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/internal/poly1305.h>
  37 #include <crypto/nhpoly1305.h>
  38 #include <linux/crypto.h>
  39 #include <linux/kernel.h>
  40 #include <linux/module.h>
  41
  42 static void nh_generic(const u32 *key, const u8 *message, size_t message_len,
  43                        __le64 hash[NH_NUM_PASSES])
  44 {
  45         u64 sums[4] = { 0, 0, 0, 0 };
  46
  47         BUILD_BUG_ON(NH_PAIR_STRIDE != 2);
  48         BUILD_BUG_ON(NH_NUM_PASSES != 4);
  49
  50         while (message_len) {
  51                 u32 m0 = get_unaligned_le32(message + 0);
  52                 u32 m1 = get_unaligned_le32(message + 4);
  53                 u32 m2 = get_unaligned_le32(message + 8);
  54                 u32 m3 = get_unaligned_le32(message + 12);
  55
  56                 sums[0] += (u64)(u32)(m0 + key[ 0]) * (u32)(m2 + key[ 2]);
  57                 sums[1] += (u64)(u32)(m0 + key[ 4]) * (u32)(m2 + key[ 6]);
  58                 sums[2] += (u64)(u32)(m0 + key[ 8]) * (u32)(m2 + key[10]);
  59                 sums[3] += (u64)(u32)(m0 + key[12]) * (u32)(m2 + key[14]);
  60                 sums[0] += (u64)(u32)(m1 + key[ 1]) * (u32)(m3 + key[ 3]);
  61                 sums[1] += (u64)(u32)(m1 + key[ 5]) * (u32)(m3 + key[ 7]);
  62                 sums[2] += (u64)(u32)(m1 + key[ 9]) * (u32)(m3 + key[11]);
  63                 sums[3] += (u64)(u32)(m1 + key[13]) * (u32)(m3 + key[15]);
  64                 key += NH_MESSAGE_UNIT / sizeof(key[0]);
  65                 message += NH_MESSAGE_UNIT;
  66                 message_len -= NH_MESSAGE_UNIT;
  67         }
  68
  69         hash[0] = cpu_to_le64(sums[0]);
  70         hash[1] = cpu_to_le64(sums[1]);
  71         hash[2] = cpu_to_le64(sums[2]);
  72         hash[3] = cpu_to_le64(sums[3]);
  73 }
  74
  75 /* Pass the next NH hash value through Poly1305 */
  76 static void process_nh_hash_value(struct nhpoly1305_state *state,
  77                                   const struct nhpoly1305_key *key)
  78 {
  79         BUILD_BUG_ON(NH_HASH_BYTES % POLY1305_BLOCK_SIZE != 0);
  80
  81         poly1305_core_blocks(&state->poly_state, &key->poly_key, state->nh_hash,
  82                              NH_HASH_BYTES / POLY1305_BLOCK_SIZE, 1);
  83 }
  84
  85 /*
  86  * Feed the next portion of the source data, as a whole number of 16-byte
  87  * "NH message units", through NH and Poly1305.  Each NH hash is taken over
  88  * 1024 bytes, except possibly the final one which is taken over a multiple of
  89  * 16 bytes up to 1024.  Also, in the case where data is passed in misaligned
  90  * chunks, we combine partial hashes; the end result is the same either way.
  91  */
  92 static void nhpoly1305_units(struct nhpoly1305_state *state,
  93                              const struct nhpoly1305_key *key,
  94                              const u8 *src, unsigned int srclen, nh_t nh_fn)
  95 {
  96         do {
  97                 unsigned int bytes;
  98
  99                 if (state->nh_remaining == 0) {
 100                         /* Starting a new NH message */
 101                         bytes = min_t(unsigned int, srclen, NH_MESSAGE_BYTES);
 102                         nh_fn(key->nh_key, src, bytes, state->nh_hash);
 103                         state->nh_remaining = NH_MESSAGE_BYTES - bytes;
 104                 } else {
 105                         /* Continuing a previous NH message */
 106                         __le64 tmp_hash[NH_NUM_PASSES];
 107                         unsigned int pos;
 108                         int i;
 109
 110                         pos = NH_MESSAGE_BYTES - state->nh_remaining;
 111                         bytes = min(srclen, state->nh_remaining);
 112                         nh_fn(&key->nh_key[pos / 4], src, bytes, tmp_hash);
 113                         for (i = 0; i < NH_NUM_PASSES; i++)
 114                                 le64_add_cpu(&state->nh_hash[i],
 115                                              le64_to_cpu(tmp_hash[i]));
 116                         state->nh_remaining -= bytes;
 117                 }
 118                 if (state->nh_remaining == 0)
 119                         process_nh_hash_value(state, key);
 120                 src += bytes;
 121                 srclen -= bytes;
 122         } while (srclen);
 123 }
 124
 125 int crypto_nhpoly1305_setkey(struct crypto_shash *tfm,
 126                              const u8 *key, unsigned int keylen)
 127 {
 128         struct nhpoly1305_key *ctx = crypto_shash_ctx(tfm);
 129         int i;
 130
 131         if (keylen != NHPOLY1305_KEY_SIZE)
 132                 return -EINVAL;
 133
 134         poly1305_core_setkey(&ctx->poly_key, key);
 135         key += POLY1305_BLOCK_SIZE;
 136
 137         for (i = 0; i < NH_KEY_WORDS; i++)
 138                 ctx->nh_key[i] = get_unaligned_le32(key + i * sizeof(u32));
 139
 140         return 0;
 141 }
 142 EXPORT_SYMBOL(crypto_nhpoly1305_setkey);
 143
 144 int crypto_nhpoly1305_init(struct shash_desc *desc)
 145 {
 146         struct nhpoly1305_state *state = shash_desc_ctx(desc);
 147
 148         poly1305_core_init(&state->poly_state);
 149         state->buflen = 0;
 150         state->nh_remaining = 0;
 151         return 0;
 152 }
 153 EXPORT_SYMBOL(crypto_nhpoly1305_init);
 154
 155 int crypto_nhpoly1305_update_helper(struct shash_desc *desc,
 156                                     const u8 *src, unsigned int srclen,
 157                                     nh_t nh_fn)
 158 {
 159         struct nhpoly1305_state *state = shash_desc_ctx(desc);
 160         const struct nhpoly1305_key *key = crypto_shash_ctx(desc->tfm);
 161         unsigned int bytes;
 162
 163         if (state->buflen) {
 164                 bytes = min(srclen, (int)NH_MESSAGE_UNIT - state->buflen);
 165                 memcpy(&state->buffer[state->buflen], src, bytes);
 166                 state->buflen += bytes;
 167                 if (state->buflen < NH_MESSAGE_UNIT)
 168                         return 0;
 169                 nhpoly1305_units(state, key, state->buffer, NH_MESSAGE_UNIT,
 170                                  nh_fn);
 171                 state->buflen = 0;
 172                 src += bytes;
 173                 srclen -= bytes;
 174         }
 175
 176         if (srclen >= NH_MESSAGE_UNIT) {
 177                 bytes = round_down(srclen, NH_MESSAGE_UNIT);
 178                 nhpoly1305_units(state, key, src, bytes, nh_fn);
 179                 src += bytes;
 180                 srclen -= bytes;
 181         }
 182
 183         if (srclen) {
 184                 memcpy(state->buffer, src, srclen);
 185                 state->buflen = srclen;
 186         }
 187         return 0;
 188 }
 189 EXPORT_SYMBOL(crypto_nhpoly1305_update_helper);
 190
 191 int crypto_nhpoly1305_update(struct shash_desc *desc,
 192                              const u8 *src, unsigned int srclen)
 193 {
 194         return crypto_nhpoly1305_update_helper(desc, src, srclen, nh_generic);
 195 }
 196 EXPORT_SYMBOL(crypto_nhpoly1305_update);
 197
 198 int crypto_nhpoly1305_final_helper(struct shash_desc *desc, u8 *dst, nh_t nh_fn)
 199 {
 200         struct nhpoly1305_state *state = shash_desc_ctx(desc);
 201         const struct nhpoly1305_key *key = crypto_shash_ctx(desc->tfm);
 202
 203         if (state->buflen) {
 204                 memset(&state->buffer[state->buflen], 0,
 205                        NH_MESSAGE_UNIT - state->buflen);
 206                 nhpoly1305_units(state, key, state->buffer, NH_MESSAGE_UNIT,
 207                                  nh_fn);
 208         }
 209
 210         if (state->nh_remaining)
 211                 process_nh_hash_value(state, key);
 212
 213         poly1305_core_emit(&state->poly_state, NULL, dst);
 214         return 0;
 215 }
 216 EXPORT_SYMBOL(crypto_nhpoly1305_final_helper);
 217
 218 int crypto_nhpoly1305_final(struct shash_desc *desc, u8 *dst)
 219 {
 220         return crypto_nhpoly1305_final_helper(desc, dst, nh_generic);
 221 }
 222 EXPORT_SYMBOL(crypto_nhpoly1305_final);
 223
 224 static struct shash_alg nhpoly1305_alg = {
 225         .base.cra_name          = "nhpoly1305",
 226         .base.cra_driver_name   = "nhpoly1305-generic",
 227         .base.cra_priority      = 100,
 228         .base.cra_ctxsize       = sizeof(struct nhpoly1305_key),
 229         .base.cra_module        = THIS_MODULE,
 230         .digestsize             = POLY1305_DIGEST_SIZE,
 231         .init                   = crypto_nhpoly1305_init,
 232         .update                 = crypto_nhpoly1305_update,
 233         .final                  = crypto_nhpoly1305_final,
 234         .setkey                 = crypto_nhpoly1305_setkey,
 235         .descsize               = sizeof(struct nhpoly1305_state),
 236 };
 237
 238 static int __init nhpoly1305_mod_init(void)
 239 {
 240         return crypto_register_shash(&nhpoly1305_alg);
 241 }
 242
 243 static void __exit nhpoly1305_mod_exit(void)
 244 {
 245         crypto_unregister_shash(&nhpoly1305_alg);
 246 }
 247
 248 subsys_initcall(nhpoly1305_mod_init);
 249 module_exit(nhpoly1305_mod_exit);
 250
 251 MODULE_DESCRIPTION("NHPoly1305 ε-almost-∆-universal hash function");
 252 MODULE_LICENSE("GPL v2");
 253 MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
 254 MODULE_ALIAS_CRYPTO("nhpoly1305");
 255 MODULE_ALIAS_CRYPTO("nhpoly1305-generic");