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 md5 implements the MD5 hash algorithm as defined in RFC 1321. 6package md5 7 8import ( 9 "crypto" 10 "hash" 11) 12 13func init() { 14 crypto.RegisterHash(crypto.MD5, New) 15} 16 17// The size of an MD5 checksum in bytes. 18const Size = 16 19 20// The blocksize of MD5 in bytes. 21const BlockSize = 64 22 23const ( 24 chunk = 64 25 init0 = 0x67452301 26 init1 = 0xEFCDAB89 27 init2 = 0x98BADCFE 28 init3 = 0x10325476 29) 30 31// digest represents the partial evaluation of a checksum. 32type digest struct { 33 s [4]uint32 34 x [chunk]byte 35 nx int 36 len uint64 37} 38 39func (d *digest) Reset() { 40 d.s[0] = init0 41 d.s[1] = init1 42 d.s[2] = init2 43 d.s[3] = init3 44 d.nx = 0 45 d.len = 0 46} 47 48// New returns a new hash.Hash computing the MD5 checksum. 49func New() hash.Hash { 50 d := new(digest) 51 d.Reset() 52 return d 53} 54 55func (d *digest) Size() int { return Size } 56 57func (d *digest) BlockSize() int { return BlockSize } 58 59func (d *digest) Write(p []byte) (nn int, err error) { 60 nn = len(p) 61 d.len += uint64(nn) 62 if d.nx > 0 { 63 n := len(p) 64 if n > chunk-d.nx { 65 n = chunk - d.nx 66 } 67 for i := 0; i < n; i++ { 68 d.x[d.nx+i] = p[i] 69 } 70 d.nx += n 71 if d.nx == chunk { 72 block(d, d.x[0:chunk]) 73 d.nx = 0 74 } 75 p = p[n:] 76 } 77 if len(p) >= chunk { 78 n := len(p) &^ (chunk - 1) 79 block(d, p[:n]) 80 p = p[n:] 81 } 82 if len(p) > 0 { 83 d.nx = copy(d.x[:], p) 84 } 85 return 86} 87 88func (d0 *digest) Sum(in []byte) []byte { 89 // Make a copy of d0 so that caller can keep writing and summing. 90 d := *d0 91 92 // Padding. Add a 1 bit and 0 bits until 56 bytes mod 64. 93 len := d.len 94 var tmp [64]byte 95 tmp[0] = 0x80 96 if len%64 < 56 { 97 d.Write(tmp[0 : 56-len%64]) 98 } else { 99 d.Write(tmp[0 : 64+56-len%64]) 100 } 101 102 // Length in bits. 103 len <<= 3 104 for i := uint(0); i < 8; i++ { 105 tmp[i] = byte(len >> (8 * i)) 106 } 107 d.Write(tmp[0:8]) 108 109 if d.nx != 0 { 110 panic("d.nx != 0") 111 } 112 113 var digest [Size]byte 114 for i, s := range d.s { 115 digest[i*4] = byte(s) 116 digest[i*4+1] = byte(s >> 8) 117 digest[i*4+2] = byte(s >> 16) 118 digest[i*4+3] = byte(s >> 24) 119 } 120 121 return append(in, digest[:]...) 122} 123