OpenWrt – Blame information for rev 4

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4 office 1 /*
2 * Copyright (C) 2008 Felix Fietkau <nbd@nbd.name>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2
6 * as published by the Free Software Foundation
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
12 */
13  
14 #include <stddef.h>
15 #include <stdint.h>
16 #include <stdlib.h>
17 #include <stdbool.h>
18 #include <string.h>
19 #include <unistd.h>
20 #include <stdio.h>
21 #include "ead.h"
22  
23 #include "sha1.c"
24 #include "aes.c"
25  
26 #if EAD_DEBUGLEVEL >= 1
27 #define DEBUG(n, format, ...) do { \
28 if (EAD_DEBUGLEVEL >= n) \
29 fprintf(stderr, format, ##__VA_ARGS__); \
30 } while (0);
31  
32 #else
33 #define DEBUG(n, format, ...) do {} while(0)
34 #endif
35  
36  
37 static uint32_t aes_enc_ctx[AES_PRIV_SIZE];
38 static uint32_t aes_dec_ctx[AES_PRIV_SIZE];
39 static uint32_t ead_rx_iv;
40 static uint32_t ead_tx_iv;
41 static uint32_t ivofs_vec;
42 static unsigned int ivofs_idx = 0;
43 static uint32_t W[80]; /* work space for sha1 */
44  
45 #define EAD_ENC_PAD 64
46  
47 void
48 ead_set_key(unsigned char *skey)
49 {
50 uint32_t *ivp = (uint32_t *)skey;
51  
52 memset(aes_enc_ctx, 0, sizeof(aes_enc_ctx));
53 memset(aes_dec_ctx, 0, sizeof(aes_dec_ctx));
54  
55 /* first 32 bytes of skey are used as aes key for
56 * encryption and decryption */
57 rijndaelKeySetupEnc(aes_enc_ctx, skey);
58 rijndaelKeySetupDec(aes_dec_ctx, skey);
59  
60 /* the following bytes are used as initialization vector for messages
61 * (highest byte cleared to avoid overflow) */
62 ivp += 8;
63 ead_rx_iv = ntohl(*ivp) & 0x00ffffff;
64 ead_tx_iv = ead_rx_iv;
65  
66 /* the last bytes are used to feed the random iv increment */
67 ivp++;
68 ivofs_vec = *ivp;
69 }
70  
71  
72 static bool
73 ead_check_rx_iv(uint32_t iv)
74 {
75 if (iv <= ead_rx_iv)
76 return false;
77  
78 if (iv > ead_rx_iv + EAD_MAX_IV_INCR)
79 return false;
80  
81 ead_rx_iv = iv;
82 return true;
83 }
84  
85  
86 static uint32_t
87 ead_get_tx_iv(void)
88 {
89 unsigned int ofs;
90  
91 ofs = 1 + ((ivofs_vec >> 2 * ivofs_idx) & 0x3);
92 ivofs_idx = (ivofs_idx + 1) % 16;
93 ead_tx_iv += ofs;
94  
95 return ead_tx_iv;
96 }
97  
98 static void
99 ead_hash_message(struct ead_msg_encrypted *enc, uint32_t *hash, int len)
100 {
101 unsigned char *data = (unsigned char *) enc;
102  
103 /* hash the packet with the stored hash part initialized to zero */
104 sha_init(hash);
105 memset(enc->hash, 0, sizeof(enc->hash));
106 while (len > 0) {
107 sha_transform(hash, data, W);
108 len -= 64;
109 data += 64;
110 }
111 }
112  
113 void
114 ead_encrypt_message(struct ead_msg *msg, unsigned int len)
115 {
116 struct ead_msg_encrypted *enc = EAD_DATA(msg, enc);
117 unsigned char *data = (unsigned char *) enc;
118 uint32_t hash[5];
119 int enclen, i;
120  
121 len += sizeof(struct ead_msg_encrypted);
122 enc->pad = (EAD_ENC_PAD - (len % EAD_ENC_PAD)) % EAD_ENC_PAD;
123 enclen = len + enc->pad;
124 msg->len = htonl(enclen);
125 enc->iv = htonl(ead_get_tx_iv());
126  
127 ead_hash_message(enc, hash, enclen);
128 for (i = 0; i < 5; i++)
129 enc->hash[i] = htonl(hash[i]);
130 DEBUG(2, "SHA1 generate (0x%08x), len=%d\n", enc->hash[0], enclen);
131  
132 while (enclen > 0) {
133 rijndaelEncrypt(aes_enc_ctx, data, data);
134 data += 16;
135 enclen -= 16;
136 }
137 }
138  
139 int
140 ead_decrypt_message(struct ead_msg *msg)
141 {
142 struct ead_msg_encrypted *enc = EAD_DATA(msg, enc);
143 unsigned char *data = (unsigned char *) enc;
144 uint32_t hash_old[5], hash_new[5];
145 int len = ntohl(msg->len);
146 int i, enclen = len;
147  
148 if (!len || (len % EAD_ENC_PAD > 0))
149 return 0;
150  
151 while (len > 0) {
152 rijndaelDecrypt(aes_dec_ctx, data, data);
153 data += 16;
154 len -= 16;
155 }
156  
157 data = (unsigned char *) enc;
158  
159 if (enc->pad >= EAD_ENC_PAD) {
160 DEBUG(2, "Invalid padding length\n");
161 return 0;
162 }
163  
164 if (!ead_check_rx_iv(ntohl(enc->iv))) {
165 DEBUG(2, "RX IV mismatch (0x%08x <> 0x%08x)\n", ead_rx_iv, ntohl(enc->iv));
166 return 0;
167 }
168  
169 for (i = 0; i < 5; i++)
170 hash_old[i] = ntohl(enc->hash[i]);
171 ead_hash_message(enc, hash_new, enclen);
172 if (memcmp(hash_old, hash_new, sizeof(hash_old)) != 0) {
173 DEBUG(2, "SHA1 mismatch (0x%08x != 0x%08x), len=%d\n", hash_old[0], hash_new[0], enclen);
174 return 0;
175 }
176  
177 enclen -= enc->pad + sizeof(struct ead_msg_encrypted);
178 return enclen;
179 }