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| <?php
/**
* Verify that a Onleihe CODE is correct (able to decrypt the .epub file)
*/
$userPassphrase = 'FIXME';//Bitte geben Sie hier Ihren Onleihe CODE ein.
$lcplFile = 'example/81f292a0-5989-4d02-8749-398cc0b5057f.lcpl';
$lcpl = json_decode(file_get_contents($lcplFile));
$licenseId = $lcpl->id;
$encLicenseId = $lcpl->encryption->user_key->key_check;
if ($lcpl->encryption->user_key->algorithm != 'http://www.w3.org/2001/04/xmlenc#sha256') {
echo "Unsupported user key hash algorithm\n";
exit(1);
}
$userKey = hash('sha256', $userPassphrase);
if ($lcpl->encryption->content_key->algorithm != 'http://www.w3.org/2001/04/xmlenc#aes256-cbc') {
echo "Unsupported content key encryption algorithm\n";
exit(1);
}
/**
* https://www.w3.org/TR/xmlenc-core1/#sec-AES
*
* [AES] is used in the Cipher Block Chaining (CBC) mode with a 128 bit
* initialization vector (IV).
* The resulting cipher text is prefixed by the IV.
* If included in XML output, it is then base64 encoded.
*/
$encLicenseIdBytes = base64_decode($encLicenseId);
$encIv = substr($encLicenseIdBytes, 0, 128 / 8);
$encLicenseIdBytesData = substr($encLicenseIdBytes, 128 / 8);
$decrypted = openssl_decrypt(
$encLicenseIdBytesData, 'AES-256-CBC',
hex2bin($userKey),
OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING,
$encIv
);
if ($decrypted === false) {
echo "Decryption failed\n";
exit(1);
}
$padLength = unpack('C', substr($decrypted, -1))[1];
$decrypted = substr($decrypted, 0, -$padLength);
echo "License ID: $licenseId\n";
echo "Decrypted ID: $decrypted\n";
?>
|
