...
Run Format

Source file src/crypto/md5/md5.go

Documentation: crypto/md5

  // Copyright 2009 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  //go:generate go run gen.go -full -output md5block.go
  
  // Package md5 implements the MD5 hash algorithm as defined in RFC 1321.
  //
  // MD5 is cryptographically broken and should not be used for secure
  // applications.
  package md5
  
  import (
  	"crypto"
  	"errors"
  	"hash"
  )
  
  func init() {
  	crypto.RegisterHash(crypto.MD5, New)
  }
  
  // The size of an MD5 checksum in bytes.
  const Size = 16
  
  // The blocksize of MD5 in bytes.
  const BlockSize = 64
  
  const (
  	chunk = 64
  	init0 = 0x67452301
  	init1 = 0xEFCDAB89
  	init2 = 0x98BADCFE
  	init3 = 0x10325476
  )
  
  // digest represents the partial evaluation of a checksum.
  type digest struct {
  	s   [4]uint32
  	x   [chunk]byte
  	nx  int
  	len uint64
  }
  
  func (d *digest) Reset() {
  	d.s[0] = init0
  	d.s[1] = init1
  	d.s[2] = init2
  	d.s[3] = init3
  	d.nx = 0
  	d.len = 0
  }
  
  const (
  	magic         = "md5\x01"
  	marshaledSize = len(magic) + 4*4 + chunk + 8
  )
  
  func (d *digest) MarshalBinary() ([]byte, error) {
  	b := make([]byte, 0, marshaledSize)
  	b = append(b, magic...)
  	b = appendUint32(b, d.s[0])
  	b = appendUint32(b, d.s[1])
  	b = appendUint32(b, d.s[2])
  	b = appendUint32(b, d.s[3])
  	b = append(b, d.x[:d.nx]...)
  	b = b[:len(b)+len(d.x)-int(d.nx)] // already zero
  	b = appendUint64(b, d.len)
  	return b, nil
  }
  
  func (d *digest) UnmarshalBinary(b []byte) error {
  	if len(b) < len(magic) || string(b[:len(magic)]) != magic {
  		return errors.New("crypto/md5: invalid hash state identifier")
  	}
  	if len(b) != marshaledSize {
  		return errors.New("crypto/md5: invalid hash state size")
  	}
  	b = b[len(magic):]
  	b, d.s[0] = consumeUint32(b)
  	b, d.s[1] = consumeUint32(b)
  	b, d.s[2] = consumeUint32(b)
  	b, d.s[3] = consumeUint32(b)
  	b = b[copy(d.x[:], b):]
  	b, d.len = consumeUint64(b)
  	d.nx = int(d.len) % chunk
  	return nil
  }
  
  func appendUint64(b []byte, x uint64) []byte {
  	a := [8]byte{
  		byte(x >> 56),
  		byte(x >> 48),
  		byte(x >> 40),
  		byte(x >> 32),
  		byte(x >> 24),
  		byte(x >> 16),
  		byte(x >> 8),
  		byte(x),
  	}
  	return append(b, a[:]...)
  }
  
  func appendUint32(b []byte, x uint32) []byte {
  	a := [4]byte{
  		byte(x >> 24),
  		byte(x >> 16),
  		byte(x >> 8),
  		byte(x),
  	}
  	return append(b, a[:]...)
  }
  
  func consumeUint64(b []byte) ([]byte, uint64) {
  	_ = b[7]
  	x := uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
  		uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
  	return b[8:], x
  }
  
  func consumeUint32(b []byte) ([]byte, uint32) {
  	_ = b[3]
  	x := uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
  	return b[4:], x
  }
  
  // New returns a new hash.Hash computing the MD5 checksum. The Hash also
  // implements encoding.BinaryMarshaler and encoding.BinaryUnmarshaler to
  // marshal and unmarshal the internal state of the hash.
  func New() hash.Hash {
  	d := new(digest)
  	d.Reset()
  	return d
  }
  
  func (d *digest) Size() int { return Size }
  
  func (d *digest) BlockSize() int { return BlockSize }
  
  func (d *digest) Write(p []byte) (nn int, err error) {
  	nn = len(p)
  	d.len += uint64(nn)
  	if d.nx > 0 {
  		n := copy(d.x[d.nx:], p)
  		d.nx += n
  		if d.nx == chunk {
  			block(d, d.x[:])
  			d.nx = 0
  		}
  		p = p[n:]
  	}
  	if len(p) >= chunk {
  		n := len(p) &^ (chunk - 1)
  		block(d, p[:n])
  		p = p[n:]
  	}
  	if len(p) > 0 {
  		d.nx = copy(d.x[:], p)
  	}
  	return
  }
  
  func (d0 *digest) Sum(in []byte) []byte {
  	// Make a copy of d0 so that caller can keep writing and summing.
  	d := *d0
  	hash := d.checkSum()
  	return append(in, hash[:]...)
  }
  
  func (d *digest) checkSum() [Size]byte {
  	// Padding. Add a 1 bit and 0 bits until 56 bytes mod 64.
  	len := d.len
  	var tmp [64]byte
  	tmp[0] = 0x80
  	if len%64 < 56 {
  		d.Write(tmp[0 : 56-len%64])
  	} else {
  		d.Write(tmp[0 : 64+56-len%64])
  	}
  
  	// Length in bits.
  	len <<= 3
  	for i := uint(0); i < 8; i++ {
  		tmp[i] = byte(len >> (8 * i))
  	}
  	d.Write(tmp[0:8])
  
  	if d.nx != 0 {
  		panic("d.nx != 0")
  	}
  
  	var digest [Size]byte
  	for i, s := range d.s {
  		digest[i*4] = byte(s)
  		digest[i*4+1] = byte(s >> 8)
  		digest[i*4+2] = byte(s >> 16)
  		digest[i*4+3] = byte(s >> 24)
  	}
  
  	return digest
  }
  
  // Sum returns the MD5 checksum of the data.
  func Sum(data []byte) [Size]byte {
  	var d digest
  	d.Reset()
  	d.Write(data)
  	return d.checkSum()
  }
  

View as plain text