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_cbcdec_init(br_aes_ct_cbcdec_keys *ctx,
30	const void *key, size_t len)
31{
32	ctx->vtable = &br_aes_ct_cbcdec_vtable;
33	ctx->num_rounds = br_aes_ct_keysched(ctx->skey, key, len);
34}
35
36/* see bearssl_block.h */
37void
38br_aes_ct_cbcdec_run(const br_aes_ct_cbcdec_keys *ctx,
39	void *iv, void *data, size_t len)
40{
41	unsigned char *buf, *ivbuf;
42	uint32_t iv0, iv1, iv2, iv3;
43	uint32_t sk_exp[120];
44
45	br_aes_ct_skey_expand(sk_exp, ctx->num_rounds, ctx->skey);
46	ivbuf = iv;
47	iv0 = br_dec32le(ivbuf);
48	iv1 = br_dec32le(ivbuf + 4);
49	iv2 = br_dec32le(ivbuf + 8);
50	iv3 = br_dec32le(ivbuf + 12);
51	buf = data;
52	while (len > 0) {
53		uint32_t q[8], sq[8];
54
55		q[0] = br_dec32le(buf);
56		q[2] = br_dec32le(buf + 4);
57		q[4] = br_dec32le(buf + 8);
58		q[6] = br_dec32le(buf + 12);
59		if (len >= 32) {
60			q[1] = br_dec32le(buf + 16);
61			q[3] = br_dec32le(buf + 20);
62			q[5] = br_dec32le(buf + 24);
63			q[7] = br_dec32le(buf + 28);
64		} else {
65			q[1] = 0;
66			q[3] = 0;
67			q[5] = 0;
68			q[7] = 0;
69		}
70		memcpy(sq, q, sizeof q);
71		br_aes_ct_ortho(q);
72		br_aes_ct_bitslice_decrypt(ctx->num_rounds, sk_exp, q);
73		br_aes_ct_ortho(q);
74		br_enc32le(buf, q[0] ^ iv0);
75		br_enc32le(buf + 4, q[2] ^ iv1);
76		br_enc32le(buf + 8, q[4] ^ iv2);
77		br_enc32le(buf + 12, q[6] ^ iv3);
78		if (len < 32) {
79			iv0 = sq[0];
80			iv1 = sq[2];
81			iv2 = sq[4];
82			iv3 = sq[6];
83			break;
84		}
85		br_enc32le(buf + 16, q[1] ^ sq[0]);
86		br_enc32le(buf + 20, q[3] ^ sq[2]);
87		br_enc32le(buf + 24, q[5] ^ sq[4]);
88		br_enc32le(buf + 28, q[7] ^ sq[6]);
89		iv0 = sq[1];
90		iv1 = sq[3];
91		iv2 = sq[5];
92		iv3 = sq[7];
93		buf += 32;
94		len -= 32;
95	}
96	br_enc32le(ivbuf, iv0);
97	br_enc32le(ivbuf + 4, iv1);
98	br_enc32le(ivbuf + 8, iv2);
99	br_enc32le(ivbuf + 12, iv3);
100}
101
102/* see bearssl_block.h */
103const br_block_cbcdec_class br_aes_ct_cbcdec_vtable = {
104	sizeof(br_aes_ct_cbcdec_keys),
105	16,
106	4,
107	(void (*)(const br_block_cbcdec_class **, const void *, size_t))
108		&br_aes_ct_cbcdec_init,
109	(void (*)(const br_block_cbcdec_class *const *, void *, void *, size_t))
110		&br_aes_ct_cbcdec_run
111};
112