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#undef _POSIX_C_SOURCE
#define _XOPEN_SOURCE 700 // for S_ISVTX
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/un.h>
#include <unistd.h>
#include <wlr/util/log.h>
#include "sockets.h"
static const char lock_fmt[] = "/tmp/.X%d-lock";
static const char socket_dir[] = "/tmp/.X11-unix";
static const char socket_fmt[] = "/tmp/.X11-unix/X%d";
#ifndef __linux__
static const char socket_fmt2[] = "/tmp/.X11-unix/X%d_";
#endif
bool set_cloexec(int fd, bool cloexec) {
int flags = fcntl(fd, F_GETFD);
if (flags == -1) {
wlr_log_errno(WLR_ERROR, "fcntl failed");
return false;
}
if (cloexec) {
flags = flags | FD_CLOEXEC;
} else {
flags = flags & ~FD_CLOEXEC;
}
if (fcntl(fd, F_SETFD, flags) == -1) {
wlr_log_errno(WLR_ERROR, "fcntl failed");
return false;
}
return true;
}
static int open_socket(struct sockaddr_un *addr, size_t path_size) {
int fd, rc;
socklen_t size = offsetof(struct sockaddr_un, sun_path) + path_size + 1;
fd = socket(AF_UNIX, SOCK_STREAM, 0);
if (fd < 0) {
wlr_log_errno(WLR_ERROR, "Failed to create socket %c%s",
addr->sun_path[0] ? addr->sun_path[0] : '@',
addr->sun_path + 1);
return -1;
}
if (!set_cloexec(fd, true)) {
close(fd);
return -1;
}
if (addr->sun_path[0]) {
unlink(addr->sun_path);
}
if (bind(fd, (struct sockaddr*)addr, size) < 0) {
rc = errno;
wlr_log_errno(WLR_ERROR, "Failed to bind socket %c%s",
addr->sun_path[0] ? addr->sun_path[0] : '@',
addr->sun_path + 1);
goto cleanup;
}
if (listen(fd, 1) < 0) {
rc = errno;
wlr_log_errno(WLR_ERROR, "Failed to listen to socket %c%s",
addr->sun_path[0] ? addr->sun_path[0] : '@',
addr->sun_path + 1);
goto cleanup;
}
return fd;
cleanup:
close(fd);
if (addr->sun_path[0]) {
unlink(addr->sun_path);
}
errno = rc;
return -1;
}
static bool check_socket_dir(void) {
struct stat buf;
if (lstat(socket_dir, &buf)) {
wlr_log_errno(WLR_ERROR, "Failed to stat %s", socket_dir);
return false;
}
if (!(buf.st_mode & S_IFDIR)) {
wlr_log(WLR_ERROR, "%s is not a directory", socket_dir);
return false;
}
if (!((buf.st_uid == 0) || (buf.st_uid == getuid()))) {
wlr_log(WLR_ERROR, "%s not owned by root or us", socket_dir);
return false;
}
if (!(buf.st_mode & S_ISVTX)) {
/* we can deal with no sticky bit... */
if ((buf.st_mode & (S_IWGRP | S_IWOTH))) {
/* but not if other users can mess with our sockets */
wlr_log(WLR_ERROR, "sticky bit not set on %s", socket_dir);
return false;
}
}
return true;
}
static bool open_sockets(int socks[2], int display) {
struct sockaddr_un addr = { .sun_family = AF_UNIX };
size_t path_size;
if (mkdir(socket_dir, 0755) == 0) {
wlr_log(WLR_INFO, "Created %s ourselves -- other users will "
"be unable to create X11 UNIX sockets of their own",
socket_dir);
} else if (errno != EEXIST) {
wlr_log_errno(WLR_ERROR, "Unable to mkdir %s", socket_dir);
return false;
} else if (!check_socket_dir()) {
return false;
}
#ifdef __linux__
addr.sun_path[0] = 0;
path_size = snprintf(addr.sun_path + 1, sizeof(addr.sun_path) - 1, socket_fmt, display);
#else
path_size = snprintf(addr.sun_path, sizeof(addr.sun_path), socket_fmt2, display);
#endif
socks[0] = open_socket(&addr, path_size);
if (socks[0] < 0) {
return false;
}
path_size = snprintf(addr.sun_path, sizeof(addr.sun_path), socket_fmt, display);
socks[1] = open_socket(&addr, path_size);
if (socks[1] < 0) {
close(socks[0]);
socks[0] = -1;
return false;
}
return true;
}
void unlink_display_sockets(int display) {
char sun_path[64];
snprintf(sun_path, sizeof(sun_path), socket_fmt, display);
unlink(sun_path);
#ifndef __linux__
snprintf(sun_path, sizeof(sun_path), socket_fmt2, display);
unlink(sun_path);
#endif
snprintf(sun_path, sizeof(sun_path), lock_fmt, display);
unlink(sun_path);
}
int open_display_sockets(int socks[2]) {
int lock_fd, display;
char lock_name[64];
for (display = 0; display <= 32; display++) {
snprintf(lock_name, sizeof(lock_name), lock_fmt, display);
if ((lock_fd = open(lock_name, O_WRONLY | O_CREAT | O_EXCL | O_CLOEXEC, 0444)) >= 0) {
if (!open_sockets(socks, display)) {
unlink(lock_name);
close(lock_fd);
continue;
}
char pid[12];
snprintf(pid, sizeof(pid), "%10d", getpid());
if (write(lock_fd, pid, sizeof(pid) - 1) != sizeof(pid) - 1) {
unlink(lock_name);
close(lock_fd);
continue;
}
close(lock_fd);
break;
}
if ((lock_fd = open(lock_name, O_RDONLY | O_CLOEXEC)) < 0) {
continue;
}
char pid[12] = { 0 }, *end_pid;
ssize_t bytes = read(lock_fd, pid, sizeof(pid) - 1);
close(lock_fd);
if (bytes != sizeof(pid) - 1) {
continue;
}
long int read_pid;
read_pid = strtol(pid, &end_pid, 10);
if (read_pid < 0 || read_pid > INT32_MAX || end_pid != pid + sizeof(pid) - 2) {
continue;
}
errno = 0;
if (kill((pid_t)read_pid, 0) != 0 && errno == ESRCH) {
if (unlink(lock_name) != 0) {
continue;
}
// retry
display--;
continue;
}
}
if (display > 32) {
wlr_log(WLR_ERROR, "No display available in the first 33");
return -1;
}
return display;
}
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