### WHAT IS IT? NsJail is a process isolation tool for Linux. It makes use of the the namespacing, resource control, and seccomp-bpf syscall filter subsystems of the Linux kernel. It can help, among others, with: * Securing networking services (e.g. web, time, DNS), by isolating them from the rest of the OS * Hosting computer security challenges (so-called CTFs) * Containing invasive syscall-level OS fuzzers This is NOT an official Google product. ### WHAT KIND OF ISOLATION DOES THIS TOOL PROVIDE? 1. Linux namespaces: UTS (hostname), MOUNT (chroot), PID (separate PID tree), IPC, NET (separate networking context), USER 2. FS constraints: chroot(), pivot_root(), RO-remounting 3. Resource limits (wall-time/CPU time limits, VM/mem address space limits, etc.) 4. Programmable seccomp-bpf syscall filters 5. Cloned and separated Ethernet interfaces ### WHAT KIND OF USE-CASES ARE SUPPORTED? #### Isolation of network services (inetd-style) + Server: ``` $ ./nsjail -Ml --port 9000 --chroot /chroot/ --user 99999 --group 99999 -- /bin/sh -i ``` + Client: ``` $ nc 127.0.0.1 9000 / $ ifconfig / $ ifconfig -a lo Link encap:Local Loopback LOOPBACK MTU:65536 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) / $ ps wuax PID USER COMMAND 1 99999 /bin/sh -i 3 99999 {busybox} ps wuax / $ ``` #### Isolation, with access to a private, cloned interface (requires euid==0) ``` $ sudo ./nsjail --user 9999 --group 9999 --iface eth0 --chroot /chroot/ -Mo --iface_vs_ip 192.168.0.44 --iface_vs_nm 255.255.255.0 --iface_vs_gw 192.168.0.1 -- /bin/sh -i / $ id uid=9999 gid=9999 / $ ip addr sh 1: lo: mtu 65536 qdisc noqueue link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: vs: mtu 1500 qdisc noqueue link/ether ca:a2:69:21:33:66 brd ff:ff:ff:ff:ff:ff inet 192.168.0.44/24 brd 192.168.0.255 scope global vs valid_lft forever preferred_lft forever inet6 fe80::c8a2:69ff:fe21:cd66/64 scope link valid_lft forever preferred_lft forever / $ nc 217.146.165.209 80 GET / HTTP/1.0 HTTP/1.0 302 Found Cache-Control: private Content-Type: text/html; charset=UTF-8 Location: http://www.google.ch/?gfe_rd=cr&ei=cEzWVrG2CeTI8ge88ofwDA Content-Length: 258 Date: Wed, 02 Mar 2016 02:14:08 GMT 302 Moved

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The document has moved here. / $ ``` #### Isolation of local processes ``` $ ./nsjail -Mo --chroot /chroot/ --user 99999 --group 99999 -- /bin/sh -i / $ ifconfig -a lo Link encap:Local Loopback LOOPBACK MTU:65536 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) / $ id uid=99999 gid=99999 / $ ps wuax PID USER COMMAND 1 99999 /bin/sh -i 4 99999 {busybox} ps wuax / $exit $ ``` #### Isolation of local processes (and re-running them) ``` $ ./nsjail -Mr --chroot /chroot/ --user 99999 --group 99999 -- /bin/sh -i BusyBox v1.21.1 (Ubuntu 1:1.21.0-1ubuntu1) built-in shell (ash) Enter 'help' for a list of built-in commands. / $ ps wuax PID USER COMMAND 1 99999 /bin/sh -i 2 99999 {busybox} ps wuax / $ exit BusyBox v1.21.1 (Ubuntu 1:1.21.0-1ubuntu1) built-in shell (ash) Enter 'help' for a list of built-in commands. / $ ps wuax PID USER COMMAND 1 99999 /bin/sh -i 2 99999 {busybox} ps wuax / $ ``` ### MORE INFO? Type: ``` ./nsjail --help' ``` The commandline options are reasonably well-documented ``` Usage: ./nsjail [options] -- path_to_command [args] Options: --help|-h Help plz.. --mode|-M [val] Execution mode (default: l [MODE_LISTEN_TCP]): l: Wait for connections on a TCP port (specified with --port) [MODE_LISTEN_TCP] o: Immediately launch a single process on a console using clone/execve [MODE_STANDALONE_ONCE] e: Immediately launch a single process on a console using execve [MODE_STANDALONE_EXECVE] r: Immediately launch a single process on a console, keep doing it forever [MODE_STANDALONE_RERUN] --cmd Equivalent of -Mo (MODE_STANDALONE_ONCE), run command on a local console, once --chroot|-c [val] Directory containing / of the jail (default: "/"). Skip mounting it if "" --rw Mount / as RW (default: RO) --user|-u [val] Username/uid of processess inside the jail (default: your current uid). You can also use inside_ns_uid:outside_ns_uid convention here --group|-g [val] Groupname/gid of processess inside the jail (default: your current gid). You can also use inside_ns_gid:global_ns_gid convention here --hostname|-H [val] UTS name (hostname) of the jail (default: 'NSJAIL') --cwd|-D [val] Directory in the namespace the process will run (default: '/') --port|-p [val] TCP port to bind to (only in [MODE_LISTEN_TCP]) (default: 31337) --bindhost [val] IP address port to bind to (only in [MODE_LISTEN_TCP]) (default: '::') --max_conns_per_ip|-i [val] Maximum number of connections per one IP (default: 0 (unlimited)) --log|-l [val] Log file (default: /proc/self/fd/2) --time_limit|-t [val] Maximum time that a jail can exist, in seconds (default: 600) --daemon|-d Daemonize after start --verbose|-v Verbose output --keep_env|-e Should all environment variables be passed to the child? --env|-E [val] Environment variable (can be used multiple times) --keep_caps Don't drop capabilities (DANGEROUS) --silent Redirect child's fd:0/1/2 to /dev/null --disable_sandbox Don't enable the seccomp-bpf sandboxing --skip_setsid Don't call setsid(), allows for terminal signal handling in the sandboxed process --rlimit_as [val] RLIMIT_AS in MB, 'max' for RLIM_INFINITY, 'def' for the current value (default: 512) --rlimit_core [val] RLIMIT_CORE in MB, 'max' for RLIM_INFINITY, 'def' for the current value (default: 0) --rlimit_cpu [val] RLIMIT_CPU, 'max' for RLIM_INFINITY, 'def' for the current value (default: 600) --rlimit_fsize [val] RLIMIT_FSIZE in MB, 'max' for RLIM_INFINITY, 'def' for the current value (default: 1) --rlimit_nofile [val] RLIMIT_NOFILE, 'max' for RLIM_INFINITY, 'def' for the current value (default: 32) --rlimit_nproc [val] RLIMIT_NPROC, 'max' for RLIM_INFINITY, 'def' for the current value (default: 'def') --rlimit_stack [val] RLIMIT_STACK in MB, 'max' for RLIM_INFINITY, 'def' for the current value (default: 'def') --persona_addr_compat_layout personality(ADDR_COMPAT_LAYOUT) --persona_mmap_page_zero personality(MMAP_PAGE_ZERO) --persona_read_implies_exec personality(READ_IMPLIES_EXEC) --persona_addr_limit_3gb personality(ADDR_LIMIT_3GB) --persona_addr_no_randomize personality(ADDR_NO_RANDOMIZE) --disable_clone_newnet|-N Don't use CLONE_NEWNET. Enable networking inside the jail --disable_clone_newuser Don't use CLONE_NEWUSER. Requires euid==0 --disable_clone_newns Don't use CLONE_NEWNS --disable_clone_newpid Don't use CLONE_NEWPID --disable_clone_newipc Don't use CLONE_NEWIPC --disable_clone_newuts Don't use CLONE_NEWUTS --bindmount_ro|-R [val] List of mountpoints to be mounted --bind (ro) inside the container. Can be specified multiple times. Supports 'source' syntax, or 'source:dest' --bindmount|-B [val] List of mountpoints to be mounted --bind (rw) inside the container. Can be specified multiple times. Supports 'source' syntax, or 'source:dest' --tmpfsmount|-T [val] List of mountpoints to be mounted as RW/tmpfs inside the container. Can be specified multiple times. Supports 'dest' syntax --tmpfs_size [val] Number of bytes to allocate for tmpfsmounts (default: 4194304) --disable_proc Disable mounting /proc in the jail --iface_no_lo Don't bring up the 'lo' interface --iface|-I [val] Interface which will be cloned (MACVTAP) and put inside the subprocess' namespace as 'vs' --iface_vs_ip [val] IP of the 'vs' interface --iface_vs_nm [val] Netmask of the 'vs' interface --iface_vs_gw [val] Default GW for the 'vs' interface ```