md5.go

     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 -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  	"crypto/internal/fips140only"
    16  	"errors"
    17  	"hash"
    18  	"internal/byteorder"
    19  )
    20  
    21  func init() {
    22  	crypto.RegisterHash(crypto.MD5, New)
    23  }
    24  
    25  // The size of an MD5 checksum in bytes.
    26  const Size = 16
    27  
    28  // The blocksize of MD5 in bytes.
    29  const BlockSize = 64
    30  
    31  const (
    32  	init0 = 0x67452301
    33  	init1 = 0xEFCDAB89
    34  	init2 = 0x98BADCFE
    35  	init3 = 0x10325476
    36  )
    37  
    38  // digest represents the partial evaluation of a checksum.
    39  type digest struct {
    40  	s   [4]uint32
    41  	x   [BlockSize]byte
    42  	nx  int
    43  	len uint64
    44  }
    45  
    46  func (d *digest) Reset() {
    47  	d.s[0] = init0
    48  	d.s[1] = init1
    49  	d.s[2] = init2
    50  	d.s[3] = init3
    51  	d.nx = 0
    52  	d.len = 0
    53  }
    54  
    55  const (
    56  	magic         = "md5\x01"
    57  	marshaledSize = len(magic) + 4*4 + BlockSize + 8
    58  )
    59  
    60  func (d *digest) MarshalBinary() ([]byte, error) {
    61  	return d.AppendBinary(make([]byte, 0, marshaledSize))
    62  }
    63  
    64  func (d *digest) AppendBinary(b []byte) ([]byte, error) {
    65  	b = append(b, magic...)
    66  	b = byteorder.BEAppendUint32(b, d.s[0])
    67  	b = byteorder.BEAppendUint32(b, d.s[1])
    68  	b = byteorder.BEAppendUint32(b, d.s[2])
    69  	b = byteorder.BEAppendUint32(b, d.s[3])
    70  	b = append(b, d.x[:d.nx]...)
    71  	b = append(b, make([]byte, len(d.x)-d.nx)...)
    72  	b = byteorder.BEAppendUint64(b, d.len)
    73  	return b, nil
    74  }
    75  
    76  func (d *digest) UnmarshalBinary(b []byte) error {
    77  	if len(b) < len(magic) || string(b[:len(magic)]) != magic {
    78  		return errors.New("crypto/md5: invalid hash state identifier")
    79  	}
    80  	if len(b) != marshaledSize {
    81  		return errors.New("crypto/md5: invalid hash state size")
    82  	}
    83  	b = b[len(magic):]
    84  	b, d.s[0] = consumeUint32(b)
    85  	b, d.s[1] = consumeUint32(b)
    86  	b, d.s[2] = consumeUint32(b)
    87  	b, d.s[3] = consumeUint32(b)
    88  	b = b[copy(d.x[:], b):]
    89  	b, d.len = consumeUint64(b)
    90  	d.nx = int(d.len % BlockSize)
    91  	return nil
    92  }
    93  
    94  func consumeUint64(b []byte) ([]byte, uint64) {
    95  	return b[8:], byteorder.BEUint64(b[0:8])
    96  }
    97  
    98  func consumeUint32(b []byte) ([]byte, uint32) {
    99  	return b[4:], byteorder.BEUint32(b[0:4])
   100  }
   101  
   102  // New returns a new [hash.Hash] computing the MD5 checksum. The Hash
   103  // also implements [encoding.BinaryMarshaler], [encoding.BinaryAppender] and
   104  // [encoding.BinaryUnmarshaler] to marshal and unmarshal the internal
   105  // state of the hash.
   106  func New() hash.Hash {
   107  	d := new(digest)
   108  	d.Reset()
   109  	return d
   110  }
   111  
   112  func (d *digest) Size() int { return Size }
   113  
   114  func (d *digest) BlockSize() int { return BlockSize }
   115  
   116  func (d *digest) Write(p []byte) (nn int, err error) {
   117  	if fips140only.Enabled {
   118  		return 0, errors.New("crypto/md5: use of MD5 is not allowed in FIPS 140-only mode")
   119  	}
   120  	// Note that we currently call block or blockGeneric
   121  	// directly (guarded using haveAsm) because this allows
   122  	// escape analysis to see that p and d don't escape.
   123  	nn = len(p)
   124  	d.len += uint64(nn)
   125  	if d.nx > 0 {
   126  		n := copy(d.x[d.nx:], p)
   127  		d.nx += n
   128  		if d.nx == BlockSize {
   129  			if haveAsm {
   130  				block(d, d.x[:])
   131  			} else {
   132  				blockGeneric(d, d.x[:])
   133  			}
   134  			d.nx = 0
   135  		}
   136  		p = p[n:]
   137  	}
   138  	if len(p) >= BlockSize {
   139  		n := len(p) &^ (BlockSize - 1)
   140  		if haveAsm {
   141  			block(d, p[:n])
   142  		} else {
   143  			blockGeneric(d, p[:n])
   144  		}
   145  		p = p[n:]
   146  	}
   147  	if len(p) > 0 {
   148  		d.nx = copy(d.x[:], p)
   149  	}
   150  	return
   151  }
   152  
   153  func (d *digest) Sum(in []byte) []byte {
   154  	// Make a copy of d so that caller can keep writing and summing.
   155  	d0 := *d
   156  	hash := d0.checkSum()
   157  	return append(in, hash[:]...)
   158  }
   159  
   160  func (d *digest) checkSum() [Size]byte {
   161  	if fips140only.Enabled {
   162  		panic("crypto/md5: use of MD5 is not allowed in FIPS 140-only mode")
   163  	}
   164  
   165  	// Append 0x80 to the end of the message and then append zeros
   166  	// until the length is a multiple of 56 bytes. Finally append
   167  	// 8 bytes representing the message length in bits.
   168  	//
   169  	// 1 byte end marker :: 0-63 padding bytes :: 8 byte length
   170  	tmp := [1 + 63 + 8]byte{0x80}
   171  	pad := (55 - d.len) % 64                     // calculate number of padding bytes
   172  	byteorder.LEPutUint64(tmp[1+pad:], d.len<<3) // append length in bits
   173  	d.Write(tmp[:1+pad+8])
   174  
   175  	// The previous write ensures that a whole number of
   176  	// blocks (i.e. a multiple of 64 bytes) have been hashed.
   177  	if d.nx != 0 {
   178  		panic("d.nx != 0")
   179  	}
   180  
   181  	var digest [Size]byte
   182  	byteorder.LEPutUint32(digest[0:], d.s[0])
   183  	byteorder.LEPutUint32(digest[4:], d.s[1])
   184  	byteorder.LEPutUint32(digest[8:], d.s[2])
   185  	byteorder.LEPutUint32(digest[12:], d.s[3])
   186  	return digest
   187  }
   188  
   189  // Sum returns the MD5 checksum of the data.
   190  func Sum(data []byte) [Size]byte {
   191  	var d digest
   192  	d.Reset()
   193  	d.Write(data)
   194  	return d.checkSum()
   195  }
   196
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