1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
|
// Copyright 2018 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 poly1305
import "encoding/binary"
const (
msgBlock = uint32(1 << 24)
finalBlock = uint32(0)
)
// sumGeneric generates an authenticator for msg using a one-time key and
// puts the 16-byte result into out. This is the generic implementation of
// Sum and should be called if no assembly implementation is available.
func sumGeneric(out *[TagSize]byte, msg []byte, key *[32]byte) {
h := newMACGeneric(key)
h.Write(msg)
h.Sum(out)
}
func newMACGeneric(key *[32]byte) (h macGeneric) {
h.r[0] = binary.LittleEndian.Uint32(key[0:]) & 0x3ffffff
h.r[1] = (binary.LittleEndian.Uint32(key[3:]) >> 2) & 0x3ffff03
h.r[2] = (binary.LittleEndian.Uint32(key[6:]) >> 4) & 0x3ffc0ff
h.r[3] = (binary.LittleEndian.Uint32(key[9:]) >> 6) & 0x3f03fff
h.r[4] = (binary.LittleEndian.Uint32(key[12:]) >> 8) & 0x00fffff
h.s[0] = binary.LittleEndian.Uint32(key[16:])
h.s[1] = binary.LittleEndian.Uint32(key[20:])
h.s[2] = binary.LittleEndian.Uint32(key[24:])
h.s[3] = binary.LittleEndian.Uint32(key[28:])
return
}
type macGeneric struct {
h, r [5]uint32
s [4]uint32
buffer [TagSize]byte
offset int
}
func (h *macGeneric) Write(p []byte) (n int, err error) {
n = len(p)
if h.offset > 0 {
remaining := TagSize - h.offset
if n < remaining {
h.offset += copy(h.buffer[h.offset:], p)
return n, nil
}
copy(h.buffer[h.offset:], p[:remaining])
p = p[remaining:]
h.offset = 0
updateGeneric(h.buffer[:], msgBlock, &(h.h), &(h.r))
}
if nn := len(p) - (len(p) % TagSize); nn > 0 {
updateGeneric(p, msgBlock, &(h.h), &(h.r))
p = p[nn:]
}
if len(p) > 0 {
h.offset += copy(h.buffer[h.offset:], p)
}
return n, nil
}
func (h *macGeneric) Sum(out *[16]byte) {
H, R := h.h, h.r
if h.offset > 0 {
var buffer [TagSize]byte
copy(buffer[:], h.buffer[:h.offset])
buffer[h.offset] = 1 // invariant: h.offset < TagSize
updateGeneric(buffer[:], finalBlock, &H, &R)
}
finalizeGeneric(out, &H, &(h.s))
}
func updateGeneric(msg []byte, flag uint32, h, r *[5]uint32) {
h0, h1, h2, h3, h4 := h[0], h[1], h[2], h[3], h[4]
r0, r1, r2, r3, r4 := uint64(r[0]), uint64(r[1]), uint64(r[2]), uint64(r[3]), uint64(r[4])
R1, R2, R3, R4 := r1*5, r2*5, r3*5, r4*5
for len(msg) >= TagSize {
// h += msg
h0 += binary.LittleEndian.Uint32(msg[0:]) & 0x3ffffff
h1 += (binary.LittleEndian.Uint32(msg[3:]) >> 2) & 0x3ffffff
h2 += (binary.LittleEndian.Uint32(msg[6:]) >> 4) & 0x3ffffff
h3 += (binary.LittleEndian.Uint32(msg[9:]) >> 6) & 0x3ffffff
h4 += (binary.LittleEndian.Uint32(msg[12:]) >> 8) | flag
// h *= r
d0 := (uint64(h0) * r0) + (uint64(h1) * R4) + (uint64(h2) * R3) + (uint64(h3) * R2) + (uint64(h4) * R1)
d1 := (d0 >> 26) + (uint64(h0) * r1) + (uint64(h1) * r0) + (uint64(h2) * R4) + (uint64(h3) * R3) + (uint64(h4) * R2)
d2 := (d1 >> 26) + (uint64(h0) * r2) + (uint64(h1) * r1) + (uint64(h2) * r0) + (uint64(h3) * R4) + (uint64(h4) * R3)
d3 := (d2 >> 26) + (uint64(h0) * r3) + (uint64(h1) * r2) + (uint64(h2) * r1) + (uint64(h3) * r0) + (uint64(h4) * R4)
d4 := (d3 >> 26) + (uint64(h0) * r4) + (uint64(h1) * r3) + (uint64(h2) * r2) + (uint64(h3) * r1) + (uint64(h4) * r0)
// h %= p
h0 = uint32(d0) & 0x3ffffff
h1 = uint32(d1) & 0x3ffffff
h2 = uint32(d2) & 0x3ffffff
h3 = uint32(d3) & 0x3ffffff
h4 = uint32(d4) & 0x3ffffff
h0 += uint32(d4>>26) * 5
h1 += h0 >> 26
h0 = h0 & 0x3ffffff
msg = msg[TagSize:]
}
h[0], h[1], h[2], h[3], h[4] = h0, h1, h2, h3, h4
}
func finalizeGeneric(out *[TagSize]byte, h *[5]uint32, s *[4]uint32) {
h0, h1, h2, h3, h4 := h[0], h[1], h[2], h[3], h[4]
// h %= p reduction
h2 += h1 >> 26
h1 &= 0x3ffffff
h3 += h2 >> 26
h2 &= 0x3ffffff
h4 += h3 >> 26
h3 &= 0x3ffffff
h0 += 5 * (h4 >> 26)
h4 &= 0x3ffffff
h1 += h0 >> 26
h0 &= 0x3ffffff
// h - p
t0 := h0 + 5
t1 := h1 + (t0 >> 26)
t2 := h2 + (t1 >> 26)
t3 := h3 + (t2 >> 26)
t4 := h4 + (t3 >> 26) - (1 << 26)
t0 &= 0x3ffffff
t1 &= 0x3ffffff
t2 &= 0x3ffffff
t3 &= 0x3ffffff
// select h if h < p else h - p
t_mask := (t4 >> 31) - 1
h_mask := ^t_mask
h0 = (h0 & h_mask) | (t0 & t_mask)
h1 = (h1 & h_mask) | (t1 & t_mask)
h2 = (h2 & h_mask) | (t2 & t_mask)
h3 = (h3 & h_mask) | (t3 & t_mask)
h4 = (h4 & h_mask) | (t4 & t_mask)
// h %= 2^128
h0 |= h1 << 26
h1 = ((h1 >> 6) | (h2 << 20))
h2 = ((h2 >> 12) | (h3 << 14))
h3 = ((h3 >> 18) | (h4 << 8))
// s: the s part of the key
// tag = (h + s) % (2^128)
t := uint64(h0) + uint64(s[0])
h0 = uint32(t)
t = uint64(h1) + uint64(s[1]) + (t >> 32)
h1 = uint32(t)
t = uint64(h2) + uint64(s[2]) + (t >> 32)
h2 = uint32(t)
t = uint64(h3) + uint64(s[3]) + (t >> 32)
h3 = uint32(t)
binary.LittleEndian.PutUint32(out[0:], h0)
binary.LittleEndian.PutUint32(out[4:], h1)
binary.LittleEndian.PutUint32(out[8:], h2)
binary.LittleEndian.PutUint32(out[12:], h3)
}
|
