1 /*
2  * Copyright (c) 2022 Omar Polo <op@omarpolo.com>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include <sys/socket.h>
18 #include <sys/stat.h>
19 #include <sys/tree.h>
20 #include <sys/types.h>
21 #include <sys/un.h>
22 #include <sys/wait.h>
23 
24 #include <errno.h>
25 #include <event.h>
26 #include <fcntl.h>
27 #include <grp.h>
28 #include <limits.h>
29 #include <pwd.h>
30 #include <signal.h>
31 #include <stdio.h>
32 #include <stdlib.h>
33 #include <string.h>
34 #include <syslog.h>
35 #include <unistd.h>
36 
37 #include "log.h"
38 #include "pkg.h"
39 
40 #ifndef PKG_FCGI_DB
41 #define PKG_FCGI_DB "/pkg_fcgi/pkgs.sqlite3"
42 #endif
43 
44 #ifndef PKG_FCGI_SOCK
45 #define PKG_FCGI_SOCK "/run/pkg_fcgi.sock"
46 #endif
47 
48 #ifndef PKG_FCGI_USER
49 #define PKG_FCGI_USER "www"
50 #endif
51 
52 #define MAX_CHILDREN	32
53 
54 static const char		*argv0;
55 static pid_t			 pids[MAX_CHILDREN];
56 static int			 children = 3;
57 
58 static volatile sig_atomic_t	 got_sigchld;
59 
60 static void
61 handle_sigchld(int sig)
62 {
63 	int	i, saved_errno;
64 
65 	if (got_sigchld)
66 		return;
67 
68 	got_sigchld = 1;
69 	saved_errno = errno;
70 
71 	for (i = 0; i < children; ++i)
72 		(void) kill(pids[i], SIGTERM);
73 
74 	errno = saved_errno;
75 }
76 
77 static int
78 bind_socket(const char *path, struct passwd *pw)
79 {
80 	struct sockaddr_un	 sun;
81 	int			 fd, old_umask;
82 
83 	if ((fd = socket(AF_UNIX, SOCK_STREAM|SOCK_NONBLOCK, 0)) == -1) {
84 		log_warn("%s: socket", __func__);
85 		return (-1);
86 	}
87 
88 	memset(&sun, 0, sizeof(sun));
89 	sun.sun_family = AF_UNIX;
90 
91 	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
92 	    sizeof(sun.sun_path)) {
93 		log_warnx("%s: path too long: %s", __func__, path);
94 		close(fd);
95 		return (-1);
96 	}
97 
98 	if (unlink(path) == -1 && errno != ENOENT) {
99 		log_warn("%s: unlink %s", __func__, path);
100 		close(fd);
101 		return (-1);
102 	}
103 
104 	old_umask = umask(S_IXUSR|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH);
105 	if (bind(fd, (struct sockaddr *)&sun, sizeof(sun)) == -1) {
106 		log_warn("%s: bind: %s (%d)", __func__, path, geteuid());
107 		close(fd);
108 		umask(old_umask);
109 		return (-1);
110 	}
111 	umask(old_umask);
112 
113 	if (chmod(path, S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP) == -1) {
114 		log_warn("%s: chmod %s", __func__, path);
115 		close(fd);
116 		(void) unlink(path);
117 		return (-1);
118 	}
119 
120 	if (chown(path, pw->pw_uid, pw->pw_gid) == -1) {
121 		log_warn("%s: chown %s %s", __func__, pw->pw_name, path);
122 		close(fd);
123 		(void) unlink(path);
124 		return (-1);
125 	}
126 
127 	if (listen(fd, 5) == -1) {
128 		log_warn("%s: listen", __func__);
129 		close(fd);
130 		(void) unlink(path);
131 		return (-1);
132 	}
133 
134 	return (fd);
135 }
136 
137 static pid_t
138 start_child(const char *root, const char *user, const char *db,
139     int daemonize, int verbose, int fd)
140 {
141 	char	*argv[10];
142 	int	 argc = 0;
143 	pid_t	 pid;
144 
145 	switch (pid = fork()) {
146 	case -1:
147 		fatal("cannot fork");
148 	case 0:
149 		break;
150 	default:
151 		close(fd);
152 		return (pid);
153 	}
154 
155 	if (fd != 3) {
156 		if (dup2(fd, 3) == -1)
157 			fatal("cannot setup imsg fd");
158 	} else if (fcntl(fd, F_SETFD, 0) == -1)
159 		fatal("cannot setup imsg fd");
160 
161 	argv[argc++] = (char *)argv0;
162 	argv[argc++] = (char *)"-S";
163 	argv[argc++] = (char *)"-p"; argv[argc++] = (char *)root;
164 	argv[argc++] = (char *)"-u"; argv[argc++] = (char *)user;
165 	if (!daemonize)
166 		argv[argc++] = (char *)"-d";
167 	if (verbose)
168 		argv[argc++] = (char *)"-v";
169 	argv[argc++] = (char *)db;
170 	argv[argc++] = NULL;
171 
172 	execvp(argv0, argv);
173 	fatal("execvp");
174 }
175 
176 static void __dead
177 usage(void)
178 {
179 	fprintf(stderr,
180 	    "usage: %s [-dv] [-j n] [-p path] [-s socket] [-u user] [db]\n",
181 	    getprogname());
182 	exit(1);
183 }
184 
185 int
186 main(int argc, char **argv)
187 {
188 	struct stat	 sb;
189 	struct passwd	*pw;
190 	pid_t		 pid;
191 	char		 path[PATH_MAX];
192 	const char	*cause;
193 	const char	*root = NULL;
194 	const char	*sock = PKG_FCGI_SOCK;
195 	const char	*user = PKG_FCGI_USER;
196 	const char	*db = PKG_FCGI_DB;
197 	const char	*errstr;
198 	int		 ch, i, daemonize = 1, verbosity = 0;
199 	int		 server = 0, fd = -1;
200 	int		 status;
201 
202 	/*
203 	 * Ensure we have fds 0-2 open so that we have no issue with
204 	 * calling bind_socket before daemon(3).
205 	 */
206 	for (i = 0; i < 3; ++i) {
207 		if (fstat(i, &sb) == -1) {
208 			if ((fd = open("/dev/null", O_RDWR)) != -1) {
209 				if (dup2(fd, i) == -1)
210 					exit(1);
211 				if (fd > i)
212 					close(fd);
213 			} else
214 				exit(1);
215 		}
216 	}
217 
218 	log_init(1, LOG_DAEMON); /* Log to stderr until daemonized. */
219 
220 	if ((argv0 = argv[0]) == NULL)
221 		fatalx("argv[0] is NULL");
222 
223 	while ((ch = getopt(argc, argv, "dj:p:Ss:u:v")) != -1) {
224 		switch (ch) {
225 		case 'd':
226 			daemonize = 0;
227 			break;
228 		case 'j':
229 			children = strtonum(optarg, 1, MAX_CHILDREN, &errstr);
230 			if (errstr)
231 				fatalx("number of children is %s: %s",
232 				    errstr, optarg);
233 			break;
234 		case 'p':
235 			root = optarg;
236 			break;
237 		case 'S':
238 			server = 1;
239 			break;
240 		case 's':
241 			sock = optarg;
242 			break;
243 		case 'u':
244 			user = optarg;
245 			break;
246 		case 'v':
247 			verbosity++;
248 			break;
249 		default:
250 			usage();
251 		}
252 	}
253 	argc -= optind;
254 	argv += optind;
255 
256 	if (argc > 1)
257 		usage();
258 	if (argc == 1)
259 		db = argv[0];
260 
261 	if (geteuid())
262 		fatalx("need root privileges");
263 
264 	pw = getpwnam(user);
265 	if (pw == NULL)
266 		fatalx("user %s not found", user);
267 	if (pw->pw_uid == 0)
268 		fatalx("cannot run as %s: must not be the superuser", user);
269 
270 	if (root == NULL)
271 		root = pw->pw_dir;
272 
273 	if (!server) {
274 		int ret;
275 
276 		ret = snprintf(path, sizeof(path), "%s/%s", root, sock);
277 		if (ret < 0 || (size_t)ret >= sizeof(path))
278 			fatalx("socket path too long");
279 
280 		if ((fd = bind_socket(path, pw)) == -1)
281 			fatalx("failed to open socket %s", sock);
282 
283 		for (i = 0; i < children; ++i) {
284 			int d;
285 
286 			if ((d = dup(fd)) == -1)
287 				fatalx("dup");
288 			pids[i] = start_child(root, user, db,
289 			    daemonize, verbosity, d);
290 			log_debug("forking child %d (pid %lld)", i,
291 			    (long long)pids[i]);
292 		}
293 
294 		signal(SIGCHLD, handle_sigchld);
295 	}
296 
297 	if (chroot(root) == -1)
298 		fatal("chroot %s", root);
299 	if (chdir("/") == -1)
300 		fatal("chdir /");
301 
302 	if (setgroups(1, &pw->pw_gid) == -1 ||
303 	    setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1 ||
304 	    setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1)
305 		fatal("failed to drop privileges");
306 
307 	log_init(daemonize ? 0 : 1, LOG_DAEMON);
308 	log_setverbose(verbosity);
309 
310 	if (server)
311 		exit(server_main(db));
312 
313 	if (daemonize && daemon(1, 0) == -1)
314 		fatal("daemon");
315 
316 	if (pledge("stdio proc", NULL) == -1)
317 		fatal("pledge");
318 
319 	for (;;) {
320 		do {
321 			pid = waitpid(WAIT_ANY, &status, 0);
322 		} while (pid != -1 || errno == EINTR);
323 
324 		if (pid == -1) {
325 			if (errno == ECHILD)
326 				break;
327 			fatal("waitpid failed");
328 		}
329 
330 		if (WIFSIGNALED(status))
331 			cause = "was terminated";
332 		else if (WIFEXITED(status)) {
333 			if (WEXITSTATUS(status) != 0)
334 				cause = "exited abnormally";
335 			else
336 				cause = "exited successfully";
337 		} else
338 			cause = "died";
339 
340 		log_warnx("child process %lld %s", (long long)pid, cause);
341 	}
342 
343 	return (1);
344 }