1// Copyright 2009 The Go Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style 3// license that can be found in the LICENSE file. 4 5// Package sha1 implements the SHA1 hash algorithm as defined in RFC 3174. 6package sha1 7 8import ( 9 "crypto" 10 "hash" 11) 12 13func init() { 14 crypto.RegisterHash(crypto.SHA1, New) 15} 16 17// The size of a SHA1 checksum in bytes. 18const Size = 20 19 20// The blocksize of SHA1 in bytes. 21const BlockSize = 64 22 23const ( 24 chunk = 64 25 init0 = 0x67452301 26 init1 = 0xEFCDAB89 27 init2 = 0x98BADCFE 28 init3 = 0x10325476 29 init4 = 0xC3D2E1F0 30) 31 32// digest represents the partial evaluation of a checksum. 33type digest struct { 34 h [5]uint32 35 x [chunk]byte 36 nx int 37 len uint64 38} 39 40func (d *digest) Reset() { 41 d.h[0] = init0 42 d.h[1] = init1 43 d.h[2] = init2 44 d.h[3] = init3 45 d.h[4] = init4 46 d.nx = 0 47 d.len = 0 48} 49 50// New returns a new hash.Hash computing the SHA1 checksum. 51func New() hash.Hash { 52 d := new(digest) 53 d.Reset() 54 return d 55} 56 57func (d *digest) Size() int { return Size } 58 59func (d *digest) BlockSize() int { return BlockSize } 60 61func (d *digest) Write(p []byte) (nn int, err error) { 62 nn = len(p) 63 d.len += uint64(nn) 64 if d.nx > 0 { 65 n := len(p) 66 if n > chunk-d.nx { 67 n = chunk - d.nx 68 } 69 for i := 0; i < n; i++ { 70 d.x[d.nx+i] = p[i] 71 } 72 d.nx += n 73 if d.nx == chunk { 74 block(d, d.x[0:]) 75 d.nx = 0 76 } 77 p = p[n:] 78 } 79 if len(p) >= chunk { 80 n := len(p) &^ (chunk - 1) 81 block(d, p[:n]) 82 p = p[n:] 83 } 84 if len(p) > 0 { 85 d.nx = copy(d.x[:], p) 86 } 87 return 88} 89 90func (d0 *digest) Sum(in []byte) []byte { 91 // Make a copy of d0 so that caller can keep writing and summing. 92 d := *d0 93 hash := d.checkSum() 94 return append(in, hash[:]...) 95} 96 97func (d *digest) checkSum() [Size]byte { 98 len := d.len 99 // Padding. Add a 1 bit and 0 bits until 56 bytes mod 64. 100 var tmp [64]byte 101 tmp[0] = 0x80 102 if len%64 < 56 { 103 d.Write(tmp[0 : 56-len%64]) 104 } else { 105 d.Write(tmp[0 : 64+56-len%64]) 106 } 107 108 // Length in bits. 109 len <<= 3 110 for i := uint(0); i < 8; i++ { 111 tmp[i] = byte(len >> (56 - 8*i)) 112 } 113 d.Write(tmp[0:8]) 114 115 if d.nx != 0 { 116 panic("d.nx != 0") 117 } 118 119 var digest [Size]byte 120 for i, s := range d.h { 121 digest[i*4] = byte(s >> 24) 122 digest[i*4+1] = byte(s >> 16) 123 digest[i*4+2] = byte(s >> 8) 124 digest[i*4+3] = byte(s) 125 } 126 127 return digest 128} 129 130// Sum returns the SHA1 checksum of the data. 131func Sum(data []byte) [Size]byte { 132 var d digest 133 d.Reset() 134 d.Write(data) 135 return d.checkSum() 136} 137