Source file src/crypto/sha256/sha256.go

Documentation: crypto/sha256

     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 sha256 implements the SHA224 and SHA256 hash algorithms as defined
     6  // in FIPS 180-4.
     7  package sha256
     8  
     9  import (
    10  	"crypto"
    11  	"encoding/binary"
    12  	"errors"
    13  	"hash"
    14  )
    15  
    16  func init() {
    17  	crypto.RegisterHash(crypto.SHA224, New224)
    18  	crypto.RegisterHash(crypto.SHA256, New)
    19  }
    20  
    21  // The size of a SHA256 checksum in bytes.
    22  const Size = 32
    23  
    24  // The size of a SHA224 checksum in bytes.
    25  const Size224 = 28
    26  
    27  // The blocksize of SHA256 and SHA224 in bytes.
    28  const BlockSize = 64
    29  
    30  const (
    31  	chunk     = 64
    32  	init0     = 0x6A09E667
    33  	init1     = 0xBB67AE85
    34  	init2     = 0x3C6EF372
    35  	init3     = 0xA54FF53A
    36  	init4     = 0x510E527F
    37  	init5     = 0x9B05688C
    38  	init6     = 0x1F83D9AB
    39  	init7     = 0x5BE0CD19
    40  	init0_224 = 0xC1059ED8
    41  	init1_224 = 0x367CD507
    42  	init2_224 = 0x3070DD17
    43  	init3_224 = 0xF70E5939
    44  	init4_224 = 0xFFC00B31
    45  	init5_224 = 0x68581511
    46  	init6_224 = 0x64F98FA7
    47  	init7_224 = 0xBEFA4FA4
    48  )
    49  
    50  // digest represents the partial evaluation of a checksum.
    51  type digest struct {
    52  	h     [8]uint32
    53  	x     [chunk]byte
    54  	nx    int
    55  	len   uint64
    56  	is224 bool // mark if this digest is SHA-224
    57  }
    58  
    59  const (
    60  	magic224      = "sha\x02"
    61  	magic256      = "sha\x03"
    62  	marshaledSize = len(magic256) + 8*4 + chunk + 8
    63  )
    64  
    65  func (d *digest) MarshalBinary() ([]byte, error) {
    66  	b := make([]byte, 0, marshaledSize)
    67  	if d.is224 {
    68  		b = append(b, magic224...)
    69  	} else {
    70  		b = append(b, magic256...)
    71  	}
    72  	b = appendUint32(b, d.h[0])
    73  	b = appendUint32(b, d.h[1])
    74  	b = appendUint32(b, d.h[2])
    75  	b = appendUint32(b, d.h[3])
    76  	b = appendUint32(b, d.h[4])
    77  	b = appendUint32(b, d.h[5])
    78  	b = appendUint32(b, d.h[6])
    79  	b = appendUint32(b, d.h[7])
    80  	b = append(b, d.x[:d.nx]...)
    81  	b = b[:len(b)+len(d.x)-int(d.nx)] // already zero
    82  	b = appendUint64(b, d.len)
    83  	return b, nil
    84  }
    85  
    86  func (d *digest) UnmarshalBinary(b []byte) error {
    87  	if len(b) < len(magic224) || (d.is224 && string(b[:len(magic224)]) != magic224) || (!d.is224 && string(b[:len(magic256)]) != magic256) {
    88  		return errors.New("crypto/sha256: invalid hash state identifier")
    89  	}
    90  	if len(b) != marshaledSize {
    91  		return errors.New("crypto/sha256: invalid hash state size")
    92  	}
    93  	b = b[len(magic224):]
    94  	b, d.h[0] = consumeUint32(b)
    95  	b, d.h[1] = consumeUint32(b)
    96  	b, d.h[2] = consumeUint32(b)
    97  	b, d.h[3] = consumeUint32(b)
    98  	b, d.h[4] = consumeUint32(b)
    99  	b, d.h[5] = consumeUint32(b)
   100  	b, d.h[6] = consumeUint32(b)
   101  	b, d.h[7] = consumeUint32(b)
   102  	b = b[copy(d.x[:], b):]
   103  	b, d.len = consumeUint64(b)
   104  	d.nx = int(d.len % chunk)
   105  	return nil
   106  }
   107  
   108  func appendUint64(b []byte, x uint64) []byte {
   109  	var a [8]byte
   110  	binary.BigEndian.PutUint64(a[:], x)
   111  	return append(b, a[:]...)
   112  }
   113  
   114  func appendUint32(b []byte, x uint32) []byte {
   115  	var a [4]byte
   116  	binary.BigEndian.PutUint32(a[:], x)
   117  	return append(b, a[:]...)
   118  }
   119  
   120  func consumeUint64(b []byte) ([]byte, uint64) {
   121  	_ = b[7]
   122  	x := uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
   123  		uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
   124  	return b[8:], x
   125  }
   126  
   127  func consumeUint32(b []byte) ([]byte, uint32) {
   128  	_ = b[3]
   129  	x := uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
   130  	return b[4:], x
   131  }
   132  
   133  func (d *digest) Reset() {
   134  	if !d.is224 {
   135  		d.h[0] = init0
   136  		d.h[1] = init1
   137  		d.h[2] = init2
   138  		d.h[3] = init3
   139  		d.h[4] = init4
   140  		d.h[5] = init5
   141  		d.h[6] = init6
   142  		d.h[7] = init7
   143  	} else {
   144  		d.h[0] = init0_224
   145  		d.h[1] = init1_224
   146  		d.h[2] = init2_224
   147  		d.h[3] = init3_224
   148  		d.h[4] = init4_224
   149  		d.h[5] = init5_224
   150  		d.h[6] = init6_224
   151  		d.h[7] = init7_224
   152  	}
   153  	d.nx = 0
   154  	d.len = 0
   155  }
   156  
   157  // New returns a new hash.Hash computing the SHA256 checksum. The Hash
   158  // also implements encoding.BinaryMarshaler and
   159  // encoding.BinaryUnmarshaler to marshal and unmarshal the internal
   160  // state of the hash.
   161  func New() hash.Hash {
   162  	d := new(digest)
   163  	d.Reset()
   164  	return d
   165  }
   166  
   167  // New224 returns a new hash.Hash computing the SHA224 checksum.
   168  func New224() hash.Hash {
   169  	d := new(digest)
   170  	d.is224 = true
   171  	d.Reset()
   172  	return d
   173  }
   174  
   175  func (d *digest) Size() int {
   176  	if !d.is224 {
   177  		return Size
   178  	}
   179  	return Size224
   180  }
   181  
   182  func (d *digest) BlockSize() int { return BlockSize }
   183  
   184  func (d *digest) Write(p []byte) (nn int, err error) {
   185  	nn = len(p)
   186  	d.len += uint64(nn)
   187  	if d.nx > 0 {
   188  		n := copy(d.x[d.nx:], p)
   189  		d.nx += n
   190  		if d.nx == chunk {
   191  			block(d, d.x[:])
   192  			d.nx = 0
   193  		}
   194  		p = p[n:]
   195  	}
   196  	if len(p) >= chunk {
   197  		n := len(p) &^ (chunk - 1)
   198  		block(d, p[:n])
   199  		p = p[n:]
   200  	}
   201  	if len(p) > 0 {
   202  		d.nx = copy(d.x[:], p)
   203  	}
   204  	return
   205  }
   206  
   207  func (d *digest) Sum(in []byte) []byte {
   208  	// Make a copy of d so that caller can keep writing and summing.
   209  	d0 := *d
   210  	hash := d0.checkSum()
   211  	if d0.is224 {
   212  		return append(in, hash[:Size224]...)
   213  	}
   214  	return append(in, hash[:]...)
   215  }
   216  
   217  func (d *digest) checkSum() [Size]byte {
   218  	len := d.len
   219  	// Padding. Add a 1 bit and 0 bits until 56 bytes mod 64.
   220  	var tmp [64]byte
   221  	tmp[0] = 0x80
   222  	if len%64 < 56 {
   223  		d.Write(tmp[0 : 56-len%64])
   224  	} else {
   225  		d.Write(tmp[0 : 64+56-len%64])
   226  	}
   227  
   228  	// Length in bits.
   229  	len <<= 3
   230  	binary.BigEndian.PutUint64(tmp[:], len)
   231  	d.Write(tmp[0:8])
   232  
   233  	if d.nx != 0 {
   234  		panic("d.nx != 0")
   235  	}
   236  
   237  	var digest [Size]byte
   238  
   239  	binary.BigEndian.PutUint32(digest[0:], d.h[0])
   240  	binary.BigEndian.PutUint32(digest[4:], d.h[1])
   241  	binary.BigEndian.PutUint32(digest[8:], d.h[2])
   242  	binary.BigEndian.PutUint32(digest[12:], d.h[3])
   243  	binary.BigEndian.PutUint32(digest[16:], d.h[4])
   244  	binary.BigEndian.PutUint32(digest[20:], d.h[5])
   245  	binary.BigEndian.PutUint32(digest[24:], d.h[6])
   246  	if !d.is224 {
   247  		binary.BigEndian.PutUint32(digest[28:], d.h[7])
   248  	}
   249  
   250  	return digest
   251  }
   252  
   253  // Sum256 returns the SHA256 checksum of the data.
   254  func Sum256(data []byte) [Size]byte {
   255  	var d digest
   256  	d.Reset()
   257  	d.Write(data)
   258  	return d.checkSum()
   259  }
   260  
   261  // Sum224 returns the SHA224 checksum of the data.
   262  func Sum224(data []byte) (sum224 [Size224]byte) {
   263  	var d digest
   264  	d.is224 = true
   265  	d.Reset()
   266  	d.Write(data)
   267  	sum := d.checkSum()
   268  	copy(sum224[:], sum[:Size224])
   269  	return
   270  }
   271  

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