rename SODIUM_ENCRYPTION_KEY to SESSION_ENCRYPTION_KEY and move related stuff to Sessions class

1 files changed, 49 insertions, 5 deletions

diff --git a/classes/Sessions.php b/classes/Sessions.php
index e8cba1765..d8f14eed0 100644
--- a/classes/Sessions.php
+++ b/classes/Sessions.php
@@ -8,6 +8,8 @@ class Sessions implements \SessionHandlerInterface {
 	private int $session_expire;
 	private string $session_name;
 
+	private const SODIUM_ALGO = 'xchacha20poly1305_ietf';
+
 	public function __construct() {
 		$this->session_expire = min(2147483647 - time() - 1, Config::get(Config::SESSION_COOKIE_LIFETIME));
 		$this->session_name = Config::get(Config::SESSION_NAME);
@@ -53,6 +55,48 @@ class Sessions implements \SessionHandlerInterface {
 		return true;
 	}
 
+	/** encrypts provided ciphertext using Sodium symmetric encryption key if available via Config::SESSION_ENCRYPTION_KEY
+	 *
+	 * @return array<string,mixed> encrypted data object containing algo, nonce, and encrypted data
+	 *
+	*/
+	private function encrypt_string(string $ciphertext) : array {
+		$key = Config::get(Config::SESSION_ENCRYPTION_KEY);
+		$nonce = \random_bytes(\SODIUM_CRYPTO_AEAD_XCHACHA20POLY1305_IETF_NPUBBYTES);
+
+		$payload = sodium_crypto_aead_xchacha20poly1305_ietf_encrypt($ciphertext, '', $nonce, hex2bin($key));
+
+		if ($payload) {
+			$encrypted_data = [
+				'algo' => self::SODIUM_ALGO,
+				'nonce' => $nonce,
+				'payload' => $payload,
+			];
+
+			return $encrypted_data;
+		}
+
+		throw new Exception("Config::encrypt_string() failed to encrypt ciphertext");
+	}
+
+	/** decrypts payload of encrypted object if Config::SESSION_ENCRYPTION_KEY is available and object is in correct format
+	 *
+	 * @param array<string,mixed> $encrypted_data
+	 *
+	 * @return string decrypted string payload
+	 */
+	private function decrypt_string(array $encrypted_data) : string {
+		$key = Config::get(Config::SESSION_ENCRYPTION_KEY);
+
+		if ($encrypted_data['algo'] === self::SODIUM_ALGO) {
+			$payload = sodium_crypto_aead_xchacha20poly1305_ietf_decrypt($encrypted_data['payload'], '', $encrypted_data['nonce'], hex2bin($key));
+
+			return $payload;
+		}
+
+		throw new Exception('Config::decrypt_string() failed to decrypt passed encrypted data');
+	}
+
 	public function read(string $id): false|string {
 		$sth = Db::pdo()->prepare('SELECT data FROM ttrss_sessions WHERE id=?');
 		$sth->execute([$id]);
@@ -60,11 +104,11 @@ class Sessions implements \SessionHandlerInterface {
 		if ($row = $sth->fetch()) {
 			$data = base64_decode($row['data']);
 
-			if (Config::get(Config::SODIUM_ENCRYPTION_KEY)) {
-				$unserialized_data = unserialize($data);
+			if (Config::get(Config::SESSION_ENCRYPTION_KEY)) {
+				$unserialized_data = @unserialize($data); // avoid leaking plaintext session via error message
 
 				if ($unserialized_data !== false)
-					return Config::decrypt_string($unserialized_data);
+					return $this->decrypt_string($unserialized_data);
 			}
 
 			// if Sodium key is missing or session data is not in serialized format, return as-is
@@ -80,8 +124,8 @@ class Sessions implements \SessionHandlerInterface {
 
 	public function write(string $id, string $data): bool {
 
-		if (Config::get(Config::SODIUM_ENCRYPTION_KEY))
-			$data = serialize(Config::encrypt_string($data));
+		if (Config::get(Config::SESSION_ENCRYPTION_KEY))
+			$data = serialize($this->encrypt_string($data));
 
 		$data = base64_encode($data);