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/* 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++;
if ('A' <= ch && ch <= 'Z') {
ch = ch - 'A';
} else if ('a' <= ch && ch <= 'z') {
ch = ch - 'a';
} else if ('0' <= ch && ch <= '5') {
ch = ch - '0' + 26;
} else {
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;
}
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