poly1305.cpp raw
1 // Copyright (c) 2019 The Limenka developers
2 // Distributed under the MIT software license, see the accompanying
3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5 #include <crypto/common.h>
6 #include <crypto/poly1305.h>
7
8 #include <string.h>
9
10 namespace poly1305_donna {
11
12 // Based on the public domain implementation by Andrew Moon
13 // poly1305-donna-32.h from https://github.com/floodyberry/poly1305-donna
14
15 void poly1305_init(poly1305_context *st, const unsigned char key[32]) noexcept {
16 /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
17 st->r[0] = (ReadLE32(&key[ 0]) ) & 0x3ffffff;
18 st->r[1] = (ReadLE32(&key[ 3]) >> 2) & 0x3ffff03;
19 st->r[2] = (ReadLE32(&key[ 6]) >> 4) & 0x3ffc0ff;
20 st->r[3] = (ReadLE32(&key[ 9]) >> 6) & 0x3f03fff;
21 st->r[4] = (ReadLE32(&key[12]) >> 8) & 0x00fffff;
22
23 /* h = 0 */
24 st->h[0] = 0;
25 st->h[1] = 0;
26 st->h[2] = 0;
27 st->h[3] = 0;
28 st->h[4] = 0;
29
30 /* save pad for later */
31 st->pad[0] = ReadLE32(&key[16]);
32 st->pad[1] = ReadLE32(&key[20]);
33 st->pad[2] = ReadLE32(&key[24]);
34 st->pad[3] = ReadLE32(&key[28]);
35
36 st->leftover = 0;
37 st->final = 0;
38 }
39
40 static void poly1305_blocks(poly1305_context *st, const unsigned char *m, size_t bytes) noexcept {
41 const uint32_t hibit = (st->final) ? 0 : (1UL << 24); /* 1 << 128 */
42 uint32_t r0,r1,r2,r3,r4;
43 uint32_t s1,s2,s3,s4;
44 uint32_t h0,h1,h2,h3,h4;
45 uint64_t d0,d1,d2,d3,d4;
46 uint32_t c;
47
48 r0 = st->r[0];
49 r1 = st->r[1];
50 r2 = st->r[2];
51 r3 = st->r[3];
52 r4 = st->r[4];
53
54 s1 = r1 * 5;
55 s2 = r2 * 5;
56 s3 = r3 * 5;
57 s4 = r4 * 5;
58
59 h0 = st->h[0];
60 h1 = st->h[1];
61 h2 = st->h[2];
62 h3 = st->h[3];
63 h4 = st->h[4];
64
65 while (bytes >= POLY1305_BLOCK_SIZE) {
66 /* h += m[i] */
67 h0 += (ReadLE32(m+ 0) ) & 0x3ffffff;
68 h1 += (ReadLE32(m+ 3) >> 2) & 0x3ffffff;
69 h2 += (ReadLE32(m+ 6) >> 4) & 0x3ffffff;
70 h3 += (ReadLE32(m+ 9) >> 6) & 0x3ffffff;
71 h4 += (ReadLE32(m+12) >> 8) | hibit;
72
73 /* h *= r */
74 d0 = ((uint64_t)h0 * r0) + ((uint64_t)h1 * s4) + ((uint64_t)h2 * s3) + ((uint64_t)h3 * s2) + ((uint64_t)h4 * s1);
75 d1 = ((uint64_t)h0 * r1) + ((uint64_t)h1 * r0) + ((uint64_t)h2 * s4) + ((uint64_t)h3 * s3) + ((uint64_t)h4 * s2);
76 d2 = ((uint64_t)h0 * r2) + ((uint64_t)h1 * r1) + ((uint64_t)h2 * r0) + ((uint64_t)h3 * s4) + ((uint64_t)h4 * s3);
77 d3 = ((uint64_t)h0 * r3) + ((uint64_t)h1 * r2) + ((uint64_t)h2 * r1) + ((uint64_t)h3 * r0) + ((uint64_t)h4 * s4);
78 d4 = ((uint64_t)h0 * r4) + ((uint64_t)h1 * r3) + ((uint64_t)h2 * r2) + ((uint64_t)h3 * r1) + ((uint64_t)h4 * r0);
79
80 /* (partial) h %= p */
81 c = (uint32_t)(d0 >> 26); h0 = (uint32_t)d0 & 0x3ffffff;
82 d1 += c; c = (uint32_t)(d1 >> 26); h1 = (uint32_t)d1 & 0x3ffffff;
83 d2 += c; c = (uint32_t)(d2 >> 26); h2 = (uint32_t)d2 & 0x3ffffff;
84 d3 += c; c = (uint32_t)(d3 >> 26); h3 = (uint32_t)d3 & 0x3ffffff;
85 d4 += c; c = (uint32_t)(d4 >> 26); h4 = (uint32_t)d4 & 0x3ffffff;
86 h0 += c * 5; c = (h0 >> 26); h0 = h0 & 0x3ffffff;
87 h1 += c;
88
89 m += POLY1305_BLOCK_SIZE;
90 bytes -= POLY1305_BLOCK_SIZE;
91 }
92
93 st->h[0] = h0;
94 st->h[1] = h1;
95 st->h[2] = h2;
96 st->h[3] = h3;
97 st->h[4] = h4;
98 }
99
100 void poly1305_finish(poly1305_context *st, unsigned char mac[16]) noexcept {
101 uint32_t h0,h1,h2,h3,h4,c;
102 uint32_t g0,g1,g2,g3,g4;
103 uint64_t f;
104 uint32_t mask;
105
106 /* process the remaining block */
107 if (st->leftover) {
108 size_t i = st->leftover;
109 st->buffer[i++] = 1;
110 for (; i < POLY1305_BLOCK_SIZE; i++) {
111 st->buffer[i] = 0;
112 }
113 st->final = 1;
114 poly1305_blocks(st, st->buffer, POLY1305_BLOCK_SIZE);
115 }
116
117 /* fully carry h */
118 h0 = st->h[0];
119 h1 = st->h[1];
120 h2 = st->h[2];
121 h3 = st->h[3];
122 h4 = st->h[4];
123
124 c = h1 >> 26; h1 = h1 & 0x3ffffff;
125 h2 += c; c = h2 >> 26; h2 = h2 & 0x3ffffff;
126 h3 += c; c = h3 >> 26; h3 = h3 & 0x3ffffff;
127 h4 += c; c = h4 >> 26; h4 = h4 & 0x3ffffff;
128 h0 += c * 5; c = h0 >> 26; h0 = h0 & 0x3ffffff;
129 h1 += c;
130
131 /* compute h + -p */
132 g0 = h0 + 5; c = g0 >> 26; g0 &= 0x3ffffff;
133 g1 = h1 + c; c = g1 >> 26; g1 &= 0x3ffffff;
134 g2 = h2 + c; c = g2 >> 26; g2 &= 0x3ffffff;
135 g3 = h3 + c; c = g3 >> 26; g3 &= 0x3ffffff;
136 g4 = h4 + c - (1UL << 26);
137
138 /* select h if h < p, or h + -p if h >= p */
139 mask = (g4 >> ((sizeof(uint32_t) * 8) - 1)) - 1;
140 g0 &= mask;
141 g1 &= mask;
142 g2 &= mask;
143 g3 &= mask;
144 g4 &= mask;
145 mask = ~mask;
146 h0 = (h0 & mask) | g0;
147 h1 = (h1 & mask) | g1;
148 h2 = (h2 & mask) | g2;
149 h3 = (h3 & mask) | g3;
150 h4 = (h4 & mask) | g4;
151
152 /* h = h % (2^128) */
153 h0 = ((h0 ) | (h1 << 26)) & 0xffffffff;
154 h1 = ((h1 >> 6) | (h2 << 20)) & 0xffffffff;
155 h2 = ((h2 >> 12) | (h3 << 14)) & 0xffffffff;
156 h3 = ((h3 >> 18) | (h4 << 8)) & 0xffffffff;
157
158 /* mac = (h + pad) % (2^128) */
159 f = (uint64_t)h0 + st->pad[0] ; h0 = (uint32_t)f;
160 f = (uint64_t)h1 + st->pad[1] + (f >> 32); h1 = (uint32_t)f;
161 f = (uint64_t)h2 + st->pad[2] + (f >> 32); h2 = (uint32_t)f;
162 f = (uint64_t)h3 + st->pad[3] + (f >> 32); h3 = (uint32_t)f;
163
164 WriteLE32(mac + 0, h0);
165 WriteLE32(mac + 4, h1);
166 WriteLE32(mac + 8, h2);
167 WriteLE32(mac + 12, h3);
168
169 /* zero out the state */
170 st->h[0] = 0;
171 st->h[1] = 0;
172 st->h[2] = 0;
173 st->h[3] = 0;
174 st->h[4] = 0;
175 st->r[0] = 0;
176 st->r[1] = 0;
177 st->r[2] = 0;
178 st->r[3] = 0;
179 st->r[4] = 0;
180 st->pad[0] = 0;
181 st->pad[1] = 0;
182 st->pad[2] = 0;
183 st->pad[3] = 0;
184 }
185
186 void poly1305_update(poly1305_context *st, const unsigned char *m, size_t bytes) noexcept {
187 size_t i;
188
189 /* handle leftover */
190 if (st->leftover) {
191 size_t want = (POLY1305_BLOCK_SIZE - st->leftover);
192 if (want > bytes) {
193 want = bytes;
194 }
195 for (i = 0; i < want; i++) {
196 st->buffer[st->leftover + i] = m[i];
197 }
198 bytes -= want;
199 m += want;
200 st->leftover += want;
201 if (st->leftover < POLY1305_BLOCK_SIZE) return;
202 poly1305_blocks(st, st->buffer, POLY1305_BLOCK_SIZE);
203 st->leftover = 0;
204 }
205
206 /* process full blocks */
207 if (bytes >= POLY1305_BLOCK_SIZE) {
208 size_t want = (bytes & ~(POLY1305_BLOCK_SIZE - 1));
209 poly1305_blocks(st, m, want);
210 m += want;
211 bytes -= want;
212 }
213
214 /* store leftover */
215 if (bytes) {
216 for (i = 0; i < bytes; i++) {
217 st->buffer[st->leftover + i] = m[i];
218 }
219 st->leftover += bytes;
220 }
221 }
222
223 } // namespace poly1305_donna
224