1 /*
2 * AES-128 EAX
3 *
4 * Copyright (c) 2003-2007, 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 /**
17 * aes_128_eax_encrypt - AES-128 EAX mode encryption
18 * @key: Key for encryption (16 bytes)
19 * @nonce: Nonce for counter mode
20 * @nonce_len: Nonce length in bytes
21 * @hdr: Header data to be authenticity protected
22 * @hdr_len: Length of the header data bytes
23 * @data: Data to encrypt in-place
24 * @data_len: Length of data in bytes
25 * @tag: 16-byte tag value
26 * Returns: 0 on success, -1 on failure
27 */
aes_128_eax_encrypt(const u8 * key,const u8 * nonce,size_t nonce_len,const u8 * hdr,size_t hdr_len,u8 * data,size_t data_len,u8 * tag)28 int aes_128_eax_encrypt(const u8 *key, const u8 *nonce, size_t nonce_len,
29 const u8 *hdr, size_t hdr_len,
30 u8 *data, size_t data_len, u8 *tag)
31 {
32 u8 *buf;
33 size_t buf_len;
34 u8 nonce_mac[AES_BLOCK_SIZE], hdr_mac[AES_BLOCK_SIZE],
35 data_mac[AES_BLOCK_SIZE];
36 int i, ret = -1;
37
38 if (nonce_len > data_len)
39 buf_len = nonce_len;
40 else
41 buf_len = data_len;
42 if (hdr_len > buf_len)
43 buf_len = hdr_len;
44 buf_len += 16;
45
46 buf = os_malloc(buf_len);
47 if (buf == NULL)
48 return -1;
49
50 os_memset(buf, 0, 15);
51
52 buf[15] = 0;
53 os_memcpy(buf + 16, nonce, nonce_len);
54 if (omac1_aes_128(key, buf, 16 + nonce_len, nonce_mac))
55 goto fail;
56
57 buf[15] = 1;
58 os_memcpy(buf + 16, hdr, hdr_len);
59 if (omac1_aes_128(key, buf, 16 + hdr_len, hdr_mac))
60 goto fail;
61
62 if (aes_128_ctr_encrypt(key, nonce_mac, data, data_len))
63 goto fail;
64 buf[15] = 2;
65 os_memcpy(buf + 16, data, data_len);
66 if (omac1_aes_128(key, buf, 16 + data_len, data_mac))
67 goto fail;
68
69 for (i = 0; i < AES_BLOCK_SIZE; i++)
70 tag[i] = nonce_mac[i] ^ data_mac[i] ^ hdr_mac[i];
71
72 ret = 0;
73 fail:
74 bin_clear_free(buf, buf_len);
75
76 return ret;
77 }
78
79
80 /**
81 * aes_128_eax_decrypt - AES-128 EAX mode decryption
82 * @key: Key for decryption (16 bytes)
83 * @nonce: Nonce for counter mode
84 * @nonce_len: Nonce length in bytes
85 * @hdr: Header data to be authenticity protected
86 * @hdr_len: Length of the header data bytes
87 * @data: Data to encrypt in-place
88 * @data_len: Length of data in bytes
89 * @tag: 16-byte tag value
90 * Returns: 0 on success, -1 on failure, -2 if tag does not match
91 */
aes_128_eax_decrypt(const u8 * key,const u8 * nonce,size_t nonce_len,const u8 * hdr,size_t hdr_len,u8 * data,size_t data_len,const u8 * tag)92 int aes_128_eax_decrypt(const u8 *key, const u8 *nonce, size_t nonce_len,
93 const u8 *hdr, size_t hdr_len,
94 u8 *data, size_t data_len, const u8 *tag)
95 {
96 u8 *buf;
97 size_t buf_len;
98 u8 nonce_mac[AES_BLOCK_SIZE], hdr_mac[AES_BLOCK_SIZE],
99 data_mac[AES_BLOCK_SIZE];
100 int i;
101
102 if (nonce_len > data_len)
103 buf_len = nonce_len;
104 else
105 buf_len = data_len;
106 if (hdr_len > buf_len)
107 buf_len = hdr_len;
108 buf_len += 16;
109
110 buf = os_malloc(buf_len);
111 if (buf == NULL)
112 return -1;
113
114 os_memset(buf, 0, 15);
115
116 buf[15] = 0;
117 os_memcpy(buf + 16, nonce, nonce_len);
118 if (omac1_aes_128(key, buf, 16 + nonce_len, nonce_mac)) {
119 os_free(buf);
120 return -1;
121 }
122
123 buf[15] = 1;
124 os_memcpy(buf + 16, hdr, hdr_len);
125 if (omac1_aes_128(key, buf, 16 + hdr_len, hdr_mac)) {
126 os_free(buf);
127 return -1;
128 }
129
130 buf[15] = 2;
131 os_memcpy(buf + 16, data, data_len);
132 if (omac1_aes_128(key, buf, 16 + data_len, data_mac)) {
133 os_free(buf);
134 return -1;
135 }
136
137 os_free(buf);
138
139 for (i = 0; i < AES_BLOCK_SIZE; i++) {
140 if (tag[i] != (nonce_mac[i] ^ data_mac[i] ^ hdr_mac[i]))
141 return -2;
142 }
143
144 return aes_128_ctr_encrypt(key, nonce_mac, data, data_len);
145 }
146