sha1.go

Documentation: crypto/sha1

     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  	"encoding/binary"
    15  	"errors"
    16  	"hash"
    17  )
    18  
    19  func init() {
    20  	crypto.RegisterHash(crypto.SHA1, New)
    21  }
    22  
    23  // The size of a SHA-1 checksum in bytes.
    24  const Size = 20
    25  
    26  // The blocksize of SHA-1 in bytes.
    27  const BlockSize = 64
    28  
    29  const (
    30  	chunk = 64
    31  	init0 = 0x67452301
    32  	init1 = 0xEFCDAB89
    33  	init2 = 0x98BADCFE
    34  	init3 = 0x10325476
    35  	init4 = 0xC3D2E1F0
    36  )
    37  
    38  // digest represents the partial evaluation of a checksum.
    39  type digest struct {
    40  	h   [5]uint32
    41  	x   [chunk]byte
    42  	nx  int
    43  	len uint64
    44  }
    45  
    46  const (
    47  	magic         = "sha\x01"
    48  	marshaledSize = len(magic) + 5*4 + chunk + 8
    49  )
    50  
    51  func (d *digest) MarshalBinary() ([]byte, error) {
    52  	b := make([]byte, 0, marshaledSize)
    53  	b = append(b, magic...)
    54  	b = binary.BigEndian.AppendUint32(b, d.h[0])
    55  	b = binary.BigEndian.AppendUint32(b, d.h[1])
    56  	b = binary.BigEndian.AppendUint32(b, d.h[2])
    57  	b = binary.BigEndian.AppendUint32(b, d.h[3])
    58  	b = binary.BigEndian.AppendUint32(b, d.h[4])
    59  	b = append(b, d.x[:d.nx]...)
    60  	b = b[:len(b)+len(d.x)-d.nx] // already zero
    61  	b = binary.BigEndian.AppendUint64(b, d.len)
    62  	return b, nil
    63  }
    64  
    65  func (d *digest) UnmarshalBinary(b []byte) error {
    66  	if len(b) < len(magic) || string(b[:len(magic)]) != magic {
    67  		return errors.New("crypto/sha1: invalid hash state identifier")
    68  	}
    69  	if len(b) != marshaledSize {
    70  		return errors.New("crypto/sha1: invalid hash state size")
    71  	}
    72  	b = b[len(magic):]
    73  	b, d.h[0] = consumeUint32(b)
    74  	b, d.h[1] = consumeUint32(b)
    75  	b, d.h[2] = consumeUint32(b)
    76  	b, d.h[3] = consumeUint32(b)
    77  	b, d.h[4] = consumeUint32(b)
    78  	b = b[copy(d.x[:], b):]
    79  	b, d.len = consumeUint64(b)
    80  	d.nx = int(d.len % chunk)
    81  	return nil
    82  }
    83  
    84  func consumeUint64(b []byte) ([]byte, uint64) {
    85  	_ = b[7]
    86  	x := uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
    87  		uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
    88  	return b[8:], x
    89  }
    90  
    91  func consumeUint32(b []byte) ([]byte, uint32) {
    92  	_ = b[3]
    93  	x := uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
    94  	return b[4:], x
    95  }
    96  
    97  func (d *digest) Reset() {
    98  	d.h[0] = init0
    99  	d.h[1] = init1
   100  	d.h[2] = init2
   101  	d.h[3] = init3
   102  	d.h[4] = init4
   103  	d.nx = 0
   104  	d.len = 0
   105  }
   106  
   107  // New returns a new hash.Hash computing the SHA1 checksum. The Hash also
   108  // implements [encoding.BinaryMarshaler] and [encoding.BinaryUnmarshaler] to
   109  // marshal and unmarshal the internal 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  	boring.Unreachable()
   125  	nn = len(p)
   126  	d.len += uint64(nn)
   127  	if d.nx > 0 {
   128  		n := copy(d.x[d.nx:], p)
   129  		d.nx += n
   130  		if d.nx == chunk {
   131  			block(d, d.x[:])
   132  			d.nx = 0
   133  		}
   134  		p = p[n:]
   135  	}
   136  	if len(p) >= chunk {
   137  		n := len(p) &^ (chunk - 1)
   138  		block(d, p[:n])
   139  		p = p[n:]
   140  	}
   141  	if len(p) > 0 {
   142  		d.nx = copy(d.x[:], p)
   143  	}
   144  	return
   145  }
   146  
   147  func (d *digest) Sum(in []byte) []byte {
   148  	boring.Unreachable()
   149  	// Make a copy of d so that caller can keep writing and summing.
   150  	d0 := *d
   151  	hash := d0.checkSum()
   152  	return append(in, hash[:]...)
   153  }
   154  
   155  func (d *digest) checkSum() [Size]byte {
   156  	len := d.len
   157  	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
   158  	var tmp [64 + 8]byte // padding + length buffer
   159  	tmp[0] = 0x80
   160  	var t uint64
   161  	if len%64 < 56 {
   162  		t = 56 - len%64
   163  	} else {
   164  		t = 64 + 56 - len%64
   165  	}
   166  
   167  	// Length in bits.
   168  	len <<= 3
   169  	padlen := tmp[:t+8]
   170  	binary.BigEndian.PutUint64(padlen[t:], len)
   171  	d.Write(padlen)
   172  
   173  	if d.nx != 0 {
   174  		panic("d.nx != 0")
   175  	}
   176  
   177  	var digest [Size]byte
   178  
   179  	binary.BigEndian.PutUint32(digest[0:], d.h[0])
   180  	binary.BigEndian.PutUint32(digest[4:], d.h[1])
   181  	binary.BigEndian.PutUint32(digest[8:], d.h[2])
   182  	binary.BigEndian.PutUint32(digest[12:], d.h[3])
   183  	binary.BigEndian.PutUint32(digest[16:], d.h[4])
   184  
   185  	return digest
   186  }
   187  
   188  // ConstantTimeSum computes the same result of [Sum] but in constant time
   189  func (d *digest) ConstantTimeSum(in []byte) []byte {
   190  	d0 := *d
   191  	hash := d0.constSum()
   192  	return append(in, hash[:]...)
   193  }
   194  
   195  func (d *digest) constSum() [Size]byte {
   196  	var length [8]byte
   197  	l := d.len << 3
   198  	for i := uint(0); i < 8; i++ {
   199  		length[i] = byte(l >> (56 - 8*i))
   200  	}
   201  
   202  	nx := byte(d.nx)
   203  	t := nx - 56                 // if nx < 56 then the MSB of t is one
   204  	mask1b := byte(int8(t) >> 7) // mask1b is 0xFF iff one block is enough
   205  
   206  	separator := byte(0x80) // gets reset to 0x00 once used
   207  	for i := byte(0); i < chunk; i++ {
   208  		mask := byte(int8(i-nx) >> 7) // 0x00 after the end of data
   209  
   210  		// if we reached the end of the data, replace with 0x80 or 0x00
   211  		d.x[i] = (^mask & separator) | (mask & d.x[i])
   212  
   213  		// zero the separator once used
   214  		separator &= mask
   215  
   216  		if i >= 56 {
   217  			// we might have to write the length here if all fit in one block
   218  			d.x[i] |= mask1b & length[i-56]
   219  		}
   220  	}
   221  
   222  	// compress, and only keep the digest if all fit in one block
   223  	block(d, d.x[:])
   224  
   225  	var digest [Size]byte
   226  	for i, s := range d.h {
   227  		digest[i*4] = mask1b & byte(s>>24)
   228  		digest[i*4+1] = mask1b & byte(s>>16)
   229  		digest[i*4+2] = mask1b & byte(s>>8)
   230  		digest[i*4+3] = mask1b & byte(s)
   231  	}
   232  
   233  	for i := byte(0); i < chunk; i++ {
   234  		// second block, it's always past the end of data, might start with 0x80
   235  		if i < 56 {
   236  			d.x[i] = separator
   237  			separator = 0
   238  		} else {
   239  			d.x[i] = length[i-56]
   240  		}
   241  	}
   242  
   243  	// compress, and only keep the digest if we actually needed the second block
   244  	block(d, d.x[:])
   245  
   246  	for i, s := range d.h {
   247  		digest[i*4] |= ^mask1b & byte(s>>24)
   248  		digest[i*4+1] |= ^mask1b & byte(s>>16)
   249  		digest[i*4+2] |= ^mask1b & byte(s>>8)
   250  		digest[i*4+3] |= ^mask1b & byte(s)
   251  	}
   252  
   253  	return digest
   254  }
   255  
   256  // Sum returns the SHA-1 checksum of the data.
   257  func Sum(data []byte) [Size]byte {
   258  	if boring.Enabled {
   259  		return boring.SHA1(data)
   260  	}
   261  	var d digest
   262  	d.Reset()
   263  	d.Write(data)
   264  	return d.checkSum()
   265  }
   266
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