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Diffstat (limited to 'www/wiki/includes/libs/CryptRand.php')
| -rw-r--r-- | www/wiki/includes/libs/CryptRand.php | 401 |
1 files changed, 401 insertions, 0 deletions
diff --git a/www/wiki/includes/libs/CryptRand.php b/www/wiki/includes/libs/CryptRand.php new file mode 100644 index 00000000..f7702dd3 --- /dev/null +++ b/www/wiki/includes/libs/CryptRand.php @@ -0,0 +1,401 @@ +<?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() { + // $_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 ) { + Wikimedia\suppressWarnings(); + $stat = stat( $file ); + Wikimedia\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 PHP 7's random_bytes + // On Linux, getrandom syscall will be used if available. + // On Windows CryptGenRandom will always be used + // On other platforms, /dev/urandom will be used. + // Avoids polyfills from before php 7.0 + // All error situations will throw Exceptions and or Errors + if ( PHP_VERSION_ID >= 70000 + || ( defined( 'HHVM_VERSION_ID' ) && HHVM_VERSION_ID >= 31101 ) + ) { + $rem = $bytes - strlen( $buffer ); + $buffer .= random_bytes( $rem ); + } + if ( strlen( $buffer ) >= $bytes ) { + $this->strong = true; + } + } + + if ( strlen( $buffer ) < $bytes && function_exists( 'mcrypt_create_iv' ) ) { + // 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. + $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 && function_exists( 'openssl_random_pseudo_bytes' ) ) { + $rem = $bytes - strlen( $buffer ); + $openssl_strong = false; + $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. + Wikimedia\suppressWarnings(); + $urandom = fopen( "/dev/urandom", "rb" ); + Wikimedia\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 ); + } +} |