xref: /freebsd/contrib/bearssl/src/symcipher/aes_big_cbcdec.c (revision 5ca8e32633c4ffbbcd6762e5888b6a4ba0708c6c)
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_big_cbcdec_init(br_aes_big_cbcdec_keys *ctx,
30 	const void *key, size_t len)
31 {
32 	ctx->vtable = &br_aes_big_cbcdec_vtable;
33 	ctx->num_rounds = br_aes_big_keysched_inv(ctx->skey, key, len);
34 }
35 
36 /* see bearssl_block.h */
37 void
38 br_aes_big_cbcdec_run(const br_aes_big_cbcdec_keys *ctx,
39 	void *iv, void *data, size_t len)
40 {
41 	unsigned char *buf, *ivbuf;
42 
43 	ivbuf = iv;
44 	buf = data;
45 	while (len > 0) {
46 		unsigned char tmp[16];
47 		int i;
48 
49 		memcpy(tmp, buf, 16);
50 		br_aes_big_decrypt(ctx->num_rounds, ctx->skey, buf);
51 		for (i = 0; i < 16; i ++) {
52 			buf[i] ^= ivbuf[i];
53 		}
54 		memcpy(ivbuf, tmp, 16);
55 		buf += 16;
56 		len -= 16;
57 	}
58 }
59 
60 /* see bearssl_block.h */
61 const br_block_cbcdec_class br_aes_big_cbcdec_vtable = {
62 	sizeof(br_aes_big_cbcdec_keys),
63 	16,
64 	4,
65 	(void (*)(const br_block_cbcdec_class **, const void *, size_t))
66 		&br_aes_big_cbcdec_init,
67 	(void (*)(const br_block_cbcdec_class *const *, void *, void *, size_t))
68 		&br_aes_big_cbcdec_run
69 };
70