https://www.mediawiki.org/wiki/Special:Code/MediaWiki/111964
Revision: 111964
Author: dantman
Date: 2012-02-20 21:22:52 +0000 (Mon, 20 Feb 2012)
Log Message:
-----------
Commit a new cryptographic random generator class for use in MediaWiki.
Waiting for it to be reviewed before actually making use of it inside code and
adding a RELEASE-NOTES entry.
Modified Paths:
--------------
trunk/phase3/includes/AutoLoader.php
Added Paths:
-----------
trunk/phase3/includes/CryptRand.php
Modified: trunk/phase3/includes/AutoLoader.php
===================================================================
--- trunk/phase3/includes/AutoLoader.php 2012-02-20 21:14:12 UTC (rev
111963)
+++ trunk/phase3/includes/AutoLoader.php 2012-02-20 21:22:52 UTC (rev
111964)
@@ -49,6 +49,7 @@
'ConfEditorToken' => 'includes/ConfEditor.php',
'Cookie' => 'includes/Cookie.php',
'CookieJar' => 'includes/Cookie.php',
+ 'MWCryptRand' => 'includes/CryptRand.php',
'CurlHttpRequest' => 'includes/HttpFunctions.php',
// 'DBDataObject' => 'includes/DBDataObject.php',
// 'DBTable' => 'includes/DBTable.php',
Added: trunk/phase3/includes/CryptRand.php
===================================================================
--- trunk/phase3/includes/CryptRand.php (rev 0)
+++ trunk/phase3/includes/CryptRand.php 2012-02-20 21:22:52 UTC (rev 111964)
@@ -0,0 +1,252 @@
+<?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 );
+ }
+
+}
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