<?php
/**
 * Part of the Joomla Framework Crypt Package
 *
 * @copyright  Copyright (C) 2005 - 2021 Open Source Matters, Inc. All rights reserved.
 * @license    GNU General Public License version 2 or later; see LICENSE
 */

namespace Joomla\Crypt\Cipher;

use Joomla\Crypt\CipherInterface;
use Joomla\Crypt\Exception\DecryptionException;
use Joomla\Crypt\Exception\EncryptionException;
use Joomla\Crypt\Exception\InvalidKeyException;
use Joomla\Crypt\Exception\InvalidKeyTypeException;
use Joomla\Crypt\Exception\UnsupportedCipherException;
use Joomla\Crypt\Key;
use ParagonIE\Sodium\Compat;

/**
 * Cipher for sodium algorithm encryption, decryption and key generation.
 *
 * @since  1.4.0
 */
class Sodium implements CipherInterface
{
	/**
	 * The message nonce to be used with encryption/decryption
	 *
	 * @var    string
	 * @since  1.4.0
	 */
	private $nonce;

	/**
	 * Method to decrypt a data string.
	 *
	 * @param   string  $data  The encrypted string to decrypt.
	 * @param   Key     $key   The key object to use for decryption.
	 *
	 * @return  string  The decrypted data string.
	 *
	 * @since   1.4.0
	 * @throws  DecryptionException if the data cannot be decrypted
	 * @throws  InvalidKeyTypeException if the key is not valid for the cipher
	 */
	public function decrypt($data, Key $key)
	{
		// Validate key.
		if ($key->getType() !== 'sodium')
		{
			throw new InvalidKeyTypeException('sodium', $key->getType());
		}

		if (!$this->nonce)
		{
			throw new DecryptionException('Missing nonce to decrypt data');
		}

		// Use the sodium extension (PHP 7.2 native, PECL 2.x, or paragonie/sodium_compat) if able
		if (\function_exists('sodium_crypto_box_open'))
		{
			try
			{
				$decrypted = sodium_crypto_box_open(
					$data,
					$this->nonce,
					sodium_crypto_box_keypair_from_secretkey_and_publickey($key->getPrivate(), $key->getPublic())
				);

				if ($decrypted === false)
				{
					throw new DecryptionException('Malformed message or invalid MAC');
				}
			}
			catch (\SodiumException $exception)
			{
				throw new DecryptionException('Malformed message or invalid MAC', $exception->getCode(), $exception);
			}

			return $decrypted;
		}

		// Use the libsodium extension (PECL 1.x) if able; purposefully skipping sodium_compat fallback here as that will match the above check
		if (\extension_loaded('libsodium'))
		{
			$decrypted = \Sodium\crypto_box_open(
				$data,
				$this->nonce,
				\Sodium\crypto_box_keypair_from_secretkey_and_publickey($key->getPrivate(), $key->getPublic())
			);

			if ($decrypted === false)
			{
				throw new DecryptionException('Malformed message or invalid MAC');
			}

			return $decrypted;
		}

		// Well this is awkward
		throw new UnsupportedCipherException(static::class);
	}

	/**
	 * Method to encrypt a data string.
	 *
	 * @param   string  $data  The data string to encrypt.
	 * @param   Key     $key   The key object to use for encryption.
	 *
	 * @return  string  The encrypted data string.
	 *
	 * @since   1.4.0
	 * @throws  EncryptionException if the data cannot be encrypted
	 * @throws  InvalidKeyTypeException if the key is not valid for the cipher
	 */
	public function encrypt($data, Key $key)
	{
		// Validate key.
		if ($key->getType() !== 'sodium')
		{
			throw new InvalidKeyTypeException('sodium', $key->getType());
		}

		if (!$this->nonce)
		{
			throw new EncryptionException('Missing nonce to decrypt data');
		}

		// Use the sodium extension (PHP 7.2 native, PECL 2.x, or paragonie/sodium_compat) if able
		if (\function_exists('sodium_crypto_box'))
		{
			try
			{
				return sodium_crypto_box(
					$data,
					$this->nonce,
					sodium_crypto_box_keypair_from_secretkey_and_publickey($key->getPrivate(), $key->getPublic())
				);
			}
			catch (\SodiumException $exception)
			{
				throw new EncryptionException('Could not encrypt file.', $exception->getCode(), $exception);
			}
		}

		// Use the libsodium extension (PECL 1.x) if able; purposefully skipping sodium_compat fallback here as that will match the above check
		if (\extension_loaded('libsodium'))
		{
			return \Sodium\crypto_box(
				$data,
				$this->nonce,
				\Sodium\crypto_box_keypair_from_secretkey_and_publickey($key->getPrivate(), $key->getPublic())
			);
		}

		// Well this is awkward
		throw new UnsupportedCipherException(static::class);
	}

	/**
	 * Method to generate a new encryption key object.
	 *
	 * @param   array  $options  Key generation options.
	 *
	 * @return  Key
	 *
	 * @since   1.4.0
	 * @throws  InvalidKeyException if the key cannot be generated
	 * @throws  UnsupportedCipherException if the cipher is not supported on the current environment
	 */
	public function generateKey(array $options = [])
	{
		// Use the sodium extension (PHP 7.2 native, PECL 2.x, or paragonie/sodium_compat) if able
		if (\function_exists('sodium_crypto_box_keypair'))
		{
			try
			{
				// Generate the encryption key.
				$pair = sodium_crypto_box_keypair();

				return new Key('sodium', sodium_crypto_box_secretkey($pair), sodium_crypto_box_publickey($pair));
			}
			catch (\SodiumException $exception)
			{
				throw new InvalidKeyException('Could not generate encryption key.', $exception->getCode(), $exception);
			}
		}

		// Use the libsodium extension (PECL 1.x) if able; purposefully skipping sodium_compat fallback here as that will match the above check
		if (\extension_loaded('libsodium'))
		{
			// Generate the encryption key.
			$pair = \Sodium\crypto_box_keypair();

			return new Key('sodium', \Sodium\crypto_box_secretkey($pair), \Sodium\crypto_box_publickey($pair));
		}

		// Well this is awkward
		throw new UnsupportedCipherException(static::class);
	}

	/**
	 * Check if the cipher is supported in this environment.
	 *
	 * @return  boolean
	 *
	 * @since   2.0.0
	 */
	public static function isSupported(): bool
	{
		// Prefer ext/sodium, then ext/libsodium, then presence of paragonie/sodium_compat
		return \function_exists('sodium_crypto_box') || \extension_loaded('libsodium') || class_exists(Compat::class);
	}

	/**
	 * Set the nonce to use for encrypting/decrypting messages
	 *
	 * @param   string  $nonce  The message nonce
	 *
	 * @return  void
	 *
	 * @since   1.4.0
	 */
	public function setNonce($nonce)
	{
		$this->nonce = $nonce;
	}
}