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/*
* Copyright (C) 2014-2020 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 <grp.h>
#define MAX_BUF 4096
int is_container(const char *str) {
assert(str);
if (strcmp(str, "lxc") == 0 ||
strcmp(str, "docker") == 0 ||
strcmp(str, "lxc-libvirt") == 0 ||
strcmp(str, "systemd-nspawn") == 0 ||
strcmp(str, "rkt") == 0)
return 1;
return 0;
}
// returns 1 if we are running under LXC
int check_namespace_virt(void) {
EUID_ASSERT();
// check container environment variable
char *str = getenv("container");
if (str && is_container(str))
return 1;
// check PID 1 container environment variable
EUID_ROOT();
FILE *fp = fopen("/proc/1/environ", "r");
if (fp) {
int c = 0;
while (c != EOF) {
// read one line
char buf[MAX_BUF];
int i = 0;
while ((c = fgetc(fp)) != EOF) {
if (c == 0)
break;
buf[i] = (char) c;
if (++i == (MAX_BUF - 1))
break;
}
buf[i] = '\0';
// check env var name
if (strncmp(buf, "container=", 10) == 0) {
// found it
if (is_container(buf + 10)) {
fclose(fp);
EUID_USER();
return 1;
}
}
// printf("i %d c %d, buf #%s#\n", i, c, buf);
}
fclose(fp);
}
EUID_USER();
return 0;
}
// check process space for kernel processes
// return 1 if found, 0 if not found
int check_kernel_procs(void) {
// we run this function with EUID set in order to detect grsecurity
// only user processes are available in /proc when running grsecurity
// EUID_ASSERT();
static char *kern_proc[] = {
"kthreadd",
"ksoftirqd",
"kworker",
"rcu_sched",
"rcu_bh",
NULL // NULL terminated list
};
int i;
if (arg_debug)
printf("Looking for kernel processes\n");
// look at the first 10 processes
// if a kernel process is found, return 1
for (i = 1; i <= 10; i++) {
struct stat s;
char *fname;
if (asprintf(&fname, "/proc/%d/comm", i) == -1)
errExit("asprintf");
if (stat(fname, &s) == -1) {
free(fname);
continue;
}
// open file
/* coverity[toctou] */
FILE *fp = fopen(fname, "r");
if (!fp) {
fwarning("cannot open %s\n", fname);
free(fname);
continue;
}
// read file
char buf[100];
if (fgets(buf, 10, fp) == NULL) {
fwarning("cannot read %s\n", fname);
fclose(fp);
free(fname);
continue;
}
// clean /n
char *ptr;
if ((ptr = strchr(buf, '\n')) != NULL)
*ptr = '\0';
// check process name against the kernel list
int j = 0;
while (kern_proc[j] != NULL) {
if (strncmp(buf, kern_proc[j], strlen(kern_proc[j])) == 0) {
if (arg_debug)
printf("Found %s process, we are not running in a sandbox\n", buf);
fclose(fp);
free(fname);
return 1;
}
j++;
}
fclose(fp);
free(fname);
}
if (arg_debug)
printf("No kernel processes found, we are already running in a sandbox\n");
return 0;
}
void run_no_sandbox(int argc, char **argv) {
EUID_ASSERT();
// drop privileges
if (setresgid(-1, getgid(), getgid()) != 0)
errExit("setresgid");
if (setresuid(-1, getuid(), getuid()) != 0)
errExit("setresuid");
// process limited subset of options
int i;
for (i = 0; i < argc; i++) {
if (strcmp(argv[i], "--debug") == 0)
arg_debug = 1;
else if (strncmp(argv[i], "--shell=", 8) == 0)
fwarning("shell-related command line options are disregarded - using SHELL environment variable\n");
}
// use $SHELL to get shell used in sandbox, guess shell otherwise
assert(login_shell == 0);
cfg.shell = guess_shell();
if (!cfg.shell) {
fprintf(stderr, "Error: unable to guess your shell, please set SHELL environment variable\n");
exit(1);
}
else if (arg_debug)
printf("Selecting %s as shell\n", cfg.shell);
int prog_index = 0;
// find first non option arg:
// - first argument not starting with --,
// - whatever follows after -c (example: firejail -c ls)
for (i = 1; i < argc; i++) {
if (strcmp(argv[i], "-c") == 0) {
prog_index = i + 1;
if (prog_index == argc) {
fprintf(stderr, "Error: option -c requires an argument\n");
exit(1);
}
break;
}
// check first argument not starting with --
if (strncmp(argv[i],"--",2) != 0) {
prog_index = i;
break;
}
}
// if shell is /usr/bin/firejail, replace it with /bin/bash
if (strcmp(cfg.shell, PATH_FIREJAIL) == 0) {
cfg.shell = "/bin/bash";
prog_index = 0;
}
if (prog_index == 0) {
cfg.command_line = cfg.shell;
cfg.window_title = cfg.shell;
} else {
build_cmdline(&cfg.command_line, &cfg.window_title, argc, argv, prog_index);
}
cfg.original_argv = argv;
cfg.original_program_index = prog_index;
char *command;
if (prog_index == 0)
command = cfg.shell;
else
command = argv[prog_index];
fwarning("an existing sandbox was detected. "
"%s will run without any additional sandboxing features\n", command);
arg_quiet = 1;
start_application(1, NULL);
}
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