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
br_aes_ct_ctr_init(br_aes_ct_ctr_keys * ctx,const void * key,size_t len)29 br_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 
36 static void
xorbuf(void * dst,const void * src,size_t len)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
br_aes_ct_ctr_run(const br_aes_ct_ctr_keys * ctx,const void * iv,uint32_t cc,void * data,size_t len)51 br_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 */
107 const 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