forked from curvedns/curvedns
/
dns.c
275 lines (228 loc) · 9.44 KB
/
dns.c
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
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
/*
* Copyright 2010 CurveDNS Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification, are
* permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this list of
* conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice, this list
* of conditions and the following disclaimer in the documentation and/or other materials
* provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY CurveDNS Project ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL CurveDNS Project OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* The views and conclusions contained in the software and documentation are those of the
* authors and should not be interpreted as representing official policies, either expressed
* or implied, of CurveDNS Project.
*
*/
/*
* $Id$
* $Author$
* $Date$
* $Revision$
*/
#include "dns.h"
#include "misc.h"
#include "dnscurve.h"
// From Matthew Demspky's prototype code
// (Indirectly from djbdns' dns_packet.c)
unsigned int dns_packet_getname(uint8_t *name, unsigned int namemax, const uint8_t *buf, unsigned int len, unsigned int pos) {
unsigned int loop = 0;
unsigned int state = 0;
unsigned int firstcompress = 0;
unsigned int where;
uint8_t ch;
unsigned int namelen = 0;
for (;;) {
if (pos >= len) goto PROTO;
ch = buf[pos++];
if (++loop >= 4096) goto PROTO;
if (state) {
if (namelen + 1 > namemax) goto PROTO;
name[namelen++] = ch;
--state;
} else {
while (ch >= 192) {
where = ch; where -= 192; where <<= 8;
if (pos >= len) goto PROTO;
ch = buf[pos++];
if (!firstcompress) firstcompress = pos;
pos = where + ch;
if (pos >= len) goto PROTO;
ch = buf[pos++];
if (++loop >= 4096) goto PROTO;
}
if (ch >= 64) goto PROTO;
if (namelen + 1 > namemax) goto PROTO;
name[namelen++] = ch;
if (!ch) break;
state = ch;
}
}
if (firstcompress) return firstcompress;
return pos;
PROTO:
errno = EPROTO;
return 0;
}
int dns_analyze_query(event_entry_t *general_entry) {
// There is nothing to analyze in regular DNS, so go directly to DNSCurve analyzement:
return dnscurve_analyze_query(general_entry);
}
int dns_forward_query_udp(event_entry_t *general_entry) {
int sock, n;
struct event_udp_entry *entry = &general_entry->udp;
if (!ip_udp_open(&sock, &global_target_address)) {
debug_log(DEBUG_ERROR, "dns_forward_query_udp(): unable to open a UDP socket to forward query to authoritative server\n");
goto wrong;
}
// randomize the outgoing source port and set the source IP address, if needed
if (!ip_bind_random(sock)) {
// if this fails, let the kernel handle it (would mean source IP address is not guaranteed...)
debug_log(DEBUG_WARN, "dns_forward_query_udp(): unable to bind to source IP address and/or random port\n");
}
entry->state = EVENT_UDP_INT_WRITING;
entry->read_int_watcher.data = general_entry;
entry->timeout_int_watcher.data = general_entry;
entry->retries++;
// Now generate a new TXID to forecome any poisoning:
entry->buffer[0] = misc_crypto_random(256);
entry->buffer[1] = misc_crypto_random(256);
// XXX: do this platform safe (i.e. ntoh)
entry->dns.dsttxid = (entry->buffer[0] << 8) + entry->buffer[1];
ev_io_init(&entry->read_int_watcher, event_udp_int_cb, sock, EV_READ);
ev_timer_init(&entry->timeout_int_watcher, event_udp_timeout_cb, 0., global_ip_internal_timeout);
ev_io_start(event_default_loop, &entry->read_int_watcher);
ev_timer_again(event_default_loop, &entry->timeout_int_watcher);
debug_log(DEBUG_INFO, "dns_forward_query_udp(): forwarding query to authoritative name server (prev id = %d, new id = %d)\n",
(entry->dns.type == DNS_DNSCURVE_STREAMLINED || entry->dns.type == DNS_NON_DNSCURVE) ? entry->dns.srctxid : entry->dns.srcinsidetxid,
entry->dns.dsttxid);
n = sendto(sock, entry->buffer, entry->packetsize, MSG_DONTWAIT,
(struct sockaddr *) &global_target_address.sa, global_target_address_len);
if (n == -1) {
debug_log(DEBUG_ERROR, "dns_forward_query_udp(): unable to forward the query to authoritative name server (%s)\n", strerror(errno));
goto wrong;
}
return 1;
wrong:
return 0;
}
int dns_forward_query_tcp(event_entry_t *general_entry) {
struct event_tcp_entry *entry = &general_entry->tcp;
if (!ip_tcp_open(&entry->intsock, &global_target_address)) {
debug_log(DEBUG_ERROR, "dns_forward_query_tcp(): unable to open TCP socket\n");
goto wrong;
}
// randomizing port is not really necessary, as TCP is invulnerable to cache poisoning
// however, the source IP address is set in ip_bind_random...
if (!ip_bind_random(entry->intsock)) {
// if this fails, let the kernel handle it (would mean source IP address is not guaranteed...)
debug_log(DEBUG_WARN, "dns_forward_query_tcp(): unable to bind to source IP address and/or random port\n");
}
if (!ip_connect(entry->intsock, &global_target_address)) {
debug_log(DEBUG_ERROR, "dns_forward_query_tcp(): unable to connect to authoritative name server (%s)\n", strerror(errno));
goto wrong;
}
// Now generate a new TXID to forecome any poisoning:
entry->buffer[0] = misc_crypto_random(256);
entry->buffer[1] = misc_crypto_random(256);
// XXX: do this platform safe (i.e. ntoh)
entry->dns.dsttxid = (entry->buffer[0] << 8) + entry->buffer[1];
debug_log(DEBUG_INFO, "dns_forward_query_tcp(): forwarding query to authoritative name server (prev id = %d, new id = %d)\n",
entry->dns.srctxid, entry->dns.dsttxid);
return 1;
wrong:
return 0;
}
int dns_analyze_reply_query(event_entry_t *general_entry) {
struct event_general_entry *entry = &general_entry->general;
uint16_t recvtxid;
if (entry->packetsize < 12) {
debug_log(DEBUG_INFO, "dns_analyze_reply_query(): received response is too small (no DNS header)\n");
goto wrong;
}
// Check the received id with the one we sent:
recvtxid = (entry->buffer[0] << 8) + entry->buffer[1];
if (entry->dns.dsttxid != recvtxid) {
debug_log(DEBUG_WARN, "dns_analyze_reply_query(): received txid differ!\n");
goto wrong;
}
// Now set the right response id, depending on the query type:
if ((entry->dns.type == DNS_NON_DNSCURVE) || (entry->dns.type == DNS_DNSCURVE_STREAMLINED)) {
entry->buffer[0] = entry->dns.srctxid >> 8;
entry->buffer[1] = entry->dns.srctxid & 0xff;
} else {
entry->buffer[0] = entry->dns.srcinsidetxid >> 8;
entry->buffer[1] = entry->dns.srcinsidetxid & 0xff;
}
return 1;
wrong:
return 0;
}
int dns_reply_query_udp(event_entry_t *general_entry) {
struct event_udp_entry *entry = &general_entry->udp;
socklen_t addresslen;
int n;
if (entry->dns.type == DNS_NON_DNSCURVE) {
debug_log(DEBUG_INFO, "dns_reply_query_udp(): sending DNS response in regular format\n");
} else if (entry->dns.type == DNS_DNSCURVE_STREAMLINED) {
debug_log(DEBUG_INFO, "dns_reply_query_udp(): sending DNS response in streamlined DNSCurve format\n");
if (!dnscurve_reply_streamlined_query(general_entry)) {
debug_log(DEBUG_WARN, "dns_reply_query_udp(): failed to reply in streamlined format\n");
goto wrong;
}
} else if ((entry->dns.type == DNS_DNSCURVE_TXT_RD_SET) || (entry->dns.type == DNS_DNSCURVE_TXT_RD_UNSET)) {
debug_log(DEBUG_INFO, "dns_reply_query_udp(): sending DNS response in DNSCurve TXT format\n");
if (!dnscurve_reply_txt_query(general_entry)) {
debug_log(DEBUG_WARN, "dns_reply_query_udp(): failed to reply in TXT format\n");
goto wrong;
}
}
entry->state = EVENT_UDP_EXT_WRITING;
if (entry->address.sa.sa_family == AF_INET) {
addresslen = sizeof(struct sockaddr_in);
} else {
addresslen = sizeof(struct sockaddr_in6);
}
n = sendto(entry->sock->fd, entry->buffer, entry->packetsize, MSG_DONTWAIT,
(struct sockaddr *) &entry->address.sa, addresslen);
if (n == -1) {
debug_log(DEBUG_ERROR, "dns_reply_query_udp(): unable to send the response to the client (%s)\n", strerror(errno));
goto wrong;
}
return 1;
wrong:
return 0;
}
int dns_reply_query_tcp(event_entry_t *general_entry) {
struct event_tcp_entry *entry = &general_entry->tcp;
if (entry->dns.type == DNS_NON_DNSCURVE) {
debug_log(DEBUG_INFO, "dns_reply_query_tcp(): sending DNS response in regular format\n");
} else if (entry->dns.type == DNS_DNSCURVE_STREAMLINED) {
debug_log(DEBUG_INFO, "dns_reply_query_tcp(): sending DNS response in streamlined DNSCurve format\n");
if (!dnscurve_reply_streamlined_query(general_entry)) {
debug_log(DEBUG_INFO, "dns_reply_query_tcp(): failed to reply in streamlined format\n");
goto wrong;
}
} else if ((entry->dns.type == DNS_DNSCURVE_TXT_RD_SET) || (entry->dns.type == DNS_DNSCURVE_TXT_RD_UNSET)) {
debug_log(DEBUG_INFO, "dns_reply_query_tcp(): doing reply in TXT format\n");
if (!dnscurve_reply_txt_query(general_entry)) {
debug_log(DEBUG_INFO, "dns_reply_query_tcp(): failed to reply in TXT format\n");
goto wrong;
}
}
return 1;
wrong:
return 0;
}