1/* 2 * Copyright (c) 2014, Yawning Angel <yawning at torproject dot org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions are met: 7 * 8 * * Redistributions of source code must retain the above copyright notice, 9 * this list of conditions and the following disclaimer. 10 * 11 * * Redistributions in binary form must reproduce the above copyright notice, 12 * this list of conditions and the following disclaimer in the documentation 13 * and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 16 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 19 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 20 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 21 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 22 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 23 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 24 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 25 * POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28// Package csrand implements the math/rand interface over crypto/rand, along 29// with some utility functions for common random number/byte related tasks. 30// 31// Not all of the convinience routines are replicated, only those that are 32// immediately useful. The Rand variable provides access to the full math/rand 33// API. 34package csrand // import "gitlab.com/yawning/obfs4.git/common/csrand" 35 36import ( 37 cryptRand "crypto/rand" 38 "encoding/binary" 39 "fmt" 40 "io" 41 "math/rand" 42) 43 44var ( 45 csRandSourceInstance csRandSource 46 47 // Rand is a math/rand instance backed by crypto/rand CSPRNG. 48 Rand = rand.New(csRandSourceInstance) 49) 50 51type csRandSource struct { 52 // This does not keep any state as it is backed by crypto/rand. 53} 54 55func (r csRandSource) Int63() int64 { 56 var src [8]byte 57 if err := Bytes(src[:]); err != nil { 58 panic(err) 59 } 60 val := binary.BigEndian.Uint64(src[:]) 61 val &= (1<<63 - 1) 62 63 return int64(val) 64} 65 66func (r csRandSource) Seed(seed int64) { 67 // No-op. 68} 69 70// Intn returns, as a int, a pseudo random number in [0, n). 71func Intn(n int) int { 72 return Rand.Intn(n) 73} 74 75// Float64 returns, as a float64, a pesudo random number in [0.0,1.0). 76func Float64() float64 { 77 return Rand.Float64() 78} 79 80// IntRange returns a uniformly distributed int [min, max]. 81func IntRange(min, max int) int { 82 if max < min { 83 panic(fmt.Sprintf("IntRange: min > max (%d, %d)", min, max)) 84 } 85 86 r := (max + 1) - min 87 ret := Rand.Intn(r) 88 return ret + min 89} 90 91// Bytes fills the slice with random data. 92func Bytes(buf []byte) error { 93 if _, err := io.ReadFull(cryptRand.Reader, buf); err != nil { 94 return err 95 } 96 97 return nil 98} 99 100// Reader is a alias of rand.Reader. 101var Reader = cryptRand.Reader 102