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<?php
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namespace Aws\Crypto\Polyfill;
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/**
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 * Class Key
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 *
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 * Wraps a string to keep it hidden from stack traces.
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 */
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class Key
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{
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    /**
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     * @var string $internalString
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     */
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    private $internalString;
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    /**
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     * Hide contents of
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     *
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     * @return array
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     */
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    public function __debugInfo()
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    {
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        return [];
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    }
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    /**
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     * Key constructor.
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     * @param string $str
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     */
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    public function __construct($str)
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    {
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        $this->internalString = $str;
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    }
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    /**
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     * Defense in depth:
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     *
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     * PHP 7.2 includes the Sodium cryptography library, which (among other things)
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     * exposes a function called sodium_memzero() that we can use to zero-fill strings
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     * to minimize the risk of sensitive cryptographic materials persisting in memory.
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     *
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     * If this function is not available, we XOR the string in-place with itself as a
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     * best-effort attempt.
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     */
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    public function __destruct()
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    {
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        if (extension_loaded('sodium') && function_exists('sodium_memzero')) {
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            try {
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                \sodium_memzero($this->internalString);
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            } catch (\SodiumException $ex) {
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                // This is a best effort, but does not provide the same guarantees as sodium_memzero():
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                $this->internalString ^= $this->internalString;
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            }
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        }
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    }
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    /**
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     * @return string
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     */
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    public function get()
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    {
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        return $this->internalString;
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    }
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    /**
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     * @return int
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     */
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    public function length()
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    {
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        if (\is_callable('\\mb_strlen')) {
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            return (int) \mb_strlen($this->internalString, '8bit');
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        }
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        return (int) \strlen($this->internalString);
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    }
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}