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         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");