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 static void poly1305_setrkey(struct poly1305_desc_ctx *dctx, const u8 *key) 51 { 52 /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */ 53 dctx->r[0] = (get_unaligned_le32(key + 0) >> 0) & 0x3ffffff; 54 dctx->r[1] = (get_unaligned_le32(key + 3) >> 2) & 0x3ffff03; 55 dctx->r[2] = (get_unaligned_le32(key + 6) >> 4) & 0x3ffc0ff; 56 dctx->r[3] = (get_unaligned_le32(key + 9) >> 6) & 0x3f03fff; 57 dctx->r[4] = (get_unaligned_le32(key + 12) >> 8) & 0x00fffff; 58 } 59 60 static void poly1305_setskey(struct poly1305_desc_ctx *dctx, const u8 *key) 61 { 62 dctx->s[0] = get_unaligned_le32(key + 0); 63 dctx->s[1] = get_unaligned_le32(key + 4); 64 dctx->s[2] = get_unaligned_le32(key + 8); 65 dctx->s[3] = get_unaligned_le32(key + 12); 66 } 67 68 /* 69 * Poly1305 requires a unique key for each tag, which implies that we can't set 70 * it on the tfm that gets accessed by multiple users simultaneously. Instead we 71 * expect the key as the first 32 bytes in the update() call. 72 */ 73 unsigned int crypto_poly1305_setdesckey(struct poly1305_desc_ctx *dctx, 74 const u8 *src, unsigned int srclen) 75 { 76 if (!dctx->sset) { 77 if (!dctx->rset && srclen >= POLY1305_BLOCK_SIZE) { 78 poly1305_setrkey(dctx, src); 79 src += POLY1305_BLOCK_SIZE; 80 srclen -= POLY1305_BLOCK_SIZE; 81 dctx->rset = true; 82 } 83 if (srclen >= POLY1305_BLOCK_SIZE) { 84 poly1305_setskey(dctx, src); 85 src += POLY1305_BLOCK_SIZE; 86 srclen -= POLY1305_BLOCK_SIZE; 87 dctx->sset = true; 88 } 89 } 90 return srclen; 91 } 92 EXPORT_SYMBOL_GPL(crypto_poly1305_setdesckey); 93 94 static unsigned int poly1305_blocks(struct poly1305_desc_ctx *dctx, 95 const u8 *src, unsigned int srclen, 96 u32 hibit) 97 { 98 u32 r0, r1, r2, r3, r4; 99 u32 s1, s2, s3, s4; 100 u32 h0, h1, h2, h3, h4; 101 u64 d0, d1, d2, d3, d4; 102 unsigned int datalen; 103 104 if (unlikely(!dctx->sset)) { 105 datalen = crypto_poly1305_setdesckey(dctx, src, srclen); 106 src += srclen - datalen; 107 srclen = datalen; 108 } 109 110 r0 = dctx->r[0]; 111 r1 = dctx->r[1]; 112 r2 = dctx->r[2]; 113 r3 = dctx->r[3]; 114 r4 = dctx->r[4]; 115 116 s1 = r1 * 5; 117 s2 = r2 * 5; 118 s3 = r3 * 5; 119 s4 = r4 * 5; 120 121 h0 = dctx->h[0]; 122 h1 = dctx->h[1]; 123 h2 = dctx->h[2]; 124 h3 = dctx->h[3]; 125 h4 = dctx->h[4]; 126 127 while (likely(srclen >= POLY1305_BLOCK_SIZE)) { 128 129 /* h += m[i] */ 130 h0 += (get_unaligned_le32(src + 0) >> 0) & 0x3ffffff; 131 h1 += (get_unaligned_le32(src + 3) >> 2) & 0x3ffffff; 132 h2 += (get_unaligned_le32(src + 6) >> 4) & 0x3ffffff; 133 h3 += (get_unaligned_le32(src + 9) >> 6) & 0x3ffffff; 134 h4 += (get_unaligned_le32(src + 12) >> 8) | hibit; 135 136 /* h *= r */ 137 d0 = mlt(h0, r0) + mlt(h1, s4) + mlt(h2, s3) + 138 mlt(h3, s2) + mlt(h4, s1); 139 d1 = mlt(h0, r1) + mlt(h1, r0) + mlt(h2, s4) + 140 mlt(h3, s3) + mlt(h4, s2); 141 d2 = mlt(h0, r2) + mlt(h1, r1) + mlt(h2, r0) + 142 mlt(h3, s4) + mlt(h4, s3); 143 d3 = mlt(h0, r3) + mlt(h1, r2) + mlt(h2, r1) + 144 mlt(h3, r0) + mlt(h4, s4); 145 d4 = mlt(h0, r4) + mlt(h1, r3) + mlt(h2, r2) + 146 mlt(h3, r1) + mlt(h4, r0); 147 148 /* (partial) h %= p */ 149 d1 += sr(d0, 26); h0 = and(d0, 0x3ffffff); 150 d2 += sr(d1, 26); h1 = and(d1, 0x3ffffff); 151 d3 += sr(d2, 26); h2 = and(d2, 0x3ffffff); 152 d4 += sr(d3, 26); h3 = and(d3, 0x3ffffff); 153 h0 += sr(d4, 26) * 5; h4 = and(d4, 0x3ffffff); 154 h1 += h0 >> 26; h0 = h0 & 0x3ffffff; 155 156 src += POLY1305_BLOCK_SIZE; 157 srclen -= POLY1305_BLOCK_SIZE; 158 } 159 160 dctx->h[0] = h0; 161 dctx->h[1] = h1; 162 dctx->h[2] = h2; 163 dctx->h[3] = h3; 164 dctx->h[4] = h4; 165 166 return srclen; 167 } 168 169 int crypto_poly1305_update(struct shash_desc *desc, 170 const u8 *src, unsigned int srclen) 171 { 172 struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); 173 unsigned int bytes; 174 175 if (unlikely(dctx->buflen)) { 176 bytes = min(srclen, POLY1305_BLOCK_SIZE - dctx->buflen); 177 memcpy(dctx->buf + dctx->buflen, src, bytes); 178 src += bytes; 179 srclen -= bytes; 180 dctx->buflen += bytes; 181 182 if (dctx->buflen == POLY1305_BLOCK_SIZE) { 183 poly1305_blocks(dctx, dctx->buf, 184 POLY1305_BLOCK_SIZE, 1 << 24); 185 dctx->buflen = 0; 186 } 187 } 188 189 if (likely(srclen >= POLY1305_BLOCK_SIZE)) { 190 bytes = poly1305_blocks(dctx, src, srclen, 1 << 24); 191 src += srclen - bytes; 192 srclen = bytes; 193 } 194 195 if (unlikely(srclen)) { 196 dctx->buflen = srclen; 197 memcpy(dctx->buf, src, srclen); 198 } 199 200 return 0; 201 } 202 EXPORT_SYMBOL_GPL(crypto_poly1305_update); 203 204 int crypto_poly1305_final(struct shash_desc *desc, u8 *dst) 205 { 206 struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); 207 u32 h0, h1, h2, h3, h4; 208 u32 g0, g1, g2, g3, g4; 209 u32 mask; 210 u64 f = 0; 211 212 if (unlikely(!dctx->sset)) 213 return -ENOKEY; 214 215 if (unlikely(dctx->buflen)) { 216 dctx->buf[dctx->buflen++] = 1; 217 memset(dctx->buf + dctx->buflen, 0, 218 POLY1305_BLOCK_SIZE - dctx->buflen); 219 poly1305_blocks(dctx, dctx->buf, POLY1305_BLOCK_SIZE, 0); 220 } 221 222 /* fully carry h */ 223 h0 = dctx->h[0]; 224 h1 = dctx->h[1]; 225 h2 = dctx->h[2]; 226 h3 = dctx->h[3]; 227 h4 = dctx->h[4]; 228 229 h2 += (h1 >> 26); h1 = h1 & 0x3ffffff; 230 h3 += (h2 >> 26); h2 = h2 & 0x3ffffff; 231 h4 += (h3 >> 26); h3 = h3 & 0x3ffffff; 232 h0 += (h4 >> 26) * 5; h4 = h4 & 0x3ffffff; 233 h1 += (h0 >> 26); h0 = h0 & 0x3ffffff; 234 235 /* compute h + -p */ 236 g0 = h0 + 5; 237 g1 = h1 + (g0 >> 26); g0 &= 0x3ffffff; 238 g2 = h2 + (g1 >> 26); g1 &= 0x3ffffff; 239 g3 = h3 + (g2 >> 26); g2 &= 0x3ffffff; 240 g4 = h4 + (g3 >> 26) - (1 << 26); g3 &= 0x3ffffff; 241 242 /* select h if h < p, or h + -p if h >= p */ 243 mask = (g4 >> ((sizeof(u32) * 8) - 1)) - 1; 244 g0 &= mask; 245 g1 &= mask; 246 g2 &= mask; 247 g3 &= mask; 248 g4 &= mask; 249 mask = ~mask; 250 h0 = (h0 & mask) | g0; 251 h1 = (h1 & mask) | g1; 252 h2 = (h2 & mask) | g2; 253 h3 = (h3 & mask) | g3; 254 h4 = (h4 & mask) | g4; 255 256 /* h = h % (2^128) */ 257 h0 = (h0 >> 0) | (h1 << 26); 258 h1 = (h1 >> 6) | (h2 << 20); 259 h2 = (h2 >> 12) | (h3 << 14); 260 h3 = (h3 >> 18) | (h4 << 8); 261 262 /* mac = (h + s) % (2^128) */ 263 f = (f >> 32) + h0 + dctx->s[0]; put_unaligned_le32(f, dst + 0); 264 f = (f >> 32) + h1 + dctx->s[1]; put_unaligned_le32(f, dst + 4); 265 f = (f >> 32) + h2 + dctx->s[2]; put_unaligned_le32(f, dst + 8); 266 f = (f >> 32) + h3 + dctx->s[3]; put_unaligned_le32(f, dst + 12); 267 268 return 0; 269 } 270 EXPORT_SYMBOL_GPL(crypto_poly1305_final); 271 272 static struct shash_alg poly1305_alg = { 273 .digestsize = POLY1305_DIGEST_SIZE, 274 .init = crypto_poly1305_init, 275 .update = crypto_poly1305_update, 276 .final = crypto_poly1305_final, 277 .descsize = sizeof(struct poly1305_desc_ctx), 278 .base = { 279 .cra_name = "poly1305", 280 .cra_driver_name = "poly1305-generic", 281 .cra_priority = 100, 282 .cra_blocksize = POLY1305_BLOCK_SIZE, 283 .cra_module = THIS_MODULE, 284 }, 285 }; 286 287 static int __init poly1305_mod_init(void) 288 { 289 return crypto_register_shash(&poly1305_alg); 290 } 291 292 static void __exit poly1305_mod_exit(void) 293 { 294 crypto_unregister_shash(&poly1305_alg); 295 } 296 297 module_init(poly1305_mod_init); 298 module_exit(poly1305_mod_exit); 299 300 MODULE_LICENSE("GPL"); 301 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>"); 302 MODULE_DESCRIPTION("Poly1305 authenticator"); 303 MODULE_ALIAS_CRYPTO("poly1305"); 304 MODULE_ALIAS_CRYPTO("poly1305-generic"); 305