http://www.cyberciti.biz/faq/linux-unix-ssh-proxycommand-passing-through-one-host-gateway-server
How do I use and jump through one server to reach another using ssh on a Linux or Unix-like systems? Is it possible to connect to another host via an intermediary so that the client can act as if the connection were direct using ssh?
You can jump host using ProxyCommand.
Some times you can only access a remote server via ssh by first login into an intermediary server (or firewall/jump host). So you first login into to the intermediary server and then ssh to another server. You need to authenticate twice and the chain can be long and is not limited to just two hosts.
Next, I must ssh through the intermediary system as follows:
Where,
The netcat (nc) command is needed to set and establish a TCP pipe between Jumphost (or firewall) and FooServer. Now, my laptop (local system) is connected to Jumphost it now connected FooServer. In this example, the utility netcat (nc) is for reading and writing network connections directly. It can be used to pass connections to a 2nd server such as FooServer.
Append the following configuration:
To see the details, pass the -v option to the ssh command. Here is another snippet:
Sample outputs:
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: Sending environment.
Welcome to Ubuntu 14.04.2 LTS (GNU/Linux 3.13.0-52-generic x86_64)
* Documentation: https://help.ubuntu.com/
Last login: Sun May 17 15:41:26 2015 from 10.70.203.66How do I use and jump through one server to reach another using ssh on a Linux or Unix-like systems? Is it possible to connect to another host via an intermediary so that the client can act as if the connection were direct using ssh?
You can jump host using ProxyCommand.
Some times you can only access a remote server via ssh by first login into an intermediary server (or firewall/jump host). So you first login into to the intermediary server and then ssh to another server. You need to authenticate twice and the chain can be long and is not limited to just two hosts.
Sample setup
+-------+ +----------+ +-----------+
| Laptop| <---> | Jumphost | <--> | FooServer |
+-------+ +----------+ +-----------+
OR
+-------+ +----------+ +-----------+
| Laptop| <---> | Firewall | <--> | FooServer |
+-------+ +----------+ +-----------+
192.168.1.5 121.1.2.3 10.10.29.68
I can can only access a remote server named 'FooServer' via ssh
by first login into an intermediary server called 'Jumphost'. First,
login to Jumphost:$ ssh vivek@JumphostNext, I must ssh through the intermediary system as follows:
$ ssh vivek@FooServerPassing through a gateway or two
Instead of typing two ssh command, I can type the following all-in-one command. This is useful for connecting to FooServer via firewall called 'Jumphost' as the jump host:$ ssh -tt Jumphost ssh -tt FooServer
$ ssh -tt vivek@Jumphost ssh -tt vivek@FooServer
$ ssh -tt vivek@Jumphost ssh -tt vivek@FooServer command1 arg1 arg2
$ ssh -tt vivek@Jumphost ssh -tt vivek@FooServer htop
$ ssh -tt vivek@Jumphost ssh -tt vivek@FooServer screen -dRWhere,
- The -t option passed to the ssh command force pseudo-tty allocation. This can be used to execute arbitrary screen-based programs on a remote machine. Multiple -tt options force tty allocation, even if ssh has no local tty.
Say hello to the ProxyCommand
The syntax is:$ ssh -o ProxyCommand='ssh firewall nc remote_server1 22' remote_server1
$ ssh -o ProxyCommand='ssh vivek@Jumphost nc FooServer 22' vivek@FooServer
##########################################
## -t option is needed to run commands ###
##########################################
$ ssh -t -o ProxyCommand='ssh vivek@Jumphost nc FooServer 22' vivek@FooServer htopThe netcat (nc) command is needed to set and establish a TCP pipe between Jumphost (or firewall) and FooServer. Now, my laptop (local system) is connected to Jumphost it now connected FooServer. In this example, the utility netcat (nc) is for reading and writing network connections directly. It can be used to pass connections to a 2nd server such as FooServer.
Update ~/.ssh/config file
Edit the $HOME/.ssh/config file using a text editor such as vi, enter:$ vi ~/.ssh/configAppend the following configuration:
Host fooserver HostName FooServer User vivek ProxyCommand ssh vivek@Jumphost nc %h %pSave and close the file. Where,
- Host fooserver : Set nickname of your choice.
- HostName FooServer : Set the real remote server/host name.
- User vivek : Set the real user name for remote server/host.
- ProxyCommand ssh vivek@Jumphost nc %h %p : Specifies the command to use to connect to the server. In this example, I'm using nc command. Any occurrence of %h will be substituted by the host name to connect, %p by the port, and %r by the remote user name.
$ ssh fooserverTo see the details, pass the -v option to the ssh command. Here is another snippet:
Host server1
HostName v.server1
User root
Port 22
ProxyCommand ssh root@v.backup2 nc %h %p %r
Now, run:$ ssh -v server1Sample outputs:
OpenSSH_6.2p2, OSSLShim 0.9.8r 8 Dec 2011
debug1: Reading configuration data /Users/veryv/.ssh/config
debug1: /Users/veryv/.ssh/config line 1: Applying options for server1
debug1: Reading configuration data /etc/ssh_config
debug1: /etc/ssh_config line 20: Applying options for *
debug1: /etc/ssh_config line 102: Applying options for *
debug1: Executing proxy command: exec ssh root@v.backup2 nc v.server1 22 root
debug1: permanently_drop_suid: 501
debug1: identity file /Users/veryv/.ssh/id_rsa type 1
debug1: identity file /Users/veryv/.ssh/id_rsa-cert type -1
debug1: identity file /Users/veryv/.ssh/id_dsa type -1
debug1: identity file /Users/veryv/.ssh/id_dsa-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.2
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1p1 Ubuntu-2ubuntu2
debug1: match: OpenSSH_6.6.1p1 Ubuntu-2ubuntu2 pat OpenSSH*
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5-etm@openssh.com none
debug1: kex: client->server aes128-ctr hmac-md5-etm@openssh.com none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024 279="" accepts="" allowed="" and="" authentication="" authentications="" blen="" by="" can="" continue:="" correct="" d2:07:84:79:21:a7:84:84:14:ef:f1:7a:84:a5:a1:7s="" debug1:="" expecting="" found="" host="" id_rsa="" in="" is="" key.="" key:="" key="" keyboard-interactive="" known="" known_hosts:37="" matches="" method:="" next="" not="" offering="" password="" pkalg="" public="" publickey="" received="" roaming="" rsa="" sent="" sers="" server="" signature="" span="" ssh-rsa="" ssh2_msg_kex_dh_gex_group="" ssh2_msg_kex_dh_gex_init="" ssh2_msg_kex_dh_gex_reply="" ssh2_msg_newkeys="" ssh2_msg_service_accept="" ssh2_msg_service_request="" ssh="" ssh_rsa_verify:="" style="color: #009900;" succeeded="" that="" the="" v.server1="" veryv="">Authenticated to v.server1 (via proxy).
The sftp syntax
The syntax is as follows:sftp -o 'ProxyCommand=ssh %h nc firewall.nixcraft.net.in 22' \ -o 'HostKeyAlias=firewall.nixcraft.net.in' \ vivek@server1.nixcraft.net.inSee man pages for more info: ssh(1), ssh_config(5), nc(1)
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