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 #include <asm/unaligned.h> 21 22 static inline u64 mlt(u64 a, u64 b) 23 { 24 return a * b; 25 } 26 27 static inline u32 sr(u64 v, u_char n) 28 { 29 return v >> n; 30 } 31 32 static inline u32 and(u32 v, u32 mask) 33 { 34 return v & mask; 35 } 36 37 int crypto_poly1305_init(struct shash_desc *desc) 38 { 39 struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); 40 41 memset(dctx->h, 0, sizeof(dctx->h)); 42 dctx->buflen = 0; 43 dctx->rset = false; 44 dctx->sset = false; 45 46 return 0; 47 } 48 EXPORT_SYMBOL_GPL(crypto_poly1305_init); 49 50 int crypto_poly1305_setkey(struct crypto_shash *tfm, 51 const u8 *key, unsigned int keylen) 52 { 53 /* Poly1305 requires a unique key for each tag, which implies that 54 * we can't set it on the tfm that gets accessed by multiple users 55 * simultaneously. Instead we expect the key as the first 32 bytes in 56 * the update() call. */ 57 return -ENOTSUPP; 58 } 59 EXPORT_SYMBOL_GPL(crypto_poly1305_setkey); 60 61 static void poly1305_setrkey(struct poly1305_desc_ctx *dctx, const u8 *key) 62 { 63 /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */ 64 dctx->r[0] = (get_unaligned_le32(key + 0) >> 0) & 0x3ffffff; 65 dctx->r[1] = (get_unaligned_le32(key + 3) >> 2) & 0x3ffff03; 66 dctx->r[2] = (get_unaligned_le32(key + 6) >> 4) & 0x3ffc0ff; 67 dctx->r[3] = (get_unaligned_le32(key + 9) >> 6) & 0x3f03fff; 68 dctx->r[4] = (get_unaligned_le32(key + 12) >> 8) & 0x00fffff; 69 } 70 71 static void poly1305_setskey(struct poly1305_desc_ctx *dctx, const u8 *key) 72 { 73 dctx->s[0] = get_unaligned_le32(key + 0); 74 dctx->s[1] = get_unaligned_le32(key + 4); 75 dctx->s[2] = get_unaligned_le32(key + 8); 76 dctx->s[3] = get_unaligned_le32(key + 12); 77 } 78 79 unsigned int crypto_poly1305_setdesckey(struct poly1305_desc_ctx *dctx, 80 const u8 *src, unsigned int srclen) 81 { 82 if (!dctx->sset) { 83 if (!dctx->rset && srclen >= POLY1305_BLOCK_SIZE) { 84 poly1305_setrkey(dctx, src); 85 src += POLY1305_BLOCK_SIZE; 86 srclen -= POLY1305_BLOCK_SIZE; 87 dctx->rset = true; 88 } 89 if (srclen >= POLY1305_BLOCK_SIZE) { 90 poly1305_setskey(dctx, src); 91 src += POLY1305_BLOCK_SIZE; 92 srclen -= POLY1305_BLOCK_SIZE; 93 dctx->sset = true; 94 } 95 } 96 return srclen; 97 } 98 EXPORT_SYMBOL_GPL(crypto_poly1305_setdesckey); 99 100 static unsigned int poly1305_blocks(struct poly1305_desc_ctx *dctx, 101 const u8 *src, unsigned int srclen, 102 u32 hibit) 103 { 104 u32 r0, r1, r2, r3, r4; 105 u32 s1, s2, s3, s4; 106 u32 h0, h1, h2, h3, h4; 107 u64 d0, d1, d2, d3, d4; 108 unsigned int datalen; 109 110 if (unlikely(!dctx->sset)) { 111 datalen = crypto_poly1305_setdesckey(dctx, src, srclen); 112 src += srclen - datalen; 113 srclen = datalen; 114 } 115 116 r0 = dctx->r[0]; 117 r1 = dctx->r[1]; 118 r2 = dctx->r[2]; 119 r3 = dctx->r[3]; 120 r4 = dctx->r[4]; 121 122 s1 = r1 * 5; 123 s2 = r2 * 5; 124 s3 = r3 * 5; 125 s4 = r4 * 5; 126 127 h0 = dctx->h[0]; 128 h1 = dctx->h[1]; 129 h2 = dctx->h[2]; 130 h3 = dctx->h[3]; 131 h4 = dctx->h[4]; 132 133 while (likely(srclen >= POLY1305_BLOCK_SIZE)) { 134 135 /* h += m[i] */ 136 h0 += (get_unaligned_le32(src + 0) >> 0) & 0x3ffffff; 137 h1 += (get_unaligned_le32(src + 3) >> 2) & 0x3ffffff; 138 h2 += (get_unaligned_le32(src + 6) >> 4) & 0x3ffffff; 139 h3 += (get_unaligned_le32(src + 9) >> 6) & 0x3ffffff; 140 h4 += (get_unaligned_le32(src + 12) >> 8) | hibit; 141 142 /* h *= r */ 143 d0 = mlt(h0, r0) + mlt(h1, s4) + mlt(h2, s3) + 144 mlt(h3, s2) + mlt(h4, s1); 145 d1 = mlt(h0, r1) + mlt(h1, r0) + mlt(h2, s4) + 146 mlt(h3, s3) + mlt(h4, s2); 147 d2 = mlt(h0, r2) + mlt(h1, r1) + mlt(h2, r0) + 148 mlt(h3, s4) + mlt(h4, s3); 149 d3 = mlt(h0, r3) + mlt(h1, r2) + mlt(h2, r1) + 150 mlt(h3, r0) + mlt(h4, s4); 151 d4 = mlt(h0, r4) + mlt(h1, r3) + mlt(h2, r2) + 152 mlt(h3, r1) + mlt(h4, r0); 153 154 /* (partial) h %= p */ 155 d1 += sr(d0, 26); h0 = and(d0, 0x3ffffff); 156 d2 += sr(d1, 26); h1 = and(d1, 0x3ffffff); 157 d3 += sr(d2, 26); h2 = and(d2, 0x3ffffff); 158 d4 += sr(d3, 26); h3 = and(d3, 0x3ffffff); 159 h0 += sr(d4, 26) * 5; h4 = and(d4, 0x3ffffff); 160 h1 += h0 >> 26; h0 = h0 & 0x3ffffff; 161 162 src += POLY1305_BLOCK_SIZE; 163 srclen -= POLY1305_BLOCK_SIZE; 164 } 165 166 dctx->h[0] = h0; 167 dctx->h[1] = h1; 168 dctx->h[2] = h2; 169 dctx->h[3] = h3; 170 dctx->h[4] = h4; 171 172 return srclen; 173 } 174 175 int crypto_poly1305_update(struct shash_desc *desc, 176 const u8 *src, unsigned int srclen) 177 { 178 struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); 179 unsigned int bytes; 180 181 if (unlikely(dctx->buflen)) { 182 bytes = min(srclen, POLY1305_BLOCK_SIZE - dctx->buflen); 183 memcpy(dctx->buf + dctx->buflen, src, bytes); 184 src += bytes; 185 srclen -= bytes; 186 dctx->buflen += bytes; 187 188 if (dctx->buflen == POLY1305_BLOCK_SIZE) { 189 poly1305_blocks(dctx, dctx->buf, 190 POLY1305_BLOCK_SIZE, 1 << 24); 191 dctx->buflen = 0; 192 } 193 } 194 195 if (likely(srclen >= POLY1305_BLOCK_SIZE)) { 196 bytes = poly1305_blocks(dctx, src, srclen, 1 << 24); 197 src += srclen - bytes; 198 srclen = bytes; 199 } 200 201 if (unlikely(srclen)) { 202 dctx->buflen = srclen; 203 memcpy(dctx->buf, src, srclen); 204 } 205 206 return 0; 207 } 208 EXPORT_SYMBOL_GPL(crypto_poly1305_update); 209 210 int crypto_poly1305_final(struct shash_desc *desc, u8 *dst) 211 { 212 struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); 213 __le32 *mac = (__le32 *)dst; 214 u32 h0, h1, h2, h3, h4; 215 u32 g0, g1, g2, g3, g4; 216 u32 mask; 217 u64 f = 0; 218 219 if (unlikely(!dctx->sset)) 220 return -ENOKEY; 221 222 if (unlikely(dctx->buflen)) { 223 dctx->buf[dctx->buflen++] = 1; 224 memset(dctx->buf + dctx->buflen, 0, 225 POLY1305_BLOCK_SIZE - dctx->buflen); 226 poly1305_blocks(dctx, dctx->buf, POLY1305_BLOCK_SIZE, 0); 227 } 228 229 /* fully carry h */ 230 h0 = dctx->h[0]; 231 h1 = dctx->h[1]; 232 h2 = dctx->h[2]; 233 h3 = dctx->h[3]; 234 h4 = dctx->h[4]; 235 236 h2 += (h1 >> 26); h1 = h1 & 0x3ffffff; 237 h3 += (h2 >> 26); h2 = h2 & 0x3ffffff; 238 h4 += (h3 >> 26); h3 = h3 & 0x3ffffff; 239 h0 += (h4 >> 26) * 5; h4 = h4 & 0x3ffffff; 240 h1 += (h0 >> 26); h0 = h0 & 0x3ffffff; 241 242 /* compute h + -p */ 243 g0 = h0 + 5; 244 g1 = h1 + (g0 >> 26); g0 &= 0x3ffffff; 245 g2 = h2 + (g1 >> 26); g1 &= 0x3ffffff; 246 g3 = h3 + (g2 >> 26); g2 &= 0x3ffffff; 247 g4 = h4 + (g3 >> 26) - (1 << 26); g3 &= 0x3ffffff; 248 249 /* select h if h < p, or h + -p if h >= p */ 250 mask = (g4 >> ((sizeof(u32) * 8) - 1)) - 1; 251 g0 &= mask; 252 g1 &= mask; 253 g2 &= mask; 254 g3 &= mask; 255 g4 &= mask; 256 mask = ~mask; 257 h0 = (h0 & mask) | g0; 258 h1 = (h1 & mask) | g1; 259 h2 = (h2 & mask) | g2; 260 h3 = (h3 & mask) | g3; 261 h4 = (h4 & mask) | g4; 262 263 /* h = h % (2^128) */ 264 h0 = (h0 >> 0) | (h1 << 26); 265 h1 = (h1 >> 6) | (h2 << 20); 266 h2 = (h2 >> 12) | (h3 << 14); 267 h3 = (h3 >> 18) | (h4 << 8); 268 269 /* mac = (h + s) % (2^128) */ 270 f = (f >> 32) + h0 + dctx->s[0]; mac[0] = cpu_to_le32(f); 271 f = (f >> 32) + h1 + dctx->s[1]; mac[1] = cpu_to_le32(f); 272 f = (f >> 32) + h2 + dctx->s[2]; mac[2] = cpu_to_le32(f); 273 f = (f >> 32) + h3 + dctx->s[3]; mac[3] = cpu_to_le32(f); 274 275 return 0; 276 } 277 EXPORT_SYMBOL_GPL(crypto_poly1305_final); 278 279 static struct shash_alg poly1305_alg = { 280 .digestsize = POLY1305_DIGEST_SIZE, 281 .init = crypto_poly1305_init, 282 .update = crypto_poly1305_update, 283 .final = crypto_poly1305_final, 284 .setkey = crypto_poly1305_setkey, 285 .descsize = sizeof(struct poly1305_desc_ctx), 286 .base = { 287 .cra_name = "poly1305", 288 .cra_driver_name = "poly1305-generic", 289 .cra_priority = 100, 290 .cra_flags = CRYPTO_ALG_TYPE_SHASH, 291 .cra_alignmask = sizeof(u32) - 1, 292 .cra_blocksize = POLY1305_BLOCK_SIZE, 293 .cra_module = THIS_MODULE, 294 }, 295 }; 296 297 static int __init poly1305_mod_init(void) 298 { 299 return crypto_register_shash(&poly1305_alg); 300 } 301 302 static void __exit poly1305_mod_exit(void) 303 { 304 crypto_unregister_shash(&poly1305_alg); 305 } 306 307 module_init(poly1305_mod_init); 308 module_exit(poly1305_mod_exit); 309 310 MODULE_LICENSE("GPL"); 311 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>"); 312 MODULE_DESCRIPTION("Poly1305 authenticator"); 313 MODULE_ALIAS_CRYPTO("poly1305"); 314 MODULE_ALIAS_CRYPTO("poly1305-generic"); 315