1 /* 2 * Poly1305 authenticator algorithm, RFC7539 3 * 4 * Copyright (C) 2015 Martin Willi 5 * 6 * Based on public domain code by Andrew Moon and Daniel J. Bernstein. 7 * 8 * This program is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU General Public License as published by 10 * the Free Software Foundation; either version 2 of the License, or 11 * (at your option) any later version. 12 */ 13 14 #include <crypto/algapi.h> 15 #include <crypto/internal/hash.h> 16 #include <linux/crypto.h> 17 #include <linux/kernel.h> 18 #include <linux/module.h> 19 20 #define POLY1305_BLOCK_SIZE 16 21 #define POLY1305_KEY_SIZE 32 22 #define POLY1305_DIGEST_SIZE 16 23 24 struct poly1305_desc_ctx { 25 /* key */ 26 u32 r[5]; 27 /* finalize key */ 28 u32 s[4]; 29 /* accumulator */ 30 u32 h[5]; 31 /* partial buffer */ 32 u8 buf[POLY1305_BLOCK_SIZE]; 33 /* bytes used in partial buffer */ 34 unsigned int buflen; 35 /* r key has been set */ 36 bool rset; 37 /* s key has been set */ 38 bool sset; 39 }; 40 41 static inline u64 mlt(u64 a, u64 b) 42 { 43 return a * b; 44 } 45 46 static inline u32 sr(u64 v, u_char n) 47 { 48 return v >> n; 49 } 50 51 static inline u32 and(u32 v, u32 mask) 52 { 53 return v & mask; 54 } 55 56 static inline u32 le32_to_cpuvp(const void *p) 57 { 58 return le32_to_cpup(p); 59 } 60 61 static int poly1305_init(struct shash_desc *desc) 62 { 63 struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); 64 65 memset(dctx->h, 0, sizeof(dctx->h)); 66 dctx->buflen = 0; 67 dctx->rset = false; 68 dctx->sset = false; 69 70 return 0; 71 } 72 73 static int poly1305_setkey(struct crypto_shash *tfm, 74 const u8 *key, unsigned int keylen) 75 { 76 /* Poly1305 requires a unique key for each tag, which implies that 77 * we can't set it on the tfm that gets accessed by multiple users 78 * simultaneously. Instead we expect the key as the first 32 bytes in 79 * the update() call. */ 80 return -ENOTSUPP; 81 } 82 83 static void poly1305_setrkey(struct poly1305_desc_ctx *dctx, const u8 *key) 84 { 85 /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */ 86 dctx->r[0] = (le32_to_cpuvp(key + 0) >> 0) & 0x3ffffff; 87 dctx->r[1] = (le32_to_cpuvp(key + 3) >> 2) & 0x3ffff03; 88 dctx->r[2] = (le32_to_cpuvp(key + 6) >> 4) & 0x3ffc0ff; 89 dctx->r[3] = (le32_to_cpuvp(key + 9) >> 6) & 0x3f03fff; 90 dctx->r[4] = (le32_to_cpuvp(key + 12) >> 8) & 0x00fffff; 91 } 92 93 static void poly1305_setskey(struct poly1305_desc_ctx *dctx, const u8 *key) 94 { 95 dctx->s[0] = le32_to_cpuvp(key + 0); 96 dctx->s[1] = le32_to_cpuvp(key + 4); 97 dctx->s[2] = le32_to_cpuvp(key + 8); 98 dctx->s[3] = le32_to_cpuvp(key + 12); 99 } 100 101 static unsigned int poly1305_blocks(struct poly1305_desc_ctx *dctx, 102 const u8 *src, unsigned int srclen, 103 u32 hibit) 104 { 105 u32 r0, r1, r2, r3, r4; 106 u32 s1, s2, s3, s4; 107 u32 h0, h1, h2, h3, h4; 108 u64 d0, d1, d2, d3, d4; 109 110 if (unlikely(!dctx->sset)) { 111 if (!dctx->rset && srclen >= POLY1305_BLOCK_SIZE) { 112 poly1305_setrkey(dctx, src); 113 src += POLY1305_BLOCK_SIZE; 114 srclen -= POLY1305_BLOCK_SIZE; 115 dctx->rset = true; 116 } 117 if (srclen >= POLY1305_BLOCK_SIZE) { 118 poly1305_setskey(dctx, src); 119 src += POLY1305_BLOCK_SIZE; 120 srclen -= POLY1305_BLOCK_SIZE; 121 dctx->sset = true; 122 } 123 } 124 125 r0 = dctx->r[0]; 126 r1 = dctx->r[1]; 127 r2 = dctx->r[2]; 128 r3 = dctx->r[3]; 129 r4 = dctx->r[4]; 130 131 s1 = r1 * 5; 132 s2 = r2 * 5; 133 s3 = r3 * 5; 134 s4 = r4 * 5; 135 136 h0 = dctx->h[0]; 137 h1 = dctx->h[1]; 138 h2 = dctx->h[2]; 139 h3 = dctx->h[3]; 140 h4 = dctx->h[4]; 141 142 while (likely(srclen >= POLY1305_BLOCK_SIZE)) { 143 144 /* h += m[i] */ 145 h0 += (le32_to_cpuvp(src + 0) >> 0) & 0x3ffffff; 146 h1 += (le32_to_cpuvp(src + 3) >> 2) & 0x3ffffff; 147 h2 += (le32_to_cpuvp(src + 6) >> 4) & 0x3ffffff; 148 h3 += (le32_to_cpuvp(src + 9) >> 6) & 0x3ffffff; 149 h4 += (le32_to_cpuvp(src + 12) >> 8) | hibit; 150 151 /* h *= r */ 152 d0 = mlt(h0, r0) + mlt(h1, s4) + mlt(h2, s3) + 153 mlt(h3, s2) + mlt(h4, s1); 154 d1 = mlt(h0, r1) + mlt(h1, r0) + mlt(h2, s4) + 155 mlt(h3, s3) + mlt(h4, s2); 156 d2 = mlt(h0, r2) + mlt(h1, r1) + mlt(h2, r0) + 157 mlt(h3, s4) + mlt(h4, s3); 158 d3 = mlt(h0, r3) + mlt(h1, r2) + mlt(h2, r1) + 159 mlt(h3, r0) + mlt(h4, s4); 160 d4 = mlt(h0, r4) + mlt(h1, r3) + mlt(h2, r2) + 161 mlt(h3, r1) + mlt(h4, r0); 162 163 /* (partial) h %= p */ 164 d1 += sr(d0, 26); h0 = and(d0, 0x3ffffff); 165 d2 += sr(d1, 26); h1 = and(d1, 0x3ffffff); 166 d3 += sr(d2, 26); h2 = and(d2, 0x3ffffff); 167 d4 += sr(d3, 26); h3 = and(d3, 0x3ffffff); 168 h0 += sr(d4, 26) * 5; h4 = and(d4, 0x3ffffff); 169 h1 += h0 >> 26; h0 = h0 & 0x3ffffff; 170 171 src += POLY1305_BLOCK_SIZE; 172 srclen -= POLY1305_BLOCK_SIZE; 173 } 174 175 dctx->h[0] = h0; 176 dctx->h[1] = h1; 177 dctx->h[2] = h2; 178 dctx->h[3] = h3; 179 dctx->h[4] = h4; 180 181 return srclen; 182 } 183 184 static int poly1305_update(struct shash_desc *desc, 185 const u8 *src, unsigned int srclen) 186 { 187 struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); 188 unsigned int bytes; 189 190 if (unlikely(dctx->buflen)) { 191 bytes = min(srclen, POLY1305_BLOCK_SIZE - dctx->buflen); 192 memcpy(dctx->buf + dctx->buflen, src, bytes); 193 src += bytes; 194 srclen -= bytes; 195 dctx->buflen += bytes; 196 197 if (dctx->buflen == POLY1305_BLOCK_SIZE) { 198 poly1305_blocks(dctx, dctx->buf, 199 POLY1305_BLOCK_SIZE, 1 << 24); 200 dctx->buflen = 0; 201 } 202 } 203 204 if (likely(srclen >= POLY1305_BLOCK_SIZE)) { 205 bytes = poly1305_blocks(dctx, src, srclen, 1 << 24); 206 src += srclen - bytes; 207 srclen = bytes; 208 } 209 210 if (unlikely(srclen)) { 211 dctx->buflen = srclen; 212 memcpy(dctx->buf, src, srclen); 213 } 214 215 return 0; 216 } 217 218 static int poly1305_final(struct shash_desc *desc, u8 *dst) 219 { 220 struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); 221 __le32 *mac = (__le32 *)dst; 222 u32 h0, h1, h2, h3, h4; 223 u32 g0, g1, g2, g3, g4; 224 u32 mask; 225 u64 f = 0; 226 227 if (unlikely(!dctx->sset)) 228 return -ENOKEY; 229 230 if (unlikely(dctx->buflen)) { 231 dctx->buf[dctx->buflen++] = 1; 232 memset(dctx->buf + dctx->buflen, 0, 233 POLY1305_BLOCK_SIZE - dctx->buflen); 234 poly1305_blocks(dctx, dctx->buf, POLY1305_BLOCK_SIZE, 0); 235 } 236 237 /* fully carry h */ 238 h0 = dctx->h[0]; 239 h1 = dctx->h[1]; 240 h2 = dctx->h[2]; 241 h3 = dctx->h[3]; 242 h4 = dctx->h[4]; 243 244 h2 += (h1 >> 26); h1 = h1 & 0x3ffffff; 245 h3 += (h2 >> 26); h2 = h2 & 0x3ffffff; 246 h4 += (h3 >> 26); h3 = h3 & 0x3ffffff; 247 h0 += (h4 >> 26) * 5; h4 = h4 & 0x3ffffff; 248 h1 += (h0 >> 26); h0 = h0 & 0x3ffffff; 249 250 /* compute h + -p */ 251 g0 = h0 + 5; 252 g1 = h1 + (g0 >> 26); g0 &= 0x3ffffff; 253 g2 = h2 + (g1 >> 26); g1 &= 0x3ffffff; 254 g3 = h3 + (g2 >> 26); g2 &= 0x3ffffff; 255 g4 = h4 + (g3 >> 26) - (1 << 26); g3 &= 0x3ffffff; 256 257 /* select h if h < p, or h + -p if h >= p */ 258 mask = (g4 >> ((sizeof(u32) * 8) - 1)) - 1; 259 g0 &= mask; 260 g1 &= mask; 261 g2 &= mask; 262 g3 &= mask; 263 g4 &= mask; 264 mask = ~mask; 265 h0 = (h0 & mask) | g0; 266 h1 = (h1 & mask) | g1; 267 h2 = (h2 & mask) | g2; 268 h3 = (h3 & mask) | g3; 269 h4 = (h4 & mask) | g4; 270 271 /* h = h % (2^128) */ 272 h0 = (h0 >> 0) | (h1 << 26); 273 h1 = (h1 >> 6) | (h2 << 20); 274 h2 = (h2 >> 12) | (h3 << 14); 275 h3 = (h3 >> 18) | (h4 << 8); 276 277 /* mac = (h + s) % (2^128) */ 278 f = (f >> 32) + h0 + dctx->s[0]; mac[0] = cpu_to_le32(f); 279 f = (f >> 32) + h1 + dctx->s[1]; mac[1] = cpu_to_le32(f); 280 f = (f >> 32) + h2 + dctx->s[2]; mac[2] = cpu_to_le32(f); 281 f = (f >> 32) + h3 + dctx->s[3]; mac[3] = cpu_to_le32(f); 282 283 return 0; 284 } 285 286 static struct shash_alg poly1305_alg = { 287 .digestsize = POLY1305_DIGEST_SIZE, 288 .init = poly1305_init, 289 .update = poly1305_update, 290 .final = poly1305_final, 291 .setkey = poly1305_setkey, 292 .descsize = sizeof(struct poly1305_desc_ctx), 293 .base = { 294 .cra_name = "poly1305", 295 .cra_driver_name = "poly1305-generic", 296 .cra_priority = 100, 297 .cra_flags = CRYPTO_ALG_TYPE_SHASH, 298 .cra_alignmask = sizeof(u32) - 1, 299 .cra_blocksize = POLY1305_BLOCK_SIZE, 300 .cra_module = THIS_MODULE, 301 }, 302 }; 303 304 static int __init poly1305_mod_init(void) 305 { 306 return crypto_register_shash(&poly1305_alg); 307 } 308 309 static void __exit poly1305_mod_exit(void) 310 { 311 crypto_unregister_shash(&poly1305_alg); 312 } 313 314 module_init(poly1305_mod_init); 315 module_exit(poly1305_mod_exit); 316 317 MODULE_LICENSE("GPL"); 318 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>"); 319 MODULE_DESCRIPTION("Poly1305 authenticator"); 320 MODULE_ALIAS_CRYPTO("poly1305"); 321 MODULE_ALIAS_CRYPTO("poly1305-generic"); 322