github.com/flyinox/gosm@v0.0.0-20171117061539-16768cb62077/src/crypto/md5/md5.go (about)

     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  //go:generate go run gen.go -full -output md5block.go
     6  
     7  // Package md5 implements the MD5 hash algorithm as defined in RFC 1321.
     8  //
     9  // MD5 is cryptographically broken and should not be used for secure
    10  // applications.
    11  package md5
    12  
    13  import (
    14  	"crypto"
    15  	"hash"
    16  )
    17  
    18  func init() {
    19  	crypto.RegisterHash(crypto.MD5, New)
    20  }
    21  
    22  // The size of an MD5 checksum in bytes.
    23  const Size = 16
    24  
    25  // The blocksize of MD5 in bytes.
    26  const BlockSize = 64
    27  
    28  const (
    29  	chunk = 64
    30  	init0 = 0x67452301
    31  	init1 = 0xEFCDAB89
    32  	init2 = 0x98BADCFE
    33  	init3 = 0x10325476
    34  )
    35  
    36  // digest represents the partial evaluation of a checksum.
    37  type digest struct {
    38  	s   [4]uint32
    39  	x   [chunk]byte
    40  	nx  int
    41  	len uint64
    42  }
    43  
    44  func (d *digest) Reset() {
    45  	d.s[0] = init0
    46  	d.s[1] = init1
    47  	d.s[2] = init2
    48  	d.s[3] = init3
    49  	d.nx = 0
    50  	d.len = 0
    51  }
    52  
    53  // New returns a new hash.Hash computing the MD5 checksum.
    54  func New() hash.Hash {
    55  	d := new(digest)
    56  	d.Reset()
    57  	return d
    58  }
    59  
    60  func (d *digest) Size() int { return Size }
    61  
    62  func (d *digest) BlockSize() int { return BlockSize }
    63  
    64  func (d *digest) Write(p []byte) (nn int, err error) {
    65  	nn = len(p)
    66  	d.len += uint64(nn)
    67  	if d.nx > 0 {
    68  		n := copy(d.x[d.nx:], p)
    69  		d.nx += n
    70  		if d.nx == chunk {
    71  			block(d, d.x[:])
    72  			d.nx = 0
    73  		}
    74  		p = p[n:]
    75  	}
    76  	if len(p) >= chunk {
    77  		n := len(p) &^ (chunk - 1)
    78  		block(d, p[:n])
    79  		p = p[n:]
    80  	}
    81  	if len(p) > 0 {
    82  		d.nx = copy(d.x[:], p)
    83  	}
    84  	return
    85  }
    86  
    87  func (d0 *digest) Sum(in []byte) []byte {
    88  	// Make a copy of d0 so that caller can keep writing and summing.
    89  	d := *d0
    90  	hash := d.checkSum()
    91  	return append(in, hash[:]...)
    92  }
    93  
    94  func (d *digest) checkSum() [Size]byte {
    95  	// Padding. Add a 1 bit and 0 bits until 56 bytes mod 64.
    96  	len := d.len
    97  	var tmp [64]byte
    98  	tmp[0] = 0x80
    99  	if len%64 < 56 {
   100  		d.Write(tmp[0 : 56-len%64])
   101  	} else {
   102  		d.Write(tmp[0 : 64+56-len%64])
   103  	}
   104  
   105  	// Length in bits.
   106  	len <<= 3
   107  	for i := uint(0); i < 8; i++ {
   108  		tmp[i] = byte(len >> (8 * i))
   109  	}
   110  	d.Write(tmp[0:8])
   111  
   112  	if d.nx != 0 {
   113  		panic("d.nx != 0")
   114  	}
   115  
   116  	var digest [Size]byte
   117  	for i, s := range d.s {
   118  		digest[i*4] = byte(s)
   119  		digest[i*4+1] = byte(s >> 8)
   120  		digest[i*4+2] = byte(s >> 16)
   121  		digest[i*4+3] = byte(s >> 24)
   122  	}
   123  
   124  	return digest
   125  }
   126  
   127  // Sum returns the MD5 checksum of the data.
   128  func Sum(data []byte) [Size]byte {
   129  	var d digest
   130  	d.Reset()
   131  	d.Write(data)
   132  	return d.checkSum()
   133  }