about summary refs log tree commit diff
path: root/dispatch.c
blob: 0de7434d6c5a40abbb4e01173df590b58bef9746 (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
/* Copyright (C) 2019  C. McEnroe <june@causal.agency>
 *
 * 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 <https://www.gnu.org/licenses/>.
 */

#include <err.h>
#include <fcntl.h>
#include <netdb.h>
#include <netinet/in.h>
#include <poll.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sysexits.h>
#include <unistd.h>

#ifdef __FreeBSD__
#include <sys/capsicum.h>
#endif

#include "compat.h"

static struct {
	struct pollfd *ptr;
	size_t len, cap;
} event;

static void eventAdd(int fd) {
	if (event.len == event.cap) {
		event.cap = (event.cap ? event.cap * 2 : 8);
		event.ptr = realloc(event.ptr, sizeof(*event.ptr) * event.cap);
		if (!event.ptr) err(EX_OSERR, "malloc");
	}
	event.ptr[event.len++] = (struct pollfd) {
		.fd = fd,
		.events = POLLIN,
	};
}

static void eventRemove(size_t i) {
	close(event.ptr[i].fd);
	event.ptr[i] = event.ptr[--event.len];
}

static ssize_t sendfd(int sock, int fd) {
	char buf[CMSG_SPACE(sizeof(int))];

	char x = 0;
	struct iovec iov = { .iov_base = &x, .iov_len = 1 };
	struct msghdr msg = {
		.msg_iov = &iov,
		.msg_iovlen = 1,
		.msg_control = buf,
		.msg_controllen = sizeof(buf),
	};

	struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
	cmsg->cmsg_len = CMSG_LEN(sizeof(int));
	cmsg->cmsg_level = SOL_SOCKET;
	cmsg->cmsg_type = SCM_RIGHTS;
	*(int *)CMSG_DATA(cmsg) = fd;

	return sendmsg(sock, &msg, 0);
}

static struct {
	uint8_t buf[4096];
	uint8_t *ptr;
	size_t len;
} peek;

static void (size_t skip) {
	if (peek.len < skip) skip = peek.len;
	peek.ptr += skip;
	peek.len -= skip;
}
static uint8_t uint8(void) {
	if (peek.len < 1) return 0;
	peek.len--;
	return *peek.ptr++;
}
static uint16_t uint16(void) {
	uint16_t val = uint8();
	return val << 8 | uint8();
}

static char *serverName(void) {
	peek.ptr = peek.buf;
	// TLSPlaintext
	if (uint8() != 22) return NULL;
	skip(4);
	// Handshake
	if (uint8() != 1) return NULL;
	skip(3);
	// ClientHello
	skip(34);
	skip(uint8());
	skip(uint16());
	skip(uint8());
	peek.len = uint16();
	while (peek.len) {
		// Extension
		uint16_t type = uint16();
		uint16_t len = uint16();
		if (type != 0) {
			skip(len);
			continue;
		}
		// ServerNameList
		skip(2);
		// ServerName
		if (uint8() != 0) return NULL;
		// HostName
		len = uint16();
		char *name = (char *)peek.ptr;
		skip(len);
		*peek.ptr = '\0';
		return name;
	}
	return NULL;
}

static const uint8_t Alert[] = {
	0x15, 0x03, 0x03, 0x00, 0x02, // TLSPlaintext
	0x02, 0x70, // Alert fatal unrecognized_name
};

static void alert(int sock) {
	ssize_t len = send(sock, Alert, sizeof(Alert), 0);
	if (len < 0) warn("send");
}

int main(int argc, char *argv[]) {
	const char *host = "localhost";
	const char *port = "6697";
	const char *path = NULL;
	int timeout = 1000;

	for (int opt; 0 < (opt = getopt(argc, argv, "H:P:t:"));) {
		switch (opt) {
			break; case 'H': host = optarg;
			break; case 'P': port = optarg;
			break; case 't': {
				char *rest;
				timeout = strtol(optarg, &rest, 0);
				if (*rest) errx(EX_USAGE, "invalid timeout: %s", optarg);
			}
			break; default:  return EX_USAGE;
		}
	}
	if (optind < argc) {
		path = argv[optind];
	} else {
		errx(EX_USAGE, "directory required");
	}

	int dir = open(path, O_DIRECTORY);
	if (dir < 0) err(EX_NOINPUT, "%s", path);

	int error = fchdir(dir);
	if (error) err(EX_NOINPUT, "%s", path);

	struct addrinfo *head;
	struct addrinfo hints = {
		.ai_family = AF_UNSPEC,
		.ai_socktype = SOCK_STREAM,
		.ai_protocol = IPPROTO_TCP,
	};
	error = getaddrinfo(host, port, &hints, &head);
	if (error) errx(EX_NOHOST, "%s:%s: %s", host, port, gai_strerror(error));

	size_t binds = 0;
	for (struct addrinfo *ai = head; ai; ai = ai->ai_next) {
		int sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
		if (sock < 0) err(EX_OSERR, "socket");

		int yes = 1;
		error = setsockopt(
			sock, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)
		);
		if (error) err(EX_OSERR, "setsockopt");

		error = bind(sock, ai->ai_addr, ai->ai_addrlen);
		if (error) {
			warn("%s:%s", host, port);
			close(sock);
			continue;
		}

		eventAdd(sock);
		binds++;
	}
	if (!binds) errx(EX_UNAVAILABLE, "could not bind any sockets");
	freeaddrinfo(head);

#ifdef __FreeBSD__
	error = cap_enter();
	if (error) err(EX_OSERR, "cap_enter");

	cap_rights_t dirRights, sockRights, unixRights, bindRights;
	cap_rights_init(&dirRights, CAP_CONNECTAT);
	cap_rights_init(&sockRights, CAP_EVENT, CAP_RECV, CAP_SEND);
	cap_rights_init(&unixRights, CAP_CONNECT, CAP_SEND);
	cap_rights_init(&bindRights, CAP_LISTEN, CAP_ACCEPT);
	cap_rights_merge(&bindRights, &sockRights);

	error = cap_rights_limit(dir, &dirRights);
	if (error) err(EX_OSERR, "cap_rights_limit");
	for (size_t i = 0; i < binds; ++i) {
		error = cap_rights_limit(event.ptr[i].fd, &bindRights);
		if (error) err(EX_OSERR, "cap_rights_limit");
	}
#endif

	for (size_t i = 0; i < binds; ++i) {
		error = listen(event.ptr[i].fd, -1);
		if (error) err(EX_IOERR, "listen");
	}

	signal(SIGPIPE, SIG_IGN);
	for (;;) {
		int nfds = poll(
			event.ptr, event.len, (event.len > binds ? timeout : -1)
		);
		if (nfds < 0) err(EX_IOERR, "poll");

		if (!nfds) {
			for (size_t i = event.len - 1; i >= binds; --i) {
				eventRemove(i);
			}
			continue;
		}

		for (size_t i = event.len - 1; i < event.len; --i) {
			if (!event.ptr[i].revents) continue;

			if (i < binds) {
				int sock = accept(event.ptr[i].fd, NULL, NULL);
				if (sock < 0) {
					warn("accept");
					continue;
				}
				eventAdd(sock);
				continue;
			}

			if (event.ptr[i].revents & (POLLHUP | POLLERR)) {
				eventRemove(i);
				continue;
			}

			ssize_t len = recv(
				event.ptr[i].fd, peek.buf, sizeof(peek.buf) - 1, MSG_PEEK
			);
			if (len < 0) {
				warn("recv");
				eventRemove(i);
				continue;
			}
			peek.len = len;

			char *name = serverName();
			if (!name || name[0] == '.' || name[0] == '/') {
				alert(event.ptr[i].fd);
				eventRemove(i);
				continue;
			}

			struct sockaddr_un addr = { .sun_family = AF_UNIX };
			strlcpy(addr.sun_path, name, sizeof(addr.sun_path));

			int sock = socket(PF_UNIX, SOCK_STREAM, 0);
			if (sock < 0) err(EX_OSERR, "socket");

#ifdef __FreeBSD__
			error = cap_rights_limit(sock, &unixRights);
			if (error) err(EX_OSERR, "cap_rights_limit");

			error = connectat(
				dir, sock, (struct sockaddr *)&addr, SUN_LEN(&addr)
			);
#else
			error = connect(sock, (struct sockaddr *)&addr, SUN_LEN(&addr));
#endif

			if (error) {
				warn("%s", name);
				alert(event.ptr[i].fd);
			} else {
				len = sendfd(sock, event.ptr[i].fd);
				if (len < 0) {
					warn("%s", name);
					alert(event.ptr[i].fd);
				}
			}

			close(sock);
			eventRemove(i);
		}
	}
}