GCM\Cipher\AES\AESCipher

Complexity

Total Complexity

7

Size/Duplication

Total Lines	86
Duplicated Lines	0 %

Coupling/Cohesion

Components	1
Dependencies	0

Test Coverage

Coverage

100%

Importance

Changes

0

4 Methods

Rating	Name	Duplication	Size	Complexity
	_cipherName()	0	1	?
	_keySize()	0	1	?
A	fromKeyLength()	0	10	2
A	encrypt()	0	15	3

<?php

declare(strict_types = 1);

namespace Sop\GCM\Cipher\AES;

use Sop\GCM\Cipher\Cipher;

/**
 * Base class for AES ciphers for the GCM.
 */
abstract class AESCipher implements Cipher
{
    /**
     * Mapping from key size in bits to AES cipher implementation class name.
     *
     * @internal
     *
     * @var array
     */
    const MAP_KEYSIZE_TO_CLS = array(
        /* @formatter:off */
        128 => AES128Cipher::class,
        192 => AES192Cipher::class,
        256 => AES256Cipher::class
        /* @formatter:on */
    );
    
    /**
     * Get the cipher method name recognized by OpenSSL.
     *
     * @return string
     */
    abstract protected function _cipherName(): string;
    
    /**
     * Get the key size in bytes.
     *
     * @return int
     */
    abstract protected function _keySize(): int;
    
    /**
     * Get AES cipher instance by key length.
     *
     * @param int $len Key length in bytes
     * @throws \UnexpectedValueException
     * @return self
     */
    public static function fromKeyLength(int $len): self
    {
        $bits = $len << 3;
        if (!array_key_exists($bits, self::MAP_KEYSIZE_TO_CLS)) {
            throw new \UnexpectedValueException(
                "No AES implementation for $bits-bit key size.");
        }
        $cls = self::MAP_KEYSIZE_TO_CLS[$bits];
        return new $cls();
    }
    
    /**
     *
     * @see \Sop\GCM\Cipher\Cipher::encrypt()
     * @throws \UnexpectedValueException If key size is incorrect
     * @throws \RuntimeException For generic errors
     * @return string
     */
    public function encrypt(string $data, string $key): string
    {
        $key_size = $this->_keySize();
        if (strlen($key) != $key_size) {
            throw new \UnexpectedValueException(
                "Key size must be $key_size bytes.");
        }
        $result = openssl_encrypt($data, $this->_cipherName(), $key,
            OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING);
        if (false === $result) {
            throw new \RuntimeException(
                "openssl_encrypt() failed: " . self::_getLastOpenSSLError());
        }
        return $result;
    }
    
    /**
     * Get latest OpenSSL error message.
     *
     * @return string
     */
    protected static function _getLastOpenSSLError(): string
    {
        $msg = '';
        while (false !== ($err = openssl_error_string())) {
            $msg = $err;
        }
        return $msg;
    }
}