crypto/nhpoly1305.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * NHPoly1305 - ε-almost-∆-universal hash function for Adiantum
   4  *
   5  * Copyright 2018 Google LLC
   6  */
   7
   8 /*
   9  * "NHPoly1305" is the main component of Adiantum hashing.
  10  * Specifically, it is the calculation
  11  *
  12  *      H_L ← Poly1305_{K_L}(NH_{K_N}(pad_{128}(L)))
  13  *
  14  * from the procedure in section 6.4 of the Adiantum paper [1].  It is an
  15  * ε-almost-∆-universal (ε-∆U) hash function for equal-length inputs over
  16  * Z/(2^{128}Z), where the "∆" operation is addition.  It hashes 1024-byte
  17  * chunks of the input with the NH hash function [2], reducing the input length
  18  * by 32x.  The resulting NH digests are evaluated as a polynomial in
  19  * GF(2^{130}-5), like in the Poly1305 MAC [3].  Note that the polynomial
  20  * evaluation by itself would suffice to achieve the ε-∆U property; NH is used
  21  * for performance since it's over twice as fast as Poly1305.
  22  *
  23  * This is *not* a cryptographic hash function; do not use it as such!
  24  *
  25  * [1] Adiantum: length-preserving encryption for entry-level processors
  26  *     (https://eprint.iacr.org/2018/720.pdf)
  27  * [2] UMAC: Fast and Secure Message Authentication
  28  *     (https://fastcrypto.org/umac/umac_proc.pdf)
  29  * [3] The Poly1305-AES message-authentication code
  30  *     (https://cr.yp.to/mac/poly1305-20050329.pdf)
  31  */
  32
  33 #include <asm/unaligned.h>
  34 #include <crypto/algapi.h>
  35 #include <crypto/internal/hash.h>
  36 #include <crypto/nhpoly1305.h>
  37 #include <linux/crypto.h>
  38 #include <linux/kernel.h>
  39 #include <linux/module.h>
  40
  41 static void nh_generic(const u32 *key, const u8 *message, size_t message_len,
  42                        __le64 hash[NH_NUM_PASSES])
  43 {
  44         u64 sums[4] = { 0, 0, 0, 0 };
  45
  46         BUILD_BUG_ON(NH_PAIR_STRIDE != 2);
  47         BUILD_BUG_ON(NH_NUM_PASSES != 4);
  48
  49         while (message_len) {
  50                 u32 m0 = get_unaligned_le32(message + 0);
  51                 u32 m1 = get_unaligned_le32(message + 4);
  52                 u32 m2 = get_unaligned_le32(message + 8);
  53                 u32 m3 = get_unaligned_le32(message + 12);
  54
  55                 sums[0] += (u64)(u32)(m0 + key[ 0]) * (u32)(m2 + key[ 2]);
  56                 sums[1] += (u64)(u32)(m0 + key[ 4]) * (u32)(m2 + key[ 6]);
  57                 sums[2] += (u64)(u32)(m0 + key[ 8]) * (u32)(m2 + key[10]);
  58                 sums[3] += (u64)(u32)(m0 + key[12]) * (u32)(m2 + key[14]);
  59                 sums[0] += (u64)(u32)(m1 + key[ 1]) * (u32)(m3 + key[ 3]);
  60                 sums[1] += (u64)(u32)(m1 + key[ 5]) * (u32)(m3 + key[ 7]);
  61                 sums[2] += (u64)(u32)(m1 + key[ 9]) * (u32)(m3 + key[11]);
  62                 sums[3] += (u64)(u32)(m1 + key[13]) * (u32)(m3 + key[15]);
  63                 key += NH_MESSAGE_UNIT / sizeof(key[0]);
  64                 message += NH_MESSAGE_UNIT;
  65                 message_len -= NH_MESSAGE_UNIT;
  66         }
  67
  68         hash[0] = cpu_to_le64(sums[0]);
  69         hash[1] = cpu_to_le64(sums[1]);
  70         hash[2] = cpu_to_le64(sums[2]);
  71         hash[3] = cpu_to_le64(sums[3]);
  72 }
  73
  74 /* Pass the next NH hash value through Poly1305 */
  75 static void process_nh_hash_value(struct nhpoly1305_state *state,
  76                                   const struct nhpoly1305_key *key)
  77 {
  78         BUILD_BUG_ON(NH_HASH_BYTES % POLY1305_BLOCK_SIZE != 0);
  79
  80         poly1305_core_blocks(&state->poly_state, &key->poly_key, state->nh_hash,
  81                              NH_HASH_BYTES / POLY1305_BLOCK_SIZE);
  82 }
  83
  84 /*
  85  * Feed the next portion of the source data, as a whole number of 16-byte
  86  * "NH message units", through NH and Poly1305.  Each NH hash is taken over
  87  * 1024 bytes, except possibly the final one which is taken over a multiple of
  88  * 16 bytes up to 1024.  Also, in the case where data is passed in misaligned
  89  * chunks, we combine partial hashes; the end result is the same either way.
  90  */
  91 static void nhpoly1305_units(struct nhpoly1305_state *state,
  92                              const struct nhpoly1305_key *key,
  93                              const u8 *src, unsigned int srclen, nh_t nh_fn)
  94 {
  95         do {
  96                 unsigned int bytes;
  97
  98                 if (state->nh_remaining == 0) {
  99                         /* Starting a new NH message */
 100                         bytes = min_t(unsigned int, srclen, NH_MESSAGE_BYTES);
 101                         nh_fn(key->nh_key, src, bytes, state->nh_hash);
 102                         state->nh_remaining = NH_MESSAGE_BYTES - bytes;
 103                 } else {
 104                         /* Continuing a previous NH message */
 105                         __le64 tmp_hash[NH_NUM_PASSES];
 106                         unsigned int pos;
 107                         int i;
 108
 109                         pos = NH_MESSAGE_BYTES - state->nh_remaining;
 110                         bytes = min(srclen, state->nh_remaining);
 111                         nh_fn(&key->nh_key[pos / 4], src, bytes, tmp_hash);
 112                         for (i = 0; i < NH_NUM_PASSES; i++)
 113                                 le64_add_cpu(&state->nh_hash[i],
 114                                              le64_to_cpu(tmp_hash[i]));
 115                         state->nh_remaining -= bytes;
 116                 }
 117                 if (state->nh_remaining == 0)
 118                         process_nh_hash_value(state, key);
 119                 src += bytes;
 120                 srclen -= bytes;
 121         } while (srclen);
 122 }
 123
 124 int crypto_nhpoly1305_setkey(struct crypto_shash *tfm,
 125                              const u8 *key, unsigned int keylen)
 126 {
 127         struct nhpoly1305_key *ctx = crypto_shash_ctx(tfm);
 128         int i;
 129
 130         if (keylen != NHPOLY1305_KEY_SIZE)
 131                 return -EINVAL;
 132
 133         poly1305_core_setkey(&ctx->poly_key, key);
 134         key += POLY1305_BLOCK_SIZE;
 135
 136         for (i = 0; i < NH_KEY_WORDS; i++)
 137                 ctx->nh_key[i] = get_unaligned_le32(key + i * sizeof(u32));
 138
 139         return 0;
 140 }
 141 EXPORT_SYMBOL(crypto_nhpoly1305_setkey);
 142
 143 int crypto_nhpoly1305_init(struct shash_desc *desc)
 144 {
 145         struct nhpoly1305_state *state = shash_desc_ctx(desc);
 146
 147         poly1305_core_init(&state->poly_state);
 148         state->buflen = 0;
 149         state->nh_remaining = 0;
 150         return 0;
 151 }
 152 EXPORT_SYMBOL(crypto_nhpoly1305_init);
 153
 154 int crypto_nhpoly1305_update_helper(struct shash_desc *desc,
 155                                     const u8 *src, unsigned int srclen,
 156                                     nh_t nh_fn)
 157 {
 158         struct nhpoly1305_state *state = shash_desc_ctx(desc);
 159         const struct nhpoly1305_key *key = crypto_shash_ctx(desc->tfm);
 160         unsigned int bytes;
 161
 162         if (state->buflen) {
 163                 bytes = min(srclen, (int)NH_MESSAGE_UNIT - state->buflen);
 164                 memcpy(&state->buffer[state->buflen], src, bytes);
 165                 state->buflen += bytes;
 166                 if (state->buflen < NH_MESSAGE_UNIT)
 167                         return 0;
 168                 nhpoly1305_units(state, key, state->buffer, NH_MESSAGE_UNIT,
 169                                  nh_fn);
 170                 state->buflen = 0;
 171                 src += bytes;
 172                 srclen -= bytes;
 173         }
 174
 175         if (srclen >= NH_MESSAGE_UNIT) {
 176                 bytes = round_down(srclen, NH_MESSAGE_UNIT);
 177                 nhpoly1305_units(state, key, src, bytes, nh_fn);
 178                 src += bytes;
 179                 srclen -= bytes;
 180         }
 181
 182         if (srclen) {
 183                 memcpy(state->buffer, src, srclen);
 184                 state->buflen = srclen;
 185         }
 186         return 0;
 187 }
 188 EXPORT_SYMBOL(crypto_nhpoly1305_update_helper);
 189
 190 int crypto_nhpoly1305_update(struct shash_desc *desc,
 191                              const u8 *src, unsigned int srclen)
 192 {
 193         return crypto_nhpoly1305_update_helper(desc, src, srclen, nh_generic);
 194 }
 195 EXPORT_SYMBOL(crypto_nhpoly1305_update);
 196
 197 int crypto_nhpoly1305_final_helper(struct shash_desc *desc, u8 *dst, nh_t nh_fn)
 198 {
 199         struct nhpoly1305_state *state = shash_desc_ctx(desc);
 200         const struct nhpoly1305_key *key = crypto_shash_ctx(desc->tfm);
 201
 202         if (state->buflen) {
 203                 memset(&state->buffer[state->buflen], 0,
 204                        NH_MESSAGE_UNIT - state->buflen);
 205                 nhpoly1305_units(state, key, state->buffer, NH_MESSAGE_UNIT,
 206                                  nh_fn);
 207         }
 208
 209         if (state->nh_remaining)
 210                 process_nh_hash_value(state, key);
 211
 212         poly1305_core_emit(&state->poly_state, dst);
 213         return 0;
 214 }
 215 EXPORT_SYMBOL(crypto_nhpoly1305_final_helper);
 216
 217 int crypto_nhpoly1305_final(struct shash_desc *desc, u8 *dst)
 218 {
 219         return crypto_nhpoly1305_final_helper(desc, dst, nh_generic);
 220 }
 221 EXPORT_SYMBOL(crypto_nhpoly1305_final);
 222
 223 static struct shash_alg nhpoly1305_alg = {
 224         .base.cra_name          = "nhpoly1305",
 225         .base.cra_driver_name   = "nhpoly1305-generic",
 226         .base.cra_priority      = 100,
 227         .base.cra_ctxsize       = sizeof(struct nhpoly1305_key),
 228         .base.cra_module        = THIS_MODULE,
 229         .digestsize             = POLY1305_DIGEST_SIZE,
 230         .init                   = crypto_nhpoly1305_init,
 231         .update                 = crypto_nhpoly1305_update,
 232         .final                  = crypto_nhpoly1305_final,
 233         .setkey                 = crypto_nhpoly1305_setkey,
 234         .descsize               = sizeof(struct nhpoly1305_state),
 235 };
 236
 237 static int __init nhpoly1305_mod_init(void)
 238 {
 239         return crypto_register_shash(&nhpoly1305_alg);
 240 }
 241
 242 static void __exit nhpoly1305_mod_exit(void)
 243 {
 244         crypto_unregister_shash(&nhpoly1305_alg);
 245 }
 246
 247 module_init(nhpoly1305_mod_init);
 248 module_exit(nhpoly1305_mod_exit);
 249
 250 MODULE_DESCRIPTION("NHPoly1305 ε-almost-∆-universal hash function");
 251 MODULE_LICENSE("GPL v2");
 252 MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
 253 MODULE_ALIAS_CRYPTO("nhpoly1305");
 254 MODULE_ALIAS_CRYPTO("nhpoly1305-generic");