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");