LXR linux/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
  41static 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 */
  75static 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 */
  91static 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
 124int 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}
 141EXPORT_SYMBOL(crypto_nhpoly1305_setkey);
 142
 143int 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}
 152EXPORT_SYMBOL(crypto_nhpoly1305_init);
 153
 154int 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}
 188EXPORT_SYMBOL(crypto_nhpoly1305_update_helper);
 189
 190int 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}
 195EXPORT_SYMBOL(crypto_nhpoly1305_update);
 196
 197int 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}
 215EXPORT_SYMBOL(crypto_nhpoly1305_final_helper);
 216
 217int crypto_nhpoly1305_final(struct shash_desc *desc, u8 *dst)
 218{
 219        return crypto_nhpoly1305_final_helper(desc, dst, nh_generic);
 220}
 221EXPORT_SYMBOL(crypto_nhpoly1305_final);
 222
 223static 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
 237static int __init nhpoly1305_mod_init(void)
 238{
 239        return crypto_register_shash(&nhpoly1305_alg);
 240}
 241
 242static void __exit nhpoly1305_mod_exit(void)
 243{
 244        crypto_unregister_shash(&nhpoly1305_alg);
 245}
 246
 247subsys_initcall(nhpoly1305_mod_init);
 248module_exit(nhpoly1305_mod_exit);
 249
 250MODULE_DESCRIPTION("NHPoly1305 ε-almost-∆-universal hash function");
 251MODULE_LICENSE("GPL v2");
 252MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
 253MODULE_ALIAS_CRYPTO("nhpoly1305");
 254MODULE_ALIAS_CRYPTO("nhpoly1305-generic");
 255