CryptRand::randomState() - Code Metrics - wikimedia/mediawiki - Measure and Improve Code Quality continuously with Scrutinizer

CryptRand::randomState() A
last analyzed 2016-11-13 17:42 UTC

↳ Parent: CryptRand

Complexity

Conditions	2
Paths	2

Size

Total Lines	14
Code Lines	6

Duplication

Lines	0
Ratio	0 %

Importance

Changes

Metric	Value
cc	2
eloc	6
nc	2
nop	0
dl	0
loc	14
rs	9.4285
c	0
b	0
f	0

<?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.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @author Daniel Friesen
 * @file
 */
use Psr\Log\LoggerInterface;

class CryptRand {
	/**
	 * 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;

	/**
	 * A boolean indicating whether the previous random generation was done using
	 * cryptographically strong random number generator or not.
	 */
	protected $strong = null;

	/**
	 * List of functions to call to generate some random state
	 *
	 * @var callable[]
	 */
	protected $randomFuncs = [];

	/**
	 * List of files to generate some random state from
	 *
	 * @var string[]
	 */
	protected $randomFiles = [];

	/**
	 * @var LoggerInterface
	 */
	protected $logger;

	public function __construct( array $randomFuncs, array $randomFiles, LoggerInterface $logger ) {
		$this->randomFuncs = $randomFuncs;
		$this->randomFiles = $randomFiles;
		$this->logger = $logger;
	}

	/**
	 * Initialize an initial random state based off of whatever we can find
	 * @return string
	 */
	protected function initialRandomState() {
// Bad
class Router
{
    public function generate($path)
    {
        return $_SERVER['HOST'].$path;
    }
}

// Better
class Router
{
    private $host;

    public function __construct($host)
    {
        $this->host = $host;
    }

    public function generate($path)
    {
        return $this->host.$path;
    }
}

class Controller
{
    public function myAction(Request $request)
    {
        // Instead of
        $page = isset($_GET['page']) ? intval($_GET['page']) : 1;

        // Better (assuming you use the Symfony2 request)
        $page = $request->query->get('page', 1);
    }
}
		// $_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 );

		// 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 = $this->randomFiles;

		// We know this file is here so grab some info about ourselves
		$files[] = __FILE__;

		// We must also have a parent folder, and with the usual file structure, a grandparent
		$files[] = __DIR__;
		$files[] = dirname( __DIR__ );

		foreach ( $files as $file ) {
			MediaWiki\suppressWarnings();
			$stat = stat( $file );
			MediaWiki\restoreWarnings();
			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
				$path = realpath( $file );
				if ( $path !== false ) {
					$state .= $path;
				} else {
					$state .= $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 );
		}

		foreach ( $this->randomFuncs as $randomFunc ) {
			$state .= call_user_func( $randomFunc );
		}

		return $state;
	}

	/**
	 * Randomly hash data while mixing in clock drift data for randomness
	 *
	 * @param string $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 ) * MWCryptHash::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 $minIterations 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 = MWCryptHash::hash( $data );

		$this->logger->debug( "Clock drift calculation " .
			"(time-taken=" . ( $timeTaken * 1000 ) . "ms, " .
			"iterations=$iterations, " .
			"time-per-iteration=" . ( $timeTaken / $iterations * 1e6 ) . "us)" );

		return $data;
	}

	/**
	 * Return a rolling random state initially build using data from unstable sources
	 * @return string 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 = MWCryptHash::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;
	}

	/**
	 * 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 function wasStrong() {
		if ( is_null( $this->strong ) ) {
			throw new RuntimeException( __METHOD__ . ' called before generation of random data' );
		}

		return $this->strong;
	}

	/**
	 * Generate a run of (ideally) cryptographically random data and return
	 * it in raw binary form.
	 * You can use CryptRand::wasStrong() if you wish to know if the source used
	 * was cryptographically strong.
	 *
	 * @param int $bytes The number of bytes of random data to generate
	 * @param bool $forceStrong 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 function generate( $bytes, $forceStrong = false ) {

		$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 openbasedir 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' ) ) {
				$rem = $bytes - strlen( $buffer );
				$iv = mcrypt_create_iv( $rem, MCRYPT_DEV_URANDOM );
				if ( $iv === false ) {
					$this->logger->debug( "mcrypt_create_iv returned false." );
				} else {
					$buffer .= $iv;
					$this->logger->debug( "mcrypt_create_iv generated " . strlen( $iv ) .
						" bytes of randomness." );
				}
			}
		}

		if ( strlen( $buffer ) < $bytes ) {
			if ( function_exists( 'openssl_random_pseudo_bytes' ) ) {
				$rem = $bytes - strlen( $buffer );
				$openssl_bytes = openssl_random_pseudo_bytes( $rem, $openssl_strong );
				if ( $openssl_bytes === false ) {
					$this->logger->debug( "openssl_random_pseudo_bytes returned false." );
				} else {
					$buffer .= $openssl_bytes;
					$this->logger->debug( "openssl_random_pseudo_bytes generated " .
						strlen( $openssl_bytes ) . " bytes of " .
						( $openssl_strong ? "strong" : "weak" ) . " randomness." );
				}
				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;
				}
			}
		}

		// 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 )
		) {
			$rem = $bytes - strlen( $buffer );
			if ( !function_exists( 'stream_set_read_buffer' ) && $forceStrong ) {
				$this->logger->debug( "Was forced to read from /dev/urandom " .
					"without control over the buffer size." );
			}
			// /dev/urandom is generally considered the best possible commonly
			// available random source, and is available on most *nix systems.
			MediaWiki\suppressWarnings();
			$urandom = fopen( "/dev/urandom", "rb" );
			MediaWiki\restoreWarnings();

			// 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 );
				$this->logger->debug( "/dev/urandom generated " . strlen( $random_bytes ) .
					" bytes of randomness." );

				if ( strlen( $buffer ) >= $bytes ) {
					// urandom is always strong, set to true if all our data was generated using it
					$this->strong = true;
				}
			} else {
				$this->logger->debug( "/dev/urandom could not be opened." );
			}
		}

		// 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 ) {
			$this->logger->debug( __METHOD__ .
				": Falling back to using a pseudo random state to generate randomness." );
		}
		while ( strlen( $buffer ) < $bytes ) {
			$buffer .= MWCryptHash::hmac( $this->randomState(), strval( mt_rand() ) );
			// This code is never really cryptographically strong, if we use it
			// at all, then set strong to false.
			$this->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 );

		$this->logger->debug( strlen( $buffer ) .
			" bytes of randomness leftover in the buffer." );

		return $generated;
	}

	/**
	 * Generate a run of (ideally) cryptographically random data and return
	 * it in hexadecimal string format.
	 * You can use CryptRand::wasStrong() if you wish to know if the source used
	 * was cryptographically strong.
	 *
	 * @param int $chars The number of hex chars of random data to generate
	 * @param bool $forceStrong 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 function generateHex( $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 );
	}
}


1			<?php
2			/**
3			* A cryptographic random generator class used for generating secret keys
4			*
5			* This is based in part on Drupal code as well as what we used in our own code
6			* prior to introduction of this class.
7			*
8			* This program is free software; you can redistribute it and/or modify
9			* it under the terms of the GNU General Public License as published by
10			* the Free Software Foundation; either version 2 of the License, or
11			* (at your option) any later version.
12			*
13			* This program is distributed in the hope that it will be useful,
14			* but WITHOUT ANY WARRANTY; without even the implied warranty of
15			* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16			* GNU General Public License for more details.
17			*
18			* You should have received a copy of the GNU General Public License along
19			* with this program; if not, write to the Free Software Foundation, Inc.,
20			* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
21			* http://www.gnu.org/copyleft/gpl.html
22			*
23			* @author Daniel Friesen
24			* @file
25			*/
26			use Psr\Log\LoggerInterface;
27
28			class CryptRand {
29			/**
30			* Minimum number of iterations we want to make in our drift calculations.
31			*/
32			const MIN_ITERATIONS = 1000;
33
34			/**
35			* Number of milliseconds we want to spend generating each separate byte
36			* of the final generated bytes.
37			* This is used in combination with the hash length to determine the duration
38			* we should spend doing drift calculations.
39			*/
40			const MSEC_PER_BYTE = 0.5;
41
42			/**
43			* A boolean indicating whether the previous random generation was done using
44			* cryptographically strong random number generator or not.
45			*/
46			protected $strong = null;
47
48			/**
49			* List of functions to call to generate some random state
50			*
51			* @var callable[]
52			*/
53			protected $randomFuncs = [];
54
55			/**
56			* List of files to generate some random state from
57			*
58			* @var string[]
59			*/
60			protected $randomFiles = [];
61
62			/**
63			* @var LoggerInterface
64			*/
65			protected $logger;
66
67			public function __construct( array $randomFuncs, array $randomFiles, LoggerInterface $logger ) {
68			$this->randomFuncs = $randomFuncs;
69			$this->randomFiles = $randomFiles;
70			$this->logger = $logger;
71			}
72
73			/**
74			* Initialize an initial random state based off of whatever we can find
75			* @return string
76			*/
77			protected function initialRandomState() {
			0 ignored issues – show Coding Style introduced 2016-01-16 18:00 UTC by Report Bug Copy Issue Report `initialRandomState` uses the super-global variable `$_SERVER` which is generally not recommended. Instead of super-globals, we recommend to explicitly inject the dependencies of your class. This makes your code less dependent on global state and it becomes generally more testable: // Bad class Router { public function generate($path) { return $_SERVER['HOST'].$path; } } // Better class Router { private $host; public function __construct($host) { $this->host = $host; } public function generate($path) { return $this->host.$path; } } class Controller { public function myAction(Request $request) { // Instead of $page = isset($_GET['page']) ? intval($_GET['page']) : 1; // Better (assuming you use the Symfony2 request) $page = $request->query->get('page', 1); } } Loading history...
78			// $_SERVER contains a variety of unstable user and system specific information
79			// It'll vary a little with each page, and vary even more with separate users
80			// It'll also vary slightly across different machines
81			$state = serialize( $_SERVER );
82
83			// Try to gather a little entropy from the different php rand sources
84			$state .= rand() . uniqid( mt_rand(), true );
85
86			// Include some information about the filesystem's current state in the random state
87			$files = $this->randomFiles;
88
89			// We know this file is here so grab some info about ourselves
90			$files[] = __FILE__;
91
92			// We must also have a parent folder, and with the usual file structure, a grandparent
93			$files[] = __DIR__;
94			$files[] = dirname( __DIR__ );
95
96			foreach ( $files as $file ) {
97			MediaWiki\suppressWarnings();
98			$stat = stat( $file );
99			MediaWiki\restoreWarnings();
100			if ( $stat ) {
101			// stat() duplicates data into numeric and string keys so kill off all the numeric ones
102			foreach ( $stat as $k => $v ) {
103			if ( is_numeric( $k ) ) {
104			unset( $k );
105			}
106			}
107			// The absolute filename itself will differ from install to install so don't leave it out
108			$path = realpath( $file );
109			if ( $path !== false ) {
110			$state .= $path;
111			} else {
112			$state .= $file;
113			}
114			$state .= implode( '', $stat );
115			} else {
116			// The fact that the file isn't there is worth at least a
117			// minuscule amount of entropy.
118			$state .= '0';
119			}
120			}
121
122			// Try and make this a little more unstable by including the varying process
123			// id of the php process we are running inside of if we are able to access it
124			if ( function_exists( 'getmypid' ) ) {
125			$state .= getmypid();
126			}
127
128			// If available try to increase the instability of the data by throwing in
129			// the precise amount of memory that we happen to be using at the moment.
130			if ( function_exists( 'memory_get_usage' ) ) {
131			$state .= memory_get_usage( true );
132			}
133
134			foreach ( $this->randomFuncs as $randomFunc ) {
135			$state .= call_user_func( $randomFunc );
136			}
137
138			return $state;
139			}
140
141			/**
142			* Randomly hash data while mixing in clock drift data for randomness
143			*
144			* @param string $data The data to randomly hash.
145			* @return string The hashed bytes
146			* @author Tim Starling
147			*/
148			protected function driftHash( $data ) {
149			// Minimum number of iterations (to avoid slow operations causing the
150			// loop to gather little entropy)
151			$minIterations = self::MIN_ITERATIONS;
152			// Duration of time to spend doing calculations (in seconds)
153			$duration = ( self::MSEC_PER_BYTE / 1000 ) * MWCryptHash::hashLength();
154			// Create a buffer to use to trigger memory operations
155			$bufLength = 10000000;
156			$buffer = str_repeat( ' ', $bufLength );
157			$bufPos = 0;
158
159			// Iterate for $duration seconds or at least $minIterations number of iterations
160			$iterations = 0;
161			$startTime = microtime( true );
162			$currentTime = $startTime;
163			while ( $iterations < $minIterations \|\| $currentTime - $startTime < $duration ) {
164			// Trigger some memory writing to trigger some bus activity
165			// This may create variance in the time between iterations
166			$bufPos = ( $bufPos + 13 ) % $bufLength;
167			$buffer[$bufPos] = ' ';
168			// Add the drift between this iteration and the last in as entropy
169			$nextTime = microtime( true );
170			$delta = (int)( ( $nextTime - $currentTime ) * 1000000 );
171			$data .= $delta;
172			// Every 100 iterations hash the data and entropy
173			if ( $iterations % 100 === 0 ) {
174			$data = sha1( $data );
175			}
176			$currentTime = $nextTime;
177			$iterations++;
178			}
179			$timeTaken = $currentTime - $startTime;
180			$data = MWCryptHash::hash( $data );
181
182			$this->logger->debug( "Clock drift calculation " .
183			"(time-taken=" . ( $timeTaken * 1000 ) . "ms, " .
184			"iterations=$iterations, " .
185			"time-per-iteration=" . ( $timeTaken / $iterations * 1e6 ) . "us)" );
186
187			return $data;
188			}
189
190			/**
191			* Return a rolling random state initially build using data from unstable sources
192			* @return string A new weak random state
193			*/
194			protected function randomState() {
195			static $state = null;
196			if ( is_null( $state ) ) {
197			// Initialize the state with whatever unstable data we can find
198			// It's important that this data is hashed right afterwards to prevent
199			// it from being leaked into the output stream
200			$state = MWCryptHash::hash( $this->initialRandomState() );
201			}
202			// Generate a new random state based on the initial random state or previous
203			// random state by combining it with clock drift
204			$state = $this->driftHash( $state );
205
206			return $state;
207			}
208
209			/**
210			* Return a boolean indicating whether or not the source used for cryptographic
211			* random bytes generation in the previously run generate* call
212			* was cryptographically strong.
213			*
214			* @return bool Returns true if the source was strong, false if not.
215			*/
216			public function wasStrong() {
217			if ( is_null( $this->strong ) ) {
218			throw new RuntimeException( __METHOD__ . ' called before generation of random data' );
219			}
220
221			return $this->strong;
222			}
223
224			/**
225			* Generate a run of (ideally) cryptographically random data and return
226			* it in raw binary form.
227			* You can use CryptRand::wasStrong() if you wish to know if the source used
228			* was cryptographically strong.
229			*
230			* @param int $bytes The number of bytes of random data to generate
231			* @param bool $forceStrong Pass true if you want generate to prefer cryptographically
232			* strong sources of entropy even if reading from them may steal
233			* more entropy from the system than optimal.
234			* @return string Raw binary random data
235			*/
236			public function generate( $bytes, $forceStrong = false ) {
237
238			$bytes = floor( $bytes );
239			static $buffer = '';
240			if ( is_null( $this->strong ) ) {
241			// Set strength to false initially until we know what source data is coming from
242			$this->strong = true;
243			}
244
245			if ( strlen( $buffer ) < $bytes ) {
246			// If available make use of mcrypt_create_iv URANDOM source to generate randomness
247			// On unix-like systems this reads from /dev/urandom but does it without any buffering
248			// and bypasses openbasedir restrictions, so it's preferable to reading directly
249			// On Windows starting in PHP 5.3.0 Windows' native CryptGenRandom is used to generate
250			// entropy so this is also preferable to just trying to read urandom because it may work
251			// on Windows systems as well.
252			if ( function_exists( 'mcrypt_create_iv' ) ) {
253			$rem = $bytes - strlen( $buffer );
254			$iv = mcrypt_create_iv( $rem, MCRYPT_DEV_URANDOM );
255			if ( $iv === false ) {
256			$this->logger->debug( "mcrypt_create_iv returned false." );
257			} else {
258			$buffer .= $iv;
259			$this->logger->debug( "mcrypt_create_iv generated " . strlen( $iv ) .
260			" bytes of randomness." );
261			}
262			}
263			}
264
265			if ( strlen( $buffer ) < $bytes ) {
266			if ( function_exists( 'openssl_random_pseudo_bytes' ) ) {
267			$rem = $bytes - strlen( $buffer );
268			$openssl_bytes = openssl_random_pseudo_bytes( $rem, $openssl_strong );
269			if ( $openssl_bytes === false ) {
270			$this->logger->debug( "openssl_random_pseudo_bytes returned false." );
271			} else {
272			$buffer .= $openssl_bytes;
273			$this->logger->debug( "openssl_random_pseudo_bytes generated " .
274			strlen( $openssl_bytes ) . " bytes of " .
275			( $openssl_strong ? "strong" : "weak" ) . " randomness." );
276			}
277			if ( strlen( $buffer ) >= $bytes ) {
278			// openssl tells us if the random source was strong, if some of our data was generated
279			// using it use it's say on whether the randomness is strong
280			$this->strong = !!$openssl_strong;
281			}
282			}
283			}
284
285			// Only read from urandom if we can control the buffer size or were passed forceStrong
286			if ( strlen( $buffer ) < $bytes &&
287			( function_exists( 'stream_set_read_buffer' ) \|\| $forceStrong )
288			) {
289			$rem = $bytes - strlen( $buffer );
290			if ( !function_exists( 'stream_set_read_buffer' ) && $forceStrong ) {
291			$this->logger->debug( "Was forced to read from /dev/urandom " .
292			"without control over the buffer size." );
293			}
294			// /dev/urandom is generally considered the best possible commonly
295			// available random source, and is available on most *nix systems.
296			MediaWiki\suppressWarnings();
297			$urandom = fopen( "/dev/urandom", "rb" );
298			MediaWiki\restoreWarnings();
299
300			// Attempt to read all our random data from urandom
301			// php's fread always does buffered reads based on the stream's chunk_size
302			// so in reality it will usually read more than the amount of data we're
303			// asked for and not storing that risks depleting the system's random pool.
304			// If stream_set_read_buffer is available set the chunk_size to the amount
305			// of data we need. Otherwise read 8k, php's default chunk_size.
306			if ( $urandom ) {
307			// php's default chunk_size is 8k
308			$chunk_size = 1024 * 8;
309			if ( function_exists( 'stream_set_read_buffer' ) ) {
310			// If possible set the chunk_size to the amount of data we need
311			stream_set_read_buffer( $urandom, $rem );
312			$chunk_size = $rem;
313			}
314			$random_bytes = fread( $urandom, max( $chunk_size, $rem ) );
315			$buffer .= $random_bytes;
316			fclose( $urandom );
317			$this->logger->debug( "/dev/urandom generated " . strlen( $random_bytes ) .
318			" bytes of randomness." );
319
320			if ( strlen( $buffer ) >= $bytes ) {
321			// urandom is always strong, set to true if all our data was generated using it
322			$this->strong = true;
323			}
324			} else {
325			$this->logger->debug( "/dev/urandom could not be opened." );
326			}
327			}
328
329			// If we cannot use or generate enough data from a secure source
330			// use this loop to generate a good set of pseudo random data.
331			// This works by initializing a random state using a pile of unstable data
332			// and continually shoving it through a hash along with a variable salt.
333			// We hash the random state with more salt to avoid the state from leaking
334			// out and being used to predict the /randomness/ that follows.
335			if ( strlen( $buffer ) < $bytes ) {
336			$this->logger->debug( __METHOD__ .
337			": Falling back to using a pseudo random state to generate randomness." );
338			}
339			while ( strlen( $buffer ) < $bytes ) {
340			$buffer .= MWCryptHash::hmac( $this->randomState(), strval( mt_rand() ) );
341			// This code is never really cryptographically strong, if we use it
342			// at all, then set strong to false.
343			$this->strong = false;
344			}
345
346			// Once the buffer has been filled up with enough random data to fulfill
347			// the request shift off enough data to handle the request and leave the
348			// unused portion left inside the buffer for the next request for random data
349			$generated = substr( $buffer, 0, $bytes );
350			$buffer = substr( $buffer, $bytes );
351
352			$this->logger->debug( strlen( $buffer ) .
353			" bytes of randomness leftover in the buffer." );
354
355			return $generated;
356			}
357
358			/**
359			* Generate a run of (ideally) cryptographically random data and return
360			* it in hexadecimal string format.
361			* You can use CryptRand::wasStrong() if you wish to know if the source used
362			* was cryptographically strong.
363			*
364			* @param int $chars The number of hex chars of random data to generate
365			* @param bool $forceStrong Pass true if you want generate to prefer cryptographically
366			* strong sources of entropy even if reading from them may steal
367			* more entropy from the system than optimal.
368			* @return string Hexadecimal random data
369			*/
370			public function generateHex( $chars, $forceStrong = false ) {
371			// hex strings are 2x the length of raw binary so we divide the length in half
372			// odd numbers will result in a .5 that leads the generate() being 1 character
373			// short, so we use ceil() to ensure that we always have enough bytes
374			$bytes = ceil( $chars / 2 );
375			// Generate the data and then convert it to a hex string
376			$hex = bin2hex( $this->generate( $bytes, $forceStrong ) );
377
378			// A bit of paranoia here, the caller asked for a specific length of string
379			// here, and it's possible (eg when given an odd number) that we may actually
380			// have at least 1 char more than they asked for. Just in case they made this
381			// call intending to insert it into a database that does truncation we don't
382			// want to give them too much and end up with their database and their live
383			// code having two different values because part of what we gave them is truncated
384			// hence, we strip out any run of characters longer than what we were asked for.
385			return substr( $hex, 0, $chars );
386			}
387			}
388

wikimedia / mediawiki

CryptRand::randomState() A last analyzed 2016-11-13 17:42 UTC

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CryptRand::randomState() A
last analyzed 2016-11-13 17:42 UTC