// SPDX-License-Identifier: GPL-2.0
/*
* NHPoly1305 - ε-almost-∆-universal hash function for Adiantum
*
* Copyright 2018 Google LLC
*/
/*
* "NHPoly1305" is the main component of Adiantum hashing.
* Specifically, it is the calculation
*
* H_L ← Poly1305_{K_L}(NH_{K_N}(pad_{128}(L)))
*
* from the procedure in section 6.4 of the Adiantum paper [1]. It is an
* ε-almost-∆-universal (ε-∆U) hash function for equal-length inputs over
* Z/(2^{128}Z), where the "∆" operation is addition. It hashes 1024-byte
* chunks of the input with the NH hash function [2], reducing the input length
* by 32x. The resulting NH digests are evaluated as a polynomial in
* GF(2^{130}-5), like in the Poly1305 MAC [3]. Note that the polynomial
* evaluation by itself would suffice to achieve the ε-∆U property; NH is used
* for performance since it's over twice as fast as Poly1305.
*
* This is *not* a cryptographic hash function; do not use it as such!
*
* [1] Adiantum: length-preserving encryption for entry-level processors
* (https://eprint.iacr.org/2018/720.pdf)
* [2] UMAC: Fast and Secure Message Authentication
* (https://fastcrypto.org/umac/umac_proc.pdf)
* [3] The Poly1305-AES message-authentication code
* (https://cr.yp.to/mac/poly1305-20050329.pdf)
*/
#include <asm/unaligned.h>
#include <crypto/algapi.h>
#include <crypto/internal/hash.h>
#include <crypto/nhpoly1305.h>
#include <linux/crypto.h>
#include <linux/kernel.h>
#include <linux/module.h>
static void nh_generic(const u32 *key, const u8 *message, size_t message_len,
__le64 hash[NH_NUM_PASSES])
{
u64 sums[4] = { 0, 0, 0, 0 };
BUILD_BUG_ON(NH_PAIR_STRIDE != 2);
BUILD_BUG_ON(NH_NUM_PASSES != 4);
while (message_len) {
u32 m0 = get_unaligned_le32(message + 0);
u32 m1 = get_unaligned_le32(message + 4);
u32 m2 = get_unaligned_le32(message + 8);
u32 m3 = get_unaligned_le32(message + 12);
sums[0] += (u64)(u32)(m0 + key[ 0]) * (u32)(m2 + key[ 2]);
sums[1] += (u64)(u32)(m0 + key[ 4]) * (u32)(m2 + key[ 6]);
sums[2] += (u64)(u32)(m0 + key[ 8]) * (u32)(m2 + key[10]);
sums[3] += (u64)(u32)(m0 + key[12]) * (u32)(m2 + key[14]);
sums[0] += (u64)(u32)(m1 + key[ 1]) * (u32)(m3 + key[ 3]);
sums[1] += (u64)(u32)(m1 + key[ 5]) * (u32)(m3 + key[ 7]);
sums[2] += (u64)(u32)(m1 + key[ 9]) * (u32)(m3 + key[11]);
sums[3] += (u64)(u32)(m1 + key[13]) * (u32)(m3 + key[15]);
key += NH_MESSAGE_UNIT / sizeof(key[0]);
message += NH_MESSAGE_UNIT;
message_len -= NH_MESSAGE_UNIT;
}
hash[0] = cpu_to_le64(sums[0]);
hash[1] = cpu_to_le64(sums[1]);
hash[2] = cpu_to_le64(sums[2]);
hash[3] = cpu_to_le64(sums[3]);
}
/* Pass the next NH hash value through Poly1305 */
static void process_nh_hash_value(struct nhpoly1305_state *state,
const struct nhpoly1305_key *key)
{
BUILD_BUG_ON(NH_HASH_BYTES % POLY1305_BLOCK_SIZE != 0);
poly1305_core_blocks(&state->poly_state, &key->poly_key, state->nh_hash,
NH_HASH_BYTES / POLY1305_BLOCK_SIZE);
}
/*
* Feed the next portion of the source data, as a whole number of 16-byte
* "NH message units", through NH and Poly1305. Each NH hash is taken over
* 1024 bytes, except possibly the final one which is taken over a multiple of
* 16 bytes up to 1024. Also, in the case where data is passed in misaligned
* chunks, we combine partial hashes; the end result is the same either way.
*/
static void nhpoly1305_units(struct nhpoly1305_state *state,
const struct nhpoly1305_key *key,
const u8 *src, unsigned int srclen, nh_t nh_fn)
{
do {
unsigned int bytes;
if (state->nh_remaining == 0) {
/* Starting a new NH message */
bytes = min_t(unsigned int, srclen, NH_MESSAGE_BYTES);
nh_fn(key->nh_key, src, bytes, state->nh_hash);
state->nh_remaining = NH_MESSAGE_BYTES - bytes;
} else {
/* Continuing a previous NH message */
__le64 tmp_hash[NH_NUM_PASSES];
unsigned int pos;
int i;
pos = NH_MESSAGE_BYTES - state->nh_remaining;
bytes = min(srclen, state->nh_remaining);
nh_fn(&key->nh_key[pos / 4], src, bytes, tmp_hash);
for (i = 0; i < NH_NUM_PASSES; i++)
le64_add_cpu(&state->nh_hash[i],
le64_to_cpu(tmp_hash[i]));
state->nh_remaining -= bytes;
}
if (state->nh_remaining == 0)
process_nh_hash_value(state, key);
src += bytes;
srclen -= bytes;
} while (srclen);
}
int crypto_nhpoly1305_setkey(struct crypto_shash *tfm,
const u8 *key, unsigned int keylen)
{
struct nhpoly1305_key *ctx = crypto_shash_ctx(tfm);
int i;
if (keylen != NHPOLY1305_KEY_SIZE)
return -EINVAL;
poly1305_core_setkey(&ctx->poly_key, key);
key += POLY1305_BLOCK_SIZE;
for (i = 0; i < NH_KEY_WORDS; i++)
ctx->nh_key[i] = get_unaligned_le32(key + i * sizeof(u32));
return 0;
}
EXPORT_SYMBOL(crypto_nhpoly1305_setkey);
int crypto_nhpoly1305_init(struct shash_desc *desc)
{
struct nhpoly1305_state *state = shash_desc_ctx(desc);
poly1305_core_init(&state->poly_state);
state->buflen = 0;
state->nh_remaining = 0;
return 0;
}
EXPORT_SYMBOL(crypto_nhpoly1305_init);
int crypto_nhpoly1305_update_helper(struct shash_desc *desc,
const u8 *src, unsigned int srclen,
nh_t nh_fn)
{
struct nhpoly1305_state *state = shash_desc_ctx(desc);
const struct nhpoly1305_key *key = crypto_shash_ctx(desc->tfm);
unsigned int bytes;
if (state->buflen) {
bytes = min(srclen, (int)NH_MESSAGE_UNIT - state->buflen);
memcpy(&state->buffer[state->buflen], src, bytes);
state->buflen += bytes;
if (state->buflen < NH_MESSAGE_UNIT)
return 0;
nhpoly1305_units(state, key, state->buffer, NH_MESSAGE_UNIT,
nh_fn);
state->buflen = 0;
src += bytes;
srclen -= bytes;
}
if (srclen >= NH_MESSAGE_UNIT) {
bytes = round_down(srclen, NH_MESSAGE_UNIT);
nhpoly1305_units(state, key, src, bytes, nh_fn);
src += bytes;
srclen -= bytes;
}
if (srclen) {
memcpy(state->buffer, src, srclen);
state->buflen = srclen;
}
return 0;
}
EXPORT_SYMBOL(crypto_nhpoly1305_update_helper);
int crypto_nhpoly1305_update(struct shash_desc *desc,
const u8 *src, unsigned int srclen)
{
return crypto_nhpoly1305_update_helper(desc, src, srclen, nh_generic);
}
EXPORT_SYMBOL(crypto_nhpoly1305_update);
int crypto_nhpoly1305_final_helper(struct shash_desc *desc, u8 *dst, nh_t nh_fn)
{
struct nhpoly1305_state *state = shash_desc_ctx(desc);
const struct nhpoly1305_key *key = crypto_shash_ctx(desc->tfm);
if (state->buflen) {
memset(&state->buffer[state->buflen], 0,
NH_MESSAGE_UNIT - state->buflen);
nhpoly1305_units(state, key, state->buffer, NH_MESSAGE_UNIT,
nh_fn);
}
if (state->nh_remaining)
process_nh_hash_value(state, key);
poly1305_core_emit(&state->poly_state, dst);
return 0;
}
EXPORT_SYMBOL(crypto_nhpoly1305_final_helper);
int crypto_nhpoly1305_final(struct shash_desc *desc, u8 *dst)
{
return crypto_nhpoly1305_final_helper(desc, dst, nh_generic);
}
EXPORT_SYMBOL(crypto_nhpoly1305_final);
static struct shash_alg nhpoly1305_alg = {
.base.cra_name = "nhpoly1305",
.base.cra_driver_name = "nhpoly1305-generic",
.base.cra_priority = 100,
.base.cra_ctxsize = sizeof(struct nhpoly1305_key),
.base.cra_module = THIS_MODULE,
.digestsize = POLY1305_DIGEST_SIZE,
.init = crypto_nhpoly1305_init,
.update = crypto_nhpoly1305_update,
.final = crypto_nhpoly1305_final,
.setkey = crypto_nhpoly1305_setkey,
.descsize = sizeof(struct nhpoly1305_state),
};
static int __init nhpoly1305_mod_init(void)
{
return crypto_register_shash(&nhpoly1305_alg);
}
static void __exit nhpoly1305_mod_exit(void)
{
crypto_unregister_shash(&nhpoly1305_alg);
}
subsys_initcall(nhpoly1305_mod_init);
module_exit(nhpoly1305_mod_exit);
MODULE_DESCRIPTION("NHPoly1305 ε-almost-∆-universal hash function");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
MODULE_ALIAS_CRYPTO("nhpoly1305");
MODULE_ALIAS_CRYPTO("nhpoly1305-generic");
