nsjail/README.md

### 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 servers (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 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
```