1 /* $OpenBSD: poly1305.c,v 1.2 2020/07/22 13:54:30 tobhe Exp $ */ 2 /* 3 * Public Domain poly1305 from Andrew Moon 4 * Based on poly1305-donna.c, poly1305-donna-32.h and poly1305-donna.h from: 5 * https://github.com/floodyberry/poly1305-donna 6 */ 7 8 #include <sys/types.h> 9 #include <sys/systm.h> 10 11 #include <crypto/poly1305/poly1305.h> 12 13 /* 14 * poly1305 implementation using 32 bit * 32 bit = 64 bit multiplication 15 * and 64 bit addition. 16 */ 17 18 /* interpret four 8 bit unsigned integers as a 32 bit unsigned integer in little endian */ 19 static inline unsigned long 20 U8TO32(const uint8_t *p) 21 { 22 return (((unsigned long)(p[0] & 0xff)) | 23 ((unsigned long)(p[1] & 0xff) << 8) | 24 ((unsigned long)(p[2] & 0xff) << 16) | 25 ((unsigned long)(p[3] & 0xff) << 24)); 26 } 27 28 /* store a 32 bit unsigned integer as four 8 bit unsigned integers in little endian */ 29 static inline void 30 U32TO8(uint8_t *p, unsigned long v) 31 { 32 p[0] = (v) & 0xff; 33 p[1] = (v >> 8) & 0xff; 34 p[2] = (v >> 16) & 0xff; 35 p[3] = (v >> 24) & 0xff; 36 } 37 38 void 39 poly1305_init(poly1305_state *st, const uint8_t key[POLY1305_KEY_SIZE]) 40 { 41 /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */ 42 st->r[0] = (U8TO32(&key[0])) & 0x3ffffff; 43 st->r[1] = (U8TO32(&key[3]) >> 2) & 0x3ffff03; 44 st->r[2] = (U8TO32(&key[6]) >> 4) & 0x3ffc0ff; 45 st->r[3] = (U8TO32(&key[9]) >> 6) & 0x3f03fff; 46 st->r[4] = (U8TO32(&key[12]) >> 8) & 0x00fffff; 47 48 /* h = 0 */ 49 st->h[0] = 0; 50 st->h[1] = 0; 51 st->h[2] = 0; 52 st->h[3] = 0; 53 st->h[4] = 0; 54 55 /* save pad for later */ 56 st->pad[0] = U8TO32(&key[16]); 57 st->pad[1] = U8TO32(&key[20]); 58 st->pad[2] = U8TO32(&key[24]); 59 st->pad[3] = U8TO32(&key[28]); 60 61 st->leftover = 0; 62 st->final = 0; 63 } 64 65 static void 66 poly1305_blocks(poly1305_state *st, const uint8_t *m, size_t bytes) 67 { 68 const unsigned long hibit = (st->final) ? 0 : (1 << 24); /* 1 << 128 */ 69 unsigned long r0, r1, r2, r3, r4; 70 unsigned long s1, s2, s3, s4; 71 unsigned long h0, h1, h2, h3, h4; 72 unsigned long long d0, d1, d2, d3, d4; 73 unsigned long c; 74 75 r0 = st->r[0]; 76 r1 = st->r[1]; 77 r2 = st->r[2]; 78 r3 = st->r[3]; 79 r4 = st->r[4]; 80 81 s1 = r1 * 5; 82 s2 = r2 * 5; 83 s3 = r3 * 5; 84 s4 = r4 * 5; 85 86 h0 = st->h[0]; 87 h1 = st->h[1]; 88 h2 = st->h[2]; 89 h3 = st->h[3]; 90 h4 = st->h[4]; 91 92 while (bytes >= POLY1305_BLOCK_SIZE) { 93 /* h += m[i] */ 94 h0 += (U8TO32(m + 0)) & 0x3ffffff; 95 h1 += (U8TO32(m + 3) >> 2) & 0x3ffffff; 96 h2 += (U8TO32(m + 6) >> 4) & 0x3ffffff; 97 h3 += (U8TO32(m + 9) >> 6) & 0x3ffffff; 98 h4 += (U8TO32(m + 12) >> 8) | hibit; 99 100 /* h *= r */ 101 d0 = ((unsigned long long)h0 * r0) + 102 ((unsigned long long)h1 * s4) + 103 ((unsigned long long)h2 * s3) + 104 ((unsigned long long)h3 * s2) + 105 ((unsigned long long)h4 * s1); 106 d1 = ((unsigned long long)h0 * r1) + 107 ((unsigned long long)h1 * r0) + 108 ((unsigned long long)h2 * s4) + 109 ((unsigned long long)h3 * s3) + 110 ((unsigned long long)h4 * s2); 111 d2 = ((unsigned long long)h0 * r2) + 112 ((unsigned long long)h1 * r1) + 113 ((unsigned long long)h2 * r0) + 114 ((unsigned long long)h3 * s4) + 115 ((unsigned long long)h4 * s3); 116 d3 = ((unsigned long long)h0 * r3) + 117 ((unsigned long long)h1 * r2) + 118 ((unsigned long long)h2 * r1) + 119 ((unsigned long long)h3 * r0) + 120 ((unsigned long long)h4 * s4); 121 d4 = ((unsigned long long)h0 * r4) + 122 ((unsigned long long)h1 * r3) + 123 ((unsigned long long)h2 * r2) + 124 ((unsigned long long)h3 * r1) + 125 ((unsigned long long)h4 * r0); 126 127 /* (partial) h %= p */ 128 c = (unsigned long)(d0 >> 26); 129 h0 = (unsigned long)d0 & 0x3ffffff; 130 d1 += c; 131 c = (unsigned long)(d1 >> 26); 132 h1 = (unsigned long)d1 & 0x3ffffff; 133 d2 += c; 134 c = (unsigned long)(d2 >> 26); 135 h2 = (unsigned long)d2 & 0x3ffffff; 136 d3 += c; 137 c = (unsigned long)(d3 >> 26); 138 h3 = (unsigned long)d3 & 0x3ffffff; 139 d4 += c; 140 c = (unsigned long)(d4 >> 26); 141 h4 = (unsigned long)d4 & 0x3ffffff; 142 h0 += c * 5; 143 c = (h0 >> 26); 144 h0 = h0 & 0x3ffffff; 145 h1 += c; 146 147 m += POLY1305_BLOCK_SIZE; 148 bytes -= POLY1305_BLOCK_SIZE; 149 } 150 151 st->h[0] = h0; 152 st->h[1] = h1; 153 st->h[2] = h2; 154 st->h[3] = h3; 155 st->h[4] = h4; 156 } 157 158 void 159 poly1305_update(poly1305_state *st, const uint8_t *m, size_t bytes) 160 { 161 size_t i; 162 163 /* handle leftover */ 164 if (st->leftover) { 165 size_t want = (POLY1305_BLOCK_SIZE - st->leftover); 166 if (want > bytes) 167 want = bytes; 168 for (i = 0; i < want; i++) 169 st->buffer[st->leftover + i] = m[i]; 170 bytes -= want; 171 m += want; 172 st->leftover += want; 173 if (st->leftover < POLY1305_BLOCK_SIZE) 174 return; 175 poly1305_blocks(st, st->buffer, POLY1305_BLOCK_SIZE); 176 st->leftover = 0; 177 } 178 179 /* process full blocks */ 180 if (bytes >= POLY1305_BLOCK_SIZE) { 181 size_t want = (bytes & ~(POLY1305_BLOCK_SIZE - 1)); 182 poly1305_blocks(st, m, want); 183 m += want; 184 bytes -= want; 185 } 186 187 /* store leftover */ 188 if (bytes) { 189 for (i = 0; i < bytes; i++) 190 st->buffer[st->leftover + i] = m[i]; 191 st->leftover += bytes; 192 } 193 } 194 195 void 196 poly1305_finish(poly1305_state *st, uint8_t mac[POLY1305_MAC_SIZE]) 197 { 198 unsigned long h0, h1, h2, h3, h4, c; 199 unsigned long g0, g1, g2, g3, g4; 200 unsigned long long f; 201 unsigned long mask; 202 203 /* process the remaining block */ 204 if (st->leftover) { 205 size_t i = st->leftover; 206 st->buffer[i++] = 1; 207 for (; i < POLY1305_BLOCK_SIZE; i++) 208 st->buffer[i] = 0; 209 st->final = 1; 210 poly1305_blocks(st, st->buffer, POLY1305_BLOCK_SIZE); 211 } 212 213 /* fully carry h */ 214 h0 = st->h[0]; 215 h1 = st->h[1]; 216 h2 = st->h[2]; 217 h3 = st->h[3]; 218 h4 = st->h[4]; 219 220 c = h1 >> 26; 221 h1 = h1 & 0x3ffffff; 222 h2 += c; 223 c = h2 >> 26; 224 h2 = h2 & 0x3ffffff; 225 h3 += c; 226 c = h3 >> 26; 227 h3 = h3 & 0x3ffffff; 228 h4 += c; 229 c = h4 >> 26; 230 h4 = h4 & 0x3ffffff; 231 h0 += c * 5; 232 c = h0 >> 26; 233 h0 = h0 & 0x3ffffff; 234 h1 += c; 235 236 /* compute h + -p */ 237 g0 = h0 + 5; 238 c = g0 >> 26; 239 g0 &= 0x3ffffff; 240 g1 = h1 + c; 241 c = g1 >> 26; 242 g1 &= 0x3ffffff; 243 g2 = h2 + c; 244 c = g2 >> 26; 245 g2 &= 0x3ffffff; 246 g3 = h3 + c; 247 c = g3 >> 26; 248 g3 &= 0x3ffffff; 249 g4 = h4 + c - (1 << 26); 250 251 /* select h if h < p, or h + -p if h >= p */ 252 mask = (g4 >> ((sizeof(unsigned long) * 8) - 1)) - 1; 253 g0 &= mask; 254 g1 &= mask; 255 g2 &= mask; 256 g3 &= mask; 257 g4 &= mask; 258 mask = ~mask; 259 h0 = (h0 & mask) | g0; 260 h1 = (h1 & mask) | g1; 261 h2 = (h2 & mask) | g2; 262 h3 = (h3 & mask) | g3; 263 h4 = (h4 & mask) | g4; 264 265 /* h = h % (2^128) */ 266 h0 = ((h0) | (h1 << 26)) & 0xffffffff; 267 h1 = ((h1 >> 6) | (h2 << 20)) & 0xffffffff; 268 h2 = ((h2 >> 12) | (h3 << 14)) & 0xffffffff; 269 h3 = ((h3 >> 18) | (h4 << 8)) & 0xffffffff; 270 271 /* mac = (h + pad) % (2^128) */ 272 f = (unsigned long long)h0 + st->pad[0]; 273 h0 = (unsigned long)f; 274 f = (unsigned long long)h1 + st->pad[1] + (f >> 32); 275 h1 = (unsigned long)f; 276 f = (unsigned long long)h2 + st->pad[2] + (f >> 32); 277 h2 = (unsigned long)f; 278 f = (unsigned long long)h3 + st->pad[3] + (f >> 32); 279 h3 = (unsigned long)f; 280 281 U32TO8(mac + 0, h0); 282 U32TO8(mac + 4, h1); 283 U32TO8(mac + 8, h2); 284 U32TO8(mac + 12, h3); 285 286 /* zero out the state */ 287 st->h[0] = 0; 288 st->h[1] = 0; 289 st->h[2] = 0; 290 st->h[3] = 0; 291 st->h[4] = 0; 292 st->r[0] = 0; 293 st->r[1] = 0; 294 st->r[2] = 0; 295 st->r[3] = 0; 296 st->r[4] = 0; 297 st->pad[0] = 0; 298 st->pad[1] = 0; 299 st->pad[2] = 0; 300 st->pad[3] = 0; 301 } 302