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_cbcdec_init(br_aes_ct_cbcdec_keys * ctx,const void * key,size_t len)29 br_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 */
37 void
br_aes_ct_cbcdec_run(const br_aes_ct_cbcdec_keys * ctx,void * iv,void * data,size_t len)38 br_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 */
103 const 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