1/*
2 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22 * SOFTWARE.
23 */
24
25#include "inner.h"
26
27/* see bearssl_block.h */
28void
29br_aes_ct_ctr_init(br_aes_ct_ctr_keys *ctx,
30	const void *key, size_t len)
31{
32	ctx->vtable = &br_aes_ct_ctr_vtable;
33	ctx->num_rounds = br_aes_ct_keysched(ctx->skey, key, len);
34}
35
36static void
37xorbuf(void *dst, const void *src, size_t len)
38{
39	unsigned char *d;
40	const unsigned char *s;
41
42	d = dst;
43	s = src;
44	while (len -- > 0) {
45		*d ++ ^= *s ++;
46	}
47}
48
49/* see bearssl_block.h */
50uint32_t
51br_aes_ct_ctr_run(const br_aes_ct_ctr_keys *ctx,
52	const void *iv, uint32_t cc, void *data, size_t len)
53{
54	unsigned char *buf;
55	const unsigned char *ivbuf;
56	uint32_t iv0, iv1, iv2;
57	uint32_t sk_exp[120];
58
59	br_aes_ct_skey_expand(sk_exp, ctx->num_rounds, ctx->skey);
60	ivbuf = iv;
61	iv0 = br_dec32le(ivbuf);
62	iv1 = br_dec32le(ivbuf + 4);
63	iv2 = br_dec32le(ivbuf + 8);
64	buf = data;
65	while (len > 0) {
66		uint32_t q[8];
67		unsigned char tmp[32];
68
69		/*
70		 * TODO: see if we can save on the first br_aes_ct_ortho()
71		 * call, since iv0/iv1/iv2 are constant for the whole run.
72		 */
73		q[0] = q[1] = iv0;
74		q[2] = q[3] = iv1;
75		q[4] = q[5] = iv2;
76		q[6] = br_swap32(cc);
77		q[7] = br_swap32(cc + 1);
78		br_aes_ct_ortho(q);
79		br_aes_ct_bitslice_encrypt(ctx->num_rounds, sk_exp, q);
80		br_aes_ct_ortho(q);
81		br_enc32le(tmp, q[0]);
82		br_enc32le(tmp + 4, q[2]);
83		br_enc32le(tmp + 8, q[4]);
84		br_enc32le(tmp + 12, q[6]);
85		br_enc32le(tmp + 16, q[1]);
86		br_enc32le(tmp + 20, q[3]);
87		br_enc32le(tmp + 24, q[5]);
88		br_enc32le(tmp + 28, q[7]);
89
90		if (len <= 32) {
91			xorbuf(buf, tmp, len);
92			cc ++;
93			if (len > 16) {
94				cc ++;
95			}
96			break;
97		}
98		xorbuf(buf, tmp, 32);
99		buf += 32;
100		len -= 32;
101		cc += 2;
102	}
103	return cc;
104}
105
106/* see bearssl_block.h */
107const br_block_ctr_class br_aes_ct_ctr_vtable = {
108	sizeof(br_aes_ct_ctr_keys),
109	16,
110	4,
111	(void (*)(const br_block_ctr_class **, const void *, size_t))
112		&br_aes_ct_ctr_init,
113	(uint32_t (*)(const br_block_ctr_class *const *,
114		const void *, uint32_t, void *, size_t))
115		&br_aes_ct_ctr_run
116};
117