summaryrefslogtreecommitdiff
path: root/toxdns/toxdns.c
blob: 186ea82b506e2e4af985860e583c4e5fd7bbf416 (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
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
/* toxdns.c
 *
 * Tox secure username DNS toxid resolving functions.
 *
 *  Copyright (C) 2013 Tox project All Rights Reserved.
 *
 *  This file is part of Tox.
 *
 *  Tox is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  Tox 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.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with Tox.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "../toxcore/Messenger.h"
#include "../toxcore/logger.h"
#include "toxdns.h"

static const char base32[32] = {"abcdefghijklmnopqrstuvwxyz012345"};

#define _encode(a, b, c) \
{ \
uint8_t i = 0; \
    while(i != c) { \
        *a++ = base32[((b[0] >> bits) | (b[1] << (8 - bits))) & 0x1F]; \
        bits += 5; \
        if(bits >= 8) { \
            bits -= 8; \
            b++; \
            i++; \
        } \
    } \
} \
 
typedef struct {
    uint8_t temp_pk[crypto_box_PUBLICKEYBYTES];
    uint8_t temp_sk[crypto_box_SECRETKEYBYTES];
    uint8_t server_public_key[crypto_box_PUBLICKEYBYTES];
    uint8_t shared_key[crypto_box_KEYBYTES];
    uint32_t nonce;
    uint32_t nonce_start;
} DNS_Object;

static void dns_new_temp_keys(DNS_Object *d)
{
    d->nonce = d->nonce_start = random_int();
    crypto_box_keypair(d->temp_pk, d->temp_sk);
    encrypt_precompute(d->server_public_key, d->temp_sk, d->shared_key);
}

/* Create a new tox_dns3 object for server with server_public_key.
 *
 * return Null on failure.
 * return pointer object on success.
 */
void *tox_dns3_new(uint8_t *server_public_key)
{
    DNS_Object *d = malloc(sizeof(DNS_Object));

    if (d == NULL)
        return NULL;

    memcpy(d->server_public_key, server_public_key, crypto_box_PUBLICKEYBYTES);
    dns_new_temp_keys(d);
    return d;
}

/* Destroy the tox dns3 object.
 */
void tox_dns3_kill(void *dns3_object)
{
    memset(dns3_object, 0, sizeof(DNS_Object));
    free(dns3_object);
}

/* Generate a dns3 string of string_max_len used to query the dns server referred to by to
 * dns3_object for a tox id registered to user with name of name_len.
 *
 * the uint32_t pointed by request_id will be set to the request id which must be passed to
 * tox_decrypt_dns3_TXT() to correctly decode the response.
 *
 * This is what the string returned looks like:
 * 4haaaaipr1o3mz0bxweox541airydbovqlbju51mb4p0ebxq.rlqdj4kkisbep2ks3fj2nvtmk4daduqiueabmexqva1jc
 *
 * returns length of string on success.
 * returns -1 on failure.
 */
int tox_generate_dns3_string(void *dns3_object, uint8_t *string, uint16_t string_max_len, uint32_t *request_id,
                             uint8_t *name, uint8_t name_len)
{
#define DOT_INTERVAL (6 * 5)
    int base = (sizeof(uint32_t) + crypto_box_PUBLICKEYBYTES + name_len + crypto_box_MACBYTES);
    int end_len = ((base * 8) / 5) + (base / DOT_INTERVAL) + !!(base % 5);
    end_len -= !(base % DOT_INTERVAL);

    if (end_len > string_max_len)
        return -1;

    DNS_Object *d = dns3_object;
    uint8_t buffer[1024];
    uint8_t nonce[crypto_box_NONCEBYTES] = {0};
    memcpy(nonce, &d->nonce, sizeof(uint32_t));
    memcpy(buffer, &d->nonce, sizeof(uint32_t));
    memcpy(buffer + sizeof(uint32_t), d->temp_pk, crypto_box_PUBLICKEYBYTES);
    int len = encrypt_data_symmetric(d->shared_key, nonce, name, name_len,
                                     buffer + sizeof(uint32_t) + crypto_box_PUBLICKEYBYTES);

    if (len == -1)
        return -1;

    int total_len = len + sizeof(uint32_t) + crypto_box_PUBLICKEYBYTES;
    uint8_t *buff = buffer, *old_str = string;
    buffer[total_len] = 0;
    uint8_t bits = 0;
    int i;

    for (i = !(total_len % DOT_INTERVAL); i < (total_len / DOT_INTERVAL); ++i) {
        _encode(string, buff, DOT_INTERVAL);
        *string = '.';
        ++string;
    }

    int left = total_len - (buff - buffer);
    _encode(string, buff, left);
#undef DOT_INTERVAL
    *request_id = d->nonce;
    ++d->nonce;

    if (d->nonce == d->nonce_start) {
        dns_new_temp_keys(d);
    }

    if (end_len != string - old_str) {
        LOGGER_ERROR("tox_generate_dns3_string Fail, %u != %lu\n", end_len, string - old_str);
        return -1;
    }

    return string - old_str;
}


static int decode(uint8_t *dest, uint8_t *src)
{
    uint8_t *p = src, *op = dest, bits = 0;
    *op = 0;

    while (*p) {
        uint8_t ch = *p++;

        switch (ch) {
            case 'A' ... 'Z': {
                ch = ch - 'A';
                break;
            }

            case 'a' ... 'z': {
                ch = ch - 'a';
                break;
            }

            case '0' ... '5': {
                ch = ch - '0' + 26;
                break;
            }

            default: {
                return - 1;
            }
        }

        *op |= (ch << bits);
        bits += 5;

        if (bits >= 8) {
            bits -= 8;
            ++op;
            *op = (ch >> (5 - bits));
        }
    }

    return op - dest;
}

/* Decode and decrypt the id_record returned of length id_record_len into
 * tox_id (needs to be at least TOX_FRIEND_ADDRESS_SIZE).
 *
 * request_id is the request id given by tox_generate_dns3_string() when creating the request.
 *
 * the id_record passed to this function should look somewhat like this:
 * 2vgcxuycbuctvauik3plsv3d3aadv4zfjfhi3thaizwxinelrvigchv0ah3qjcsx5qhmaksb2lv2hm5cwbtx0yp
 *
 * returns -1 on failure.
 * returns 0 on success.
 *
 */
int tox_decrypt_dns3_TXT(void *dns3_object, uint8_t *tox_id, uint8_t *id_record, uint32_t id_record_len,
                         uint32_t request_id)
{
    DNS_Object *d = dns3_object;

    if (id_record_len != 87)
        return -1;

    /*if (id_record_len > 255 || id_record_len <= (sizeof(uint32_t) + crypto_box_MACBYTES))
        return -1;*/

    uint8_t id_record_null[id_record_len + 1];
    memcpy(id_record_null, id_record, id_record_len);
    id_record_null[id_record_len] = 0;
    uint8_t data[id_record_len];
    int length = decode(data, id_record_null);

    if (length == -1)
        return -1;

    uint8_t nonce[crypto_box_NONCEBYTES] = {0};
    memcpy(nonce, &request_id, sizeof(uint32_t));
    nonce[sizeof(uint32_t)] = 1;
    int len = decrypt_data_symmetric(d->shared_key, nonce, data, length, tox_id);

    if (len != FRIEND_ADDRESS_SIZE)
        return -1;

    return 0;
}