[Python] SSH to a server through a jump server, with PKI

Hello,

Today's tip is regarding a topic that made me stuck for a while : how to connect to a server through another server, and all infrastructure uses public key to authenticate ?

I tried playing with ssh_agent and key forwarding, but I couldn't make it work. Then a suggestion was made to use port forwarding, which is much more straitforward and simple to handle/understand.

Here is a piece of code that should work for you :

 #!/usr/bin/python  
 #  
 # Paramiko  
 #  
 import paramiko  
 import sys  
 import subprocess  
 #  
 # we instantiate a new object referencing paramiko's SSHClient class  
 #  
 vm = paramiko.SSHClient()  
 vm.set_missing_host_key_policy(paramiko.AutoAddPolicy())  
 k = paramiko.RSAKey.from_private_key_file("/path/to/the/key",password='private_key_password')  
 vm.connect('jump_server', username='login', pkey = k)  
 #  
 vmtransport = vm.get_transport()  
 dest_addr = ('dst_server', 22)  
 local_addr = ('jump_server', 22)  
 vmchannel = vmtransport.open_channel("direct-tcpip", dest_addr, local_addr)  
 #  
 jhost = paramiko.SSHClient()  
 jhost.set_missing_host_key_policy(paramiko.AutoAddPolicy())  
 jhost.connect('dst_server', username='login', password='xxxx', sock=vmchannel)  
 #we send a simple command  
 stdin, stdout, stderr = jhost.exec_command("hostname")  
 #we read the return from the dst_server  
 print stdout.read()  
 #we don't forget to close the SSH session  
 jhost.close()  
 vm.close()  
 # End  

If you are using simple password, replace pkey by password. Enjoy !