1/*	$OpenBSD: chachapoly.c,v 1.6 2020/07/22 13:54:30 tobhe Exp $	*/
2/*
3 * Copyright (c) 2015 Mike Belopuhov
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18#include <sys/param.h>
19#include <sys/systm.h>
20#include <lib/libkern/libkern.h>
21
22#include <crypto/chacha_private.h>
23#include <crypto/poly1305.h>
24#include <crypto/chachapoly.h>
25
26int
27chacha20_setkey(void *sched, u_int8_t *key, int len)
28{
29	struct chacha20_ctx *ctx = (struct chacha20_ctx *)sched;
30
31	if (len != CHACHA20_KEYSIZE + CHACHA20_SALT)
32		return (-1);
33
34	/* initial counter is 1 */
35	ctx->nonce[0] = 1;
36	memcpy(ctx->nonce + CHACHA20_CTR, key + CHACHA20_KEYSIZE,
37	    CHACHA20_SALT);
38	chacha_keysetup((chacha_ctx *)&ctx->block, key, CHACHA20_KEYSIZE * 8);
39	return (0);
40}
41
42void
43chacha20_reinit(caddr_t key, u_int8_t *iv)
44{
45	struct chacha20_ctx *ctx = (struct chacha20_ctx *)key;
46
47	chacha_ivsetup((chacha_ctx *)ctx->block, iv, ctx->nonce);
48}
49
50void
51chacha20_crypt(caddr_t key, u_int8_t *data)
52{
53	struct chacha20_ctx *ctx = (struct chacha20_ctx *)key;
54
55	chacha_encrypt_bytes((chacha_ctx *)ctx->block, data, data,
56	    CHACHA20_BLOCK_LEN);
57}
58
59void
60Chacha20_Poly1305_Init(void *xctx)
61{
62	CHACHA20_POLY1305_CTX *ctx = xctx;
63
64	memset(ctx, 0, sizeof(*ctx));
65}
66
67void
68Chacha20_Poly1305_Setkey(void *xctx, const uint8_t *key, uint16_t klen)
69{
70	CHACHA20_POLY1305_CTX *ctx = xctx;
71
72	/* salt is provided with the key material */
73	memcpy(ctx->nonce + CHACHA20_CTR, key + CHACHA20_KEYSIZE,
74	    CHACHA20_SALT);
75	chacha_keysetup((chacha_ctx *)&ctx->chacha, key, CHACHA20_KEYSIZE * 8);
76}
77
78void
79Chacha20_Poly1305_Reinit(void *xctx, const uint8_t *iv, uint16_t ivlen)
80{
81	CHACHA20_POLY1305_CTX *ctx = xctx;
82
83	/* initial counter is 0 */
84	chacha_ivsetup((chacha_ctx *)&ctx->chacha, iv, ctx->nonce);
85	chacha_encrypt_bytes((chacha_ctx *)&ctx->chacha, ctx->key, ctx->key,
86	    POLY1305_KEYLEN);
87	poly1305_init((poly1305_state *)&ctx->poly, ctx->key);
88}
89
90int
91Chacha20_Poly1305_Update(void *xctx, const uint8_t *data, uint16_t len)
92{
93	static const char zeroes[POLY1305_BLOCK_LEN];
94	CHACHA20_POLY1305_CTX *ctx = xctx;
95	size_t rem;
96
97	poly1305_update((poly1305_state *)&ctx->poly, data, len);
98
99	/* number of bytes in the last 16 byte block */
100	rem = (len + POLY1305_BLOCK_LEN) & (POLY1305_BLOCK_LEN - 1);
101	if (rem > 0)
102		poly1305_update((poly1305_state *)&ctx->poly, zeroes,
103		    POLY1305_BLOCK_LEN - rem);
104	return (0);
105}
106
107void
108Chacha20_Poly1305_Final(uint8_t tag[POLY1305_TAGLEN], void *xctx)
109{
110	CHACHA20_POLY1305_CTX *ctx = xctx;
111
112	poly1305_finish((poly1305_state *)&ctx->poly, tag);
113	explicit_bzero(ctx, sizeof(*ctx));
114}
115
116static const uint8_t pad0[16] = { 0 };
117
118void
119chacha20poly1305_encrypt(
120    uint8_t *dst,
121    const uint8_t *src,
122    const size_t src_len,
123    const uint8_t *ad,
124    const size_t ad_len,
125    const uint64_t nonce,
126    const uint8_t key[CHACHA20POLY1305_KEY_SIZE]
127) {
128	poly1305_state poly1305_ctx;
129	chacha_ctx chacha_ctx;
130	union {
131		uint8_t b0[CHACHA20POLY1305_KEY_SIZE];
132		uint64_t lens[2];
133	} b = { { 0 } };
134	uint64_t le_nonce = htole64(nonce);
135
136	chacha_keysetup(&chacha_ctx, key, CHACHA20POLY1305_KEY_SIZE * 8);
137	chacha_ivsetup(&chacha_ctx, (uint8_t *) &le_nonce, NULL);
138	chacha_encrypt_bytes(&chacha_ctx, b.b0, b.b0, sizeof(b.b0));
139	poly1305_init(&poly1305_ctx, b.b0);
140
141	poly1305_update(&poly1305_ctx, ad, ad_len);
142	poly1305_update(&poly1305_ctx, pad0, (0x10 - ad_len) & 0xf);
143
144	chacha_encrypt_bytes(&chacha_ctx, (uint8_t *) src, dst, src_len);
145
146	poly1305_update(&poly1305_ctx, dst, src_len);
147	poly1305_update(&poly1305_ctx, pad0, (0x10 - src_len) & 0xf);
148
149	b.lens[0] = htole64(ad_len);
150	b.lens[1] = htole64(src_len);
151	poly1305_update(&poly1305_ctx, (uint8_t *)b.lens, sizeof(b.lens));
152
153	poly1305_finish(&poly1305_ctx, dst + src_len);
154
155	explicit_bzero(&chacha_ctx, sizeof(chacha_ctx));
156	explicit_bzero(&b, sizeof(b));
157}
158
159int
160chacha20poly1305_decrypt(
161    uint8_t *dst,
162    const uint8_t *src,
163    const size_t src_len,
164    const uint8_t *ad,
165    const size_t ad_len,
166    const uint64_t nonce,
167    const uint8_t key[CHACHA20POLY1305_KEY_SIZE]
168) {
169	poly1305_state poly1305_ctx;
170	chacha_ctx chacha_ctx;
171	int ret;
172	size_t dst_len;
173	union {
174		uint8_t b0[CHACHA20POLY1305_KEY_SIZE];
175		uint8_t mac[CHACHA20POLY1305_AUTHTAG_SIZE];
176		uint64_t lens[2];
177	} b = { { 0 } };
178	uint64_t le_nonce = htole64(nonce);
179
180	if (src_len < CHACHA20POLY1305_AUTHTAG_SIZE)
181		return 0;
182
183	chacha_keysetup(&chacha_ctx, key, CHACHA20POLY1305_KEY_SIZE * 8);
184	chacha_ivsetup(&chacha_ctx, (uint8_t *) &le_nonce, NULL);
185	chacha_encrypt_bytes(&chacha_ctx, b.b0, b.b0, sizeof(b.b0));
186	poly1305_init(&poly1305_ctx, b.b0);
187
188	poly1305_update(&poly1305_ctx, ad, ad_len);
189	poly1305_update(&poly1305_ctx, pad0, (0x10 - ad_len) & 0xf);
190
191	dst_len = src_len - CHACHA20POLY1305_AUTHTAG_SIZE;
192	poly1305_update(&poly1305_ctx, src, dst_len);
193	poly1305_update(&poly1305_ctx, pad0, (0x10 - dst_len) & 0xf);
194
195	b.lens[0] = htole64(ad_len);
196	b.lens[1] = htole64(dst_len);
197	poly1305_update(&poly1305_ctx, (uint8_t *)b.lens, sizeof(b.lens));
198
199	poly1305_finish(&poly1305_ctx, b.mac);
200
201	ret = timingsafe_bcmp(b.mac, src + dst_len, CHACHA20POLY1305_AUTHTAG_SIZE);
202	if (!ret)
203		chacha_encrypt_bytes(&chacha_ctx, (uint8_t *) src, dst, dst_len);
204
205	explicit_bzero(&chacha_ctx, sizeof(chacha_ctx));
206	explicit_bzero(&b, sizeof(b));
207
208	return !ret;
209}
210
211void
212xchacha20poly1305_encrypt(
213    uint8_t *dst,
214    const uint8_t *src,
215    const size_t src_len,
216    const uint8_t *ad,
217    const size_t ad_len,
218    const uint8_t nonce[XCHACHA20POLY1305_NONCE_SIZE],
219    const uint8_t key[CHACHA20POLY1305_KEY_SIZE]
220) {
221	int i;
222	uint32_t derived_key[CHACHA20POLY1305_KEY_SIZE / sizeof(uint32_t)];
223	uint64_t h_nonce;
224
225	memcpy(&h_nonce, nonce + 16, sizeof(h_nonce));
226	h_nonce = le64toh(h_nonce);
227	hchacha20(derived_key, nonce, key);
228
229	for(i = 0; i < (sizeof(derived_key)/sizeof(derived_key[0])); i++)
230		(derived_key[i]) = htole32((derived_key[i]));
231
232	chacha20poly1305_encrypt(dst, src, src_len, ad, ad_len,
233	    h_nonce, (uint8_t *)derived_key);
234	explicit_bzero(derived_key, CHACHA20POLY1305_KEY_SIZE);
235}
236
237int
238xchacha20poly1305_decrypt(
239    uint8_t *dst,
240    const uint8_t *src,
241    const size_t src_len,
242    const uint8_t *ad,
243    const size_t ad_len,
244    const uint8_t nonce[XCHACHA20POLY1305_NONCE_SIZE],
245    const uint8_t key[CHACHA20POLY1305_KEY_SIZE]
246) {
247	int ret, i;
248	uint32_t derived_key[CHACHA20POLY1305_KEY_SIZE / sizeof(uint32_t)];
249	uint64_t h_nonce;
250
251	memcpy(&h_nonce, nonce + 16, sizeof(h_nonce));
252	h_nonce = le64toh(h_nonce);
253	hchacha20(derived_key, nonce, key);
254	for(i = 0; i < (sizeof(derived_key)/sizeof(derived_key[0])); i++)
255		(derived_key[i]) = htole32((derived_key[i]));
256
257	ret = chacha20poly1305_decrypt(dst, src, src_len, ad, ad_len,
258	    h_nonce, (uint8_t *)derived_key);
259	explicit_bzero(derived_key, CHACHA20POLY1305_KEY_SIZE);
260
261	return ret;
262}
263