1 /* 2 * Public Domain poly1305 from Andrew Moon 3 * Based on poly1305-donna.c, poly1305-donna-32.h and poly1305-donna.h from: 4 * https://github.com/floodyberry/poly1305-donna 5 */ 6 7 #include <sys/types.h> 8 #include <sys/systm.h> 9 10 #include "poly1305.h" 11 12 /* 13 * poly1305 implementation using 32 bit * 32 bit = 64 bit multiplication 14 * and 64 bit addition. 15 */ 16 17 /* interpret four 8 bit unsigned integers as a 32 bit unsigned integer in little endian */ 18 static unsigned long 19 U8TO32(const unsigned char *p) 20 { 21 return (((unsigned long)(p[0] & 0xff)) | 22 ((unsigned long)(p[1] & 0xff) << 8) | 23 ((unsigned long)(p[2] & 0xff) << 16) | 24 ((unsigned long)(p[3] & 0xff) << 24)); 25 } 26 27 /* store a 32 bit unsigned integer as four 8 bit unsigned integers in little endian */ 28 static void 29 U32TO8(unsigned char *p, unsigned long v) 30 { 31 p[0] = (v) & 0xff; 32 p[1] = (v >> 8) & 0xff; 33 p[2] = (v >> 16) & 0xff; 34 p[3] = (v >> 24) & 0xff; 35 } 36 37 void 38 poly1305_init(poly1305_state *st, const unsigned char key[32]) 39 { 40 /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */ 41 st->r[0] = (U8TO32(&key[0])) & 0x3ffffff; 42 st->r[1] = (U8TO32(&key[3]) >> 2) & 0x3ffff03; 43 st->r[2] = (U8TO32(&key[6]) >> 4) & 0x3ffc0ff; 44 st->r[3] = (U8TO32(&key[9]) >> 6) & 0x3f03fff; 45 st->r[4] = (U8TO32(&key[12]) >> 8) & 0x00fffff; 46 47 /* h = 0 */ 48 st->h[0] = 0; 49 st->h[1] = 0; 50 st->h[2] = 0; 51 st->h[3] = 0; 52 st->h[4] = 0; 53 54 /* save pad for later */ 55 st->pad[0] = U8TO32(&key[16]); 56 st->pad[1] = U8TO32(&key[20]); 57 st->pad[2] = U8TO32(&key[24]); 58 st->pad[3] = U8TO32(&key[28]); 59 60 st->leftover = 0; 61 st->final = 0; 62 } 63 64 static void 65 poly1305_blocks(poly1305_state *st, const unsigned char *m, size_t bytes) 66 { 67 const unsigned long hibit = (st->final) ? 0 : (1 << 24); /* 1 << 128 */ 68 unsigned long r0, r1, r2, r3, r4; 69 unsigned long s1, s2, s3, s4; 70 unsigned long h0, h1, h2, h3, h4; 71 unsigned long long d0, d1, d2, d3, d4; 72 unsigned long c; 73 74 r0 = st->r[0]; 75 r1 = st->r[1]; 76 r2 = st->r[2]; 77 r3 = st->r[3]; 78 r4 = st->r[4]; 79 80 s1 = r1 * 5; 81 s2 = r2 * 5; 82 s3 = r3 * 5; 83 s4 = r4 * 5; 84 85 h0 = st->h[0]; 86 h1 = st->h[1]; 87 h2 = st->h[2]; 88 h3 = st->h[3]; 89 h4 = st->h[4]; 90 91 while (bytes >= poly1305_block_size) { 92 /* h += m[i] */ 93 h0 += (U8TO32(m + 0)) & 0x3ffffff; 94 h1 += (U8TO32(m + 3) >> 2) & 0x3ffffff; 95 h2 += (U8TO32(m + 6) >> 4) & 0x3ffffff; 96 h3 += (U8TO32(m + 9) >> 6) & 0x3ffffff; 97 h4 += (U8TO32(m + 12) >> 8) | hibit; 98 99 /* h *= r */ 100 d0 = ((unsigned long long)h0 * r0) + 101 ((unsigned long long)h1 * s4) + 102 ((unsigned long long)h2 * s3) + 103 ((unsigned long long)h3 * s2) + 104 ((unsigned long long)h4 * s1); 105 d1 = ((unsigned long long)h0 * r1) + 106 ((unsigned long long)h1 * r0) + 107 ((unsigned long long)h2 * s4) + 108 ((unsigned long long)h3 * s3) + 109 ((unsigned long long)h4 * s2); 110 d2 = ((unsigned long long)h0 * r2) + 111 ((unsigned long long)h1 * r1) + 112 ((unsigned long long)h2 * r0) + 113 ((unsigned long long)h3 * s4) + 114 ((unsigned long long)h4 * s3); 115 d3 = ((unsigned long long)h0 * r3) + 116 ((unsigned long long)h1 * r2) + 117 ((unsigned long long)h2 * r1) + 118 ((unsigned long long)h3 * r0) + 119 ((unsigned long long)h4 * s4); 120 d4 = ((unsigned long long)h0 * r4) + 121 ((unsigned long long)h1 * r3) + 122 ((unsigned long long)h2 * r2) + 123 ((unsigned long long)h3 * r1) + 124 ((unsigned long long)h4 * r0); 125 126 /* (partial) h %= p */ 127 c = (unsigned long)(d0 >> 26); 128 h0 = (unsigned long)d0 & 0x3ffffff; 129 d1 += c; 130 c = (unsigned long)(d1 >> 26); 131 h1 = (unsigned long)d1 & 0x3ffffff; 132 d2 += c; 133 c = (unsigned long)(d2 >> 26); 134 h2 = (unsigned long)d2 & 0x3ffffff; 135 d3 += c; 136 c = (unsigned long)(d3 >> 26); 137 h3 = (unsigned long)d3 & 0x3ffffff; 138 d4 += c; 139 c = (unsigned long)(d4 >> 26); 140 h4 = (unsigned long)d4 & 0x3ffffff; 141 h0 += c * 5; 142 c = (h0 >> 26); 143 h0 = h0 & 0x3ffffff; 144 h1 += c; 145 146 m += poly1305_block_size; 147 bytes -= poly1305_block_size; 148 } 149 150 st->h[0] = h0; 151 st->h[1] = h1; 152 st->h[2] = h2; 153 st->h[3] = h3; 154 st->h[4] = h4; 155 } 156 157 void 158 poly1305_update(poly1305_state *st, const unsigned char *m, size_t bytes) 159 { 160 size_t i; 161 162 /* handle leftover */ 163 if (st->leftover) { 164 size_t want = (poly1305_block_size - st->leftover); 165 if (want > bytes) 166 want = bytes; 167 for (i = 0; i < want; i++) 168 st->buffer[st->leftover + i] = m[i]; 169 bytes -= want; 170 m += want; 171 st->leftover += want; 172 if (st->leftover < poly1305_block_size) 173 return; 174 poly1305_blocks(st, st->buffer, poly1305_block_size); 175 st->leftover = 0; 176 } 177 178 /* process full blocks */ 179 if (bytes >= poly1305_block_size) { 180 size_t want = (bytes & ~(poly1305_block_size - 1)); 181 poly1305_blocks(st, m, want); 182 m += want; 183 bytes -= want; 184 } 185 186 /* store leftover */ 187 if (bytes) { 188 for (i = 0; i < bytes; i++) 189 st->buffer[st->leftover + i] = m[i]; 190 st->leftover += bytes; 191 } 192 } 193 194 void 195 poly1305_finish(poly1305_state *st, unsigned char mac[16]) 196 { 197 unsigned long h0, h1, h2, h3, h4, c; 198 unsigned long g0, g1, g2, g3, g4; 199 unsigned long long f; 200 unsigned long mask; 201 202 /* process the remaining block */ 203 if (st->leftover) { 204 size_t i = st->leftover; 205 st->buffer[i++] = 1; 206 for (; i < poly1305_block_size; i++) 207 st->buffer[i] = 0; 208 st->final = 1; 209 poly1305_blocks(st, st->buffer, poly1305_block_size); 210 } 211 212 /* fully carry h */ 213 h0 = st->h[0]; 214 h1 = st->h[1]; 215 h2 = st->h[2]; 216 h3 = st->h[3]; 217 h4 = st->h[4]; 218 219 c = h1 >> 26; 220 h1 = h1 & 0x3ffffff; 221 h2 += c; 222 c = h2 >> 26; 223 h2 = h2 & 0x3ffffff; 224 h3 += c; 225 c = h3 >> 26; 226 h3 = h3 & 0x3ffffff; 227 h4 += c; 228 c = h4 >> 26; 229 h4 = h4 & 0x3ffffff; 230 h0 += c * 5; 231 c = h0 >> 26; 232 h0 = h0 & 0x3ffffff; 233 h1 += c; 234 235 /* compute h + -p */ 236 g0 = h0 + 5; 237 c = g0 >> 26; 238 g0 &= 0x3ffffff; 239 g1 = h1 + c; 240 c = g1 >> 26; 241 g1 &= 0x3ffffff; 242 g2 = h2 + c; 243 c = g2 >> 26; 244 g2 &= 0x3ffffff; 245 g3 = h3 + c; 246 c = g3 >> 26; 247 g3 &= 0x3ffffff; 248 g4 = h4 + c - (1 << 26); 249 250 /* select h if h < p, or h + -p if h >= p */ 251 mask = (g4 >> ((sizeof(unsigned long) * 8) - 1)) - 1; 252 g0 &= mask; 253 g1 &= mask; 254 g2 &= mask; 255 g3 &= mask; 256 g4 &= mask; 257 mask = ~mask; 258 h0 = (h0 & mask) | g0; 259 h1 = (h1 & mask) | g1; 260 h2 = (h2 & mask) | g2; 261 h3 = (h3 & mask) | g3; 262 h4 = (h4 & mask) | g4; 263 264 /* h = h % (2^128) */ 265 h0 = ((h0) | (h1 << 26)) & 0xffffffff; 266 h1 = ((h1 >> 6) | (h2 << 20)) & 0xffffffff; 267 h2 = ((h2 >> 12) | (h3 << 14)) & 0xffffffff; 268 h3 = ((h3 >> 18) | (h4 << 8)) & 0xffffffff; 269 270 /* mac = (h + pad) % (2^128) */ 271 f = (unsigned long long)h0 + st->pad[0]; 272 h0 = (unsigned long)f; 273 f = (unsigned long long)h1 + st->pad[1] + (f >> 32); 274 h1 = (unsigned long)f; 275 f = (unsigned long long)h2 + st->pad[2] + (f >> 32); 276 h2 = (unsigned long)f; 277 f = (unsigned long long)h3 + st->pad[3] + (f >> 32); 278 h3 = (unsigned long)f; 279 280 U32TO8(mac + 0, h0); 281 U32TO8(mac + 4, h1); 282 U32TO8(mac + 8, h2); 283 U32TO8(mac + 12, h3); 284 285 /* zero out the state */ 286 st->h[0] = 0; 287 st->h[1] = 0; 288 st->h[2] = 0; 289 st->h[3] = 0; 290 st->h[4] = 0; 291 st->r[0] = 0; 292 st->r[1] = 0; 293 st->r[2] = 0; 294 st->r[3] = 0; 295 st->r[4] = 0; 296 st->pad[0] = 0; 297 st->pad[1] = 0; 298 st->pad[2] = 0; 299 st->pad[3] = 0; 300 } 301