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      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 	"hash"
     12 )
     13 
     14 func init() {
     15 	crypto.RegisterHash(crypto.SHA224, New224)
     16 	crypto.RegisterHash(crypto.SHA256, New)
     17 }
     18 
     19 // The size of a SHA256 checksum in bytes.
     20 const Size = 32
     21 
     22 // The size of a SHA224 checksum in bytes.
     23 const Size224 = 28
     24 
     25 // The blocksize of SHA256 and SHA224 in bytes.
     26 const BlockSize = 64
     27 
     28 const (
     29 	chunk     = 64
     30 	init0     = 0x6A09E667
     31 	init1     = 0xBB67AE85
     32 	init2     = 0x3C6EF372
     33 	init3     = 0xA54FF53A
     34 	init4     = 0x510E527F
     35 	init5     = 0x9B05688C
     36 	init6     = 0x1F83D9AB
     37 	init7     = 0x5BE0CD19
     38 	init0_224 = 0xC1059ED8
     39 	init1_224 = 0x367CD507
     40 	init2_224 = 0x3070DD17
     41 	init3_224 = 0xF70E5939
     42 	init4_224 = 0xFFC00B31
     43 	init5_224 = 0x68581511
     44 	init6_224 = 0x64F98FA7
     45 	init7_224 = 0xBEFA4FA4
     46 )
     47 
     48 // digest represents the partial evaluation of a checksum.
     49 type digest struct {
     50 	h     [8]uint32
     51 	x     [chunk]byte
     52 	nx    int
     53 	len   uint64
     54 	is224 bool // mark if this digest is SHA-224
     55 }
     56 
     57 func (d *digest) Reset() {
     58 	if !d.is224 {
     59 		d.h[0] = init0
     60 		d.h[1] = init1
     61 		d.h[2] = init2
     62 		d.h[3] = init3
     63 		d.h[4] = init4
     64 		d.h[5] = init5
     65 		d.h[6] = init6
     66 		d.h[7] = init7
     67 	} else {
     68 		d.h[0] = init0_224
     69 		d.h[1] = init1_224
     70 		d.h[2] = init2_224
     71 		d.h[3] = init3_224
     72 		d.h[4] = init4_224
     73 		d.h[5] = init5_224
     74 		d.h[6] = init6_224
     75 		d.h[7] = init7_224
     76 	}
     77 	d.nx = 0
     78 	d.len = 0
     79 }
     80 
     81 // New returns a new hash.Hash computing the SHA256 checksum.
     82 func New() hash.Hash {
     83 	d := new(digest)
     84 	d.Reset()
     85 	return d
     86 }
     87 
     88 // New224 returns a new hash.Hash computing the SHA224 checksum.
     89 func New224() hash.Hash {
     90 	d := new(digest)
     91 	d.is224 = true
     92 	d.Reset()
     93 	return d
     94 }
     95 
     96 func (d *digest) Size() int {
     97 	if !d.is224 {
     98 		return Size
     99 	}
    100 	return Size224
    101 }
    102 
    103 func (d *digest) BlockSize() int { return BlockSize }
    104 
    105 func (d *digest) Write(p []byte) (nn int, err error) {
    106 	nn = len(p)
    107 	d.len += uint64(nn)
    108 	if d.nx > 0 {
    109 		n := copy(d.x[d.nx:], p)
    110 		d.nx += n
    111 		if d.nx == chunk {
    112 			block(d, d.x[:])
    113 			d.nx = 0
    114 		}
    115 		p = p[n:]
    116 	}
    117 	if len(p) >= chunk {
    118 		n := len(p) &^ (chunk - 1)
    119 		block(d, p[:n])
    120 		p = p[n:]
    121 	}
    122 	if len(p) > 0 {
    123 		d.nx = copy(d.x[:], p)
    124 	}
    125 	return
    126 }
    127 
    128 func (d0 *digest) Sum(in []byte) []byte {
    129 	// Make a copy of d0 so that caller can keep writing and summing.
    130 	d := *d0
    131 	hash := d.checkSum()
    132 	if d.is224 {
    133 		return append(in, hash[:Size224]...)
    134 	}
    135 	return append(in, hash[:]...)
    136 }
    137 
    138 func (d *digest) checkSum() [Size]byte {
    139 	len := d.len
    140 	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
    141 	var tmp [64]byte
    142 	tmp[0] = 0x80
    143 	if len%64 < 56 {
    144 		d.Write(tmp[0 : 56-len%64])
    145 	} else {
    146 		d.Write(tmp[0 : 64+56-len%64])
    147 	}
    148 
    149 	// Length in bits.
    150 	len <<= 3
    151 	for i := uint(0); i < 8; i++ {
    152 		tmp[i] = byte(len >> (56 - 8*i))
    153 	}
    154 	d.Write(tmp[0:8])
    155 
    156 	if d.nx != 0 {
    157 		panic("d.nx != 0")
    158 	}
    159 
    160 	h := d.h[:]
    161 	if d.is224 {
    162 		h = d.h[:7]
    163 	}
    164 
    165 	var digest [Size]byte
    166 	for i, s := range h {
    167 		digest[i*4] = byte(s >> 24)
    168 		digest[i*4+1] = byte(s >> 16)
    169 		digest[i*4+2] = byte(s >> 8)
    170 		digest[i*4+3] = byte(s)
    171 	}
    172 
    173 	return digest
    174 }
    175 
    176 // Sum256 returns the SHA256 checksum of the data.
    177 func Sum256(data []byte) [Size]byte {
    178 	var d digest
    179 	d.Reset()
    180 	d.Write(data)
    181 	return d.checkSum()
    182 }
    183 
    184 // Sum224 returns the SHA224 checksum of the data.
    185 func Sum224(data []byte) (sum224 [Size224]byte) {
    186 	var d digest
    187 	d.is224 = true
    188 	d.Reset()
    189 	d.Write(data)
    190 	sum := d.checkSum()
    191 	copy(sum224[:], sum[:Size224])
    192 	return
    193 }
    194