aboutsummaryrefslogtreecommitdiffstats
path: root/common.c
blob: 3edf8729c8bc3b42319304b3259593048fd2a58a (plain) (blame)
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
/* SPDX-License-Identifier: MIT
 *
 * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
 */

#define _DEFAULT_SOURCE

#include <inttypes.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <arpa/inet.h>
#include <libmnl/libmnl.h>
#include <linux/rtnetlink.h>

#include "common.h"
#include "dbg.h"

static bool parse_ip_cidr(struct wg_combined_ip *ip, char *value)
{
	uintmax_t res;
	char *endptr;
	char *sep;

	if (value[0] == '\0') {
		memset(ip, 0, ip->family == AF_INET ? 4 : 16);
		ip->cidr = 0;
		return true;
	}

	sep = strchr(value, '/');
	if (!sep)
		return false;

	*sep = '\0';
	if (inet_pton(ip->family, value, ip) != 1)
		return false;

	res = strtoumax(sep + 1, &endptr, 10);
	if (res > UINT8_MAX || *endptr != '\0' || sep + 1 == endptr)
		return false;

	// TODO: validate cidr range depending on ip->family
	ip->cidr = (uint8_t)res;

	return true;
}

static struct wg_dynamic_attr *parse_value(enum wg_dynamic_key key, char *value)
{
	struct wg_dynamic_attr *attr;
	size_t len;
	char *endptr;
	uintmax_t uresult;
	union {
		uint32_t uint32;
		char errmsg[72];
		struct wg_combined_ip ip;
	} data = { 0 };

	switch (key) {
	case WGKEY_IPV4:
		len = sizeof data.ip;
		data.ip.family = AF_INET;
		if (!parse_ip_cidr(&data.ip, value))
			return NULL;

		break;
	case WGKEY_IPV6:
		len = sizeof data.ip;
		data.ip.family = AF_INET6;
		if (!parse_ip_cidr(&data.ip, value))
			return NULL;

		break;
	case WGKEY_LEASESTART:
	case WGKEY_LEASETIME:
	case WGKEY_ERRNO:
		len = sizeof data.uint32;
		uresult = strtoumax(value, &endptr, 10);
		if (uresult > UINT32_MAX || *endptr != '\0')
			return NULL;
		data.uint32 = (uint32_t)uresult;

		break;
	case WGKEY_ERRMSG:
		strncpy(data.errmsg, value, sizeof data.errmsg - 1);
		data.errmsg[sizeof data.errmsg - 1] = '\0';
		len = MIN(sizeof data.errmsg,
			  strlen(value) + 1); /* Copying the NUL byte too. */

		break;
	default:
		debug("Invalid key %d, aborting\n", key);
		BUG();
	}

	attr = malloc(sizeof(struct wg_dynamic_attr) + len);
	if (!attr)
		fatal("malloc()");

	attr->len = len;
	attr->key = key;
	attr->next = NULL;
	memcpy(&attr->value, &data, len);

	return attr;
}

static enum wg_dynamic_key parse_key(char *key)
{
	for (enum wg_dynamic_key e = 1; e < ARRAY_SIZE(WG_DYNAMIC_KEY); ++e)
		if (!strcmp(key, WG_DYNAMIC_KEY[e]))
			return e;

	return WGKEY_UNKNOWN;
}

/* Consumes one full line from buf, or up to MAX_LINESIZE-1 bytes if no newline
 * character was found.
 * If req != NULL then we expect to parse a command and will set cmd and version
 * of req accordingly, while *attr will be set to NULL.
 * Otherwise we expect to parse a normal key=value pair, that will be stored
 * in a newly allocated wg_dynamic_attr, pointed to by *attr.
 *
 * Return values:
 *   > 0 : Amount of bytes consumed (<= MAX_LINESIZE)
 *   < 0 : Error
 *   = 0 : End of message
 */
static ssize_t parse_line(unsigned char *buf, size_t len,
			  struct wg_dynamic_attr **attr,
			  struct wg_dynamic_request *req)
{
	unsigned char *line_end, *key_end;
	enum wg_dynamic_key key;
	ssize_t line_len;
	char *endptr;
	uintmax_t res;

	line_end = memchr(buf, '\n', len > MAX_LINESIZE ? MAX_LINESIZE : len);
	if (!line_end) {
		if (len >= MAX_LINESIZE)
			return -E2BIG;

		*attr = malloc(sizeof(struct wg_dynamic_attr) + len);
		if (!*attr)
			fatal("malloc()");

		(*attr)->key = WGKEY_INCOMPLETE;
		(*attr)->len = len;
		(*attr)->next = NULL;
		memcpy((*attr)->value, buf, len);

		return len;
	}

	if (line_end == buf)
		return 0; /* \n\n - end of message */

	*line_end = '\0';
	line_len = line_end - buf + 1;

	key_end = memchr(buf, '=', line_len - 1);
	if (!key_end)
		return -EINVAL;

	*key_end = '\0';
	key = parse_key((char *)buf);
	if (key == WGKEY_UNKNOWN)
		return -ENOENT;

	if (req) {
		if (key >= WGKEY_ENDCMD)
			return -ENOENT;

		*attr = NULL;
		res = strtoumax((char *)key_end + 1, &endptr, 10);

		if (res > UINT32_MAX || *endptr != '\0')
			return -EINVAL;

		req->cmd = key;
		req->version = (uint32_t)res;

		if (req->version != 1)
			return -EPROTONOSUPPORT;
	} else {
		if (key <= WGKEY_ENDCMD)
			return -ENOENT;

		*attr = parse_value(key, (char *)key_end + 1);
		if (!*attr)
			return -EINVAL;
	}

	return line_len;
}

static int parse_request(struct wg_dynamic_request *req, unsigned char *buf,
			 size_t len)
{
	struct wg_dynamic_attr *attr;
	size_t offset = 0;
	ssize_t ret;

	if (memchr(buf, '\0', len))
		return -EINVAL; /* don't allow null bytes */

	if (req->last && req->last->key == WGKEY_INCOMPLETE) {
		len += req->last->len;

		memmove(buf + req->last->len, buf, len);
		memcpy(buf, req->last->value, req->last->len);
		free(req->last);

		if (req->first == req->last) {
			req->first = NULL;
			req->last = NULL;
		} else {
			attr = req->first;
			while (attr->next != req->last)
				attr = attr->next;

			attr->next = NULL;
			req->last = attr;
		}
	}

	while (len > 0) {
		ret = parse_line(buf + offset, len, &attr,
				 req->cmd == WGKEY_UNKNOWN ? req : NULL);
		if (ret <= 0)
			return ret; /* either error or message complete */

		len -= ret;
		offset += ret;
		if (!attr)
			continue;

		if (!req->first)
			req->first = attr;
		else
			req->last->next = attr;

		req->last = attr;
	}

	return 1;
}

bool handle_request(struct wg_dynamic_request *req,
		    bool (*success)(struct wg_dynamic_request *),
		    bool (*error)(struct wg_dynamic_request *, int))
{
	ssize_t bytes;
	int ret;
	unsigned char buf[RECV_BUFSIZE + MAX_LINESIZE];

	while (1) {
		bytes = read(req->fd, buf, RECV_BUFSIZE);
		if (bytes < 0) {
			if (errno == EWOULDBLOCK || errno == EAGAIN)
				break;

			// TODO: handle EINTR

			debug("Reading from socket %d failed: %s\n", req->fd,
			      strerror(errno));
			return true;
		} else if (bytes == 0) {
			debug("Peer disconnected unexpectedly\n");
			return true;
		}

		ret = parse_request(req, buf, bytes);
		if (ret < 0)
			return error(req, -ret);
		else if (ret == 0)
			return success(req);
	}

	return false;
}

bool send_message(struct wg_dynamic_request *req, const void *buf, size_t len)
{
	size_t offset = 0;

	while (1) {
		ssize_t written = write(req->fd, buf + offset, len - offset);
		if (written < 0) {
			if (errno == EWOULDBLOCK || errno == EAGAIN)
				break;

			// TODO: handle EINTR

			debug("Writing to socket %d failed: %s\n", req->fd,
			      strerror(errno));
			return true;
		}

		offset += written;
		if (offset == len)
			return true;
	}

	debug("Socket %d blocking on write with %lu bytes left, postponing\n",
	      req->fd, len - offset);

	if (!req->buf) {
		req->buflen = len - offset;
		req->buf = malloc(req->buflen);
		if (!req->buf)
			fatal("malloc()");

		memcpy(req->buf, buf + offset, req->buflen);
	} else {
		req->buflen = len - offset;
		memmove(req->buf, buf + offset, req->buflen);
	}

	return false;
}

void print_to_buf(char *buf, size_t bufsize, size_t *offset, char *fmt, ...)
{
	va_list ap;
	va_start(ap, fmt);
	int n = vsnprintf(buf + *offset, bufsize - *offset, fmt, ap);
	va_end(ap);

	if (n < 0) {
		fatal("vsnprintf()");
	} else if (n + *offset >= bufsize) {
		debug("Outbuffer too small: %d + %zu >= %zu\n", n, *offset,
		      bufsize);
		BUG();
	}

	*offset += n;
}

uint32_t current_time()
{
	struct timespec tp;
	if (clock_gettime(CLOCK_REALTIME, &tp))
		fatal("clock_gettime(CLOCK_REALTIME)");
	return tp.tv_sec;
}

void close_connection(struct wg_dynamic_request *req)
{
	struct wg_dynamic_attr *prev, *cur = req->first;

	if (close(req->fd))
		debug("Failed to close socket\n");

	while (cur) {
		prev = cur;
		cur = cur->next;
		free(prev);
	}

	req->cmd = WGKEY_UNKNOWN;
	req->version = 0;
	req->fd = -1;
	free(req->buf);
	req->buf = NULL;
	req->buflen = 0;
	req->first = NULL;
	req->last = NULL;
}

bool is_link_local(unsigned char *addr)
{
	/* TODO: check if the remaining 54 bits are 0 */
	return IN6_IS_ADDR_LINKLOCAL(addr);
}

void iface_get_all_addrs(uint8_t family, mnl_cb_t data_cb, void *cb_data)
{
	struct mnl_socket *nl;
	char buf[MNL_SOCKET_BUFFER_SIZE];
	struct nlmsghdr *nlh;
	/* TODO: rtln-addr-dump from libmnl uses rtgenmsg here? */
	struct ifaddrmsg *ifaddr;
	int ret;
	unsigned int seq, portid;

	nl = mnl_socket_open(NETLINK_ROUTE);
	if (nl == NULL)
		fatal("mnl_socket_open");

	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0)
		fatal("mnl_socket_bind");

	/* You'd think that we could just request addresses from a specific
	 * interface, via NLM_F_MATCH or something, but we can't. See also:
	 * https://marc.info/?l=linux-netdev&m=132508164508217
	 */
	seq = time(NULL);
	portid = mnl_socket_get_portid(nl);
	nlh = mnl_nlmsg_put_header(buf);
	nlh->nlmsg_type = RTM_GETADDR;
	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
	nlh->nlmsg_seq = seq;
	ifaddr = mnl_nlmsg_put_extra_header(nlh, sizeof(struct ifaddrmsg));
	ifaddr->ifa_family = family;

	if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0)
		fatal("mnl_socket_sendto");

	do {
		ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
		if (ret <= MNL_CB_STOP)
			break;
		ret = mnl_cb_run(buf, ret, seq, portid, data_cb, cb_data);
	} while (ret > 0);

	if (ret == -1)
		fatal("mnl_cb_run/mnl_socket_recvfrom");

	mnl_socket_close(nl);
}

int data_attr_cb(const struct nlattr *attr, void *data)
{
	const struct nlattr **tb = data;
	int type = mnl_attr_get_type(attr);

	/* skip unsupported attribute in user-space */
	if (mnl_attr_type_valid(attr, IFA_MAX) < 0)
		return MNL_CB_OK;

	switch (type) {
	case IFA_ADDRESS:
		if (mnl_attr_validate(attr, MNL_TYPE_BINARY) < 0) {
			perror("mnl_attr_validate");
			return MNL_CB_ERROR;
		}
		break;
	}
	tb[type] = attr;
	return MNL_CB_OK;
}