summaryrefslogtreecommitdiff
path: root/package/network/services/ead/src/ead-crypt.c
blob: 03721721d92e28bf2610c9c170e14440786c1802 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
/*
 * Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include "ead.h"

#include "sha1.c"
#include "aes.c"

#if EAD_DEBUGLEVEL >= 1
#define DEBUG(n, format, ...) do { \
	if (EAD_DEBUGLEVEL >= n) \
		fprintf(stderr, format, ##__VA_ARGS__); \
} while (0);

#else
#define DEBUG(n, format, ...) do {} while(0)
#endif


static uint32_t aes_enc_ctx[AES_PRIV_SIZE];
static uint32_t aes_dec_ctx[AES_PRIV_SIZE];
static uint32_t ead_rx_iv;
static uint32_t ead_tx_iv;
static uint32_t ivofs_vec;
static unsigned int ivofs_idx = 0;
static uint32_t W[80]; /* work space for sha1 */

#define EAD_ENC_PAD	64

void
ead_set_key(unsigned char *skey)
{
	uint32_t *ivp = (uint32_t *)skey;

	memset(aes_enc_ctx, 0, sizeof(aes_enc_ctx));
	memset(aes_dec_ctx, 0, sizeof(aes_dec_ctx));

	/* first 32 bytes of skey are used as aes key for
	 * encryption and decryption */
	rijndaelKeySetupEnc(aes_enc_ctx, skey);
	rijndaelKeySetupDec(aes_dec_ctx, skey);

	/* the following bytes are used as initialization vector for messages
	 * (highest byte cleared to avoid overflow) */
	ivp += 8;
	ead_rx_iv = ntohl(*ivp) & 0x00ffffff;
	ead_tx_iv = ead_rx_iv;

	/* the last bytes are used to feed the random iv increment */
	ivp++;
	ivofs_vec = *ivp;
}


static bool
ead_check_rx_iv(uint32_t iv)
{
	if (iv <= ead_rx_iv)
		return false;

	if (iv > ead_rx_iv + EAD_MAX_IV_INCR)
		return false;

	ead_rx_iv = iv;
	return true;
}


static uint32_t
ead_get_tx_iv(void)
{
	unsigned int ofs;

	ofs = 1 + ((ivofs_vec >> 2 * ivofs_idx) & 0x3);
	ivofs_idx = (ivofs_idx + 1) % 16;
	ead_tx_iv += ofs;

	return ead_tx_iv;
}

static void
ead_hash_message(struct ead_msg_encrypted *enc, uint32_t *hash, int len)
{
	unsigned char *data = (unsigned char *) enc;

	/* hash the packet with the stored hash part initialized to zero */
	sha_init(hash);
	memset(enc->hash, 0, sizeof(enc->hash));
	while (len > 0) {
		sha_transform(hash, data, W);
		len -= 64;
		data += 64;
	}
}

void
ead_encrypt_message(struct ead_msg *msg, unsigned int len)
{
	struct ead_msg_encrypted *enc = EAD_DATA(msg, enc);
	unsigned char *data = (unsigned char *) enc;
	uint32_t hash[5];
	int enclen, i;

	len += sizeof(struct ead_msg_encrypted);
	enc->pad = (EAD_ENC_PAD - (len % EAD_ENC_PAD)) % EAD_ENC_PAD;
	enclen = len + enc->pad;
	msg->len = htonl(enclen);
	enc->iv = htonl(ead_get_tx_iv());

	ead_hash_message(enc, hash, enclen);
	for (i = 0; i < 5; i++)
		enc->hash[i] = htonl(hash[i]);
	DEBUG(2, "SHA1 generate (0x%08x), len=%d\n", enc->hash[0], enclen);

	while (enclen > 0) {
		rijndaelEncrypt(aes_enc_ctx, data, data);
		data += 16;
		enclen -= 16;
	}
}

int
ead_decrypt_message(struct ead_msg *msg)
{
	struct ead_msg_encrypted *enc = EAD_DATA(msg, enc);
	unsigned char *data = (unsigned char *) enc;
	uint32_t hash_old[5], hash_new[5];
	int len = ntohl(msg->len);
	int i, enclen = len;

	if (!len || (len % EAD_ENC_PAD > 0))
		return 0;

	while (len > 0) {
		rijndaelDecrypt(aes_dec_ctx, data, data);
		data += 16;
		len -= 16;
	}

	data = (unsigned char *) enc;

	if (enc->pad >= EAD_ENC_PAD) {
		DEBUG(2, "Invalid padding length\n");
		return 0;
	}

	if (!ead_check_rx_iv(ntohl(enc->iv))) {
		DEBUG(2, "RX IV mismatch (0x%08x <> 0x%08x)\n", ead_rx_iv, ntohl(enc->iv));
		return 0;
	}

	for (i = 0; i < 5; i++)
		hash_old[i] = ntohl(enc->hash[i]);
	ead_hash_message(enc, hash_new, enclen);
	if (memcmp(hash_old, hash_new, sizeof(hash_old)) != 0) {
		DEBUG(2, "SHA1 mismatch (0x%08x != 0x%08x), len=%d\n", hash_old[0], hash_new[0], enclen);
		return 0;
	}

	enclen -= enc->pad + sizeof(struct ead_msg_encrypted);
	return enclen;
}