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<?php |
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namespace BiffBangPow\SSMonitor\Client\Helper; |
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use SilverStripe\Core\Config\Configurable; |
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use SilverStripe\Core\Environment; |
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class EncryptionHelper |
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{ |
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use Configurable; |
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/** |
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* @config |
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* @var int $hashlength |
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*/ |
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private static int $hashlength = 50; |
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/** |
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* @var string $secret |
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*/ |
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private string $secret; |
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/** |
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* @var string $salt |
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*/ |
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private string $salt; |
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public function __construct() |
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{ |
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$encSecret = Environment::getEnv('MONITORING_ENC_SECRET'); |
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$encSalt = Environment::getEnv('MONITORING_ENC_SALT'); |
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if (!$encSalt || !$encSecret) { |
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throw new \Exception("Missing encryption keys in environment"); |
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} |
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$this->setSecret($encSecret); |
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$this->setSalt($encSalt); |
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} |
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public function encrypt($plaintext) |
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{ |
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$secret = $this->getSecret(); |
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// Create a 32bit password |
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$key = $this->create_32bit_password($secret); |
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// Create a nonce: a piece of non-secret unique data that is used to randomize the cipher (safety against replay attack). |
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// The nonce should be stored or shared along with the ciphertext, because the nonce needs to be reused with the same key. |
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// In this class the nonce is shared with the ciphertext. |
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$nonce = random_bytes(SODIUM_CRYPTO_SECRETBOX_NONCEBYTES); |
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// Encrypted |
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$ciphertext = bin2hex( |
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sodium_crypto_secretbox($plaintext, $nonce, $key) |
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); |
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// Hex nonce (in order to send together with ciphertext) |
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$nonce_hex = bin2hex($nonce); |
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// Create hash from ciphertext+nonce |
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// It is not necessary, but just an extra layer of defense: |
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// - more difficult to manipulate the string |
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// - a nonce is always 48 characters. Because of a trailing hash (of unkown length), the nonce cannot be identified easily. |
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// (a nonce does not have to be secret, this is just an extra precaution) |
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$hash = $this->create_hash($ciphertext . $nonce_hex); |
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// Return ciphertext + nonce + hash |
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return $ciphertext . $nonce_hex . $hash; |
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} |
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public function decrypt($ciphertext) |
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{ |
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$secret = $this->getSecret(); |
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// Create a 32bit password |
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$key = $this->create_32bit_password($secret); |
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//Get hash |
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$hash = substr($ciphertext, -self::$hashlength); |
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//Get ciphertext + nonce (remove trailing hash) |
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$ciphertext = substr($ciphertext, 0, -self::$hashlength); |
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//Re-create hash |
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$hash_on_the_fly = $this->create_hash($ciphertext); |
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//Check if hash is correct |
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if ($hash !== $hash_on_the_fly) { |
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//Do proper error handling |
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return "error"; |
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} else { |
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// Get nonce (last 48 chars of string) |
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$nonce_hex = substr($ciphertext, -48); |
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// Get ciphertext (remove nonce) |
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$ciphertext = substr($ciphertext, 0, -48); |
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// Bin nonce |
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$nonce = hex2bin($nonce_hex); |
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// Decrypted |
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$plaintext = sodium_crypto_secretbox_open( |
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hex2bin($ciphertext), $nonce, $key |
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); |
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return $plaintext; |
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} |
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} |
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private function create_32bit_password($secret) |
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{ |
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$salt = $this->getSalt(); |
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//Openlib needs a 32bit key for encryption |
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return substr(bin2hex(sodium_crypto_generichash($secret . $salt)), 0, 32); |
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} |
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private function create_hash($ciphertext_and_nonce) |
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{ |
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$hashlength = $this->config()->get('hashlength'); |
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return substr(bin2hex(sodium_crypto_generichash($ciphertext_and_nonce)), 0, $hashlength); |
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} |
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/** |
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* @return mixed |
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*/ |
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public function getSecret() |
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{ |
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return $this->secret; |
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} |
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/** |
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* @param mixed $secret |
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*/ |
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public function setSecret($secret): void |
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{ |
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$this->secret = $secret; |
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} |
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/** |
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* @return mixed |
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*/ |
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public function getSalt() |
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{ |
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return $this->salt; |
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} |
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/** |
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* @param mixed $salt |
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*/ |
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public function setSalt($salt): void |
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{ |
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$this->salt = $salt; |
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} |
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} |
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BiffBangPow /
silverstripe-monitoring-client
