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xwayland/sockets: ensure proper permissions 

Create a private UNIX socket directory (755), or use an existing one but
ensure proper permissions are set to prevent meddling from other users.
This commit is contained in:
Ryan Farley 2021-04-13 19:41:27 -05:00 committed by Simon Ser
parent 3c6826df71
commit d87ede0d69
1 changed files with 37 additions and 2 deletions
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39
xwayland/sockets.c
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@ -1,4 +1,4 @@
#define _POSIX_C_SOURCE 200809L
#define _XOPEN_SOURCE 700
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
@ -84,11 +84,46 @@ cleanup:
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;
mkdir(socket_dir, 0777);
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;