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// Copyright © 2021 rsiddharth <s@ricketyspace.net>
// SPDX-License-Identifier: ISC
package lib
// SHA-1 implementation.
// Reference https://csrc.nist.gov/publications/detail/fips/180/4/final
type Sha1 struct {
hvs []uint32
Msg []byte
MsgLen int
}
// Initial hash value.
var sha1IHashValues []uint32 = []uint32{
0x67452301,
0xefcdab89,
0x98badcfe,
0x10325476,
0xc3d2e1f0,
}
// (a + b + ...) mod 2^32
func sha1Add(n ...uint32) uint32 {
sum := uint64(0)
for _, v := range n {
sum += uint64(v)
}
return uint32(sum & 0xFFFFFFFF)
}
// Circular Right Shift
func sha1Rotr(x uint32, n uint) uint32 {
return (x >> n) | (x << (32 - n))
}
// Circular Left Shift
func sha1Rotl(x uint32, n uint) uint32 {
return (x << n) | (x >> (32 - n))
}
// SHA-1 - Function f_t(x, y, z)
func sha1FT(t int, x, y, z uint32) uint32 {
switch {
case t <= 19:
return (x & y) ^ (^x & z)
case t >= 20 && t <= 39:
return x ^ y ^ z
case t >= 40 && t <= 59:
return (x & y) ^ (x & z) ^ (y & z)
case t >= 60 && t <= 79:
return x ^ y ^ z
default:
return uint32(0)
}
}
// SHA-1 - Constant K_t
func sha1KT(t int) uint32 {
switch {
case t <= 19:
return uint32(0x5a827999)
case t >= 20 && t <= 39:
return uint32(0x6ed9eba1)
case t >= 40 && t <= 59:
return uint32(0x8f1bbcdc)
case t >= 60 && t <= 79:
return uint32(0xca62c1d6)
default:
return uint32(0)
}
}
// Returns the message schedule W_t for message black `mb`
// The message schedule has 80 32-bit words.
func sha1MessageSchedule(mb []uint32) []uint32 {
// Message schedule.
w := make([]uint32, 0)
// Generate message schedule.
for t := 0; t <= 79; t++ {
if t <= 15 {
w = append(w, mb[t])
} else {
w = append(w, sha1Rotl(w[t-3]^w[t-8]^w[t-14]^w[t-16], 1))
}
}
return w
}
func (s *Sha1) Init(hvs []uint32) {
// Set Initial Hash Values.
h := make([]uint32, 5)
if len(hvs) == 5 {
copy(h, hvs)
s.hvs = h
} else {
copy(h, sha1IHashValues)
s.hvs = h
}
}
func (s *Sha1) Message(m []byte) {
s.Msg = m
s.MsgLen = len(m)
}
// SHA-1 - Pad message such that its length is a multiple of 512.
func (s *Sha1) Pad() []byte {
// Initialize padded message
pm := make([]byte, len(s.Msg))
copy(pm, s.Msg)
// Add padding.
pm = append(pm, MDPadding(s.MsgLen)...)
return pm
}
func (s *Sha1) Hash() []byte {
// Pad message.
pm := s.Pad()
// Break into message blocks.
mbs := shaMessageBlocks(pm)
// Initialize hash values.
h := make([]uint32, 5)
copy(h, s.hvs) // Initial hash values.
// Process each message block.
for _, mb := range mbs {
// Get message schedule.
w := sha1MessageSchedule(mb)
// Initialize working variables.
a := h[0]
b := h[1]
c := h[2]
d := h[3]
e := h[4]
for t := 0; t <= 79; t++ {
tmp := sha1Add(sha1Rotl(a, 5), sha1FT(t, b, c, d),
e, sha1KT(t), w[t])
e = d
d = c
c = sha1Rotl(b, 30)
b = a
a = tmp
}
// Compute intermediate hash values.
h[0] = sha1Add(a, h[0])
h[1] = sha1Add(b, h[1])
h[2] = sha1Add(c, h[2])
h[3] = sha1Add(d, h[3])
h[4] = sha1Add(e, h[4])
}
// Slurp sha1 digest from hash values.
d := make([]byte, 0) // sha1 digest
for i := 0; i < 5; i++ {
// Break 32-bit hash value into 4 bytes.
hb := make([]byte, 4)
for j := 3; j >= 0; j-- {
// Get last 8 bits.
hb[j] = byte(h[i] & 0xFF)
// Get rid of last 8 bits.
h[i] = h[i] >> 8
}
d = append(d, hb...)
}
return d
}
func (s *Sha1) Mac(secret, msg []byte) []byte {
s.Message(append(secret, msg...))
return s.Hash()
}
func (s *Sha1) MacVerify(secret, msg, mac []byte) bool {
s.Message(append(secret, msg...))
if BytesEqual(s.Hash(), mac) {
return true
}
return false
}
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