crypto/poly1305_generic.c

   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         poly1305_core_init(&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 void poly1305_core_setkey(struct poly1305_key *key, const u8 *raw_key)
  51 {
  52         /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
  53         key->r[0] = (get_unaligned_le32(raw_key +  0) >> 0) & 0x3ffffff;
  54         key->r[1] = (get_unaligned_le32(raw_key +  3) >> 2) & 0x3ffff03;
  55         key->r[2] = (get_unaligned_le32(raw_key +  6) >> 4) & 0x3ffc0ff;
  56         key->r[3] = (get_unaligned_le32(raw_key +  9) >> 6) & 0x3f03fff;
  57         key->r[4] = (get_unaligned_le32(raw_key + 12) >> 8) & 0x00fffff;
  58 }
  59 EXPORT_SYMBOL_GPL(poly1305_core_setkey);
  60
  61 /*
  62  * Poly1305 requires a unique key for each tag, which implies that we can't set
  63  * it on the tfm that gets accessed by multiple users simultaneously. Instead we
  64  * expect the key as the first 32 bytes in the update() call.
  65  */
  66 unsigned int crypto_poly1305_setdesckey(struct poly1305_desc_ctx *dctx,
  67                                         const u8 *src, unsigned int srclen)
  68 {
  69         if (!dctx->sset) {
  70                 if (!dctx->rset && srclen >= POLY1305_BLOCK_SIZE) {
  71                         poly1305_core_setkey(&dctx->r, src);
  72                         src += POLY1305_BLOCK_SIZE;
  73                         srclen -= POLY1305_BLOCK_SIZE;
  74                         dctx->rset = true;
  75                 }
  76                 if (srclen >= POLY1305_BLOCK_SIZE) {
  77                         dctx->s[0] = get_unaligned_le32(src +  0);
  78                         dctx->s[1] = get_unaligned_le32(src +  4);
  79                         dctx->s[2] = get_unaligned_le32(src +  8);
  80                         dctx->s[3] = get_unaligned_le32(src + 12);
  81                         src += POLY1305_BLOCK_SIZE;
  82                         srclen -= POLY1305_BLOCK_SIZE;
  83                         dctx->sset = true;
  84                 }
  85         }
  86         return srclen;
  87 }
  88 EXPORT_SYMBOL_GPL(crypto_poly1305_setdesckey);
  89
  90 static void poly1305_blocks_internal(struct poly1305_state *state,
  91                                      const struct poly1305_key *key,
  92                                      const void *src, unsigned int nblocks,
  93                                      u32 hibit)
  94 {
  95         u32 r0, r1, r2, r3, r4;
  96         u32 s1, s2, s3, s4;
  97         u32 h0, h1, h2, h3, h4;
  98         u64 d0, d1, d2, d3, d4;
  99
 100         if (!nblocks)
 101                 return;
 102
 103         r0 = key->r[0];
 104         r1 = key->r[1];
 105         r2 = key->r[2];
 106         r3 = key->r[3];
 107         r4 = key->r[4];
 108
 109         s1 = r1 * 5;
 110         s2 = r2 * 5;
 111         s3 = r3 * 5;
 112         s4 = r4 * 5;
 113
 114         h0 = state->h[0];
 115         h1 = state->h[1];
 116         h2 = state->h[2];
 117         h3 = state->h[3];
 118         h4 = state->h[4];
 119
 120         do {
 121                 /* h += m[i] */
 122                 h0 += (get_unaligned_le32(src +  0) >> 0) & 0x3ffffff;
 123                 h1 += (get_unaligned_le32(src +  3) >> 2) & 0x3ffffff;
 124                 h2 += (get_unaligned_le32(src +  6) >> 4) & 0x3ffffff;
 125                 h3 += (get_unaligned_le32(src +  9) >> 6) & 0x3ffffff;
 126                 h4 += (get_unaligned_le32(src + 12) >> 8) | hibit;
 127
 128                 /* h *= r */
 129                 d0 = mlt(h0, r0) + mlt(h1, s4) + mlt(h2, s3) +
 130                      mlt(h3, s2) + mlt(h4, s1);
 131                 d1 = mlt(h0, r1) + mlt(h1, r0) + mlt(h2, s4) +
 132                      mlt(h3, s3) + mlt(h4, s2);
 133                 d2 = mlt(h0, r2) + mlt(h1, r1) + mlt(h2, r0) +
 134                      mlt(h3, s4) + mlt(h4, s3);
 135                 d3 = mlt(h0, r3) + mlt(h1, r2) + mlt(h2, r1) +
 136                      mlt(h3, r0) + mlt(h4, s4);
 137                 d4 = mlt(h0, r4) + mlt(h1, r3) + mlt(h2, r2) +
 138                      mlt(h3, r1) + mlt(h4, r0);
 139
 140                 /* (partial) h %= p */
 141                 d1 += sr(d0, 26);     h0 = and(d0, 0x3ffffff);
 142                 d2 += sr(d1, 26);     h1 = and(d1, 0x3ffffff);
 143                 d3 += sr(d2, 26);     h2 = and(d2, 0x3ffffff);
 144                 d4 += sr(d3, 26);     h3 = and(d3, 0x3ffffff);
 145                 h0 += sr(d4, 26) * 5; h4 = and(d4, 0x3ffffff);
 146                 h1 += h0 >> 26;       h0 = h0 & 0x3ffffff;
 147
 148                 src += POLY1305_BLOCK_SIZE;
 149         } while (--nblocks);
 150
 151         state->h[0] = h0;
 152         state->h[1] = h1;
 153         state->h[2] = h2;
 154         state->h[3] = h3;
 155         state->h[4] = h4;
 156 }
 157
 158 void poly1305_core_blocks(struct poly1305_state *state,
 159                           const struct poly1305_key *key,
 160                           const void *src, unsigned int nblocks)
 161 {
 162         poly1305_blocks_internal(state, key, src, nblocks, 1 << 24);
 163 }
 164 EXPORT_SYMBOL_GPL(poly1305_core_blocks);
 165
 166 static void poly1305_blocks(struct poly1305_desc_ctx *dctx,
 167                             const u8 *src, unsigned int srclen, u32 hibit)
 168 {
 169         unsigned int datalen;
 170
 171         if (unlikely(!dctx->sset)) {
 172                 datalen = crypto_poly1305_setdesckey(dctx, src, srclen);
 173                 src += srclen - datalen;
 174                 srclen = datalen;
 175         }
 176
 177         poly1305_blocks_internal(&dctx->h, &dctx->r,
 178                                  src, srclen / POLY1305_BLOCK_SIZE, hibit);
 179 }
 180
 181 int crypto_poly1305_update(struct shash_desc *desc,
 182                            const u8 *src, unsigned int srclen)
 183 {
 184         struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);
 185         unsigned int bytes;
 186
 187         if (unlikely(dctx->buflen)) {
 188                 bytes = min(srclen, POLY1305_BLOCK_SIZE - dctx->buflen);
 189                 memcpy(dctx->buf + dctx->buflen, src, bytes);
 190                 src += bytes;
 191                 srclen -= bytes;
 192                 dctx->buflen += bytes;
 193
 194                 if (dctx->buflen == POLY1305_BLOCK_SIZE) {
 195                         poly1305_blocks(dctx, dctx->buf,
 196                                         POLY1305_BLOCK_SIZE, 1 << 24);
 197                         dctx->buflen = 0;
 198                 }
 199         }
 200
 201         if (likely(srclen >= POLY1305_BLOCK_SIZE)) {
 202                 poly1305_blocks(dctx, src, srclen, 1 << 24);
 203                 src += srclen - (srclen % POLY1305_BLOCK_SIZE);
 204                 srclen %= POLY1305_BLOCK_SIZE;
 205         }
 206
 207         if (unlikely(srclen)) {
 208                 dctx->buflen = srclen;
 209                 memcpy(dctx->buf, src, srclen);
 210         }
 211
 212         return 0;
 213 }
 214 EXPORT_SYMBOL_GPL(crypto_poly1305_update);
 215
 216 void poly1305_core_emit(const struct poly1305_state *state, void *dst)
 217 {
 218         u32 h0, h1, h2, h3, h4;
 219         u32 g0, g1, g2, g3, g4;
 220         u32 mask;
 221
 222         /* fully carry h */
 223         h0 = state->h[0];
 224         h1 = state->h[1];
 225         h2 = state->h[2];
 226         h3 = state->h[3];
 227         h4 = state->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         put_unaligned_le32((h0 >>  0) | (h1 << 26), dst +  0);
 258         put_unaligned_le32((h1 >>  6) | (h2 << 20), dst +  4);
 259         put_unaligned_le32((h2 >> 12) | (h3 << 14), dst +  8);
 260         put_unaligned_le32((h3 >> 18) | (h4 <<  8), dst + 12);
 261 }
 262 EXPORT_SYMBOL_GPL(poly1305_core_emit);
 263
 264 int crypto_poly1305_final(struct shash_desc *desc, u8 *dst)
 265 {
 266         struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);
 267         __le32 digest[4];
 268         u64 f = 0;
 269
 270         if (unlikely(!dctx->sset))
 271                 return -ENOKEY;
 272
 273         if (unlikely(dctx->buflen)) {
 274                 dctx->buf[dctx->buflen++] = 1;
 275                 memset(dctx->buf + dctx->buflen, 0,
 276                        POLY1305_BLOCK_SIZE - dctx->buflen);
 277                 poly1305_blocks(dctx, dctx->buf, POLY1305_BLOCK_SIZE, 0);
 278         }
 279
 280         poly1305_core_emit(&dctx->h, digest);
 281
 282         /* mac = (h + s) % (2^128) */
 283         f = (f >> 32) + le32_to_cpu(digest[0]) + dctx->s[0];
 284         put_unaligned_le32(f, dst + 0);
 285         f = (f >> 32) + le32_to_cpu(digest[1]) + dctx->s[1];
 286         put_unaligned_le32(f, dst + 4);
 287         f = (f >> 32) + le32_to_cpu(digest[2]) + dctx->s[2];
 288         put_unaligned_le32(f, dst + 8);
 289         f = (f >> 32) + le32_to_cpu(digest[3]) + dctx->s[3];
 290         put_unaligned_le32(f, dst + 12);
 291
 292         return 0;
 293 }
 294 EXPORT_SYMBOL_GPL(crypto_poly1305_final);
 295
 296 static struct shash_alg poly1305_alg = {
 297         .digestsize     = POLY1305_DIGEST_SIZE,
 298         .init           = crypto_poly1305_init,
 299         .update         = crypto_poly1305_update,
 300         .final          = crypto_poly1305_final,
 301         .descsize       = sizeof(struct poly1305_desc_ctx),
 302         .base           = {
 303                 .cra_name               = "poly1305",
 304                 .cra_driver_name        = "poly1305-generic",
 305                 .cra_priority           = 100,
 306                 .cra_blocksize          = POLY1305_BLOCK_SIZE,
 307                 .cra_module             = THIS_MODULE,
 308         },
 309 };
 310
 311 static int __init poly1305_mod_init(void)
 312 {
 313         return crypto_register_shash(&poly1305_alg);
 314 }
 315
 316 static void __exit poly1305_mod_exit(void)
 317 {
 318         crypto_unregister_shash(&poly1305_alg);
 319 }
 320
 321 module_init(poly1305_mod_init);
 322 module_exit(poly1305_mod_exit);
 323
 324 MODULE_LICENSE("GPL");
 325 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
 326 MODULE_DESCRIPTION("Poly1305 authenticator");
 327 MODULE_ALIAS_CRYPTO("poly1305");
 328 MODULE_ALIAS_CRYPTO("poly1305-generic");