1 /*
2 * Counter with CBC-MAC (CCM) with AES
3 *
4 * Copyright (c) 2010-2012, Jouni Malinen <j@w1.fi>
5 *
6 * This software may be distributed under the terms of the BSD license.
7 * See README for more details.
8 */
9
10 #include "rtw_crypto_wrap.h"
11
12 #include "aes.h"
13 #include "aes_wrap.h"
14
15
xor_aes_block(u8 * dst,const u8 * src)16 static void xor_aes_block(u8 *dst, const u8 *src)
17 {
18 u32 *d = (u32 *) dst;
19 u32 *s = (u32 *) src;
20 *d++ ^= *s++;
21 *d++ ^= *s++;
22 *d++ ^= *s++;
23 *d++ ^= *s++;
24 }
25
26
aes_ccm_auth_start(void * aes,size_t M,size_t L,const u8 * nonce,const u8 * aad,size_t aad_len,size_t plain_len,u8 * x)27 static void aes_ccm_auth_start(void *aes, size_t M, size_t L, const u8 *nonce,
28 const u8 *aad, size_t aad_len, size_t plain_len,
29 u8 *x)
30 {
31 u8 aad_buf[2 * AES_BLOCK_SIZE];
32 u8 b[AES_BLOCK_SIZE];
33
34 /* Authentication */
35 /* B_0: Flags | Nonce N | l(m) */
36 b[0] = aad_len ? 0x40 : 0 /* Adata */;
37 b[0] |= (((M - 2) / 2) /* M' */ << 3);
38 b[0] |= (L - 1) /* L' */;
39 os_memcpy(&b[1], nonce, 15 - L);
40 WPA_PUT_BE16(&b[AES_BLOCK_SIZE - L], plain_len);
41
42 wpa_hexdump_key(_MSG_EXCESSIVE_, "CCM B_0", b, AES_BLOCK_SIZE);
43 aes_encrypt(aes, b, x); /* X_1 = E(K, B_0) */
44
45 if (!aad_len)
46 return;
47
48 WPA_PUT_BE16(aad_buf, aad_len);
49 os_memcpy(aad_buf + 2, aad, aad_len);
50 os_memset(aad_buf + 2 + aad_len, 0, sizeof(aad_buf) - 2 - aad_len);
51
52 xor_aes_block(aad_buf, x);
53 aes_encrypt(aes, aad_buf, x); /* X_2 = E(K, X_1 XOR B_1) */
54
55 if (aad_len > AES_BLOCK_SIZE - 2) {
56 xor_aes_block(&aad_buf[AES_BLOCK_SIZE], x);
57 /* X_3 = E(K, X_2 XOR B_2) */
58 aes_encrypt(aes, &aad_buf[AES_BLOCK_SIZE], x);
59 }
60 }
61
62
aes_ccm_auth(void * aes,const u8 * data,size_t len,u8 * x)63 static void aes_ccm_auth(void *aes, const u8 *data, size_t len, u8 *x)
64 {
65 size_t last = len % AES_BLOCK_SIZE;
66 size_t i;
67
68 for (i = 0; i < len / AES_BLOCK_SIZE; i++) {
69 /* X_i+1 = E(K, X_i XOR B_i) */
70 xor_aes_block(x, data);
71 data += AES_BLOCK_SIZE;
72 aes_encrypt(aes, x, x);
73 }
74 if (last) {
75 /* XOR zero-padded last block */
76 for (i = 0; i < last; i++)
77 x[i] ^= *data++;
78 aes_encrypt(aes, x, x);
79 }
80 }
81
82
aes_ccm_encr_start(size_t L,const u8 * nonce,u8 * a)83 static void aes_ccm_encr_start(size_t L, const u8 *nonce, u8 *a)
84 {
85 /* A_i = Flags | Nonce N | Counter i */
86 a[0] = L - 1; /* Flags = L' */
87 os_memcpy(&a[1], nonce, 15 - L);
88 }
89
90
aes_ccm_encr(void * aes,size_t L,const u8 * in,size_t len,u8 * out,u8 * a)91 static void aes_ccm_encr(void *aes, size_t L, const u8 *in, size_t len, u8 *out,
92 u8 *a)
93 {
94 size_t last = len % AES_BLOCK_SIZE;
95 size_t i;
96
97 /* crypt = msg XOR (S_1 | S_2 | ... | S_n) */
98 for (i = 1; i <= len / AES_BLOCK_SIZE; i++) {
99 WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], i);
100 /* S_i = E(K, A_i) */
101 aes_encrypt(aes, a, out);
102 xor_aes_block(out, in);
103 out += AES_BLOCK_SIZE;
104 in += AES_BLOCK_SIZE;
105 }
106 if (last) {
107 WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], i);
108 aes_encrypt(aes, a, out);
109 /* XOR zero-padded last block */
110 for (i = 0; i < last; i++)
111 *out++ ^= *in++;
112 }
113 }
114
115
aes_ccm_encr_auth(void * aes,size_t M,u8 * x,u8 * a,u8 * auth)116 static void aes_ccm_encr_auth(void *aes, size_t M, u8 *x, u8 *a, u8 *auth)
117 {
118 size_t i;
119 u8 tmp[AES_BLOCK_SIZE];
120
121 wpa_hexdump_key(_MSG_EXCESSIVE_, "CCM T", x, M);
122 /* U = T XOR S_0; S_0 = E(K, A_0) */
123 WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], 0);
124 aes_encrypt(aes, a, tmp);
125 for (i = 0; i < M; i++)
126 auth[i] = x[i] ^ tmp[i];
127 wpa_hexdump_key(_MSG_EXCESSIVE_, "CCM U", auth, M);
128 }
129
130
aes_ccm_decr_auth(void * aes,size_t M,u8 * a,const u8 * auth,u8 * t)131 static void aes_ccm_decr_auth(void *aes, size_t M, u8 *a, const u8 *auth, u8 *t)
132 {
133 size_t i;
134 u8 tmp[AES_BLOCK_SIZE];
135
136 wpa_hexdump_key(_MSG_EXCESSIVE_, "CCM U", auth, M);
137 /* U = T XOR S_0; S_0 = E(K, A_0) */
138 WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], 0);
139 aes_encrypt(aes, a, tmp);
140 for (i = 0; i < M; i++)
141 t[i] = auth[i] ^ tmp[i];
142 wpa_hexdump_key(_MSG_EXCESSIVE_, "CCM T", t, M);
143 }
144
145
146 /* AES-CCM with fixed L=2 and aad_len <= 30 assumption */
aes_ccm_ae(const u8 * key,size_t key_len,const u8 * nonce,size_t M,const u8 * plain,size_t plain_len,const u8 * aad,size_t aad_len,u8 * crypt,u8 * auth)147 int aes_ccm_ae(const u8 *key, size_t key_len, const u8 *nonce,
148 size_t M, const u8 *plain, size_t plain_len,
149 const u8 *aad, size_t aad_len, u8 *crypt, u8 *auth)
150 {
151 const size_t L = 2;
152 void *aes;
153 u8 x[AES_BLOCK_SIZE], a[AES_BLOCK_SIZE];
154
155 if (aad_len > 30 || M > AES_BLOCK_SIZE)
156 return -1;
157
158 aes = aes_encrypt_init(key, key_len);
159 if (aes == NULL)
160 return -1;
161
162 aes_ccm_auth_start(aes, M, L, nonce, aad, aad_len, plain_len, x);
163 aes_ccm_auth(aes, plain, plain_len, x);
164
165 /* Encryption */
166 aes_ccm_encr_start(L, nonce, a);
167 aes_ccm_encr(aes, L, plain, plain_len, crypt, a);
168 aes_ccm_encr_auth(aes, M, x, a, auth);
169
170 aes_encrypt_deinit(aes);
171
172 return 0;
173 }
174
175
176 /* AES-CCM with fixed L=2 and aad_len <= 30 assumption */
aes_ccm_ad(const u8 * key,size_t key_len,const u8 * nonce,size_t M,const u8 * crypt,size_t crypt_len,const u8 * aad,size_t aad_len,const u8 * auth,u8 * plain)177 int aes_ccm_ad(const u8 *key, size_t key_len, const u8 *nonce,
178 size_t M, const u8 *crypt, size_t crypt_len,
179 const u8 *aad, size_t aad_len, const u8 *auth, u8 *plain)
180 {
181 const size_t L = 2;
182 void *aes;
183 u8 x[AES_BLOCK_SIZE], a[AES_BLOCK_SIZE];
184 u8 t[AES_BLOCK_SIZE];
185
186 if (aad_len > 30 || M > AES_BLOCK_SIZE)
187 return -1;
188
189 aes = aes_encrypt_init(key, key_len);
190 if (aes == NULL)
191 return -1;
192
193 /* Decryption */
194 aes_ccm_encr_start(L, nonce, a);
195 aes_ccm_decr_auth(aes, M, a, auth, t);
196
197 /* plaintext = msg XOR (S_1 | S_2 | ... | S_n) */
198 aes_ccm_encr(aes, L, crypt, crypt_len, plain, a);
199
200 aes_ccm_auth_start(aes, M, L, nonce, aad, aad_len, crypt_len, x);
201 aes_ccm_auth(aes, plain, crypt_len, x);
202
203 aes_encrypt_deinit(aes);
204
205 if (os_memcmp_const(x, t, M) != 0) {
206 wpa_printf(_MSG_EXCESSIVE_, "CCM: Auth mismatch");
207 return -1;
208 }
209
210 return 0;
211 }
212