--- /dev/null
+<?php
+/**
+ * A static 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.
+ *
+ * @file
+ */
+
+final class MWCryptRand {
+
+ /**
+ * Initialize an initial random state based off of whatever we can find
+ */
+ private static 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 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;
+ }
+
+ /**
+ * Return a rolling random state initially build using data from unstable sources
+ * @return A new weak random state
+ */
+ public static 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 = self::initialRandomState();
+ }
+ // Generate a new random state based on the initial random state or previous
+ // random state by combining it with both the current time and a random value
+ // Simple append/prepend based methods of combining data and a salt have
+ // weaknesses in them, take advantage of the availability of hmac to abuse
+ // it's method of combining data and a key into a hash which is free of
+ // the typical weakness of simple concatenation
+ // Note that in hmac large keys are reduced in size and the key is then
+ // xor-ed to create two separate keys. For this reason we use the smaller
+ // time+rand as the key and the larger state as the data.
+ // We also don't bother passing numbers to mt_rand since you can't make
+ // it generate with any more entropy than it's default max value.
+ $state = self::hmac( $state, microtime() . mt_rand() );
+ return $state;
+ }
+
+ /**
+ * Decide on the best acceptable hash algorithm we have available for hash()
+ * @return String A hash algorithm
+ */
+ private static function hashAlgo() {
+ static $algo = null;
+ if ( !is_null( $algo ) ) {
+ return $algo;
+ }
+
+ $algos = hash_algos();
+ $preference = array( 'whirlpool', 'sha256', 'sha1', 'md5' );
+
+ foreach ( $preference as $algorithm ) {
+ if ( in_array( $algorithm, $algos ) ) {
+ $algo = $algorithm; # assign to static
+ return $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()" );
+ }
+
+ /**
+ * 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
+ */
+ private static function hash( $data ) {
+ return hash( self::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
+ */
+ private static function hmac( $data, $key ) {
+ return hash_hmac( self::hashAlgo(), $data, $key, true );
+ }
+
+
+
+ private static $strong = null;
+
+ /**
+ * Return a boolean indicating whether or not the source used for cryptographic
+ * random bytes generation in the previously run generate* call
+ * was cryptographically strong.
+ *
+ * @return bool Returns true if the source was strong, false if not.
+ */
+ public static function wasStrong() {
+ if ( is_null( self::$strong ) ) {
+ throw new MWException( __METHOD__ . ' called before generation of random data' );
+ }
+ return self::$strong;
+ }
+
+ /**
+ * 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
+ * @return String Raw binary random data
+ */
+ public static function generate( $bytes ) {
+ $bytes = floor( $bytes );
+ static $buffer = '';
+ if ( is_null( self::$strong ) ) {
+ // Set strength to false initially until we know what source data is coming from
+ self::$strong = true;
+ }
+
+ if ( strlen( $buffer ) < $bytes ) {
+ // /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 it doesn't cost anything extra to store that.
+ // We don't have access to the stream's chunk_size, fread maxes out at 8k
+ // so we'll go along with Drupal's decision to read at least 4k
+ if ( $urandom ) {
+ $buffer .= fread( $urandom, max( 1024 * 4, $bytes ) );
+ fclose( $urandom );
+ if ( strlen( $buffer ) >= $bytes ) {
+ // urandom is always strong, set to true if all our data was generated using it
+ self::$strong = true;
+ }
+ }
+ }
+
+ if ( strlen( $buffer ) < $bytes ) {
+ // If available and we failed to read enough data out of urandom 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 ( ( $bytes - strlen( $buffer ) > 0 )
+ && function_exists( 'openssl_random_pseudo_bytes' )
+ && ( !wfIsWindows() || version_compare( PHP_VERSION, '5.3.4', '>=' ) )
+ ) {
+ $buffer .= openssl_random_pseudo_bytes( $bytes - strlen( $buffer ), $openssl_strong );
+ if ( strlen( $buffer ) >= $bytes ) {
+ // openssl tells us if the random source was strong, if some of our data was generated
+ // using it use it's say on whether the randomness is strong
+ self::$strong = !!$openssl_strong;
+ }
+ }
+ }
+
+
+ // If we cannot use or generate enough data from /dev/urandom or openssl
+ // use this loop to generate a good set of pesudo 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.
+ while ( strlen( $buffer ) < $bytes ) {
+ $buffer .= self::hmac( self::randomState(), mt_rand() );
+ // This code is never really cryptographically strong, if we use it
+ // at all, then set strong to false.
+ self::$strong = false;
+ }
+
+ // 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 );
+
+ return $generated;
+ }
+
+ /**
+ * 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
+ * @return String Hexadecimal random data
+ */
+ public static function generateHex( $chars ) {
+ // 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( self::generate( $bytes ) );
+ // 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 );
+ }
+
+}
dépôts / lhc / web / wiklou.git / commitdiff