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#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[]) {
(void)argc;
const char *usage = "Usage: seatd-launch [options] [--] command\n"
"\n"
" -h Show this help message\n"
" -s <path> Where to create the seatd socket\n"
" -v Show the version number\n"
"\n";
int c;
char *sockpath = NULL;
while ((c = getopt(argc, argv, "vhs:")) != -1) {
switch (c) {
case 's':
sockpath = optarg;
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];
char sockbuf[256];
if (sockpath == NULL) {
sprintf(sockbuf, "/tmp/seatd.%d.sock", getpid());
sockpath = sockbuf;
}
unlink(sockpath);
int fds[2];
if (pipe(fds) == -1) {
perror("Could not create pipe");
goto error;
}
pid_t seatd_child = fork();
if (seatd_child == -1) {
perror("Could not fork seatd process");
goto error;
} else if (seatd_child == 0) {
close(fds[0]);
char pipebuf[8];
sprintf(pipebuf, "%d", fds[1]);
execlp("seatd", "seatd", "-n", pipebuf, "-s", sockpath, NULL);
perror("Could not start seatd");
_exit(1);
}
close(fds[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 = fds[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(fds[0], buf, 1);
if (n == -1 && errno != EINTR) {
perror("Could not read from pipe");
goto error_seatd;
} else if (n > 0) {
break;
}
}
}
close(fds[0]);
uid_t uid = getuid();
gid_t gid = getgid();
// Restrict access to the socket to just us
if (chown(sockpath, uid, gid) == -1) {
perror("Could not chown seatd socket");
goto error_seatd;
}
if (chmod(sockpath, 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", sockpath, 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;
}
}
unlink(sockpath);
kill(seatd_child, SIGTERM);
if (WIFEXITED(status)) {
return WEXITSTATUS(status);
} else {
return 1;
}
error_seatd:
unlink(sockpath);
kill(seatd_child, SIGTERM);
error:
return 1;
}
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