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
- Cloned and separated Ethernet interfaces
- 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
/ $
$ 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: <LOOPBACK,UP,LOWER_UP> 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: <BROADCAST,MULTICAST,UP,LOWER_UP> 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
<HTML><HEAD><meta http-equiv="content-type" content="text/html;charset=utf-8">
<TITLE>302 Moved</TITLE></HEAD><BODY>
<H1>302 Moved</H1>
The document has moved
<A HREF="http://www.google.ch/?gfe_rd=cr&ei=cEzWVrG2CeTI8ge88ofwDA">here</A>.
</BODY></HTML>
/ $
$ ./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: 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
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