Fix mcrypt fatal - Removed on PHP 7.2

includes/push-syndicate-encryption.php

@@ -1,18 +1,72 @@
 <?php
 
+function push_syndicate_get_cipher() {
+	$cipher = 'aes-256-cbc';
+
+	if ( function_exists( 'mcrypt_encrypt' ) ) {
+		return MCRYPT_RIJNDAEL_256;
+	}
+
+	if ( in_array( $cipher, openssl_get_cipher_methods(), true ) ) {
+		return array(
+			'cipher' => $cipher,
+			'iv'     => substr( md5( md5( PUSH_SYNDICATE_KEY ) ), 0, 16 ),
+			'key'    => md5( PUSH_SYNDICATE_KEY ),
+		);
+	}
+
+	return false; // @TODO: return another default cipher? return exception?
+}
+
 function push_syndicate_encrypt( $data ) {
+	// @todo: replace mcrypt with openssl. problem: Rijndael AES is not available on openssl;s AES-256.
+	// Will most likely break backwards compatibility with older keys
+	// https://stackoverflow.com/questions/49997338/mcrypt-rijndael-256-to-openssl-aes-256-ecb-conversion
+
+	// Backwards compatibility with PHP < 7.2.
+	if ( function_exists( 'mcrypt_encrypt' ) ) {
+		// @codingStandardsIgnoreStart
+		$data = serialize( $data );
+		return base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, md5(PUSH_SYNDICATE_KEY), $data, MCRYPT_MODE_CBC, md5(md5(PUSH_SYNDICATE_KEY))));
+		// @codingStandardsIgnoreEnd
+	}
+
+	$data   = wp_json_encode( $data );
+	$cipher = push_syndicate_get_cipher();
 
-	$data = serialize( $data );
-	return base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, md5(PUSH_SYNDICATE_KEY), $data, MCRYPT_MODE_CBC, md5(md5(PUSH_SYNDICATE_KEY))));
+	if ( ! $cipher ) {
+		return $data;
+	}
+
+	$encrypted_data = openssl_encrypt( $data, $cipher['cipher'], $cipher['key'], 0, $cipher['iv'] );
+	return base64_encode( $encrypted_data ); // phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_encode
 
 }
 
 function push_syndicate_decrypt( $data ) {
 
-	$data = rtrim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, md5(PUSH_SYNDICATE_KEY), base64_decode($data), MCRYPT_MODE_CBC, md5(md5(PUSH_SYNDICATE_KEY))), "\0");
-	if ( !$data )
-		return false;
+	// Backwards compatibility with PHP < 7.2.
+	if ( function_exists( 'mcrypt_encrypt' ) ) {
+		// @codingStandardsIgnoreStart
+		$data = rtrim( mcrypt_decrypt( MCRYPT_RIJNDAEL_256, md5( PUSH_SYNDICATE_KEY ), base64_decode( $data ), MCRYPT_MODE_CBC, md5( md5( PUSH_SYNDICATE_KEY ) ) ), "\0" );
+		if ( ! $data ) {
+			return false;
+		}
+		return @unserialize( $data );
+		// @codingStandardsIgnoreEnd
+	}
+
+	$cipher = push_syndicate_get_cipher();
+
+	if ( ! $cipher ) {
+		return $data;
+	}
 
-	return @unserialize( $data );
+	$data = openssl_decrypt( base64_decode( $data ), $cipher['cipher'], $cipher['key'], 0, $cipher['iv'] ); //phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_decode
 
-}
+	if ( ! $data ) {
+		return false;
+	}
+
+	return json_decode( $data );
+}