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/internal/poly1305.h>
37 #include <crypto/nhpoly1305.h>
38 #include <linux/crypto.h>
39 #include <linux/kernel.h>
40 #include <linux/module.h>
41
42 static 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 */
76 static 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 */
92 static 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
125 int 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 }
142 EXPORT_SYMBOL(crypto_nhpoly1305_setkey);
143
144 int 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 }
153 EXPORT_SYMBOL(crypto_nhpoly1305_init);
154
155 int 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 }
189 EXPORT_SYMBOL(crypto_nhpoly1305_update_helper);
190
191 int 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 }
196 EXPORT_SYMBOL(crypto_nhpoly1305_update);
197
198 int 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 }
216 EXPORT_SYMBOL(crypto_nhpoly1305_final_helper);
217
218 int crypto_nhpoly1305_final(struct shash_desc *desc, u8 *dst)
219 {
220 return crypto_nhpoly1305_final_helper(desc, dst, nh_generic);
221 }
222 EXPORT_SYMBOL(crypto_nhpoly1305_final);
223
224 static 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
238 static int __init nhpoly1305_mod_init(void)
239 {
240 return crypto_register_shash(&nhpoly1305_alg);
241 }
242
243 static void __exit nhpoly1305_mod_exit(void)
244 {
245 crypto_unregister_shash(&nhpoly1305_alg);
246 }
247
248 subsys_initcall(nhpoly1305_mod_init);
249 module_exit(nhpoly1305_mod_exit);
250
251 MODULE_DESCRIPTION("NHPoly1305 ε-almost-∆-universal hash function");
252 MODULE_LICENSE("GPL v2");
253 MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
254 MODULE_ALIAS_CRYPTO("nhpoly1305");
255 MODULE_ALIAS_CRYPTO("nhpoly1305-generic");
256
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