420 lines
12 KiB
JavaScript
420 lines
12 KiB
JavaScript
/**
|
|
* A javascript implementation of a cryptographically-secure
|
|
* Pseudo Random Number Generator (PRNG). The Fortuna algorithm is followed
|
|
* here though the use of SHA-256 is not enforced; when generating an
|
|
* a PRNG context, the hashing algorithm and block cipher used for
|
|
* the generator are specified via a plugin.
|
|
*
|
|
* @author Dave Longley
|
|
*
|
|
* Copyright (c) 2010-2014 Digital Bazaar, Inc.
|
|
*/
|
|
var forge = require('./forge');
|
|
require('./util');
|
|
|
|
var _crypto = null;
|
|
if(forge.util.isNodejs && !forge.options.usePureJavaScript &&
|
|
!process.versions['node-webkit']) {
|
|
_crypto = require('crypto');
|
|
}
|
|
|
|
/* PRNG API */
|
|
var prng = module.exports = forge.prng = forge.prng || {};
|
|
|
|
/**
|
|
* Creates a new PRNG context.
|
|
*
|
|
* A PRNG plugin must be passed in that will provide:
|
|
*
|
|
* 1. A function that initializes the key and seed of a PRNG context. It
|
|
* will be given a 16 byte key and a 16 byte seed. Any key expansion
|
|
* or transformation of the seed from a byte string into an array of
|
|
* integers (or similar) should be performed.
|
|
* 2. The cryptographic function used by the generator. It takes a key and
|
|
* a seed.
|
|
* 3. A seed increment function. It takes the seed and returns seed + 1.
|
|
* 4. An api to create a message digest.
|
|
*
|
|
* For an example, see random.js.
|
|
*
|
|
* @param plugin the PRNG plugin to use.
|
|
*/
|
|
prng.create = function(plugin) {
|
|
var ctx = {
|
|
plugin: plugin,
|
|
key: null,
|
|
seed: null,
|
|
time: null,
|
|
// number of reseeds so far
|
|
reseeds: 0,
|
|
// amount of data generated so far
|
|
generated: 0,
|
|
// no initial key bytes
|
|
keyBytes: ''
|
|
};
|
|
|
|
// create 32 entropy pools (each is a message digest)
|
|
var md = plugin.md;
|
|
var pools = new Array(32);
|
|
for(var i = 0; i < 32; ++i) {
|
|
pools[i] = md.create();
|
|
}
|
|
ctx.pools = pools;
|
|
|
|
// entropy pools are written to cyclically, starting at index 0
|
|
ctx.pool = 0;
|
|
|
|
/**
|
|
* Generates random bytes. The bytes may be generated synchronously or
|
|
* asynchronously. Web workers must use the asynchronous interface or
|
|
* else the behavior is undefined.
|
|
*
|
|
* @param count the number of random bytes to generate.
|
|
* @param [callback(err, bytes)] called once the operation completes.
|
|
*
|
|
* @return count random bytes as a string.
|
|
*/
|
|
ctx.generate = function(count, callback) {
|
|
// do synchronously
|
|
if(!callback) {
|
|
return ctx.generateSync(count);
|
|
}
|
|
|
|
// simple generator using counter-based CBC
|
|
var cipher = ctx.plugin.cipher;
|
|
var increment = ctx.plugin.increment;
|
|
var formatKey = ctx.plugin.formatKey;
|
|
var formatSeed = ctx.plugin.formatSeed;
|
|
var b = forge.util.createBuffer();
|
|
|
|
// paranoid deviation from Fortuna:
|
|
// reset key for every request to protect previously
|
|
// generated random bytes should the key be discovered;
|
|
// there is no 100ms based reseeding because of this
|
|
// forced reseed for every `generate` call
|
|
ctx.key = null;
|
|
|
|
generate();
|
|
|
|
function generate(err) {
|
|
if(err) {
|
|
return callback(err);
|
|
}
|
|
|
|
// sufficient bytes generated
|
|
if(b.length() >= count) {
|
|
return callback(null, b.getBytes(count));
|
|
}
|
|
|
|
// if amount of data generated is greater than 1 MiB, trigger reseed
|
|
if(ctx.generated > 0xfffff) {
|
|
ctx.key = null;
|
|
}
|
|
|
|
if(ctx.key === null) {
|
|
// prevent stack overflow
|
|
return forge.util.nextTick(function() {
|
|
_reseed(generate);
|
|
});
|
|
}
|
|
|
|
// generate the random bytes
|
|
var bytes = cipher(ctx.key, ctx.seed);
|
|
ctx.generated += bytes.length;
|
|
b.putBytes(bytes);
|
|
|
|
// generate bytes for a new key and seed
|
|
ctx.key = formatKey(cipher(ctx.key, increment(ctx.seed)));
|
|
ctx.seed = formatSeed(cipher(ctx.key, ctx.seed));
|
|
|
|
forge.util.setImmediate(generate);
|
|
}
|
|
};
|
|
|
|
/**
|
|
* Generates random bytes synchronously.
|
|
*
|
|
* @param count the number of random bytes to generate.
|
|
*
|
|
* @return count random bytes as a string.
|
|
*/
|
|
ctx.generateSync = function(count) {
|
|
// simple generator using counter-based CBC
|
|
var cipher = ctx.plugin.cipher;
|
|
var increment = ctx.plugin.increment;
|
|
var formatKey = ctx.plugin.formatKey;
|
|
var formatSeed = ctx.plugin.formatSeed;
|
|
|
|
// paranoid deviation from Fortuna:
|
|
// reset key for every request to protect previously
|
|
// generated random bytes should the key be discovered;
|
|
// there is no 100ms based reseeding because of this
|
|
// forced reseed for every `generateSync` call
|
|
ctx.key = null;
|
|
|
|
var b = forge.util.createBuffer();
|
|
while(b.length() < count) {
|
|
// if amount of data generated is greater than 1 MiB, trigger reseed
|
|
if(ctx.generated > 0xfffff) {
|
|
ctx.key = null;
|
|
}
|
|
|
|
if(ctx.key === null) {
|
|
_reseedSync();
|
|
}
|
|
|
|
// generate the random bytes
|
|
var bytes = cipher(ctx.key, ctx.seed);
|
|
ctx.generated += bytes.length;
|
|
b.putBytes(bytes);
|
|
|
|
// generate bytes for a new key and seed
|
|
ctx.key = formatKey(cipher(ctx.key, increment(ctx.seed)));
|
|
ctx.seed = formatSeed(cipher(ctx.key, ctx.seed));
|
|
}
|
|
|
|
return b.getBytes(count);
|
|
};
|
|
|
|
/**
|
|
* Private function that asynchronously reseeds a generator.
|
|
*
|
|
* @param callback(err) called once the operation completes.
|
|
*/
|
|
function _reseed(callback) {
|
|
if(ctx.pools[0].messageLength >= 32) {
|
|
_seed();
|
|
return callback();
|
|
}
|
|
// not enough seed data...
|
|
var needed = (32 - ctx.pools[0].messageLength) << 5;
|
|
ctx.seedFile(needed, function(err, bytes) {
|
|
if(err) {
|
|
return callback(err);
|
|
}
|
|
ctx.collect(bytes);
|
|
_seed();
|
|
callback();
|
|
});
|
|
}
|
|
|
|
/**
|
|
* Private function that synchronously reseeds a generator.
|
|
*/
|
|
function _reseedSync() {
|
|
if(ctx.pools[0].messageLength >= 32) {
|
|
return _seed();
|
|
}
|
|
// not enough seed data...
|
|
var needed = (32 - ctx.pools[0].messageLength) << 5;
|
|
ctx.collect(ctx.seedFileSync(needed));
|
|
_seed();
|
|
}
|
|
|
|
/**
|
|
* Private function that seeds a generator once enough bytes are available.
|
|
*/
|
|
function _seed() {
|
|
// update reseed count
|
|
ctx.reseeds = (ctx.reseeds === 0xffffffff) ? 0 : ctx.reseeds + 1;
|
|
|
|
// goal is to update `key` via:
|
|
// key = hash(key + s)
|
|
// where 's' is all collected entropy from selected pools, then...
|
|
|
|
// create a plugin-based message digest
|
|
var md = ctx.plugin.md.create();
|
|
|
|
// consume current key bytes
|
|
md.update(ctx.keyBytes);
|
|
|
|
// digest the entropy of pools whose index k meet the
|
|
// condition 'n mod 2^k == 0' where n is the number of reseeds
|
|
var _2powK = 1;
|
|
for(var k = 0; k < 32; ++k) {
|
|
if(ctx.reseeds % _2powK === 0) {
|
|
md.update(ctx.pools[k].digest().getBytes());
|
|
ctx.pools[k].start();
|
|
}
|
|
_2powK = _2powK << 1;
|
|
}
|
|
|
|
// get digest for key bytes
|
|
ctx.keyBytes = md.digest().getBytes();
|
|
|
|
// paranoid deviation from Fortuna:
|
|
// update `seed` via `seed = hash(key)`
|
|
// instead of initializing to zero once and only
|
|
// ever incrementing it
|
|
md.start();
|
|
md.update(ctx.keyBytes);
|
|
var seedBytes = md.digest().getBytes();
|
|
|
|
// update state
|
|
ctx.key = ctx.plugin.formatKey(ctx.keyBytes);
|
|
ctx.seed = ctx.plugin.formatSeed(seedBytes);
|
|
ctx.generated = 0;
|
|
}
|
|
|
|
/**
|
|
* The built-in default seedFile. This seedFile is used when entropy
|
|
* is needed immediately.
|
|
*
|
|
* @param needed the number of bytes that are needed.
|
|
*
|
|
* @return the random bytes.
|
|
*/
|
|
function defaultSeedFile(needed) {
|
|
// use window.crypto.getRandomValues strong source of entropy if available
|
|
var getRandomValues = null;
|
|
if(typeof window !== 'undefined') {
|
|
var _crypto = window.crypto || window.msCrypto;
|
|
if(_crypto && _crypto.getRandomValues) {
|
|
getRandomValues = function(arr) {
|
|
return _crypto.getRandomValues(arr);
|
|
};
|
|
}
|
|
}
|
|
|
|
var b = forge.util.createBuffer();
|
|
if(getRandomValues) {
|
|
while(b.length() < needed) {
|
|
// max byte length is 65536 before QuotaExceededError is thrown
|
|
// http://www.w3.org/TR/WebCryptoAPI/#RandomSource-method-getRandomValues
|
|
var count = Math.max(1, Math.min(needed - b.length(), 65536) / 4);
|
|
var entropy = new Uint32Array(Math.floor(count));
|
|
try {
|
|
getRandomValues(entropy);
|
|
for(var i = 0; i < entropy.length; ++i) {
|
|
b.putInt32(entropy[i]);
|
|
}
|
|
} catch(e) {
|
|
/* only ignore QuotaExceededError */
|
|
if(!(typeof QuotaExceededError !== 'undefined' &&
|
|
e instanceof QuotaExceededError)) {
|
|
throw e;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// be sad and add some weak random data
|
|
if(b.length() < needed) {
|
|
/* Draws from Park-Miller "minimal standard" 31 bit PRNG,
|
|
implemented with David G. Carta's optimization: with 32 bit math
|
|
and without division (Public Domain). */
|
|
var hi, lo, next;
|
|
var seed = Math.floor(Math.random() * 0x010000);
|
|
while(b.length() < needed) {
|
|
lo = 16807 * (seed & 0xFFFF);
|
|
hi = 16807 * (seed >> 16);
|
|
lo += (hi & 0x7FFF) << 16;
|
|
lo += hi >> 15;
|
|
lo = (lo & 0x7FFFFFFF) + (lo >> 31);
|
|
seed = lo & 0xFFFFFFFF;
|
|
|
|
// consume lower 3 bytes of seed
|
|
for(var i = 0; i < 3; ++i) {
|
|
// throw in more pseudo random
|
|
next = seed >>> (i << 3);
|
|
next ^= Math.floor(Math.random() * 0x0100);
|
|
b.putByte(String.fromCharCode(next & 0xFF));
|
|
}
|
|
}
|
|
}
|
|
|
|
return b.getBytes(needed);
|
|
}
|
|
// initialize seed file APIs
|
|
if(_crypto) {
|
|
// use nodejs async API
|
|
ctx.seedFile = function(needed, callback) {
|
|
_crypto.randomBytes(needed, function(err, bytes) {
|
|
if(err) {
|
|
return callback(err);
|
|
}
|
|
callback(null, bytes.toString());
|
|
});
|
|
};
|
|
// use nodejs sync API
|
|
ctx.seedFileSync = function(needed) {
|
|
return _crypto.randomBytes(needed).toString();
|
|
};
|
|
} else {
|
|
ctx.seedFile = function(needed, callback) {
|
|
try {
|
|
callback(null, defaultSeedFile(needed));
|
|
} catch(e) {
|
|
callback(e);
|
|
}
|
|
};
|
|
ctx.seedFileSync = defaultSeedFile;
|
|
}
|
|
|
|
/**
|
|
* Adds entropy to a prng ctx's accumulator.
|
|
*
|
|
* @param bytes the bytes of entropy as a string.
|
|
*/
|
|
ctx.collect = function(bytes) {
|
|
// iterate over pools distributing entropy cyclically
|
|
var count = bytes.length;
|
|
for(var i = 0; i < count; ++i) {
|
|
ctx.pools[ctx.pool].update(bytes.substr(i, 1));
|
|
ctx.pool = (ctx.pool === 31) ? 0 : ctx.pool + 1;
|
|
}
|
|
};
|
|
|
|
/**
|
|
* Collects an integer of n bits.
|
|
*
|
|
* @param i the integer entropy.
|
|
* @param n the number of bits in the integer.
|
|
*/
|
|
ctx.collectInt = function(i, n) {
|
|
var bytes = '';
|
|
for(var x = 0; x < n; x += 8) {
|
|
bytes += String.fromCharCode((i >> x) & 0xFF);
|
|
}
|
|
ctx.collect(bytes);
|
|
};
|
|
|
|
/**
|
|
* Registers a Web Worker to receive immediate entropy from the main thread.
|
|
* This method is required until Web Workers can access the native crypto
|
|
* API. This method should be called twice for each created worker, once in
|
|
* the main thread, and once in the worker itself.
|
|
*
|
|
* @param worker the worker to register.
|
|
*/
|
|
ctx.registerWorker = function(worker) {
|
|
// worker receives random bytes
|
|
if(worker === self) {
|
|
ctx.seedFile = function(needed, callback) {
|
|
function listener(e) {
|
|
var data = e.data;
|
|
if(data.forge && data.forge.prng) {
|
|
self.removeEventListener('message', listener);
|
|
callback(data.forge.prng.err, data.forge.prng.bytes);
|
|
}
|
|
}
|
|
self.addEventListener('message', listener);
|
|
self.postMessage({forge: {prng: {needed: needed}}});
|
|
};
|
|
} else {
|
|
// main thread sends random bytes upon request
|
|
var listener = function(e) {
|
|
var data = e.data;
|
|
if(data.forge && data.forge.prng) {
|
|
ctx.seedFile(data.forge.prng.needed, function(err, bytes) {
|
|
worker.postMessage({forge: {prng: {err: err, bytes: bytes}}});
|
|
});
|
|
}
|
|
};
|
|
// TODO: do we need to remove the event listener when the worker dies?
|
|
worker.addEventListener('message', listener);
|
|
}
|
|
};
|
|
|
|
return ctx;
|
|
};
|