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/*
* Copyright (C) 2014-2016 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/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
#include <dirent.h>
#include <sys/mount.h>
// return 1 if xpra is installed on the system
int x11_check_xpra(void) {
struct stat s;
// check xpra
if (stat("/usr/bin/xpra", &s) == -1)
return 0;
return 1;
}
// return display number, -1 if not configured
int x11_display(void) {
// extract display
char *d = getenv("DISPLAY");
if (!d)
return - 1;
int display;
int rv = sscanf(d, ":%d", &display);
if (rv != 1)
return -1;
if (arg_debug)
printf("DISPLAY %s, %d\n", d, display);
return display;
}
void fs_x11(void) {
#ifdef HAVE_X11
int display = x11_display();
if (display <= 0)
return;
char *x11file;
if (asprintf(&x11file, "/tmp/.X11-unix/X%d", display) == -1)
errExit("asprintf");
struct stat s;
if (stat(x11file, &s) == -1)
return;
// keep a copy of real /tmp/.X11-unix directory in WHITELIST_TMP_DIR
int rv = mkdir(RUN_WHITELIST_X11_DIR, 1777);
if (rv == -1)
errExit("mkdir");
if (chown(RUN_WHITELIST_X11_DIR, 0, 0) < 0)
errExit("chown");
if (chmod(RUN_WHITELIST_X11_DIR, 1777) < 0)
errExit("chmod");
if (mount("/tmp/.X11-unix", RUN_WHITELIST_X11_DIR, NULL, MS_BIND|MS_REC, NULL) < 0)
errExit("mount bind");
// mount tmpfs on /tmp/.X11-unix
if (arg_debug || arg_debug_whitelists)
printf("Mounting tmpfs on /tmp/.X11-unix directory\n");
if (mount("tmpfs", "/tmp/.X11-unix", "tmpfs", MS_NOSUID | MS_STRICTATIME | MS_REC, "mode=1777,gid=0") < 0)
errExit("mounting tmpfs on /tmp");
fs_logger("tmpfs /tmp/.X11-unix");
// create an empty file
FILE *fp = fopen(x11file, "w");
if (!fp) {
fprintf(stderr, "Error: cannot create empty file in x11 directory\n");
exit(1);
}
fclose(fp);
// set file properties
if (chown(x11file, s.st_uid, s.st_gid) < 0)
errExit("chown");
if (chmod(x11file, s.st_mode) < 0)
errExit("chmod");
// mount
char *wx11file;
if (asprintf(&wx11file, "%s/X%d", RUN_WHITELIST_X11_DIR, display) == -1)
errExit("asprintf");
if (mount(wx11file, x11file, NULL, MS_BIND|MS_REC, NULL) < 0)
errExit("mount bind");
fs_logger2("whitelist", x11file);
free(x11file);
free(wx11file);
// block access to RUN_WHITELIST_X11_DIR
if (mount(RUN_RO_DIR, RUN_WHITELIST_X11_DIR, "none", MS_BIND, "mode=400,gid=0") == -1)
errExit("mount");
fs_logger2("blacklist", RUN_WHITELIST_X11_DIR);
#endif
}
#ifdef HAVE_X11
void x11_start(int argc, char **argv) {
EUID_ASSERT();
int i;
struct stat s;
pid_t client = 0;
pid_t server = 0;
// unfortunately, xpra does a number of wired things when started by root user!!!
if (getuid() == 0) {
fprintf(stderr, "Error: this feature is not available when running as root\n");
exit(1);
}
// check xpra
if (x11_check_xpra() == 0) {
fprintf(stderr, "\nError: Xpra program was not found in /usr/bin directory, please install it:\n");
fprintf(stderr, " Debian/Ubuntu/Mint: sudo apt-get install xpra\n");
exit(0);
}
int display;
int found = 1;
for (i = 0; i < 100; i++) {
display = rand() % 1024;
if (display < 10)
continue;
char *fname;
if (asprintf(&fname, "/tmp/.X11-unix/X%d", display) == -1)
errExit("asprintf");
if (stat(fname, &s) == -1) {
found = 1;
break;
}
}
if (!found) {
fprintf(stderr, "Error: cannot pick up a random X11 display number, exiting...\n");
exit(1);
}
// build the start command
int len = 50; // xpra start...
for (i = 0; i < argc; i++) {
len += strlen(argv[i]) + 1; // + ' '
}
char *cmd1 = malloc(len + 1); // + '\0'
if (!cmd1)
errExit("malloc");
sprintf(cmd1, "xpra start :%d --exit-with-children --start-child=\"", display);
char *ptr = cmd1 + strlen(cmd1);
for (i = 0; i < argc; i++) {
if (strcmp(argv[i], "--x11") == 0)
continue;
ptr += sprintf(ptr, "%s ", argv[i]);
}
sprintf(ptr, "\"");
if (arg_debug)
printf("xpra server: %s\n", cmd1);
// build the attach command
char *cmd2;
if (asprintf(&cmd2, "xpra attach :%d", display) == -1)
errExit("asprintf");
if (arg_debug)
printf("xpra client: %s\n", cmd2);
signal(SIGHUP,SIG_IGN); // fix sleep(1`) below
server = fork();
if (server < 0)
errExit("fork");
if (server == 0) {
if (arg_debug)
printf("Starting xpra...\n");
char *a[4];
a[0] = "/bin/bash";
a[1] = "-c";
a[2] = cmd1;
a[3] = NULL;
execvp(a[0], a);
perror("execvp");
exit(1);
}
// check X11 socket
char *fname;
if (asprintf(&fname, "/tmp/.X11-unix/X%d", display) == -1)
errExit("asprintf");
int n = 0;
// wait for x11 server to start
while (++n < 10) {
sleep(1);
if (stat(fname, &s) == 0)
break;
};
if (n == 10) {
fprintf(stderr, "Error: failed to start xpra\n");
exit(1);
}
free(fname);
sleep(1);
if (arg_debug) {
printf("X11 sockets: "); fflush(0);
int rv = system("ls /tmp/.X11-unix");
(void) rv;
}
// run attach command
client = fork();
if (client < 0)
errExit("fork");
if (client == 0) {
printf("\n*** Attaching to xpra display %d ***\n\n", display);
char *a[4];
a[0] = "/bin/bash";
a[1] = "-c";
a[2] = cmd2;
a[3] = NULL;
execvp(a[0], a);
perror("execvp");
exit(1);
}
sleep(1);
if (!arg_quiet)
printf("Xpra server pid %d, client pid %d\n", server, client);
exit(0);
}
#endif
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