summaryrefslogtreecommitdiffstats
path: root/libcli/dns/dns.c
blob: 943b4d5b33e1b4fc0582b551c5c2a9ec7754d88e (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
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
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
/*
   Unix SMB/CIFS implementation.

   Small async DNS library for Samba with socketwrapper support

   Copyright (C) 2010 Kai Blin  <kai@samba.org>

   This program 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.

   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.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "replace.h"
#include "system/network.h"
#include <tevent.h>
#include "lib/tsocket/tsocket.h"
#include "libcli/dns/libdns.h"
#include "lib/util/tevent_unix.h"
#include "lib/util/samba_util.h"
#include "lib/util/debug.h"
#include "libcli/util/error.h"
#include "librpc/ndr/libndr.h"
#include "librpc/gen_ndr/ndr_dns.h"

struct dns_udp_request_state {
	struct tevent_context *ev;
	struct tdgram_context *dgram;
	size_t query_len;
	uint8_t *reply;
	size_t reply_len;
};

#define DNS_REQUEST_TIMEOUT 10

/* Declare callback functions used below. */
static void dns_udp_request_get_reply(struct tevent_req *subreq);
static void dns_udp_request_done(struct tevent_req *subreq);

static struct tevent_req *dns_udp_request_send(TALLOC_CTX *mem_ctx,
					       struct tevent_context *ev,
					       const char *server_addr_string,
					       const uint8_t *query,
					       size_t query_len)
{
	struct tevent_req *req, *subreq;
	struct dns_udp_request_state *state;
	struct tsocket_address *local_addr, *server_addr;
	struct tdgram_context *dgram;
	int ret;

	req = tevent_req_create(mem_ctx, &state, struct dns_udp_request_state);
	if (req == NULL) {
		return NULL;
	}

	state->ev = ev;

	/* Use connected UDP sockets */
	ret = tsocket_address_inet_from_strings(state, "ip", NULL, 0,
						&local_addr);
	if (ret != 0) {
		tevent_req_error(req, errno);
		return tevent_req_post(req, ev);
	}

	ret = tsocket_address_inet_from_hostport_strings(
	    state, "ip", server_addr_string, DNS_SERVICE_PORT, &server_addr);
	if (ret != 0) {
		tevent_req_error(req, errno);
		return tevent_req_post(req, ev);
	}

	ret = tdgram_inet_udp_socket(local_addr, server_addr, state, &dgram);
	if (ret != 0) {
		tevent_req_error(req, errno);
		return tevent_req_post(req, ev);
	}

	state->dgram = dgram;
	state->query_len = query_len;

	dump_data(10, query, query_len);

	subreq = tdgram_sendto_send(state, ev, dgram, query, query_len, NULL);
	if (tevent_req_nomem(subreq, req)) {
		return tevent_req_post(req, ev);
	}

	if (!tevent_req_set_endtime(req, ev,
				timeval_current_ofs(DNS_REQUEST_TIMEOUT, 0))) {
		return tevent_req_post(req, ev);
	}

	tevent_req_set_callback(subreq, dns_udp_request_get_reply, req);
	return req;
}

static void dns_udp_request_get_reply(struct tevent_req *subreq)
{
	struct tevent_req *req = tevent_req_callback_data(subreq,
						struct tevent_req);
	struct dns_udp_request_state *state = tevent_req_data(req,
						struct dns_udp_request_state);
	ssize_t len;
	int err = 0;

	len = tdgram_sendto_recv(subreq, &err);
	TALLOC_FREE(subreq);

	if (len == -1 && err != 0) {
		tevent_req_error(req, err);
		return;
	}

	if (len != state->query_len) {
		tevent_req_error(req, EIO);
		return;
	}

	subreq = tdgram_recvfrom_send(state, state->ev, state->dgram);
	if (tevent_req_nomem(subreq, req)) {
		return;
	}

	tevent_req_set_callback(subreq, dns_udp_request_done, req);
}

static void dns_udp_request_done(struct tevent_req *subreq)
{
	struct tevent_req *req = tevent_req_callback_data(subreq,
						struct tevent_req);
	struct dns_udp_request_state *state = tevent_req_data(req,
						struct dns_udp_request_state);

	ssize_t len;
	int err = 0;

	len = tdgram_recvfrom_recv(subreq, &err, state, &state->reply, NULL);
	TALLOC_FREE(subreq);

	if (len == -1 && err != 0) {
		tevent_req_error(req, err);
		return;
	}

	state->reply_len = len;
	dump_data(10, state->reply, state->reply_len);
	tevent_req_done(req);
}

static int dns_udp_request_recv(struct tevent_req *req,
				TALLOC_CTX *mem_ctx,
				uint8_t **reply,
				size_t *reply_len)
{
	struct dns_udp_request_state *state = tevent_req_data(req,
			struct dns_udp_request_state);
	int err;

	if (tevent_req_is_unix_error(req, &err)) {
		tevent_req_received(req);
		return err;
	}

	*reply = talloc_move(mem_ctx, &state->reply);
	*reply_len = state->reply_len;
	tevent_req_received(req);

	return 0;
}

struct dns_tcp_request_state {
	struct tevent_context *ev;
	struct tstream_context *stream;
	const uint8_t *query;
	size_t query_len;

	uint8_t dns_msglen_hdr[2];
	struct iovec iov[2];

	size_t nread;
	uint8_t *reply;
};

static void dns_tcp_request_connected(struct tevent_req *subreq);
static void dns_tcp_request_sent(struct tevent_req *subreq);
static int dns_tcp_request_next_vector(struct tstream_context *stream,
				       void *private_data,
				       TALLOC_CTX *mem_ctx,
				       struct iovec **_vector,
				       size_t *_count);
static void dns_tcp_request_received(struct tevent_req *subreq);

static struct tevent_req *dns_tcp_request_send(TALLOC_CTX *mem_ctx,
					       struct tevent_context *ev,
					       const char *server_addr_string,
					       const uint8_t *query,
					       size_t query_len)
{
	struct tevent_req *req, *subreq;
	struct dns_tcp_request_state *state;
	struct tsocket_address *local, *remote;
	int ret;

	req = tevent_req_create(mem_ctx, &state,
				struct dns_tcp_request_state);
	if (req == NULL) {
		return NULL;
	}
	state->ev = ev;
	state->query = query;
	state->query_len = query_len;

	if (query_len > UINT16_MAX) {
		tevent_req_error(req, EMSGSIZE);
		return tevent_req_post(req, ev);
	}

	ret = tsocket_address_inet_from_strings(state, "ip", NULL, 0, &local);
	if (ret != 0) {
		tevent_req_error(req, errno);
		return tevent_req_post(req, ev);
	}

	ret = tsocket_address_inet_from_hostport_strings(
	    state, "ip", server_addr_string, DNS_SERVICE_PORT, &remote);
	if (ret != 0) {
		tevent_req_error(req, errno);
		return tevent_req_post(req, ev);
	}

	subreq = tstream_inet_tcp_connect_send(state, state->ev,
					       local, remote);
	if (tevent_req_nomem(subreq, req)) {
		return tevent_req_post(req, ev);
	}
	tevent_req_set_callback(subreq, dns_tcp_request_connected, req);

	return req;
}

static void dns_tcp_request_connected(struct tevent_req *subreq)
{
	struct tevent_req *req = tevent_req_callback_data(
		subreq, struct tevent_req);
	struct dns_tcp_request_state *state = tevent_req_data(
		req, struct dns_tcp_request_state);
	int ret, err;

	ret = tstream_inet_tcp_connect_recv(subreq, &err, state,
					    &state->stream, NULL);
	TALLOC_FREE(subreq);
	if (ret == -1) {
		tevent_req_error(req, err);
		return;
	}

	RSSVAL(state->dns_msglen_hdr, 0, state->query_len);
	state->iov[0] = (struct iovec) {
		.iov_base = state->dns_msglen_hdr,
		.iov_len = sizeof(state->dns_msglen_hdr)
	};
	state->iov[1] = (struct iovec) {
		.iov_base = discard_const_p(void, state->query),
		.iov_len = state->query_len
	};

	subreq = tstream_writev_send(state, state->ev, state->stream,
				     state->iov, ARRAY_SIZE(state->iov));
	if (tevent_req_nomem(subreq, req)) {
		return;
	}
	tevent_req_set_callback(subreq, dns_tcp_request_sent, req);
}

static void dns_tcp_request_sent(struct tevent_req *subreq)
{
	struct tevent_req *req = tevent_req_callback_data(
		subreq, struct tevent_req);
	struct dns_tcp_request_state *state = tevent_req_data(
		req, struct dns_tcp_request_state);
	int ret, err;

	ret = tstream_writev_recv(subreq, &err);
	TALLOC_FREE(subreq);
	if (ret == -1) {
		tevent_req_error(req, err);
		return;
	}

	subreq = tstream_readv_pdu_send(state, state->ev, state->stream,
					dns_tcp_request_next_vector, state);
	if (tevent_req_nomem(subreq, req)) {
		return;
	}
	tevent_req_set_callback(subreq, dns_tcp_request_received, req);
}

static int dns_tcp_request_next_vector(struct tstream_context *stream,
				       void *private_data,
				       TALLOC_CTX *mem_ctx,
				       struct iovec **_vector,
				       size_t *_count)
{
	struct dns_tcp_request_state *state = talloc_get_type_abort(
		private_data, struct dns_tcp_request_state);
	struct iovec *vector;
	uint16_t msglen;

	if (state->nread == 0) {
		vector = talloc_array(mem_ctx, struct iovec, 1);
		if (vector == NULL) {
			return -1;
		}
		vector[0] = (struct iovec) {
			.iov_base = state->dns_msglen_hdr,
			.iov_len = sizeof(state->dns_msglen_hdr)
		};
		state->nread = sizeof(state->dns_msglen_hdr);

		*_vector = vector;
		*_count = 1;
		return 0;
	}

	if (state->nread == sizeof(state->dns_msglen_hdr)) {
		msglen = RSVAL(state->dns_msglen_hdr, 0);

		state->reply = talloc_array(state, uint8_t, msglen);
		if (state->reply == NULL) {
			return -1;
		}

		vector = talloc_array(mem_ctx, struct iovec, 1);
		if (vector == NULL) {
			return -1;
		}
		vector[0] = (struct iovec) {
			.iov_base = state->reply,
			.iov_len = msglen
		};
		state->nread += msglen;

		*_vector = vector;
		*_count = 1;
		return 0;
	}

	*_vector = NULL;
	*_count = 0;
	return 0;
}

static void dns_tcp_request_received(struct tevent_req *subreq)
{
	struct tevent_req *req = tevent_req_callback_data(
		subreq, struct tevent_req);
	int ret, err;

	ret = tstream_readv_pdu_recv(subreq, &err);
	TALLOC_FREE(subreq);
	if (ret == -1) {
		tevent_req_error(req, err);
		return;
	}

	tevent_req_done(req);
}

static int dns_tcp_request_recv(struct tevent_req *req,
				TALLOC_CTX *mem_ctx,
				uint8_t **reply,
				size_t *reply_len)
{
	struct dns_tcp_request_state *state = tevent_req_data(
		req, struct dns_tcp_request_state);
	int err;

	if (tevent_req_is_unix_error(req, &err)) {
		tevent_req_received(req);
		return err;
	}

	*reply_len = talloc_array_length(state->reply);
	*reply = talloc_move(mem_ctx, &state->reply);
	tevent_req_received(req);

	return 0;
}

struct dns_cli_request_state {
	struct tevent_context *ev;
	const char *nameserver;

	uint16_t req_id;

	DATA_BLOB query;

	struct dns_name_packet *reply;
};

static void dns_cli_request_udp_done(struct tevent_req *subreq);
static void dns_cli_request_tcp_done(struct tevent_req *subreq);

struct tevent_req *dns_cli_request_send(TALLOC_CTX *mem_ctx,
					struct tevent_context *ev,
					const char *nameserver,
					const char *name,
					enum dns_qclass qclass,
					enum dns_qtype qtype)
{
	struct tevent_req *req, *subreq;
	struct dns_cli_request_state *state;
	struct dns_name_question question;
	struct dns_name_packet out_packet;
	enum ndr_err_code ndr_err;

	req = tevent_req_create(mem_ctx, &state,
				struct dns_cli_request_state);
	if (req == NULL) {
		return NULL;
	}
	state->ev = ev;
	state->nameserver = nameserver;

	DBG_DEBUG("Asking %s for %s/%d/%d via UDP\n", nameserver,
		  name, (int)qclass, (int)qtype);

	generate_random_buffer((uint8_t *)&state->req_id,
			       sizeof(state->req_id));

	question = (struct dns_name_question) {
		.name = discard_const_p(char, name),
		.question_type = qtype, .question_class = qclass
	};

	out_packet = (struct dns_name_packet) {
		.id = state->req_id,
		.operation = DNS_OPCODE_QUERY | DNS_FLAG_RECURSION_DESIRED,
		.qdcount = 1,
		.questions = &question
	};

	ndr_err = ndr_push_struct_blob(
		&state->query, state, &out_packet,
		(ndr_push_flags_fn_t)ndr_push_dns_name_packet);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		tevent_req_error(req, ndr_map_error2errno(ndr_err));
		return tevent_req_post(req, ev);
	}

	subreq = dns_udp_request_send(state, state->ev, state->nameserver,
				      state->query.data, state->query.length);
	if (tevent_req_nomem(subreq, req)) {
		return tevent_req_post(req, ev);
	}
	tevent_req_set_callback(subreq, dns_cli_request_udp_done, req);
	return req;
}

static void dns_cli_request_udp_done(struct tevent_req *subreq)
{
	struct tevent_req *req = tevent_req_callback_data(
		subreq, struct tevent_req);
	struct dns_cli_request_state *state = tevent_req_data(
		req, struct dns_cli_request_state);
	DATA_BLOB reply;
	enum ndr_err_code ndr_err;
	uint16_t reply_id, operation;
	int ret;

	ret = dns_udp_request_recv(subreq, state, &reply.data, &reply.length);
	TALLOC_FREE(subreq);
	if (tevent_req_error(req, ret)) {
		return;
	}

	if (reply.length < 4) {
		DBG_DEBUG("Short DNS packet: length=%zu\n", reply.length);
		tevent_req_error(req, EINVAL);
		return;
	}

	reply_id = PULL_BE_U16(reply.data, 0);
	if (reply_id != state->req_id) {
		DBG_DEBUG("Got id %"PRIu16", expected %"PRIu16"\n",
			  state->reply->id, state->req_id);
		tevent_req_error(req, ENOMSG);
		return;
	}

	operation = PULL_BE_U16(reply.data, 2);
	if ((operation & DNS_FLAG_TRUNCATION) != 0) {
		DBG_DEBUG("Reply was truncated, retrying TCP\n");
		subreq = dns_tcp_request_send(
			state,
			state->ev,
			state->nameserver,
			state->query.data,
			state->query.length);
		if (tevent_req_nomem(subreq, req)) {
			return;
		}
		tevent_req_set_callback(subreq, dns_cli_request_tcp_done, req);
		return;
	}

	state->reply = talloc(state, struct dns_name_packet);
	if (tevent_req_nomem(state->reply, req)) {
		return;
	}

	ndr_err = ndr_pull_struct_blob(
		&reply, state->reply, state->reply,
		(ndr_pull_flags_fn_t)ndr_pull_dns_name_packet);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		tevent_req_error(req, ndr_map_error2errno(ndr_err));
		return;
	}
	TALLOC_FREE(reply.data);

	tevent_req_done(req);
}

static void dns_cli_request_tcp_done(struct tevent_req *subreq)
{
	struct tevent_req *req = tevent_req_callback_data(
		subreq, struct tevent_req);
	struct dns_cli_request_state *state = tevent_req_data(
		req, struct dns_cli_request_state);
	DATA_BLOB reply;
	enum ndr_err_code ndr_err;
	int ret;

	ret = dns_tcp_request_recv(subreq, state, &reply.data, &reply.length);
	TALLOC_FREE(subreq);
	if (tevent_req_error(req, ret)) {
		return;
	}

	state->reply = talloc(state, struct dns_name_packet);
	if (tevent_req_nomem(state->reply, req)) {
		return;
	}

	ndr_err = ndr_pull_struct_blob(
		&reply, state->reply, state->reply,
		(ndr_pull_flags_fn_t)ndr_pull_dns_name_packet);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		tevent_req_error(req, ndr_map_error2errno(ndr_err));
		return;
	}
	TALLOC_FREE(reply.data);

	if (state->reply->id != state->req_id) {
		DBG_DEBUG("Got id %"PRIu16", expected %"PRIu16"\n",
			  state->reply->id, state->req_id);
		tevent_req_error(req, ENOMSG);
		return;
	}

	DBG_DEBUG("Got op=%x %"PRIu16"/%"PRIu16"/%"PRIu16"/%"PRIu16
		  " recs\n", (int)state->reply->operation,
		  state->reply->qdcount, state->reply->ancount,
		  state->reply->nscount, state->reply->nscount);

	tevent_req_done(req);
}

int dns_cli_request_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx,
			 struct dns_name_packet **reply)
{
	struct dns_cli_request_state *state = tevent_req_data(
		req, struct dns_cli_request_state);
	int err;

	if (tevent_req_is_unix_error(req, &err)) {
		return err;
	}
	*reply = talloc_move(mem_ctx, &state->reply);
	return 0;
}