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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package sha1 implements the SHA1 hash algorithm as defined in RFC 3174.
package sha1
import (
"crypto"
"hash"
)
func init() {
crypto.RegisterHash(crypto.SHA1, New)
}
// The size of a SHA1 checksum in bytes.
const Size = 20
// The blocksize of SHA1 in bytes.
const BlockSize = 64
const (
chunk = 64
init0 = 0x67452301
init1 = 0xEFCDAB89
init2 = 0x98BADCFE
init3 = 0x10325476
init4 = 0xC3D2E1F0
)
// digest represents the partial evaluation of a checksum.
type digest struct {
h [5]uint32
x [chunk]byte
nx int
len uint64
}
func (d *digest) Reset() {
d.h[0] = init0
d.h[1] = init1
d.h[2] = init2
d.h[3] = init3
d.h[4] = init4
d.nx = 0
d.len = 0
}
// New returns a new hash.Hash computing the SHA1 checksum.
func New() hash.Hash {
if boringEnabled {
return boringNewSHA1()
}
d := new(digest)
d.Reset()
return d
}
func (d *digest) Size() int { return Size }
func (d *digest) BlockSize() int { return BlockSize }
func (d *digest) Write(p []byte) (nn int, err error) {
boringUnreachable()
nn = len(p)
d.len += uint64(nn)
if d.nx > 0 {
n := copy(d.x[d.nx:], p)
d.nx += n
if d.nx == chunk {
block(d, d.x[:])
d.nx = 0
}
p = p[n:]
}
if len(p) >= chunk {
n := len(p) &^ (chunk - 1)
block(d, p[:n])
p = p[n:]
}
if len(p) > 0 {
d.nx = copy(d.x[:], p)
}
return
}
func (d0 *digest) Sum(in []byte) []byte {
boringUnreachable()
// Make a copy of d0 so that caller can keep writing and summing.
d := *d0
hash := d.checkSum()
return append(in, hash[:]...)
}
func (d *digest) checkSum() [Size]byte {
len := d.len
// Padding. Add a 1 bit and 0 bits until 56 bytes mod 64.
var tmp [64]byte
tmp[0] = 0x80
if len%64 < 56 {
d.Write(tmp[0 : 56-len%64])
} else {
d.Write(tmp[0 : 64+56-len%64])
}
// Length in bits.
len <<= 3
for i := uint(0); i < 8; i++ {
tmp[i] = byte(len >> (56 - 8*i))
}
d.Write(tmp[0:8])
if d.nx != 0 {
panic("d.nx != 0")
}
var digest [Size]byte
for i, s := range d.h {
digest[i*4] = byte(s >> 24)
digest[i*4+1] = byte(s >> 16)
digest[i*4+2] = byte(s >> 8)
digest[i*4+3] = byte(s)
}
return digest
}
// ConstantTimeSum computes the same result of Sum() but in constant time
func (d0 *digest) ConstantTimeSum(in []byte) []byte {
d := *d0
hash := d.constSum()
return append(in, hash[:]...)
}
func (d *digest) constSum() [Size]byte {
var length [8]byte
l := d.len << 3
for i := uint(0); i < 8; i++ {
length[i] = byte(l >> (56 - 8*i))
}
nx := byte(d.nx)
t := nx - 56 // if nx < 56 then the MSB of t is one
mask1b := byte(int8(t) >> 7) // mask1b is 0xFF iff one block is enough
separator := byte(0x80) // gets reset to 0x00 once used
for i := byte(0); i < chunk; i++ {
mask := byte(int8(i-nx) >> 7) // 0x00 after the end of data
// if we reached the end of the data, replace with 0x80 or 0x00
d.x[i] = (^mask & separator) | (mask & d.x[i])
// zero the separator once used
separator &= mask
if i >= 56 {
// we might have to write the length here if all fit in one block
d.x[i] |= mask1b & length[i-56]
}
}
// compress, and only keep the digest if all fit in one block
block(d, d.x[:])
var digest [Size]byte
for i, s := range d.h {
digest[i*4] = mask1b & byte(s>>24)
digest[i*4+1] = mask1b & byte(s>>16)
digest[i*4+2] = mask1b & byte(s>>8)
digest[i*4+3] = mask1b & byte(s)
}
for i := byte(0); i < chunk; i++ {
// second block, it's always past the end of data, might start with 0x80
if i < 56 {
d.x[i] = separator
separator = 0
} else {
d.x[i] = length[i-56]
}
}
// compress, and only keep the digest if we actually needed the second block
block(d, d.x[:])
for i, s := range d.h {
digest[i*4] |= ^mask1b & byte(s>>24)
digest[i*4+1] |= ^mask1b & byte(s>>16)
digest[i*4+2] |= ^mask1b & byte(s>>8)
digest[i*4+3] |= ^mask1b & byte(s)
}
return digest
}
// Sum returns the SHA1 checksum of the data.
func Sum(data []byte) [Size]byte {
if boringEnabled {
h := New()
h.Write(data)
var ret [Size]byte
h.Sum(ret[:0])
return ret
}
var d digest
d.Reset()
d.Write(data)
return d.checkSum()
}
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