointer, 0);

            // Generate a new checksum based on the changed 
            for ($i = 0; $i < $length; $i++) {
                $checksum += ord(fgetc($font));
            }
            fseek($font, $os2TableDefinition, 0);
            fputs($font, chr($checksum >> 24), 1);
            fputs($font, chr(255 & ($checksum >> 16)), 1);
            fputs($font, chr(255 & ($checksum >> 8)), 1);
            fputs($font, chr(255 & $checksum), 1);

            fclose($font);

            return true;
        }
        for ($i = 0; $i < 12; $i++) {
            fgetc($font);
            if (feof($font)) {
                fclose($font);
                throw new Exception('Could not skip a table definition of the font.');
            }
        }
    }

    fclose($font);

    return false;
}

Make sure to backup your font file before running this code and don't blame me if it corrupts.

Original source in C can be found here.