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 "includes.h"
11
12 #include "common.h"
13 #include "aes.h"
14 #include "aes_wrap.h"
15
16
xor_aes_block(u8 * dst,const u8 * src)17 static void xor_aes_block(u8 *dst, const u8 *src)
18 {
19 u32 *d = (u32 *) dst;
20 u32 *s = (u32 *) src;
21 *d++ ^= *s++;
22 *d++ ^= *s++;
23 *d++ ^= *s++;
24 *d++ ^= *s++;
25 }
26
27
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)28 static void aes_ccm_auth_start(void *aes, size_t M, size_t L, const u8 *nonce,
29 const u8 *aad, size_t aad_len, size_t plain_len,
30 u8 *x)
31 {
32 u8 aad_buf[2 * AES_BLOCK_SIZE];
33 u8 b[AES_BLOCK_SIZE];
34
35 /* Authentication */
36 /* B_0: Flags | Nonce N | l(m) */
37 b[0] = aad_len ? 0x40 : 0 /* Adata */;
38 b[0] |= (((M - 2) / 2) /* M' */ << 3);
39 b[0] |= (L - 1) /* L' */;
40 os_memcpy(&b[1], nonce, 15 - L);
41 WPA_PUT_BE16(&b[AES_BLOCK_SIZE - L], plain_len);
42
43 wpa_hexdump_key(MSG_EXCESSIVE, "CCM B_0", b, AES_BLOCK_SIZE);
44 aes_encrypt(aes, b, x); /* X_1 = E(K, B_0) */
45
46 if (!aad_len)
47 return;
48
49 WPA_PUT_BE16(aad_buf, aad_len);
50 os_memcpy(aad_buf + 2, aad, aad_len);
51 os_memset(aad_buf + 2 + aad_len, 0, sizeof(aad_buf) - 2 - aad_len);
52
53 xor_aes_block(aad_buf, x);
54 aes_encrypt(aes, aad_buf, x); /* X_2 = E(K, X_1 XOR B_1) */
55
56 if (aad_len > AES_BLOCK_SIZE - 2) {
57 xor_aes_block(&aad_buf[AES_BLOCK_SIZE], x);
58 /* X_3 = E(K, X_2 XOR B_2) */
59 aes_encrypt(aes, &aad_buf[AES_BLOCK_SIZE], x);
60 }
61 }
62
63
aes_ccm_auth(void * aes,const u8 * data,size_t len,u8 * x)64 static void aes_ccm_auth(void *aes, const u8 *data, size_t len, u8 *x)
65 {
66 size_t last = len % AES_BLOCK_SIZE;
67 size_t i;
68
69 for (i = 0; i < len / AES_BLOCK_SIZE; i++) {
70 /* X_i+1 = E(K, X_i XOR B_i) */
71 xor_aes_block(x, data);
72 data += AES_BLOCK_SIZE;
73 aes_encrypt(aes, x, x);
74 }
75 if (last) {
76 /* XOR zero-padded last block */
77 for (i = 0; i < last; i++)
78 x[i] ^= *data++;
79 aes_encrypt(aes, x, x);
80 }
81 }
82
83
aes_ccm_encr_start(size_t L,const u8 * nonce,u8 * a)84 static void aes_ccm_encr_start(size_t L, const u8 *nonce, u8 *a)
85 {
86 /* A_i = Flags | Nonce N | Counter i */
87 a[0] = L - 1; /* Flags = L' */
88 os_memcpy(&a[1], nonce, 15 - L);
89 }
90
91
aes_ccm_encr(void * aes,size_t L,const u8 * in,size_t len,u8 * out,u8 * a)92 static void aes_ccm_encr(void *aes, size_t L, const u8 *in, size_t len, u8 *out,
93 u8 *a)
94 {
95 size_t last = len % AES_BLOCK_SIZE;
96 size_t i;
97
98 /* crypt = msg XOR (S_1 | S_2 | ... | S_n) */
99 for (i = 1; i <= len / AES_BLOCK_SIZE; i++) {
100 WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], i);
101 /* S_i = E(K, A_i) */
102 aes_encrypt(aes, a, out);
103 xor_aes_block(out, in);
104 out += AES_BLOCK_SIZE;
105 in += AES_BLOCK_SIZE;
106 }
107 if (last) {
108 WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], i);
109 aes_encrypt(aes, a, out);
110 /* XOR zero-padded last block */
111 for (i = 0; i < last; i++)
112 *out++ ^= *in++;
113 }
114 }
115
116
aes_ccm_encr_auth(void * aes,size_t M,u8 * x,u8 * a,u8 * auth)117 static void aes_ccm_encr_auth(void *aes, size_t M, u8 *x, u8 *a, u8 *auth)
118 {
119 size_t i;
120 u8 tmp[AES_BLOCK_SIZE];
121
122 wpa_hexdump_key(MSG_EXCESSIVE, "CCM T", x, M);
123 /* U = T XOR S_0; S_0 = E(K, A_0) */
124 WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], 0);
125 aes_encrypt(aes, a, tmp);
126 for (i = 0; i < M; i++)
127 auth[i] = x[i] ^ tmp[i];
128 wpa_hexdump_key(MSG_EXCESSIVE, "CCM U", auth, M);
129 }
130
131
aes_ccm_decr_auth(void * aes,size_t M,u8 * a,const u8 * auth,u8 * t)132 static void aes_ccm_decr_auth(void *aes, size_t M, u8 *a, const u8 *auth, u8 *t)
133 {
134 size_t i;
135 u8 tmp[AES_BLOCK_SIZE];
136
137 wpa_hexdump_key(MSG_EXCESSIVE, "CCM U", auth, M);
138 /* U = T XOR S_0; S_0 = E(K, A_0) */
139 WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], 0);
140 aes_encrypt(aes, a, tmp);
141 for (i = 0; i < M; i++)
142 t[i] = auth[i] ^ tmp[i];
143 wpa_hexdump_key(MSG_EXCESSIVE, "CCM T", t, M);
144 }
145
146
147 /* 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)148 int aes_ccm_ae(const u8 *key, size_t key_len, const u8 *nonce,
149 size_t M, const u8 *plain, size_t plain_len,
150 const u8 *aad, size_t aad_len, u8 *crypt, u8 *auth)
151 {
152 const size_t L = 2;
153 void *aes;
154 u8 x[AES_BLOCK_SIZE], a[AES_BLOCK_SIZE];
155
156 if (aad_len > 30 || M > AES_BLOCK_SIZE)
157 return -1;
158
159 aes = aes_encrypt_init(key, key_len);
160 if (aes == NULL)
161 return -1;
162
163 aes_ccm_auth_start(aes, M, L, nonce, aad, aad_len, plain_len, x);
164 aes_ccm_auth(aes, plain, plain_len, x);
165
166 /* Encryption */
167 aes_ccm_encr_start(L, nonce, a);
168 aes_ccm_encr(aes, L, plain, plain_len, crypt, a);
169 aes_ccm_encr_auth(aes, M, x, a, auth);
170
171 aes_encrypt_deinit(aes);
172
173 return 0;
174 }
175
176
177 /* 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)178 int aes_ccm_ad(const u8 *key, size_t key_len, const u8 *nonce,
179 size_t M, const u8 *crypt, size_t crypt_len,
180 const u8 *aad, size_t aad_len, const u8 *auth, u8 *plain)
181 {
182 const size_t L = 2;
183 void *aes;
184 u8 x[AES_BLOCK_SIZE], a[AES_BLOCK_SIZE];
185 u8 t[AES_BLOCK_SIZE];
186
187 if (aad_len > 30 || M > AES_BLOCK_SIZE)
188 return -1;
189
190 aes = aes_encrypt_init(key, key_len);
191 if (aes == NULL)
192 return -1;
193
194 /* Decryption */
195 aes_ccm_encr_start(L, nonce, a);
196 aes_ccm_decr_auth(aes, M, a, auth, t);
197
198 /* plaintext = msg XOR (S_1 | S_2 | ... | S_n) */
199 aes_ccm_encr(aes, L, crypt, crypt_len, plain, a);
200
201 aes_ccm_auth_start(aes, M, L, nonce, aad, aad_len, crypt_len, x);
202 aes_ccm_auth(aes, plain, crypt_len, x);
203
204 aes_encrypt_deinit(aes);
205
206 if (os_memcmp_const(x, t, M) != 0) {
207 wpa_printf(MSG_EXCESSIVE, "CCM: Auth mismatch");
208 return -1;
209 }
210
211 return 0;
212 }
213