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 
nh_generic(const u32 * key,const u8 * message,size_t message_len,__le64 hash[NH_NUM_PASSES])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 */
process_nh_hash_value(struct nhpoly1305_state * state,const struct nhpoly1305_key * key)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  */
nhpoly1305_units(struct nhpoly1305_state * state,const struct nhpoly1305_key * key,const u8 * src,unsigned int srclen,nh_t nh_fn)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 
crypto_nhpoly1305_setkey(struct crypto_shash * tfm,const u8 * key,unsigned int keylen)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 
crypto_nhpoly1305_init(struct shash_desc * desc)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 
crypto_nhpoly1305_update_helper(struct shash_desc * desc,const u8 * src,unsigned int srclen,nh_t nh_fn)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 
crypto_nhpoly1305_update(struct shash_desc * desc,const u8 * src,unsigned int srclen)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 
crypto_nhpoly1305_final_helper(struct shash_desc * desc,u8 * dst,nh_t nh_fn)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 
crypto_nhpoly1305_final(struct shash_desc * desc,u8 * dst)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 
nhpoly1305_mod_init(void)238 static int __init nhpoly1305_mod_init(void)
239 {
240 	return crypto_register_shash(&nhpoly1305_alg);
241 }
242 
nhpoly1305_mod_exit(void)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