PhutilOpaqueEnvelope.php
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PhutilOpaqueEnvelope.php
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			<?php

			/**
			* Opaque reference to a string (like a password) that won't put any sensitive
			* data in stack traces, var_dump(), print_r(), error logs, etc. Usage:
			*
			* $envelope = new PhutilOpaqueEnvelope($password);
			* do_stuff($envelope);
			* // ...
			* $password = $envelope->openEnvelope();
			*
			* Any time you're passing sensitive data into a stack, you should obscure it
			* with an envelope to prevent it leaking if something goes wrong.
			*
			* The key for the envelope is stored elsewhere, in
			* @{class:PhutilOpaqueEnvelopeKey}. This prevents it from appearing in
			* any sort of logs related to the envelope, even if the logger is very
			* aggressive.
			*
			* @task envelope Using Opaque Envelopes
			* @task internal Internals
			*/
			final class PhutilOpaqueEnvelope {

			private $value;


			/* -( Using Opaque Envelopes )--------------------------------------------- */


			/**
			* @task envelope
			*/
			public function __construct($string) {
			$this->value = $this->mask($string, PhutilOpaqueEnvelopeKey::getKey());
			}


			/**
			* @task envelope
			*/
			public function openEnvelope() {
			return $this->mask($this->value, PhutilOpaqueEnvelopeKey::getKey());
			}


			/**
			* @task envelope
			*/
			public function __toString() {
			return '<opaque envelope>';
			}


			/* -( Internals )---------------------------------------------------------- */


			/**
			* @task internal
			*/
			private function mask($string, $noise) {
			$result = '';
			for ($ii = 0; $ii < strlen($string); $ii++) {
			$s = $string[$ii];
			$n = $noise[$ii % strlen($noise)];

			$result .= chr(ord($s) ^ ord($n));
			}
			return $result;
			}

			}