1 /*
2 * AES SIV (RFC 5297)
3 * Copyright (c) 2013 Cozybit, Inc.
4 *
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
7 */
8
9 #include "includes.h"
10
11 #include "common.h"
12 #include "aes.h"
13 #include "aes_wrap.h"
14 #include "aes_siv.h"
15
16
17 static const u8 zero[AES_BLOCK_SIZE];
18
19
dbl(u8 * pad)20 static void dbl(u8 *pad)
21 {
22 int i, carry;
23
24 carry = pad[0] & 0x80;
25 for (i = 0; i < AES_BLOCK_SIZE - 1; i++)
26 pad[i] = (pad[i] << 1) | (pad[i + 1] >> 7);
27 pad[AES_BLOCK_SIZE - 1] <<= 1;
28 if (carry)
29 pad[AES_BLOCK_SIZE - 1] ^= 0x87;
30 }
31
32
xor(u8 * a,const u8 * b)33 static void xor(u8 *a, const u8 *b)
34 {
35 int i;
36
37 for (i = 0; i < AES_BLOCK_SIZE; i++)
38 *a++ ^= *b++;
39 }
40
41
xorend(u8 * a,int alen,const u8 * b,int blen)42 static void xorend(u8 *a, int alen, const u8 *b, int blen)
43 {
44 int i;
45
46 if (alen < blen)
47 return;
48
49 for (i = 0; i < blen; i++)
50 a[alen - blen + i] ^= b[i];
51 }
52
53
pad_block(u8 * pad,const u8 * addr,size_t len)54 static void pad_block(u8 *pad, const u8 *addr, size_t len)
55 {
56 os_memset(pad, 0, AES_BLOCK_SIZE);
57 os_memcpy(pad, addr, len);
58
59 if (len < AES_BLOCK_SIZE)
60 pad[len] = 0x80;
61 }
62
63
aes_s2v(const u8 * key,size_t num_elem,const u8 * addr[],size_t * len,u8 * mac)64 static int aes_s2v(const u8 *key, size_t num_elem, const u8 *addr[],
65 size_t *len, u8 *mac)
66 {
67 u8 tmp[AES_BLOCK_SIZE], tmp2[AES_BLOCK_SIZE];
68 u8 *buf = NULL;
69 int ret;
70 size_t i;
71
72 if (!num_elem) {
73 os_memcpy(tmp, zero, sizeof(zero));
74 tmp[AES_BLOCK_SIZE - 1] = 1;
75 return omac1_aes_128(key, tmp, sizeof(tmp), mac);
76 }
77
78 ret = omac1_aes_128(key, zero, sizeof(zero), tmp);
79 if (ret)
80 return ret;
81
82 for (i = 0; i < num_elem - 1; i++) {
83 ret = omac1_aes_128(key, addr[i], len[i], tmp2);
84 if (ret)
85 return ret;
86
87 dbl(tmp);
88 xor(tmp, tmp2);
89 }
90 if (len[i] >= AES_BLOCK_SIZE) {
91 buf = os_malloc(len[i]);
92 if (!buf)
93 return -ENOMEM;
94
95 os_memcpy(buf, addr[i], len[i]);
96 xorend(buf, len[i], tmp, AES_BLOCK_SIZE);
97 ret = omac1_aes_128(key, buf, len[i], mac);
98 bin_clear_free(buf, len[i]);
99 return ret;
100 }
101
102 dbl(tmp);
103 pad_block(tmp2, addr[i], len[i]);
104 xor(tmp, tmp2);
105
106 return omac1_aes_128(key, tmp, sizeof(tmp), mac);
107 }
108
109
aes_siv_encrypt(const u8 * key,const u8 * pw,size_t pwlen,size_t num_elem,const u8 * addr[],const size_t * len,u8 * out)110 int aes_siv_encrypt(const u8 *key, const u8 *pw,
111 size_t pwlen, size_t num_elem,
112 const u8 *addr[], const size_t *len, u8 *out)
113 {
114 const u8 *_addr[6];
115 size_t _len[6];
116 const u8 *k1 = key, *k2 = key + 16;
117 u8 v[AES_BLOCK_SIZE];
118 size_t i;
119 u8 *iv, *crypt_pw;
120
121 if (num_elem > ARRAY_SIZE(_addr) - 1)
122 return -1;
123
124 for (i = 0; i < num_elem; i++) {
125 _addr[i] = addr[i];
126 _len[i] = len[i];
127 }
128 _addr[num_elem] = pw;
129 _len[num_elem] = pwlen;
130
131 if (aes_s2v(k1, num_elem + 1, _addr, _len, v))
132 return -1;
133
134 iv = out;
135 crypt_pw = out + AES_BLOCK_SIZE;
136
137 os_memcpy(iv, v, AES_BLOCK_SIZE);
138 os_memcpy(crypt_pw, pw, pwlen);
139
140 /* zero out 63rd and 31st bits of ctr (from right) */
141 v[8] &= 0x7f;
142 v[12] &= 0x7f;
143 return aes_128_ctr_encrypt(k2, v, crypt_pw, pwlen);
144 }
145
146
aes_siv_decrypt(const u8 * key,const u8 * iv_crypt,size_t iv_c_len,size_t num_elem,const u8 * addr[],const size_t * len,u8 * out)147 int aes_siv_decrypt(const u8 *key, const u8 *iv_crypt, size_t iv_c_len,
148 size_t num_elem, const u8 *addr[], const size_t *len,
149 u8 *out)
150 {
151 const u8 *_addr[6];
152 size_t _len[6];
153 const u8 *k1 = key, *k2 = key + 16;
154 size_t crypt_len;
155 size_t i;
156 int ret;
157 u8 iv[AES_BLOCK_SIZE];
158 u8 check[AES_BLOCK_SIZE];
159
160 if (iv_c_len < AES_BLOCK_SIZE || num_elem > ARRAY_SIZE(_addr) - 1)
161 return -1;
162 crypt_len = iv_c_len - AES_BLOCK_SIZE;
163
164 for (i = 0; i < num_elem; i++) {
165 _addr[i] = addr[i];
166 _len[i] = len[i];
167 }
168 _addr[num_elem] = out;
169 _len[num_elem] = crypt_len;
170
171 os_memcpy(iv, iv_crypt, AES_BLOCK_SIZE);
172 os_memcpy(out, iv_crypt + AES_BLOCK_SIZE, crypt_len);
173
174 iv[8] &= 0x7f;
175 iv[12] &= 0x7f;
176
177 ret = aes_128_ctr_encrypt(k2, iv, out, crypt_len);
178 if (ret)
179 return ret;
180
181 ret = aes_s2v(k1, num_elem + 1, _addr, _len, check);
182 if (ret)
183 return ret;
184 if (os_memcmp(check, iv_crypt, AES_BLOCK_SIZE) == 0)
185 return 0;
186
187 return -1;
188 }
189