aboutsummaryrefslogtreecommitdiff
path: root/seatd-launch/seatd-launch.c
blob: 329ccef8d3341f63a3bb73feedd467d68f3a4aed (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
#include <errno.h>
#include <poll.h>
#include <signal.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>

int main(int argc, char *argv[]) {
	const char *usage = "Usage: seatd-launch [options] [--] command\n"
			    "\n"
			    "  -l <loglevel>	Log-level to pass to seatd\n"
			    "  -h		Show this help message\n"
			    "  -v		Show the version number\n"
			    "\n";

	int c;
	char loglevel[16] = "info";
	while ((c = getopt(argc, argv, "vhl:")) != -1) {
		switch (c) {
		case 'l':
			strncpy(loglevel, optarg, sizeof loglevel);
			loglevel[sizeof loglevel - 1] = '\0';
			break;
		case 'v':
			printf("seatd-launch version %s\n", SEATD_VERSION);
			return 0;
		case 'h':
			printf("%s", usage);
			return 0;
		case '?':
			fprintf(stderr, "Try '%s -h' for more information.\n", argv[0]);
			return 1;
		default:
			abort();
		}
	}

	if (optind >= argc) {
		fprintf(stderr, "A command must be specified\n\n%s", usage);
		return 1;
	}
	char **command = &argv[optind];

	int readiness_pipe[2];
	if (pipe(readiness_pipe) == -1) {
		perror("Could not create pipe");
		goto error;
	}

	// Start seatd
	pid_t seatd_child = fork();
	if (seatd_child == -1) {
		perror("Could not fork seatd process");
		goto error;
	} else if (seatd_child == 0) {
		close(readiness_pipe[0]);

		char pipebuf[16] = {0};
		snprintf(pipebuf, sizeof pipebuf, "%d", readiness_pipe[1]);

		char *env[1] = {NULL};
		char *command[] = {"seatd", "-n", pipebuf, "-l", loglevel, "-z", NULL};
		execve(SEATD_INSTALLPATH, command, env);
		perror("Could not start seatd");
		_exit(1);
	}
	close(readiness_pipe[1]);

	// Wait for seatd to be ready
	char buf[1] = {0};
	while (true) {
		pid_t p = waitpid(seatd_child, NULL, WNOHANG);
		if (p == seatd_child) {
			fprintf(stderr, "seatd exited prematurely\n");
			goto error_seatd;
		} else if (p == -1 && (errno != EINTR && errno != ECHILD)) {
			perror("Could not wait for seatd process");
			goto error_seatd;
		}

		struct pollfd fd = {
			.fd = readiness_pipe[0],
			.events = POLLIN,
		};

		// We poll with timeout to avoid a racing on a blocking read
		if (poll(&fd, 1, 1000) == -1) {
			if (errno == EAGAIN || errno == EINTR) {
				continue;
			} else {
				perror("Could not poll notification fd");
				goto error_seatd;
			}
		}

		if (fd.revents & POLLIN) {
			ssize_t n = read(readiness_pipe[0], buf, 1);
			if (n == -1 && errno != EINTR) {
				perror("Could not read from pipe");
				goto error_seatd;
			} else if (n > 0) {
				break;
			}
		}
	}
	close(readiness_pipe[0]);

	uid_t uid = getuid();
	gid_t gid = getgid();

	// Restrict access to the socket to just us
	if (chown(SEATD_DEFAULTPATH, uid, gid) == -1) {
		perror("Could not chown seatd socket");
		goto error_seatd;
	}
	if (chmod(SEATD_DEFAULTPATH, 0700) == -1) {
		perror("Could not chmod socket");
		goto error_seatd;
	}

	// Drop privileges
	if (setgid(gid) == -1) {
		perror("Could not set gid to drop privileges");
		goto error_seatd;
	}
	if (setuid(uid) == -1) {
		perror("Could not set uid to drop privileges");
		goto error_seatd;
	}

	pid_t child = fork();
	if (child == -1) {
		perror("Could not fork target process");
		goto error_seatd;
	} else if (child == 0) {
		setenv("SEATD_SOCK", SEATD_DEFAULTPATH, 1);
		execvp(command[0], command);
		perror("Could not start target");
		_exit(1);
	}

	int status = 0;
	while (true) {
		pid_t p = waitpid(child, &status, 0);
		if (p == child) {
			break;
		} else if (p == -1 && errno != EINTR) {
			perror("Could not wait for target process");
			goto error_seatd;
		}
	}

	if (kill(seatd_child, SIGTERM) != 0) {
		perror("Could not kill seatd");
	}

	if (WIFEXITED(status)) {
		return WEXITSTATUS(status);
	} else if (WIFSIGNALED(status)) {
		return 128 + WTERMSIG(status);
	} else {
		abort(); // unreachable
	}

error_seatd:
	kill(seatd_child, SIGTERM);
error:
	return 1;
}