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Asymmetric decryption

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Stephen Paul Weber
2013-01-26 14:00:00 -05:00
parent 641c07835b
commit cd15aec6f9
5 changed files with 152 additions and 37 deletions
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84
lib/openpgp_crypt_aes_tripledes.php
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@@ -6,55 +6,67 @@ require_once 'Crypt/TripleDES.php';
class OpenPGP_Crypt_AES_TripleDES {
public static function decryptSymmetric($pass, $m) {
$epacket = self::getEncryptedData($m);
foreach($m as $p) {
if($p instanceof OpenPGP_SymmetricSessionKeyPacket) {
list($cipher, $key_bytes, $key_block_bytes) = self::getCipher($p->symmetric_algorithm);
if(!$cipher) continue;
$cipher->setKey($p->s2k->make_key($pass, $key_bytes));
if(strlen($p->encrypted_data) > 0) {
list($cipher, $key_bytes, $key_block_bytes) = self::getCipher($p->symmetric_algorithm);
if(!$cipher) continue;
$cipher->setKey($p->s2k->make_key($pass, $key_bytes));
$padAmount = $key_block_bytes - (strlen($p->encrypted_data) % $key_block_bytes);
$data = substr($cipher->decrypt($p->encrypted_data . str_repeat("\0", $padAmount)), 0, strlen($p->encrypted_data));
list($cipher, $key_bytes, $key_block_bytes) = self::getCipher(ord($data{0}));
if(!$cipher) continue;
$cipher->setKey(substr($data, 1));
}
$epacket = self::getEncryptedData($m);
$padAmount = $key_block_bytes - (strlen($epacket->data) % $key_block_bytes);
if($epacket instanceof OpenPGP_IntegrityProtectedDataPacket) {
$data = substr($cipher->decrypt($epacket->data . str_repeat("\0", $padAmount)), 0, strlen($epacket->data));
$prefix = substr($data, 0, $key_block_bytes + 2);
$mdc = substr(substr($data, -22, 22), 2);
$data = substr($data, $key_block_bytes + 2, -22);
$mkMDC = hash("sha1", $prefix . $data . "\xD3\x14", true);
if($mkMDC !== $mdc) return false;
try {
$msg = OpenPGP_Message::parse($data);
} catch (Exception $ex) { $msg = NULL; }
if($msg) return $msg; /* Otherwise keep trying */
$decrypted = self::decryptPacket($epacket, ord($data{0}), substr($data, 1));
} else {
// No MDC mean decrypt with resync
$iv = substr($epacket->data, 2, $key_block_bytes);
$edata = substr($epacket->data, $key_block_bytes + 2);
$cipher->setIV($iv);
$data = substr($cipher->decrypt($edata . str_repeat("\0", $padAmount)), 0, strlen($edata));
try {
$msg = OpenPGP_Message::parse($data);
} catch (Exception $ex) { $msg = NULL; }
if($msg) return $msg; /* Otherwise keep trying */
list($cipher, $key_bytes, $key_block_bytes) = self::getCipher($p->symmetric_algorithm);
$decrypted = self::decryptPacket($epacket, $p->symmetric_algorithm, $p->s2k->make_key($pass, $key_bytes));
}
if($decrypted) return $decrypted;
}
}
return NULL; /* If we get here, we failed */
}
public static function decryptPacket($epacket, $symmetric_algorithm, $key) {
list($cipher, $key_bytes, $key_block_bytes) = self::getCipher($symmetric_algorithm);
if(!$cipher) return NULL;
$cipher->setKey($key);
$padAmount = $key_block_bytes - (strlen($epacket->data) % $key_block_bytes);
if($epacket instanceof OpenPGP_IntegrityProtectedDataPacket) {
$data = substr($cipher->decrypt($epacket->data . str_repeat("\0", $padAmount)), 0, strlen($epacket->data));
$prefix = substr($data, 0, $key_block_bytes + 2);
$mdc = substr(substr($data, -22, 22), 2);
$data = substr($data, $key_block_bytes + 2, -22);
$mkMDC = hash("sha1", $prefix . $data . "\xD3\x14", true);
if($mkMDC !== $mdc) return false;
try {
$msg = OpenPGP_Message::parse($data);
} catch (Exception $ex) { $msg = NULL; }
if($msg) return $msg; /* Otherwise keep trying */
} else {
// No MDC mean decrypt with resync
$iv = substr($epacket->data, 2, $key_block_bytes);
$edata = substr($epacket->data, $key_block_bytes + 2);
$cipher->setIV($iv);
$data = substr($cipher->decrypt($edata . str_repeat("\0", $padAmount)), 0, strlen($edata));
try {
$msg = OpenPGP_Message::parse($data);
} catch (Exception $ex) { $msg = NULL; }
if($msg) return $msg; /* Otherwise keep trying */
}
return NULL; /* Failed */
}
public static function getCipher($algo) {
switch($algo) {
case 2: