1// SPDX-License-Identifier: GPL-2.0
2/*
3 * NHPoly1305 - ��-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 * ��-almost-���-universal (��-���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 ��-���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 ��-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