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 */
28 void
29 br_aes_small_ctr_init(br_aes_small_ctr_keys *ctx,
30 	const void *key, size_t len)
31 {
32 	ctx->vtable = &br_aes_small_ctr_vtable;
33 	ctx->num_rounds = br_aes_keysched(ctx->skey, key, len);
34 }
35 
36 static void
37 xorbuf(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 */
50 uint32_t
51 br_aes_small_ctr_run(const br_aes_small_ctr_keys *ctx,
52 	const void *iv, uint32_t cc, void *data, size_t len)
53 {
54 	unsigned char *buf;
55 
56 	buf = data;
57 	while (len > 0) {
58 		unsigned char tmp[16];
59 
60 		memcpy(tmp, iv, 12);
61 		br_enc32be(tmp + 12, cc ++);
62 		br_aes_small_encrypt(ctx->num_rounds, ctx->skey, tmp);
63 		if (len <= 16) {
64 			xorbuf(buf, tmp, len);
65 			break;
66 		}
67 		xorbuf(buf, tmp, 16);
68 		buf += 16;
69 		len -= 16;
70 	}
71 	return cc;
72 }
73 
74 /* see bearssl_block.h */
75 const br_block_ctr_class br_aes_small_ctr_vtable = {
76 	sizeof(br_aes_small_ctr_keys),
77 	16,
78 	4,
79 	(void (*)(const br_block_ctr_class **, const void *, size_t))
80 		&br_aes_small_ctr_init,
81 	(uint32_t (*)(const br_block_ctr_class *const *,
82 		const void *, uint32_t, void *, size_t))
83 		&br_aes_small_ctr_run
84 };
85