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
247module_init(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