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.
- Linux namespaces: UTS (hostname), MOUNT (chroot), PID (separate PID tree), IPC, NET (separate networking context), USER
- FS constraints: chroot(), pivot_root(), RO-remounting
- Resource limits (wall-time/CPU time limits, VM/mem address space limits, etc.)
- Programmable seccomp-bpf syscall filters
- 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
/ $
$ ./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
$
$ ./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
/ $
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: Listen to connections on a TCP port (specified with --port) [MODE_LISTEN_TCP]
o: Immediately launch a single process on a console [MODE_STANDALONE_ONCE]
r: Immediately launch a single process on a console, keep doing it forever [MODE_STANDALONE_RERUN]
--chroot|-c [val]
Directory containing / of the jail (default: '/chroot')
--user|-u [val]
Username/uid of processess inside the jail (default: 'nobody')
--group|-g [val]
Groupname/gid of processess inside the jail (default: 'nogroup')
--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)
--max_conns_per_ip|-i [val]
Maximum number of connections per one IP (default: 0 (unlimited))
--log|-l [val]
Log file (default: stderr)
--time_limit|-t [val]
Maximum time that a jail can exist, in seconds (default: 600)
--daemon|-d
--verbose|-v
Verbose output (default: false)
--keep_env|-e
Should all environment variables be passed to the child? (default: false)
--keep_caps
Don't drop capabilities (DANGEROUS) (default: false)
--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) (default: false)
--persona_mmap_page_zero
personality(MMAP_PAGE_ZERO) (default: false)
--persona_read_implies_exec
personality(READ_IMPLIES_EXEC) (default: false)
--persona_addr_limit_3gb
personality(ADDR_LIMIT_3GB) (default: false)
--persona_addr_no_randomize
personality(ADDR_NO_RANDOMIZE) (default: false)
--disable_clone_newnet|-N
Enable networking inside the jail (default: false)
--disable_clone_newuser
Don't use CLONE_NEWUSER (default: false)
--disable_clone_newns
Don't use CLONE_NEWNS (default: false)
--disable_clone_newpid
Don't use CLONE_NEWPID (default: false)
--disable_clone_newipc
Don't use CLONE_NEWIPC (default: false)
--disable_clone_newuts
Don't use CLONE_NEWUTS (default: false)
--disable_sandbox
Don't enable the seccomp-bpf sandboxing (default: false)
--rw
Mount / as RW (default: RO)
--silent
Redirect child's fd:0/1/2 to /dev/null (default: false)
--bindmount_ro [val]
List of mountpoints to be mounted --bind (ro) inside the container. Can be specified multiple times. Supports 'source' syntax, or 'source:dest'. (default: none)
--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'. (default: none)
--tmpfsmount|-T [val]
List of mountpoints to be mounted as RW/tmpfs inside the container. Can be specified multiple times. Supports 'dest' syntax. (default: none)
--iface|-I [val]
Interface which will be cloned (MACVTAP) and put inside the subprocess' namespace
--tmpfs_size [val]
Number of bytes to allocate for tmpfsmounts in bytes (default: 4194304)
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