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+<?php
+/**
+ * A cryptographic random generator class used for generating secret keys
+ *
+ * This is based in part on Drupal code as well as what we used in our own code
+ * prior to introduction of this class.
+ *
+ * @author Daniel Friesen
+ * @file
+ */
+
+class MWCryptRand {
+
+ /**
+ * Minimum number of iterations we want to make in our drift calculations.
+ */
+ const MIN_ITERATIONS = 1000;
+
+ /**
+ * Number of milliseconds we want to spend generating each separate byte
+ * of the final generated bytes.
+ * This is used in combination with the hash length to determine the duration
+ * we should spend doing drift calculations.
+ */
+ const MSEC_PER_BYTE = 0.5;
+
+ /**
+ * Singleton instance for public use
+ */
+ protected static $singleton = null;
+
+ /**
+ * The hash algorithm being used
+ */
+ protected $algo = null;
+
+ /**
+ * The number of bytes outputted by the hash algorithm
+ */
+ protected $hashLength = null;
+
+ /**
+ * A boolean indicating whether the previous random generation was done using
+ * cryptographically strong random number generator or not.
+ */
+ protected $strong = null;
+
+ /**
+ * Initialize an initial random state based off of whatever we can find
+ */
+ protected function initialRandomState() {
+ // $_SERVER contains a variety of unstable user and system specific information
+ // It'll vary a little with each page, and vary even more with separate users
+ // It'll also vary slightly across different machines
+ $state = serialize( $_SERVER );
+
+ // To try and vary the system information of the state a bit more
+ // by including the system's hostname into the state
+ $state .= wfHostname();
+
+ // Try to gather a little entropy from the different php rand sources
+ $state .= rand() . uniqid( mt_rand(), true );
+
+ // Include some information about the filesystem's current state in the random state
+ $files = array();
+ // We know this file is here so grab some info about ourself
+ $files[] = __FILE__;
+ // The config file is likely the most often edited file we know should be around
+ // so if the constant with it's location is defined include it's stat info into the state
+ if ( defined( 'MW_CONFIG_FILE' ) ) {
+ $files[] = MW_CONFIG_FILE;
+ }
+ foreach ( $files as $file ) {
+ wfSuppressWarnings();
+ $stat = stat( $file );
+ wfRestoreWarnings();
+ if ( $stat ) {
+ // stat() duplicates data into numeric and string keys so kill off all the numeric ones
+ foreach ( $stat as $k => $v ) {
+ if ( is_numeric( $k ) ) {
+ unset( $k );
+ }
+ }
+ // The absolute filename itself will differ from install to install so don't leave it out
+ $state .= realpath( $file );
+ $state .= implode( '', $stat );
+ } else {
+ // The fact that the file isn't there is worth at least a
+ // minuscule amount of entropy.
+ $state .= '0';
+ }
+ }
+
+ // Try and make this a little more unstable by including the varying process
+ // id of the php process we are running inside of if we are able to access it
+ if ( function_exists( 'getmypid' ) ) {
+ $state .= getmypid();
+ }
+
+ // If available try to increase the instability of the data by throwing in
+ // the precise amount of memory that we happen to be using at the moment.
+ if ( function_exists( 'memory_get_usage' ) ) {
+ $state .= memory_get_usage( true );
+ }
+
+ // It's mostly worthless but throw the wiki's id into the data for a little more variance
+ $state .= wfWikiID();
+
+ // If we have a secret key or proxy key set then throw it into the state as well
+ global $wgSecretKey, $wgProxyKey;
+ if ( $wgSecretKey ) {
+ $state .= $wgSecretKey;
+ } elseif ( $wgProxyKey ) {
+ $state .= $wgProxyKey;
+ }
+
+ return $state;
+ }
+
+ /**
+ * Randomly hash data while mixing in clock drift data for randomness
+ *
+ * @param $data The data to randomly hash.
+ * @return String The hashed bytes
+ * @author Tim Starling
+ */
+ protected function driftHash( $data ) {
+ // Minimum number of iterations (to avoid slow operations causing the loop to gather little entropy)
+ $minIterations = self::MIN_ITERATIONS;
+ // Duration of time to spend doing calculations (in seconds)
+ $duration = ( self::MSEC_PER_BYTE / 1000 ) * $this->hashLength();
+ // Create a buffer to use to trigger memory operations
+ $bufLength = 10000000;
+ $buffer = str_repeat( ' ', $bufLength );
+ $bufPos = 0;
+
+ // Iterate for $duration seconds or at least $minIerations number of iterations
+ $iterations = 0;
+ $startTime = microtime( true );
+ $currentTime = $startTime;
+ while ( $iterations < $minIterations || $currentTime - $startTime < $duration ) {
+ // Trigger some memory writing to trigger some bus activity
+ // This may create variance in the time between iterations
+ $bufPos = ( $bufPos + 13 ) % $bufLength;
+ $buffer[$bufPos] = ' ';
+ // Add the drift between this iteration and the last in as entropy
+ $nextTime = microtime( true );
+ $delta = (int)( ( $nextTime - $currentTime ) * 1000000 );
+ $data .= $delta;
+ // Every 100 iterations hash the data and entropy
+ if ( $iterations % 100 === 0 ) {
+ $data = sha1( $data );
+ }
+ $currentTime = $nextTime;
+ $iterations++;
+ }
+ $timeTaken = $currentTime - $startTime;
+ $data = $this->hash( $data );
+
+ wfDebug( __METHOD__ . ": Clock drift calculation " .
+ "(time-taken=" . ( $timeTaken * 1000 ) . "ms, " .
+ "iterations=$iterations, " .
+ "time-per-iteration=" . ( $timeTaken / $iterations * 1e6 ) . "us)\n" );
+ return $data;
+ }
+
+ /**
+ * Return a rolling random state initially build using data from unstable sources
+ * @return A new weak random state
+ */
+ protected function randomState() {
+ static $state = null;
+ if ( is_null( $state ) ) {
+ // Initialize the state with whatever unstable data we can find
+ // It's important that this data is hashed right afterwards to prevent
+ // it from being leaked into the output stream
+ $state = $this->hash( $this->initialRandomState() );
+ }
+ // Generate a new random state based on the initial random state or previous
+ // random state by combining it with clock drift
+ $state = $this->driftHash( $state );
+ return $state;
+ }
+
+ /**
+ * Decide on the best acceptable hash algorithm we have available for hash()
+ * @return String A hash algorithm
+ */
+ protected function hashAlgo() {
+ if ( !is_null( $this->algo ) ) {
+ return $this->algo;
+ }
+
+ $algos = hash_algos();
+ $preference = array( 'whirlpool', 'sha256', 'sha1', 'md5' );
+
+ foreach ( $preference as $algorithm ) {
+ if ( in_array( $algorithm, $algos ) ) {
+ $this->algo = $algorithm;
+ wfDebug( __METHOD__ . ": Using the {$this->algo} hash algorithm.\n" );
+ return $this->algo;
+ }
+ }
+
+ // We only reach here if no acceptable hash is found in the list, this should
+ // be a technical impossibility since most of php's hash list is fixed and
+ // some of the ones we list are available as their own native functions
+ // But since we already require at least 5.2 and hash() was default in
+ // 5.1.2 we don't bother falling back to methods like sha1 and md5.
+ throw new MWException( "Could not find an acceptable hashing function in hash_algos()" );
+ }
+
+ /**
+ * Return the byte-length output of the hash algorithm we are
+ * using in self::hash and self::hmac.
+ *
+ * @return int Number of bytes the hash outputs
+ */
+ protected function hashLength() {
+ if ( is_null( $this->hashLength ) ) {
+ $this->hashLength = strlen( $this->hash( '' ) );
+ }
+ return $this->hashLength;
+ }
+
+ /**
+ * Generate an acceptably unstable one-way-hash of some text
+ * making use of the best hash algorithm that we have available.
+ *
+ * @return String A raw hash of the data
+ */
+ protected function hash( $data ) {
+ return hash( $this->hashAlgo(), $data, true );
+ }
+
+ /**
+ * Generate an acceptably unstable one-way-hmac of some text
+ * making use of the best hash algorithm that we have available.
+ *
+ * @return String A raw hash of the data
+ */
+ protected function hmac( $data, $key ) {
+ return hash_hmac( $this->hashAlgo(), $data, $key, true );
+ }
+
+ /**
+ * @see self::wasStrong()
+ */
+ public function realWasStrong() {
+ if ( is_null( $this->strong ) ) {
+ throw new MWException( __METHOD__ . ' called before generation of random data' );
+ }
+ return $this->strong;
+ }
+
+ /**
+ * @see self::generate()
+ */
+ public function realGenerate( $bytes, $forceStrong = false ) {
+ wfProfileIn( __METHOD__ );
+
+ wfDebug( __METHOD__ . ": Generating cryptographic random bytes for " . wfGetAllCallers( 5 ) . "\n" );
+
+ $bytes = floor( $bytes );
+ static $buffer = '';
+ if ( is_null( $this->strong ) ) {
+ // Set strength to false initially until we know what source data is coming from
+ $this->strong = true;
+ }
+
+ if ( strlen( $buffer ) < $bytes ) {
+ // If available make use of mcrypt_create_iv URANDOM source to generate randomness
+ // On unix-like systems this reads from /dev/urandom but does it without any buffering
+ // and bypasses openbasdir restrictions so it's preferable to reading directly
+ // On Windows starting in PHP 5.3.0 Windows' native CryptGenRandom is used to generate
+ // entropy so this is also preferable to just trying to read urandom because it may work
+ // on Windows systems as well.
+ if ( function_exists( 'mcrypt_create_iv' ) ) {
+ wfProfileIn( __METHOD__ . '-mcrypt' );
+ $rem = $bytes - strlen( $buffer );
+ $iv = mcrypt_create_iv( $rem, MCRYPT_DEV_URANDOM );
+ if ( $iv === false ) {
+ wfDebug( __METHOD__ . ": mcrypt_create_iv returned false.\n" );
+ } else {
+ $bytes .= $iv;
+ wfDebug( __METHOD__ . ": mcrypt_create_iv generated " . strlen( $iv ) . " bytes of randomness.\n" );
+ }
+ wfProfileOut( __METHOD__ . '-mcrypt' );
+ }
+ }
+
+ if ( strlen( $buffer ) < $bytes ) {
+ // If available make use of openssl's random_pesudo_bytes method to attempt to generate randomness.
+ // However don't do this on Windows with PHP < 5.3.4 due to a bug:
+ // http://stackoverflow.com/questions/1940168/openssl-random-pseudo-bytes-is-slow-php
+ if ( function_exists( 'openssl_random_pseudo_bytes' )
+ && ( !wfIsWindows() || version_compare( PHP_VERSION, '5.3.4', '>=' ) )
+ ) {
+ wfProfileIn( __METHOD__ . '-openssl' );
+ $rem = $bytes - strlen( $buffer );
+ $openssl_bytes = openssl_random_pseudo_bytes( $rem, $openssl_strong );
+ if ( $openssl_bytes === false ) {
+ wfDebug( __METHOD__ . ": openssl_random_pseudo_bytes returned false.\n" );
+ } else {
+ $buffer .= $openssl_bytes;
+ wfDebug( __METHOD__ . ": openssl_random_pseudo_bytes generated " . strlen( $openssl_bytes ) . " bytes of " . ( $openssl_strong ? "strong" : "weak" ) . " randomness.\n" );
+ }
+ if ( strlen( $buffer ) >= $bytes ) {
+ // openssl tells us if the random source was strong, if some of our data was generated
+ // using it use it's say on whether the randomness is strong
+ $this->strong = !!$openssl_strong;
+ }
+ wfProfileOut( __METHOD__ . '-openssl' );
+ }
+ }
+
+ // Only read from urandom if we can control the buffer size or were passed forceStrong
+ if ( strlen( $buffer ) < $bytes && ( function_exists( 'stream_set_read_buffer' ) || $forceStrong ) ) {
+ wfProfileIn( __METHOD__ . '-fopen-urandom' );
+ $rem = $bytes - strlen( $buffer );
+ if ( !function_exists( 'stream_set_read_buffer' ) && $forceStrong ) {
+ wfDebug( __METHOD__ . ": Was forced to read from /dev/urandom without control over the buffer size.\n" );
+ }
+ // /dev/urandom is generally considered the best possible commonly
+ // available random source, and is available on most *nix systems.
+ wfSuppressWarnings();
+ $urandom = fopen( "/dev/urandom", "rb" );
+ wfRestoreWarnings();
+
+ // Attempt to read all our random data from urandom
+ // php's fread always does buffered reads based on the stream's chunk_size
+ // so in reality it will usually read more than the amount of data we're
+ // asked for and not storing that risks depleting the system's random pool.
+ // If stream_set_read_buffer is available set the chunk_size to the amount
+ // of data we need. Otherwise read 8k, php's default chunk_size.
+ if ( $urandom ) {
+ // php's default chunk_size is 8k
+ $chunk_size = 1024 * 8;
+ if ( function_exists( 'stream_set_read_buffer' ) ) {
+ // If possible set the chunk_size to the amount of data we need
+ stream_set_read_buffer( $urandom, $rem );
+ $chunk_size = $rem;
+ }
+ $random_bytes = fread( $urandom, max( $chunk_size, $rem ) );
+ $buffer .= $random_bytes;
+ fclose( $urandom );
+ wfDebug( __METHOD__ . ": /dev/urandom generated " . strlen( $random_bytes ) . " bytes of randomness.\n" );
+ if ( strlen( $buffer ) >= $bytes ) {
+ // urandom is always strong, set to true if all our data was generated using it
+ $this->strong = true;
+ }
+ } else {
+ wfDebug( __METHOD__ . ": /dev/urandom could not be opened.\n" );
+ }
+ wfProfileOut( __METHOD__ . '-fopen-urandom' );
+ }
+
+ // If we cannot use or generate enough data from a secure source
+ // use this loop to generate a good set of pseudo random data.
+ // This works by initializing a random state using a pile of unstable data
+ // and continually shoving it through a hash along with a variable salt.
+ // We hash the random state with more salt to avoid the state from leaking
+ // out and being used to predict the /randomness/ that follows.
+ if ( strlen( $buffer ) < $bytes ) {
+ wfDebug( __METHOD__ . ": Falling back to using a pseudo random state to generate randomness.\n" );
+ }
+ while ( strlen( $buffer ) < $bytes ) {
+ wfProfileIn( __METHOD__ . '-fallback' );
+ $buffer .= $this->hmac( $this->randomState(), mt_rand() );
+ // This code is never really cryptographically strong, if we use it
+ // at all, then set strong to false.
+ $this->strong = false;
+ wfProfileOut( __METHOD__ . '-fallback' );
+ }
+
+ // Once the buffer has been filled up with enough random data to fulfill
+ // the request shift off enough data to handle the request and leave the
+ // unused portion left inside the buffer for the next request for random data
+ $generated = substr( $buffer, 0, $bytes );
+ $buffer = substr( $buffer, $bytes );
+
+ wfDebug( __METHOD__ . ": " . strlen( $buffer ) . " bytes of randomness leftover in the buffer.\n" );
+
+ wfProfileOut( __METHOD__ );
+ return $generated;
+ }
+
+ /**
+ * @see self::generateHex()
+ */
+ public function realGenerateHex( $chars, $forceStrong = false ) {
+ // hex strings are 2x the length of raw binary so we divide the length in half
+ // odd numbers will result in a .5 that leads the generate() being 1 character
+ // short, so we use ceil() to ensure that we always have enough bytes
+ $bytes = ceil( $chars / 2 );
+ // Generate the data and then convert it to a hex string
+ $hex = bin2hex( $this->generate( $bytes, $forceStrong ) );
+ // A bit of paranoia here, the caller asked for a specific length of string
+ // here, and it's possible (eg when given an odd number) that we may actually
+ // have at least 1 char more than they asked for. Just in case they made this
+ // call intending to insert it into a database that does truncation we don't
+ // want to give them too much and end up with their database and their live
+ // code having two different values because part of what we gave them is truncated
+ // hence, we strip out any run of characters longer than what we were asked for.
+ return substr( $hex, 0, $chars );
+ }
+
+ /** Publicly exposed static methods **/
+
+ /**
+ * Return a singleton instance of MWCryptRand
+ */
+ protected static function singleton() {
+ if ( is_null( self::$singleton ) ) {
+ self::$singleton = new self;
+ }
+ return self::$singleton;
+ }
+
+ /**
+ * Return a boolean indicating whether or not the source used for cryptographic
+ * random bytes generation in the previously run generate* call
+ * was cryptographically strong.
+ *
+ * @return bool Returns true if the source was strong, false if not.
+ */
+ public static function wasStrong() {
+ return self::singleton()->realWasStrong();
+ }
+
+ /**
+ * Generate a run of (ideally) cryptographically random data and return
+ * it in raw binary form.
+ * You can use MWCryptRand::wasStrong() if you wish to know if the source used
+ * was cryptographically strong.
+ *
+ * @param $bytes int the number of bytes of random data to generate
+ * @param $forceStrong bool Pass true if you want generate to prefer cryptographically
+ * strong sources of entropy even if reading from them may steal
+ * more entropy from the system than optimal.
+ * @return String Raw binary random data
+ */
+ public static function generate( $bytes, $forceStrong = false ) {
+ return self::singleton()->realGenerate( $bytes, $forceStrong );
+ }
+
+ /**
+ * Generate a run of (ideally) cryptographically random data and return
+ * it in hexadecimal string format.
+ * You can use MWCryptRand::wasStrong() if you wish to know if the source used
+ * was cryptographically strong.
+ *
+ * @param $chars int the number of hex chars of random data to generate
+ * @param $forceStrong bool Pass true if you want generate to prefer cryptographically
+ * strong sources of entropy even if reading from them may steal
+ * more entropy from the system than optimal.
+ * @return String Hexadecimal random data
+ */
+ public static function generateHex( $chars, $forceStrong = false ) {
+ return self::singleton()->realGenerateHex( $chars, $forceStrong );
+ }
+
+}
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