linux/crypto/nhpoly1305.c
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   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
  42static 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 */
  76static 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 */
  92static 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
 125int 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}
 142EXPORT_SYMBOL(crypto_nhpoly1305_setkey);
 143
 144int 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}
 153EXPORT_SYMBOL(crypto_nhpoly1305_init);
 154
 155int 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}
 189EXPORT_SYMBOL(crypto_nhpoly1305_update_helper);
 190
 191int 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}
 196EXPORT_SYMBOL(crypto_nhpoly1305_update);
 197
 198int 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}
 216EXPORT_SYMBOL(crypto_nhpoly1305_final_helper);
 217
 218int crypto_nhpoly1305_final(struct shash_desc *desc, u8 *dst)
 219{
 220        return crypto_nhpoly1305_final_helper(desc, dst, nh_generic);
 221}
 222EXPORT_SYMBOL(crypto_nhpoly1305_final);
 223
 224static 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
 238static int __init nhpoly1305_mod_init(void)
 239{
 240        return crypto_register_shash(&nhpoly1305_alg);
 241}
 242
 243static void __exit nhpoly1305_mod_exit(void)
 244{
 245        crypto_unregister_shash(&nhpoly1305_alg);
 246}
 247
 248subsys_initcall(nhpoly1305_mod_init);
 249module_exit(nhpoly1305_mod_exit);
 250
 251MODULE_DESCRIPTION("NHPoly1305 ε-almost-∆-universal hash function");
 252MODULE_LICENSE("GPL v2");
 253MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
 254MODULE_ALIAS_CRYPTO("nhpoly1305");
 255MODULE_ALIAS_CRYPTO("nhpoly1305-generic");
 256
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