/*
 * Copyright (C) 2014-2017 Firejail Authors
 *
 * This file is part of firejail project
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "firejail.h"
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <linux/limits.h>
#include <fnmatch.h>
#include <glob.h>
#include <dirent.h>
#include <fcntl.h>
#include <errno.h>

static void fs_rdwr(const char *dir);



//***********************************************
// process profile file
//***********************************************
typedef enum {
	BLACKLIST_FILE,
	BLACKLIST_NOLOG,
	MOUNT_READONLY,
	MOUNT_TMPFS,
	MOUNT_NOEXEC,
	MOUNT_RDWR,
	OPERATION_MAX
} OPERATION;

typedef enum {
	UNSUCCESSFUL,
	SUCCESSFUL
} LAST_DISABLE_OPERATION;
LAST_DISABLE_OPERATION last_disable = UNSUCCESSFUL;

static void disable_file(OPERATION op, const char *filename) {
	assert(filename);
	assert(op <OPERATION_MAX);
	last_disable = UNSUCCESSFUL;
	
	// Resolve all symlinks
	char* fname = realpath(filename, NULL);
	if (fname == NULL && errno != EACCES) {
		return;
	}
	if (fname == NULL && errno == EACCES) {
		if (arg_debug)
			printf("Debug: no access to file %s, forcing mount\n", filename);
		// realpath and stat funtions will fail on FUSE filesystems
		// they don't seem to like a uid of 0
		// force mounting
		int rv = mount(RUN_RO_DIR, filename, "none", MS_BIND, "mode=400,gid=0");
		if (rv == 0)
			last_disable = SUCCESSFUL;
		else {
			rv = mount(RUN_RO_FILE, filename, "none", MS_BIND, "mode=400,gid=0");
			if (rv == 0)
				last_disable = SUCCESSFUL;
		}
		if (last_disable == SUCCESSFUL) {
			if (arg_debug)
				printf("Disable %s\n", filename);
			if (op == BLACKLIST_FILE)
				fs_logger2("blacklist", filename);
			else
				fs_logger2("blacklist-nolog", filename);
		}
		else {
			if (arg_debug)
				printf("Warning (blacklisting): %s is an invalid file, skipping...\n", filename);
		}
				
		return;
	}
	
	// if the file is not present, do nothing
	struct stat s;
	if (fname == NULL)
		return;
	if (stat(fname, &s) == -1) {
		if (arg_debug)
			fwarning("%s does not exist, skipping...\n", fname);
		free(fname);
		return;
	}

	// modify the file
	if (op == BLACKLIST_FILE || op == BLACKLIST_NOLOG) {
		// some distros put all executables under /usr/bin and make /bin a symbolic link
		if ((strcmp(fname, "/bin") == 0 || strcmp(fname, "/usr/bin") == 0) &&
		      is_link(filename) &&
		      S_ISDIR(s.st_mode)) {
			fwarning("%s directory link was not blacklisted\n", filename);
		}
		else {
			if (arg_debug) {
				if (strcmp(filename, fname))
					printf("Disable %s (requested %s)\n", fname, filename);
				else
					printf("Disable %s\n", fname);
			}
			else if (arg_debug_blacklists) {
				printf("Disable %s", fname);
				if (op == BLACKLIST_FILE)
					printf("\n");
				else
					printf(" - no logging\n");
			}
			
			if (S_ISDIR(s.st_mode)) {
				if (mount(RUN_RO_DIR, fname, "none", MS_BIND, "mode=400,gid=0") < 0)
					errExit("disable file");
			}
			else {
				if (mount(RUN_RO_FILE, fname, "none", MS_BIND, "mode=400,gid=0") < 0)
					errExit("disable file");
			}
			last_disable = SUCCESSFUL;
			if (op == BLACKLIST_FILE)
				fs_logger2("blacklist", fname);
			else
				fs_logger2("blacklist-nolog", fname);
		}
	}
	else if (op == MOUNT_READONLY) {
		if (arg_debug)
			printf("Mounting read-only %s\n", fname);
		fs_rdonly(fname);
// todo: last_disable = SUCCESSFUL;
	}
	else if (op == MOUNT_RDWR) {
		if (arg_debug)
			printf("Mounting read-only %s\n", fname);
		fs_rdwr(fname);
// todo: last_disable = SUCCESSFUL;
	}
	else if (op == MOUNT_NOEXEC) {
		if (arg_debug)
			printf("Mounting noexec %s\n", fname);
		fs_noexec(fname);
// todo: last_disable = SUCCESSFUL;
	}
	else if (op == MOUNT_TMPFS) {
		if (S_ISDIR(s.st_mode)) {
			if (arg_debug)
				printf("Mounting tmpfs on %s\n", fname);
			// preserve owner and mode for the directory
			if (mount("tmpfs", fname, "tmpfs", MS_NOSUID | MS_NODEV | MS_STRICTATIME | MS_REC,  0) < 0)
				errExit("mounting tmpfs");
			/* coverity[toctou] */
			if (chown(fname, s.st_uid, s.st_gid) == -1)
				errExit("mounting tmpfs chown");
			if (chmod(fname, s.st_mode) == -1)
				errExit("mounting tmpfs chmod");
			last_disable = SUCCESSFUL;
			fs_logger2("tmpfs", fname);
		}
		else
			fwarning("%s is not a directory; cannot mount a tmpfs on top of it.\n", fname);
	}
	else
		assert(0);

	free(fname);
}

// Treat pattern as a shell glob pattern and blacklist matching files
static void globbing(OPERATION op, const char *pattern, const char *noblacklist[], size_t noblacklist_len) {
	assert(pattern);

	glob_t globbuf;
	// Profiles contain blacklists for files that might not exist on a user's machine.
	// GLOB_NOCHECK makes that okay.
	int globerr = glob(pattern, GLOB_NOCHECK | GLOB_NOSORT | GLOB_PERIOD, NULL, &globbuf);
	if (globerr) {
		fprintf(stderr, "Error: failed to glob pattern %s\n", pattern);
		exit(1);
	}

	size_t i, j;
	for (i = 0; i < globbuf.gl_pathc; i++) {
		char *path = globbuf.gl_pathv[i];
		assert(path);
		// /home/me/.* can glob to /home/me/.. which would blacklist /home/
		const char *base = gnu_basename(path);
		if (strcmp(base, ".") == 0 || strcmp(base, "..") == 0)
			continue;
		// noblacklist is expected to be short in normal cases, so stupid and correct brute force is okay
		bool okay_to_blacklist = true;
		for (j = 0; j < noblacklist_len; j++) {
			int result = fnmatch(noblacklist[j], path, FNM_PATHNAME);
			if (result == FNM_NOMATCH)
				continue;
			else if (result == 0) {
				okay_to_blacklist = false;
				break;
			}
			else {
				fprintf(stderr, "Error: failed to compare path %s with pattern %s\n", path, noblacklist[j]);
				exit(1);
			}
		}

		// We don't usually need to blacklist things in private home directories
		if (okay_to_blacklist
		 && cfg.homedir
		 && arg_private
		 && (!arg_allow_private_blacklist)
		 && (strncmp(path, cfg.homedir, strlen(cfg.homedir)) == 0))
			okay_to_blacklist = false;

		if (okay_to_blacklist)
			disable_file(op, path);
		else if (arg_debug)
			printf("Not blacklist %s\n", path);
	}
	globfree(&globbuf);
}


// blacklist files or directories by mounting empty files on top of them
void fs_blacklist(void) {
	char *homedir = cfg.homedir;
	assert(homedir);
	ProfileEntry *entry = cfg.profile;
	if (!entry)
		return;
		
	size_t noblacklist_c = 0;
	size_t noblacklist_m = 32;
	char **noblacklist = calloc(noblacklist_m, sizeof(*noblacklist));

	if (noblacklist == NULL)
		errExit("failed allocating memory for noblacklist entries");

	while (entry) {
		OPERATION op = OPERATION_MAX;
		char *ptr;

		// whitelist commands handled by fs_whitelist()
		if (strncmp(entry->data, "whitelist ", 10) == 0 || 
		    strncmp(entry->data, "nowhitelist ", 12) == 0 ||
		   *entry->data == '\0') {
			entry = entry->next;
			continue;
		}

		// process bind command
		if (strncmp(entry->data, "bind ", 5) == 0)  {
			struct stat s;
			char *dname1 = entry->data + 5;
			char *dname2 = split_comma(dname1);
			if (dname2 == NULL ||
			    stat(dname1, &s) == -1 ||
			    stat(dname2, &s) == -1) {
				fprintf(stderr, "Error: invalid bind command, directory missing\n");
				entry = entry->next;
				continue;
			}
			
			// mount --bind olddir newdir
			if (arg_debug)
				printf("Mount-bind %s on top of %s\n", dname1, dname2);
			// preserve dname2 mode and ownership
			if (mount(dname1, dname2, NULL, MS_BIND|MS_REC, NULL) < 0)
				errExit("mount bind");
			/* coverity[toctou] */
			if (set_perms(dname2,  s.st_uid, s.st_gid,s.st_mode))
				errExit("set_perms"); 
				
			entry = entry->next;
			continue;
		}

		// Process noblacklist command
		if (strncmp(entry->data, "noblacklist ", 12) == 0) {
			char **enames;
			int i;

			if (strncmp(entry->data + 12, "${PATH}", 7) == 0) {
				// expand ${PATH} macro
				char **paths = build_paths();
				unsigned int npaths = count_paths();
				enames = calloc(npaths, sizeof(char *));
				if (!enames)
					errExit("calloc");

				for (i = 0; paths[i]; i++) {
					if (asprintf(&enames[i], "%s%s", paths[i],
						entry->data + 19) == -1)
						errExit("asprintf");
				}
				assert(enames[npaths-1] == 0);

			}
			else {
				// expand ${HOME} macro if found or pass as is
				enames = calloc(2, sizeof(char *));
				if (!enames)
					errExit("calloc");
				enames[0] = expand_home(entry->data + 12, homedir);
				assert(enames[1] == 0);
			}

			for (i = 0; enames[i]; i++) {
				if (noblacklist_c >= noblacklist_m) {
					noblacklist_m *= 2;
					noblacklist = realloc(noblacklist, sizeof(*noblacklist) * noblacklist_m);
					if (noblacklist == NULL)
						errExit("failed increasing memory for noblacklist entries");
				}
				noblacklist[noblacklist_c++] = enames[i];
			}

			free(enames);

			entry = entry->next;
			continue;
		}

		// process blacklist command
		if (strncmp(entry->data, "blacklist ", 10) == 0)  {
			ptr = entry->data + 10;
			op = BLACKLIST_FILE;
		}
		else if (strncmp(entry->data, "blacklist-nolog ", 16) == 0)  {
			ptr = entry->data + 16;
			op = BLACKLIST_NOLOG;
		}
		else if (strncmp(entry->data, "read-only ", 10) == 0) {
			ptr = entry->data + 10;
			op = MOUNT_READONLY;
		}			
		else if (strncmp(entry->data, "read-write ", 11) == 0) {
			ptr = entry->data + 11;
			op = MOUNT_RDWR;
		}			
		else if (strncmp(entry->data, "noexec ", 7) == 0) {
			ptr = entry->data + 7;
			op = MOUNT_NOEXEC;
		}			
		else if (strncmp(entry->data, "tmpfs ", 6) == 0) {
			ptr = entry->data + 6;
			op = MOUNT_TMPFS;
		}			
		else if (strncmp(entry->data, "mkdir ", 6) == 0) {
			EUID_USER();
			fs_mkdir(entry->data + 6);
			EUID_ROOT();
			entry = entry->next;
			continue;
		}			
		else if (strncmp(entry->data, "mkfile ", 7) == 0) {
			EUID_USER();
			fs_mkfile(entry->data + 7);
			EUID_ROOT();
			entry = entry->next;
			continue;
		}			
		else {
			fprintf(stderr, "Error: invalid profile line %s\n", entry->data);
			entry = entry->next;
			continue;
		}

		// replace home macro in blacklist array
		char *new_name = expand_home(ptr, homedir);
		ptr = new_name;

		// expand path macro - look for the file in /usr/local/bin,  /usr/local/sbin, /bin, /usr/bin, /sbin and  /usr/sbin directories
		if (ptr) {
			if (strncmp(ptr, "${PATH}", 7) == 0) {
				char *fname = ptr + 7;
				size_t fname_len = strlen(fname);
				char **paths = build_paths(); //{"/usr/local/bin", "/usr/local/sbin", "/bin", "/usr/bin/", "/sbin", "/usr/sbin", NULL};
				int i = 0;
				while (paths[i] != NULL) {
					char *path = paths[i];
					i++;
					char newname[strlen(path) + fname_len + 1];
					sprintf(newname, "%s%s", path, fname);
					globbing(op, newname, (const char**)noblacklist, noblacklist_c);
				}
			}
			else
				globbing(op, ptr, (const char**)noblacklist, noblacklist_c);
		}

		if (new_name)
			free(new_name);
		entry = entry->next;
	}

	size_t i;
	for (i = 0; i < noblacklist_c; i++) free(noblacklist[i]);
        free(noblacklist);
}

//***********************************************
// mount namespace
//***********************************************

// remount a directory read-only
void fs_rdonly(const char *dir) {
	assert(dir);
	// check directory exists
	struct stat s;
	int rv = stat(dir, &s);
	if (rv == 0) {
		// mount --bind /bin /bin
		// mount --bind -o remount,ro /bin
		if (mount(dir, dir, NULL, MS_BIND|MS_REC, NULL) < 0 ||
		    mount(NULL, dir, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY|MS_REC, NULL) < 0)
			errExit("mount read-only");
		fs_logger2("read-only", dir);
	}
}

static void fs_rdwr(const char *dir) {
	assert(dir);
	// check directory exists
	struct stat s;
	int rv = stat(dir, &s);
	if (rv == 0) {
		// if the file is outside /home directory, allow only root user
		uid_t u = getuid();
		if (u != 0 && s.st_uid != u) {
			fwarning("you are not allowed to change %s to read-write\n", dir);
			return;
		}
		
		// mount --bind /bin /bin
		// mount --bind -o remount,rw /bin
		if (mount(dir, dir, NULL, MS_BIND|MS_REC, NULL) < 0 || 
		    mount(NULL, dir, NULL, MS_BIND|MS_REMOUNT|MS_REC, NULL) < 0)
			errExit("mount read-write");
		fs_logger2("read-write", dir);
	}
}

void fs_noexec(const char *dir) {
	assert(dir);
	// check directory exists
	struct stat s;
	int rv = stat(dir, &s);
	if (rv == 0) {
		// mount --bind /bin /bin
		// mount --bind -o remount,ro /bin
		if (mount(dir, dir, NULL, MS_BIND|MS_REC, NULL) < 0 || 
		    mount(NULL, dir, NULL, MS_BIND|MS_REMOUNT|MS_NOEXEC|MS_NODEV|MS_NOSUID|MS_REC, NULL) < 0)
			errExit("mount noexec");
		fs_logger2("noexec", dir);
	}
}

// Disable /mnt, /media, /run/mount and /run/media access
void fs_mnt(void) {
	disable_file(BLACKLIST_FILE, "/mnt");
	disable_file(BLACKLIST_FILE, "/media");
	disable_file(BLACKLIST_FILE, "/run/mount");
	disable_file(BLACKLIST_FILE, "//run/media");
}


// mount /proc and /sys directories
void fs_proc_sys_dev_boot(void) {
	if (arg_debug)
		printf("Remounting /proc and /proc/sys filesystems\n");
	if (mount("proc", "/proc", "proc", MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_REC, NULL) < 0)
		errExit("mounting /proc");
	fs_logger("remount /proc");

	// remount /proc/sys readonly
	if (mount("/proc/sys", "/proc/sys", NULL, MS_BIND | MS_REC, NULL) < 0 ||
	    mount(NULL, "/proc/sys", NULL, MS_BIND | MS_REMOUNT | MS_RDONLY | MS_REC, NULL) < 0)
		errExit("mounting /proc/sys");
	fs_logger("read-only /proc/sys");


	/* Mount a version of /sys that describes the network namespace */
	if (arg_debug)
		printf("Remounting /sys directory\n");
	if (umount2("/sys", MNT_DETACH) < 0)
		fwarning("failed to unmount /sys\n");
	if (mount("sysfs", "/sys", "sysfs", MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REC, NULL) < 0)
		fwarning("failed to mount /sys\n");
	else
		fs_logger("remount /sys");
		
	disable_file(BLACKLIST_FILE, "/sys/firmware");
	disable_file(BLACKLIST_FILE, "/sys/hypervisor");
	{ // allow user access to /sys/fs if "--noblacklist=/sys/fs" is present on the command line
		EUID_USER();	
		profile_add("blacklist /sys/fs");
		EUID_ROOT();
	}
	disable_file(BLACKLIST_FILE, "/sys/module");
	disable_file(BLACKLIST_FILE, "/sys/power");
	disable_file(BLACKLIST_FILE, "/sys/kernel/debug");
	disable_file(BLACKLIST_FILE, "/sys/kernel/vmcoreinfo");
	disable_file(BLACKLIST_FILE, "/sys/kernel/uevent_helper");

	// various /proc/sys files
	disable_file(BLACKLIST_FILE, "/proc/sys/security");	
	disable_file(BLACKLIST_FILE, "/proc/sys/efi/vars");	
	disable_file(BLACKLIST_FILE, "/proc/sys/fs/binfmt_misc");	
	disable_file(BLACKLIST_FILE, "/proc/sys/kernel/core_pattern");	
	disable_file(BLACKLIST_FILE, "/proc/sys/kernel/modprobe");	
	disable_file(BLACKLIST_FILE, "/proc/sysrq-trigger");
	disable_file(BLACKLIST_FILE, "/proc/sys/kernel/hotplug");
	disable_file(BLACKLIST_FILE, "/proc/sys/vm/panic_on_oom");

	// various /proc files
	disable_file(BLACKLIST_FILE, "/proc/irq");
	disable_file(BLACKLIST_FILE, "/proc/bus");
	disable_file(BLACKLIST_FILE, "/proc/config.gz");	
	disable_file(BLACKLIST_FILE, "/proc/sched_debug");	
	disable_file(BLACKLIST_FILE, "/proc/timer_list");	
	disable_file(BLACKLIST_FILE, "/proc/timer_stats");	
	disable_file(BLACKLIST_FILE, "/proc/kcore");
	disable_file(BLACKLIST_FILE, "/proc/kallsyms");
	disable_file(BLACKLIST_FILE, "/proc/mem");
	disable_file(BLACKLIST_FILE, "/proc/kmem");
	
	// remove kernel symbol information
	if (!arg_allow_debuggers) {
		disable_file(BLACKLIST_FILE, "/usr/src/linux");
		disable_file(BLACKLIST_FILE, "/lib/modules");
		disable_file(BLACKLIST_FILE, "/usr/lib/debug");
		disable_file(BLACKLIST_FILE, "/boot");
	}
		
	// disable /selinux
	disable_file(BLACKLIST_FILE, "/selinux");
	
	// disable /dev/port
	disable_file(BLACKLIST_FILE, "/dev/port");

	

	// disable various ipc sockets in /run/user
	struct stat s; 
	
	char *fname;
	if (asprintf(&fname, "/run/usr/%d", getuid()) == -1)
		errExit("asprintf");
	if (is_dir(fname)) { // older distros don't have this directory
		// disable /run/user/{uid}/gnupg
		char *fnamegpg;
		if (asprintf(&fnamegpg, "/run/user/%d/gnupg", getuid()) == -1)
			errExit("asprintf");
		if (stat(fnamegpg, &s) == -1) 
		    mkdir_attr(fnamegpg, 0700, getuid(), getgid());
		if (stat(fnamegpg, &s) == 0)
			disable_file(BLACKLIST_FILE, fnamegpg);
		free(fnamegpg);
		
		// disable /run/user/{uid}/systemd
		char *fnamesysd;
		if (asprintf(&fnamesysd, "/run/user/%d/systemd", getuid()) == -1)
			errExit("asprintf");
		if (stat(fnamesysd, &s) == -1) 
			mkdir_attr(fnamesysd, 0755, getuid(), getgid());
		if (stat(fnamesysd, &s) == 0)
			disable_file(BLACKLIST_FILE, fnamesysd);
		free(fnamesysd);
	}
	free(fname);
	
	if (getuid() != 0) {
		// disable /dev/kmsg and /proc/kmsg
		disable_file(BLACKLIST_FILE, "/dev/kmsg");
		disable_file(BLACKLIST_FILE, "/proc/kmsg");
	}
}

// disable firejail configuration in /etc/firejail and in ~/.config/firejail
static void disable_config(void) {
	struct stat s;

	char *fname;
	if (asprintf(&fname, "%s/.config/firejail", cfg.homedir) == -1)
		errExit("asprintf");
	if (stat(fname, &s) == 0)
		disable_file(BLACKLIST_FILE, fname);
	free(fname);
	
	// disable run time information
	if (stat(RUN_FIREJAIL_NETWORK_DIR, &s) == 0)
		disable_file(BLACKLIST_FILE, RUN_FIREJAIL_NETWORK_DIR);
	if (stat(RUN_FIREJAIL_BANDWIDTH_DIR, &s) == 0)
		disable_file(BLACKLIST_FILE, RUN_FIREJAIL_BANDWIDTH_DIR);
	if (stat(RUN_FIREJAIL_NAME_DIR, &s) == 0)
		disable_file(BLACKLIST_FILE, RUN_FIREJAIL_NAME_DIR);
	if (stat(RUN_FIREJAIL_X11_DIR, &s) == 0)
		disable_file(BLACKLIST_FILE, RUN_FIREJAIL_X11_DIR);
}


// build a basic read-only filesystem
void fs_basic_fs(void) {
	uid_t uid = getuid();
	
	if (arg_debug)
		printf("Mounting read-only /bin, /sbin, /lib, /lib32, /lib64, /usr");
	if (!arg_writable_etc) {
		fs_rdonly("/etc");
		if (uid)
			fs_noexec("/etc");
		if (arg_debug) printf(", /etc");
	}
	if (!arg_writable_var) {
		fs_rdonly("/var");
		if (uid)
			fs_noexec("/var");
		if (arg_debug) printf(", /var");
	}
	if (arg_debug) printf("\n");
	fs_rdonly("/bin");
	fs_rdonly("/sbin");
	fs_rdonly("/lib");
	fs_rdonly("/lib64");
	fs_rdonly("/lib32");
	fs_rdonly("/libx32");
	fs_rdonly("/usr");

	// update /var directory in order to support multiple sandboxes running on the same root directory
	fs_var_lock();
	fs_var_tmp();
	if (!arg_writable_var_log)
		fs_var_log();
	else
		fs_rdwr("/var/log");
	
	fs_var_lib();
	fs_var_cache();
	fs_var_utmp();
	fs_machineid();
	
	// don't leak user information
	restrict_users();
	
	// when starting as root, firejail config is not disabled;
	// this mode could be used to install and test new software by chaining
	// firejail sandboxes (firejail --force)
	if (uid)
		disable_config();
}



#ifdef HAVE_OVERLAYFS
char *fs_check_overlay_dir(const char *subdirname, int allow_reuse) {
	struct stat s;
	char *dirname;

	// create ~/.firejail directory
	if (asprintf(&dirname, "%s/.firejail", cfg.homedir) == -1)
		errExit("asprintf");
		
	if (is_link(dirname)) {
		fprintf(stderr, "Error: invalid ~/.firejail directory\n");
		exit(1);
	}
	if (stat(dirname, &s) == -1) {
		// create directory
		pid_t child = fork();
		if (child < 0)
			errExit("fork");
		if (child == 0) {
			// drop privileges
			drop_privs(0);
	
			// create directory
			if (mkdir(dirname, 0700))
				errExit("mkdir");
			if (chmod(dirname, 0700) == -1)
				errExit("chmod");
			ASSERT_PERMS(dirname, getuid(), getgid(), 0700);
			_exit(0);
		}
		// wait for the child to finish
		waitpid(child, NULL, 0);
		if (stat(dirname, &s) == -1) {
			fprintf(stderr, "Error: cannot create ~/.firejail directory\n");
			exit(1);
		}
	}
	else if (s.st_uid != getuid()) {
		fprintf(stderr, "Error: invalid ~/.firejail directory\n");
		exit(1);
	}
	free(dirname);

	// check overlay directory
	if (asprintf(&dirname, "%s/.firejail/%s", cfg.homedir, subdirname) == -1)
		errExit("asprintf");
	if (is_link(dirname)) {
		fprintf(stderr, "Error: overlay directory is a symbolic link\n");
		exit(1);
	}
	if (allow_reuse == 0) {
		if (stat(dirname, &s) == 0) {
			fprintf(stderr, "Error: overlay directory already exists: %s\n", dirname);
			exit(1);
		}
	}

	return dirname;
}



// mount overlayfs on top of / directory
// mounting an overlay and chrooting into it:
//
// Old Ubuntu kernel
// # cd ~
// # mkdir -p overlay/root
// # mkdir -p overlay/diff
// # mount -t overlayfs -o lowerdir=/,upperdir=/root/overlay/diff overlayfs /root/overlay/root
// # chroot /root/overlay/root
// to shutdown, first exit the chroot and then  unmount the overlay
// # exit
// # umount /root/overlay/root
//
// Kernels 3.18+
// # cd ~
// # mkdir -p overlay/root
// # mkdir -p overlay/diff
// # mkdir -p overlay/work
// # mount -t overlay -o lowerdir=/,upperdir=/root/overlay/diff,workdir=/root/overlay/work overlay /root/overlay/root
// # cat /etc/mtab | grep overlay
// /root/overlay /root/overlay/root overlay rw,relatime,lowerdir=/,upperdir=/root/overlay/diff,workdir=/root/overlay/work 0 0
// # chroot /root/overlay/root
// to shutdown, first exit the chroot and then  unmount the overlay
// # exit
// # umount /root/overlay/root


// to do: fix the code below; also, it might work without /dev; impose seccomp/caps filters when not root
#include <sys/utsname.h>
void fs_overlayfs(void) {
	// check kernel version
	struct utsname u;
	int rv = uname(&u);
	if (rv != 0)
		errExit("uname");
	int major;
	int minor;
	if (2 != sscanf(u.release, "%d.%d", &major, &minor)) {
		fprintf(stderr, "Error: cannot extract Linux kernel version: %s\n", u.version);
		exit(1);
	}
	
	if (arg_debug)
		printf("Linux kernel version %d.%d\n", major, minor);
	int oldkernel = 0;
	if (major < 3) {
		fprintf(stderr, "Error: minimum kernel version required 3.x\n");
		exit(1);
	}
	if (major == 3 && minor < 18)
		oldkernel = 1;
	
	char *oroot;
	if(asprintf(&oroot, "%s/oroot", RUN_MNT_DIR) == -1)
		errExit("asprintf");
	mkdir_attr(oroot, 0755, 0, 0);

	struct stat s;
	char *basedir = RUN_MNT_DIR;
	if (arg_overlay_keep) {
		// set base for working and diff directories
		basedir = cfg.overlay_dir;

		// does the overlay exist?
		if (stat(basedir, &s) == 0) {
			if (arg_overlay_reuse == 0) {
				fprintf(stderr, "Error: overlay directory exists, but reuse is not allowed\n");
				exit(1);
			}
		}
		else {
			/* coverity[toctou] */
			if (mkdir(basedir, 0755) != 0) {
				fprintf(stderr, "Error: cannot create overlay directory\n");
				exit(1);
			}
		}
	}

	char *odiff;
	if(asprintf(&odiff, "%s/odiff", basedir) == -1)
		errExit("asprintf");

	// no need to check arg_overlay_reuse
	if (stat(odiff, &s) != 0) {
		mkdir_attr(odiff, 0755, 0, 0);
	}
	else if (set_perms(odiff, 0, 0, 0755))
		errExit("set_perms");
	
	char *owork;
	if(asprintf(&owork, "%s/owork", basedir) == -1)
		errExit("asprintf");

	// no need to check arg_overlay_reuse
	if (stat(owork, &s) != 0) {
		mkdir_attr(owork, 0755, 0, 0);
	}
	else if (set_perms(owork, 0, 0, 0755))
		errExit("chown");
	
	// mount overlayfs
	if (arg_debug)
		printf("Mounting OverlayFS\n");
	char *option;
	if (oldkernel) { // old Ubuntu/OpenSUSE kernels
		if (arg_overlay_keep) {
			fprintf(stderr, "Error: option --overlay= not available for kernels older than 3.18\n");
			exit(1);
		}
		if (asprintf(&option, "lowerdir=/,upperdir=%s", odiff) == -1)
			errExit("asprintf");
		if (mount("overlayfs", oroot, "overlayfs", MS_MGC_VAL, option) < 0)
			errExit("mounting overlayfs");
	}
	else { // kernel 3.18 or newer
		if (asprintf(&option, "lowerdir=/,upperdir=%s,workdir=%s", odiff, owork) == -1)
			errExit("asprintf");
		if (mount("overlay", oroot, "overlay", MS_MGC_VAL, option) < 0)
			errExit("mounting overlayfs");
			
		//***************************
		// issue #263 start code
		// My setup has a separate mount point for /home. When the overlay is mounted,
		// the overlay does not contain the original /home contents. 
		// I added code to create a second overlay for /home if the overlay home dir is empty and this seems to work
		// @dshmgh, Jan 2016
		{
			char *overlayhome;
			struct stat s;
			char *hroot;
			char *hdiff;
			char *hwork;
		
			// dons add debug
			if (arg_debug) printf ("DEBUG: chroot dirs are oroot %s  odiff %s  owork %s\n",oroot,odiff,owork);
		
			// BEFORE NEXT, WE NEED TO TEST IF /home has any contents or do we need to mount it?
			// must create var for oroot/cfg.homedir
			if (asprintf(&overlayhome,"%s%s",oroot,cfg.homedir) == -1)
				errExit("asprintf");
			if (arg_debug) printf ("DEBUG: overlayhome var holds ##%s##\n",overlayhome);
		
			// if no homedir in overlay -- create another overlay for /home
			if (stat(overlayhome, &s) == -1) {
		
				if(asprintf(&hroot, "%s/oroot/home", RUN_MNT_DIR) == -1)
					errExit("asprintf");
		
				if(asprintf(&hdiff, "%s/hdiff", basedir) == -1)
					errExit("asprintf");

				// no need to check arg_overlay_reuse
				if (stat(hdiff, &s) != 0) {
					mkdir_attr(hdiff, S_IRWXU | S_IRWXG | S_IRWXO, 0, 0);
				}
				else if (set_perms(hdiff, 0, 0, S_IRWXU  | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH))
					errExit("set_perms");
		
				if(asprintf(&hwork, "%s/hwork", basedir) == -1)
					errExit("asprintf");

				// no need to check arg_overlay_reuse
				if (stat(hwork, &s) != 0) {
					mkdir_attr(hwork, S_IRWXU | S_IRWXG | S_IRWXO, 0, 0);
				}
				else if (set_perms(hwork, 0, 0, S_IRWXU  | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH))
					errExit("set_perms");
		
				// no homedir in overlay so now mount another overlay for /home
				if (asprintf(&option, "lowerdir=/home,upperdir=%s,workdir=%s", hdiff, hwork) == -1)
					errExit("asprintf");
				if (mount("overlay", hroot, "overlay", MS_MGC_VAL, option) < 0)
					errExit("mounting overlayfs for mounted home directory");
		
				printf("OverlayFS for /home configured in %s directory\n", basedir);
			} // stat(overlayhome)
			free(overlayhome);
		}
		// issue #263 end code
		//***************************
	}
	if (!arg_quiet)
		printf("OverlayFS configured in %s directory\n", basedir);
	
	// mount-bind dev directory
	if (arg_debug)
		printf("Mounting /dev\n");
	char *dev;
	if (asprintf(&dev, "%s/dev", oroot) == -1)
		errExit("asprintf");
	if (mount("/dev", dev, NULL, MS_BIND|MS_REC, NULL) < 0)
		errExit("mounting /dev");
	fs_logger("whitelist /dev");

	// mount-bind run directory
	if (arg_debug)
		printf("Mounting /run\n");
	char *run;
	if (asprintf(&run, "%s/run", oroot) == -1)
		errExit("asprintf");
	if (mount("/run", run, NULL, MS_BIND|MS_REC, NULL) < 0)
		errExit("mounting /run");
	fs_logger("whitelist /run");

	// mount-bind /tmp/.X11-unix directory
	if (stat("/tmp/.X11-unix", &s) == 0) {
		if (arg_debug)
			printf("Mounting /tmp/.X11-unix\n");
		char *x11;
		if (asprintf(&x11, "%s/tmp/.X11-unix", oroot) == -1)
			errExit("asprintf");
		if (mount("/tmp/.X11-unix", x11, NULL, MS_BIND|MS_REC, NULL) < 0)
			fwarning("cannot mount /tmp/.X11-unix in overlay\n");
		else
			fs_logger("whitelist /tmp/.X11-unix");
		free(x11);
	}

	// chroot in the new filesystem
#ifdef HAVE_GCOV
	__gcov_flush();
#endif
	if (chroot(oroot) == -1)
		errExit("chroot");

	// update /var directory in order to support multiple sandboxes running on the same root directory
//	if (!arg_private_dev)
//		fs_dev_shm();
	fs_var_lock();
	fs_var_tmp();
	if (!arg_writable_var_log)
		fs_var_log();
	else
		fs_rdwr("/var/log");
		
	fs_var_lib();
	fs_var_cache();
	fs_var_utmp();
	fs_machineid();

	// don't leak user information
	restrict_users();

	// when starting as root, firejail config is not disabled;
	// this mode could be used to install and test new software by chaining
	// firejail sandboxes (firejail --force)
	if (getuid() != 0)
		disable_config();

	// cleanup and exit
	free(option);
	free(oroot);
	free(odiff);
}
#endif


#ifdef HAVE_CHROOT		
// return 1 if error
void fs_check_chroot_dir(const char *rootdir) {
	EUID_ASSERT();
	assert(rootdir);
	struct stat s;
	char *name;

	if (strcmp(rootdir, "/tmp") == 0 || strcmp(rootdir, "/var/tmp") == 0) {
		fprintf(stderr, "Error: invalid chroot directory\n");
		exit(1);
	}

	// rootdir has to be owned by root
	if (stat(rootdir, &s) != 0) {
		fprintf(stderr, "Error: cannot find chroot directory\n");
		exit(1);
	}
	if (s.st_uid != 0) {
		fprintf(stderr, "Error: chroot directory should be owned by root\n");
		exit(1);
	}

	// check /dev
	if (asprintf(&name, "%s/dev", rootdir) == -1)
		errExit("asprintf");
	if (stat(name, &s) == -1) {
		fprintf(stderr, "Error: cannot find /dev in chroot directory\n");
		exit(1);
	}
	if (s.st_uid != 0) {
		fprintf(stderr, "Error: chroot /dev directory should be owned by root\n");
		exit(1);
	}
	free(name);

	// check /var/tmp
	if (asprintf(&name, "%s/var/tmp", rootdir) == -1)
		errExit("asprintf");
	if (stat(name, &s) == -1) {
		fprintf(stderr, "Error: cannot find /var/tmp in chroot directory\n");
		exit(1);
	}
	if (s.st_uid != 0) {
		fprintf(stderr, "Error: chroot /var/tmp directory should be owned by root\n");
		exit(1);
	}
	free(name);
	
	// check /proc
	if (asprintf(&name, "%s/proc", rootdir) == -1)
		errExit("asprintf");
	if (stat(name, &s) == -1) {
		fprintf(stderr, "Error: cannot find /proc in chroot directory\n");
		exit(1);
	}
	if (s.st_uid != 0) {
		fprintf(stderr, "Error: chroot /proc directory should be owned by root\n");
		exit(1);
	}
	free(name);
	
	// check /tmp
	if (asprintf(&name, "%s/tmp", rootdir) == -1)
		errExit("asprintf");
	if (stat(name, &s) == -1) {
		fprintf(stderr, "Error: cannot find /tmp in chroot directory\n");
		exit(1);
	}
	if (s.st_uid != 0) {
		fprintf(stderr, "Error: chroot /tmp directory should be owned by root\n");
		exit(1);
	}
	free(name);

	// check /etc
	if (asprintf(&name, "%s/etc", rootdir) == -1)
		errExit("asprintf");
	if (stat(name, &s) == -1) {
		fprintf(stderr, "Error: cannot find /etc in chroot directory\n");
		exit(1);
	}
	if (s.st_uid != 0) {
		fprintf(stderr, "Error: chroot /etc directory should be owned by root\n");
		exit(1);
	}
	free(name);

	// check /etc/resolv.conf
	if (asprintf(&name, "%s/etc/resolv.conf", rootdir) == -1)
		errExit("asprintf");
	if (stat(name, &s) == 0) {
		if (s.st_uid != 0) {
			fprintf(stderr, "Error: chroot /etc/resolv.conf should be owned by root\n");
			exit(1);
		}
	}
	if (is_link(name)) {
		fprintf(stderr, "Error: invalid %s file\n", name);
		exit(1);
	}
	free(name);

	// check x11 socket directory
	if (getenv("FIREJAIL_X11")) {
		char *name;
		if (asprintf(&name, "%s/tmp/.X11-unix", rootdir) == -1)
			errExit("asprintf");
		if (stat(name, &s) == -1) {
			fprintf(stderr, "Error: cannot find /tmp/.X11-unix in chroot directory\n");
			exit(1);
		}
		if (s.st_uid != 0) {
			fprintf(stderr, "Error: chroot /tmp/.X11-unix directory should be owned by root\n");
			exit(1);
		}
		free(name);
	}
}

// chroot into an existing directory; mount exiting /dev and update /etc/resolv.conf
void fs_chroot(const char *rootdir) {
	assert(rootdir);
	
	if (checkcfg(CFG_CHROOT_DESKTOP)) {
		// mount-bind a /dev in rootdir
		char *newdev;
		if (asprintf(&newdev, "%s/dev", rootdir) == -1)
			errExit("asprintf");
		if (arg_debug)
			printf("Mounting /dev on %s\n", newdev);
		if (mount("/dev", newdev, NULL, MS_BIND|MS_REC, NULL) < 0)
			errExit("mounting /dev");
		free(newdev);
		
		// x11
		if (getenv("FIREJAIL_X11")) {
			char *newx11;
			if (asprintf(&newx11, "%s/tmp/.X11-unix", rootdir) == -1)
				errExit("asprintf");
			if (arg_debug)
				printf("Mounting /tmp/.X11-unix on %s\n", newx11);
			if (mount("/tmp/.X11-unix", newx11, NULL, MS_BIND|MS_REC, NULL) < 0)
				errExit("mounting /tmp/.X11-unix");
			free(newx11);
		}
		
		// some older distros don't have a /run directory
		// create one by default
		// create /run/firejail directory in chroot
		char *rundir;
		if (asprintf(&rundir, "%s/run", rootdir) == -1)
			errExit("asprintf");
		if (is_link(rundir)) {
			fprintf(stderr, "Error: invalid run directory inside chroot\n");
			exit(1);
		}
		create_empty_dir_as_root(rundir, 0755);
		free(rundir);
		if (asprintf(&rundir, "%s/run/firejail", rootdir) == -1)
			errExit("asprintf");
		create_empty_dir_as_root(rundir, 0755);
		free(rundir);
		
		// create /run/firejail/mnt directory in chroot and mount the current one
		if (asprintf(&rundir, "%s%s", rootdir, RUN_MNT_DIR) == -1)
			errExit("asprintf");
		create_empty_dir_as_root(rundir, 0755);
		if (mount(RUN_MNT_DIR, rundir, NULL, MS_BIND|MS_REC, NULL) < 0)
			errExit("mount bind");

		// copy /etc/resolv.conf in chroot directory
		// if resolv.conf in chroot is a symbolic link, this will fail
		// no exit on error, let the user deal with the problem
		char *fname;
		if (asprintf(&fname, "%s/etc/resolv.conf", rootdir) == -1)
			errExit("asprintf");
		if (arg_debug)
			printf("Updating /etc/resolv.conf in %s\n", fname);
		if (is_link(fname)) {
			fprintf(stderr, "Error: invalid %s file\n", fname);
			exit(1);
		}
		if (copy_file("/etc/resolv.conf", fname, 0, 0, 0644) == -1) // root needed
			fwarning("/etc/resolv.conf not initialized\n");
	}
	
	// chroot into the new directory
#ifdef HAVE_GCOV
	__gcov_flush();
#endif
	if (arg_debug)
		printf("Chrooting into %s\n", rootdir);
	if (chroot(rootdir) < 0)
		errExit("chroot");

	// create all other /run/firejail files and directories
	preproc_build_firejail_dir();

	if (checkcfg(CFG_CHROOT_DESKTOP)) {
		// update /var directory in order to support multiple sandboxes running on the same root directory
//		if (!arg_private_dev)
//			fs_dev_shm();
		fs_var_lock();
		fs_var_tmp();
		if (!arg_writable_var_log)
			fs_var_log();
		else
			fs_rdwr("/var/log");
			
		fs_var_lib();
		fs_var_cache();
		fs_var_utmp();
		fs_machineid();
	
		// don't leak user information
		restrict_users();
	
		// when starting as root, firejail config is not disabled;
		// this mode could be used to install and test new software by chaining
		// firejail sandboxes (firejail --force)
		if (getuid() != 0)
			disable_config();
	}
}
#endif