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 <crypto/poly1305.h> 17 #include <linux/crypto.h> 18 #include <linux/kernel.h> 19 #include <linux/module.h> 20 21 static inline u64 mlt(u64 a, u64 b) 22 { 23 return a * b; 24 } 25 26 static inline u32 sr(u64 v, u_char n) 27 { 28 return v >> n; 29 } 30 31 static inline u32 and(u32 v, u32 mask) 32 { 33 return v & mask; 34 } 35 36 static inline u32 le32_to_cpuvp(const void *p) 37 { 38 return le32_to_cpup(p); 39 } 40 41 int crypto_poly1305_init(struct shash_desc *desc) 42 { 43 struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); 44 45 memset(dctx->h, 0, sizeof(dctx->h)); 46 dctx->buflen = 0; 47 dctx->rset = false; 48 dctx->sset = false; 49 50 return 0; 51 } 52 EXPORT_SYMBOL_GPL(crypto_poly1305_init); 53 54 int crypto_poly1305_setkey(struct crypto_shash *tfm, 55 const u8 *key, unsigned int keylen) 56 { 57 /* Poly1305 requires a unique key for each tag, which implies that 58 * we can't set it on the tfm that gets accessed by multiple users 59 * simultaneously. Instead we expect the key as the first 32 bytes in 60 * the update() call. */ 61 return -ENOTSUPP; 62 } 63 EXPORT_SYMBOL_GPL(crypto_poly1305_setkey); 64 65 static void poly1305_setrkey(struct poly1305_desc_ctx *dctx, const u8 *key) 66 { 67 /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */ 68 dctx->r[0] = (le32_to_cpuvp(key + 0) >> 0) & 0x3ffffff; 69 dctx->r[1] = (le32_to_cpuvp(key + 3) >> 2) & 0x3ffff03; 70 dctx->r[2] = (le32_to_cpuvp(key + 6) >> 4) & 0x3ffc0ff; 71 dctx->r[3] = (le32_to_cpuvp(key + 9) >> 6) & 0x3f03fff; 72 dctx->r[4] = (le32_to_cpuvp(key + 12) >> 8) & 0x00fffff; 73 } 74 75 static void poly1305_setskey(struct poly1305_desc_ctx *dctx, const u8 *key) 76 { 77 dctx->s[0] = le32_to_cpuvp(key + 0); 78 dctx->s[1] = le32_to_cpuvp(key + 4); 79 dctx->s[2] = le32_to_cpuvp(key + 8); 80 dctx->s[3] = le32_to_cpuvp(key + 12); 81 } 82 83 unsigned int crypto_poly1305_setdesckey(struct poly1305_desc_ctx *dctx, 84 const u8 *src, unsigned int srclen) 85 { 86 if (!dctx->sset) { 87 if (!dctx->rset && srclen >= POLY1305_BLOCK_SIZE) { 88 poly1305_setrkey(dctx, src); 89 src += POLY1305_BLOCK_SIZE; 90 srclen -= POLY1305_BLOCK_SIZE; 91 dctx->rset = true; 92 } 93 if (srclen >= POLY1305_BLOCK_SIZE) { 94 poly1305_setskey(dctx, src); 95 src += POLY1305_BLOCK_SIZE; 96 srclen -= POLY1305_BLOCK_SIZE; 97 dctx->sset = true; 98 } 99 } 100 return srclen; 101 } 102 EXPORT_SYMBOL_GPL(crypto_poly1305_setdesckey); 103 104 static unsigned int poly1305_blocks(struct poly1305_desc_ctx *dctx, 105 const u8 *src, unsigned int srclen, 106 u32 hibit) 107 { 108 u32 r0, r1, r2, r3, r4; 109 u32 s1, s2, s3, s4; 110 u32 h0, h1, h2, h3, h4; 111 u64 d0, d1, d2, d3, d4; 112 unsigned int datalen; 113 114 if (unlikely(!dctx->sset)) { 115 datalen = crypto_poly1305_setdesckey(dctx, src, srclen); 116 src += srclen - datalen; 117 srclen = datalen; 118 } 119 120 r0 = dctx->r[0]; 121 r1 = dctx->r[1]; 122 r2 = dctx->r[2]; 123 r3 = dctx->r[3]; 124 r4 = dctx->r[4]; 125 126 s1 = r1 * 5; 127 s2 = r2 * 5; 128 s3 = r3 * 5; 129 s4 = r4 * 5; 130 131 h0 = dctx->h[0]; 132 h1 = dctx->h[1]; 133 h2 = dctx->h[2]; 134 h3 = dctx->h[3]; 135 h4 = dctx->h[4]; 136 137 while (likely(srclen >= POLY1305_BLOCK_SIZE)) { 138 139 /* h += m[i] */ 140 h0 += (le32_to_cpuvp(src + 0) >> 0) & 0x3ffffff; 141 h1 += (le32_to_cpuvp(src + 3) >> 2) & 0x3ffffff; 142 h2 += (le32_to_cpuvp(src + 6) >> 4) & 0x3ffffff; 143 h3 += (le32_to_cpuvp(src + 9) >> 6) & 0x3ffffff; 144 h4 += (le32_to_cpuvp(src + 12) >> 8) | hibit; 145 146 /* h *= r */ 147 d0 = mlt(h0, r0) + mlt(h1, s4) + mlt(h2, s3) + 148 mlt(h3, s2) + mlt(h4, s1); 149 d1 = mlt(h0, r1) + mlt(h1, r0) + mlt(h2, s4) + 150 mlt(h3, s3) + mlt(h4, s2); 151 d2 = mlt(h0, r2) + mlt(h1, r1) + mlt(h2, r0) + 152 mlt(h3, s4) + mlt(h4, s3); 153 d3 = mlt(h0, r3) + mlt(h1, r2) + mlt(h2, r1) + 154 mlt(h3, r0) + mlt(h4, s4); 155 d4 = mlt(h0, r4) + mlt(h1, r3) + mlt(h2, r2) + 156 mlt(h3, r1) + mlt(h4, r0); 157 158 /* (partial) h %= p */ 159 d1 += sr(d0, 26); h0 = and(d0, 0x3ffffff); 160 d2 += sr(d1, 26); h1 = and(d1, 0x3ffffff); 161 d3 += sr(d2, 26); h2 = and(d2, 0x3ffffff); 162 d4 += sr(d3, 26); h3 = and(d3, 0x3ffffff); 163 h0 += sr(d4, 26) * 5; h4 = and(d4, 0x3ffffff); 164 h1 += h0 >> 26; h0 = h0 & 0x3ffffff; 165 166 src += POLY1305_BLOCK_SIZE; 167 srclen -= POLY1305_BLOCK_SIZE; 168 } 169 170 dctx->h[0] = h0; 171 dctx->h[1] = h1; 172 dctx->h[2] = h2; 173 dctx->h[3] = h3; 174 dctx->h[4] = h4; 175 176 return srclen; 177 } 178 179 int crypto_poly1305_update(struct shash_desc *desc, 180 const u8 *src, unsigned int srclen) 181 { 182 struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); 183 unsigned int bytes; 184 185 if (unlikely(dctx->buflen)) { 186 bytes = min(srclen, POLY1305_BLOCK_SIZE - dctx->buflen); 187 memcpy(dctx->buf + dctx->buflen, src, bytes); 188 src += bytes; 189 srclen -= bytes; 190 dctx->buflen += bytes; 191 192 if (dctx->buflen == POLY1305_BLOCK_SIZE) { 193 poly1305_blocks(dctx, dctx->buf, 194 POLY1305_BLOCK_SIZE, 1 << 24); 195 dctx->buflen = 0; 196 } 197 } 198 199 if (likely(srclen >= POLY1305_BLOCK_SIZE)) { 200 bytes = poly1305_blocks(dctx, src, srclen, 1 << 24); 201 src += srclen - bytes; 202 srclen = bytes; 203 } 204 205 if (unlikely(srclen)) { 206 dctx->buflen = srclen; 207 memcpy(dctx->buf, src, srclen); 208 } 209 210 return 0; 211 } 212 EXPORT_SYMBOL_GPL(crypto_poly1305_update); 213 214 int crypto_poly1305_final(struct shash_desc *desc, u8 *dst) 215 { 216 struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); 217 __le32 *mac = (__le32 *)dst; 218 u32 h0, h1, h2, h3, h4; 219 u32 g0, g1, g2, g3, g4; 220 u32 mask; 221 u64 f = 0; 222 223 if (unlikely(!dctx->sset)) 224 return -ENOKEY; 225 226 if (unlikely(dctx->buflen)) { 227 dctx->buf[dctx->buflen++] = 1; 228 memset(dctx->buf + dctx->buflen, 0, 229 POLY1305_BLOCK_SIZE - dctx->buflen); 230 poly1305_blocks(dctx, dctx->buf, POLY1305_BLOCK_SIZE, 0); 231 } 232 233 /* fully carry h */ 234 h0 = dctx->h[0]; 235 h1 = dctx->h[1]; 236 h2 = dctx->h[2]; 237 h3 = dctx->h[3]; 238 h4 = dctx->h[4]; 239 240 h2 += (h1 >> 26); h1 = h1 & 0x3ffffff; 241 h3 += (h2 >> 26); h2 = h2 & 0x3ffffff; 242 h4 += (h3 >> 26); h3 = h3 & 0x3ffffff; 243 h0 += (h4 >> 26) * 5; h4 = h4 & 0x3ffffff; 244 h1 += (h0 >> 26); h0 = h0 & 0x3ffffff; 245 246 /* compute h + -p */ 247 g0 = h0 + 5; 248 g1 = h1 + (g0 >> 26); g0 &= 0x3ffffff; 249 g2 = h2 + (g1 >> 26); g1 &= 0x3ffffff; 250 g3 = h3 + (g2 >> 26); g2 &= 0x3ffffff; 251 g4 = h4 + (g3 >> 26) - (1 << 26); g3 &= 0x3ffffff; 252 253 /* select h if h < p, or h + -p if h >= p */ 254 mask = (g4 >> ((sizeof(u32) * 8) - 1)) - 1; 255 g0 &= mask; 256 g1 &= mask; 257 g2 &= mask; 258 g3 &= mask; 259 g4 &= mask; 260 mask = ~mask; 261 h0 = (h0 & mask) | g0; 262 h1 = (h1 & mask) | g1; 263 h2 = (h2 & mask) | g2; 264 h3 = (h3 & mask) | g3; 265 h4 = (h4 & mask) | g4; 266 267 /* h = h % (2^128) */ 268 h0 = (h0 >> 0) | (h1 << 26); 269 h1 = (h1 >> 6) | (h2 << 20); 270 h2 = (h2 >> 12) | (h3 << 14); 271 h3 = (h3 >> 18) | (h4 << 8); 272 273 /* mac = (h + s) % (2^128) */ 274 f = (f >> 32) + h0 + dctx->s[0]; mac[0] = cpu_to_le32(f); 275 f = (f >> 32) + h1 + dctx->s[1]; mac[1] = cpu_to_le32(f); 276 f = (f >> 32) + h2 + dctx->s[2]; mac[2] = cpu_to_le32(f); 277 f = (f >> 32) + h3 + dctx->s[3]; mac[3] = cpu_to_le32(f); 278 279 return 0; 280 } 281 EXPORT_SYMBOL_GPL(crypto_poly1305_final); 282 283 static struct shash_alg poly1305_alg = { 284 .digestsize = POLY1305_DIGEST_SIZE, 285 .init = crypto_poly1305_init, 286 .update = crypto_poly1305_update, 287 .final = crypto_poly1305_final, 288 .setkey = crypto_poly1305_setkey, 289 .descsize = sizeof(struct poly1305_desc_ctx), 290 .base = { 291 .cra_name = "poly1305", 292 .cra_driver_name = "poly1305-generic", 293 .cra_priority = 100, 294 .cra_flags = CRYPTO_ALG_TYPE_SHASH, 295 .cra_alignmask = sizeof(u32) - 1, 296 .cra_blocksize = POLY1305_BLOCK_SIZE, 297 .cra_module = THIS_MODULE, 298 }, 299 }; 300 301 static int __init poly1305_mod_init(void) 302 { 303 return crypto_register_shash(&poly1305_alg); 304 } 305 306 static void __exit poly1305_mod_exit(void) 307 { 308 crypto_unregister_shash(&poly1305_alg); 309 } 310 311 module_init(poly1305_mod_init); 312 module_exit(poly1305_mod_exit); 313 314 MODULE_LICENSE("GPL"); 315 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>"); 316 MODULE_DESCRIPTION("Poly1305 authenticator"); 317 MODULE_ALIAS_CRYPTO("poly1305"); 318 MODULE_ALIAS_CRYPTO("poly1305-generic"); 319