sha1.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  // Package sha1 implements the SHA-1 hash algorithm as defined in RFC 3174.
     6  //
     7  // SHA-1 is cryptographically broken and should not be used for secure
     8  // applications.
     9  package sha1
    10  
    11  import (
    12  	"crypto"
    13  	"crypto/internal/boring"
    14  	"crypto/internal/fips140only"
    15  	"errors"
    16  	"hash"
    17  	"internal/byteorder"
    18  )
    19  
    20  func init() {
    21  	crypto.RegisterHash(crypto.SHA1, New)
    22  }
    23  
    24  // The size of a SHA-1 checksum in bytes.
    25  const Size = 20
    26  
    27  // The blocksize of SHA-1 in bytes.
    28  const BlockSize = 64
    29  
    30  const (
    31  	chunk = 64
    32  	init0 = 0x67452301
    33  	init1 = 0xEFCDAB89
    34  	init2 = 0x98BADCFE
    35  	init3 = 0x10325476
    36  	init4 = 0xC3D2E1F0
    37  )
    38  
    39  // digest represents the partial evaluation of a checksum.
    40  type digest struct {
    41  	h   [5]uint32
    42  	x   [chunk]byte
    43  	nx  int
    44  	len uint64
    45  }
    46  
    47  const (
    48  	magic         = "sha\x01"
    49  	marshaledSize = len(magic) + 5*4 + chunk + 8
    50  )
    51  
    52  func (d *digest) MarshalBinary() ([]byte, error) {
    53  	return d.AppendBinary(make([]byte, 0, marshaledSize))
    54  }
    55  
    56  func (d *digest) AppendBinary(b []byte) ([]byte, error) {
    57  	b = append(b, magic...)
    58  	b = byteorder.BEAppendUint32(b, d.h[0])
    59  	b = byteorder.BEAppendUint32(b, d.h[1])
    60  	b = byteorder.BEAppendUint32(b, d.h[2])
    61  	b = byteorder.BEAppendUint32(b, d.h[3])
    62  	b = byteorder.BEAppendUint32(b, d.h[4])
    63  	b = append(b, d.x[:d.nx]...)
    64  	b = append(b, make([]byte, len(d.x)-d.nx)...)
    65  	b = byteorder.BEAppendUint64(b, d.len)
    66  	return b, nil
    67  }
    68  
    69  func (d *digest) UnmarshalBinary(b []byte) error {
    70  	if len(b) < len(magic) || string(b[:len(magic)]) != magic {
    71  		return errors.New("crypto/sha1: invalid hash state identifier")
    72  	}
    73  	if len(b) != marshaledSize {
    74  		return errors.New("crypto/sha1: invalid hash state size")
    75  	}
    76  	b = b[len(magic):]
    77  	b, d.h[0] = consumeUint32(b)
    78  	b, d.h[1] = consumeUint32(b)
    79  	b, d.h[2] = consumeUint32(b)
    80  	b, d.h[3] = consumeUint32(b)
    81  	b, d.h[4] = consumeUint32(b)
    82  	b = b[copy(d.x[:], b):]
    83  	b, d.len = consumeUint64(b)
    84  	d.nx = int(d.len % chunk)
    85  	return nil
    86  }
    87  
    88  func consumeUint64(b []byte) ([]byte, uint64) {
    89  	return b[8:], byteorder.BEUint64(b)
    90  }
    91  
    92  func consumeUint32(b []byte) ([]byte, uint32) {
    93  	return b[4:], byteorder.BEUint32(b)
    94  }
    95  
    96  func (d *digest) Reset() {
    97  	d.h[0] = init0
    98  	d.h[1] = init1
    99  	d.h[2] = init2
   100  	d.h[3] = init3
   101  	d.h[4] = init4
   102  	d.nx = 0
   103  	d.len = 0
   104  }
   105  
   106  // New returns a new [hash.Hash] computing the SHA1 checksum. The Hash
   107  // also implements [encoding.BinaryMarshaler], [encoding.BinaryAppender] and
   108  // [encoding.BinaryUnmarshaler] to marshal and unmarshal the internal
   109  // state of the hash.
   110  func New() hash.Hash {
   111  	if boring.Enabled {
   112  		return boring.NewSHA1()
   113  	}
   114  	d := new(digest)
   115  	d.Reset()
   116  	return d
   117  }
   118  
   119  func (d *digest) Size() int { return Size }
   120  
   121  func (d *digest) BlockSize() int { return BlockSize }
   122  
   123  func (d *digest) Write(p []byte) (nn int, err error) {
   124  	if fips140only.Enabled {
   125  		return 0, errors.New("crypto/sha1: use of SHA-1 is not allowed in FIPS 140-only mode")
   126  	}
   127  	boring.Unreachable()
   128  	nn = len(p)
   129  	d.len += uint64(nn)
   130  	if d.nx > 0 {
   131  		n := copy(d.x[d.nx:], p)
   132  		d.nx += n
   133  		if d.nx == chunk {
   134  			block(d, d.x[:])
   135  			d.nx = 0
   136  		}
   137  		p = p[n:]
   138  	}
   139  	if len(p) >= chunk {
   140  		n := len(p) &^ (chunk - 1)
   141  		block(d, p[:n])
   142  		p = p[n:]
   143  	}
   144  	if len(p) > 0 {
   145  		d.nx = copy(d.x[:], p)
   146  	}
   147  	return
   148  }
   149  
   150  func (d *digest) Sum(in []byte) []byte {
   151  	boring.Unreachable()
   152  	// Make a copy of d so that caller can keep writing and summing.
   153  	d0 := *d
   154  	hash := d0.checkSum()
   155  	return append(in, hash[:]...)
   156  }
   157  
   158  func (d *digest) checkSum() [Size]byte {
   159  	if fips140only.Enabled {
   160  		panic("crypto/sha1: use of SHA-1 is not allowed in FIPS 140-only mode")
   161  	}
   162  
   163  	len := d.len
   164  	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
   165  	var tmp [64 + 8]byte // padding + length buffer
   166  	tmp[0] = 0x80
   167  	var t uint64
   168  	if len%64 < 56 {
   169  		t = 56 - len%64
   170  	} else {
   171  		t = 64 + 56 - len%64
   172  	}
   173  
   174  	// Length in bits.
   175  	len <<= 3
   176  	padlen := tmp[:t+8]
   177  	byteorder.BEPutUint64(padlen[t:], len)
   178  	d.Write(padlen)
   179  
   180  	if d.nx != 0 {
   181  		panic("d.nx != 0")
   182  	}
   183  
   184  	var digest [Size]byte
   185  
   186  	byteorder.BEPutUint32(digest[0:], d.h[0])
   187  	byteorder.BEPutUint32(digest[4:], d.h[1])
   188  	byteorder.BEPutUint32(digest[8:], d.h[2])
   189  	byteorder.BEPutUint32(digest[12:], d.h[3])
   190  	byteorder.BEPutUint32(digest[16:], d.h[4])
   191  
   192  	return digest
   193  }
   194  
   195  // ConstantTimeSum computes the same result of [Sum] but in constant time
   196  func (d *digest) ConstantTimeSum(in []byte) []byte {
   197  	d0 := *d
   198  	hash := d0.constSum()
   199  	return append(in, hash[:]...)
   200  }
   201  
   202  func (d *digest) constSum() [Size]byte {
   203  	if fips140only.Enabled {
   204  		panic("crypto/sha1: use of SHA-1 is not allowed in FIPS 140-only mode")
   205  	}
   206  
   207  	var length [8]byte
   208  	l := d.len << 3
   209  	for i := uint(0); i < 8; i++ {
   210  		length[i] = byte(l >> (56 - 8*i))
   211  	}
   212  
   213  	nx := byte(d.nx)
   214  	t := nx - 56                 // if nx < 56 then the MSB of t is one
   215  	mask1b := byte(int8(t) >> 7) // mask1b is 0xFF iff one block is enough
   216  
   217  	separator := byte(0x80) // gets reset to 0x00 once used
   218  	for i := byte(0); i < chunk; i++ {
   219  		mask := byte(int8(i-nx) >> 7) // 0x00 after the end of data
   220  
   221  		// if we reached the end of the data, replace with 0x80 or 0x00
   222  		d.x[i] = (^mask & separator) | (mask & d.x[i])
   223  
   224  		// zero the separator once used
   225  		separator &= mask
   226  
   227  		if i >= 56 {
   228  			// we might have to write the length here if all fit in one block
   229  			d.x[i] |= mask1b & length[i-56]
   230  		}
   231  	}
   232  
   233  	// compress, and only keep the digest if all fit in one block
   234  	block(d, d.x[:])
   235  
   236  	var digest [Size]byte
   237  	for i, s := range d.h {
   238  		digest[i*4] = mask1b & byte(s>>24)
   239  		digest[i*4+1] = mask1b & byte(s>>16)
   240  		digest[i*4+2] = mask1b & byte(s>>8)
   241  		digest[i*4+3] = mask1b & byte(s)
   242  	}
   243  
   244  	for i := byte(0); i < chunk; i++ {
   245  		// second block, it's always past the end of data, might start with 0x80
   246  		if i < 56 {
   247  			d.x[i] = separator
   248  			separator = 0
   249  		} else {
   250  			d.x[i] = length[i-56]
   251  		}
   252  	}
   253  
   254  	// compress, and only keep the digest if we actually needed the second block
   255  	block(d, d.x[:])
   256  
   257  	for i, s := range d.h {
   258  		digest[i*4] |= ^mask1b & byte(s>>24)
   259  		digest[i*4+1] |= ^mask1b & byte(s>>16)
   260  		digest[i*4+2] |= ^mask1b & byte(s>>8)
   261  		digest[i*4+3] |= ^mask1b & byte(s)
   262  	}
   263  
   264  	return digest
   265  }
   266  
   267  // Sum returns the SHA-1 checksum of the data.
   268  func Sum(data []byte) [Size]byte {
   269  	if boring.Enabled {
   270  		return boring.SHA1(data)
   271  	}
   272  	if fips140only.Enabled {
   273  		panic("crypto/sha1: use of SHA-1 is not allowed in FIPS 140-only mode")
   274  	}
   275  	var d digest
   276  	d.Reset()
   277  	d.Write(data)
   278  	return d.checkSum()
   279  }
   280
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