I am learning python. I am at a step where I must connect with SSH and retrieve information. Direct connection to server A is OK. Direct connection to server B is OK. Now I'd like to make it work to connect to SSH to A and via A connect to SSH to B (because outside of my lab, there are security features that make me do that).
I went far, looked everything on the internet, but Paramiko and SSH agent don't seem to work for me. I use public key authentication on my linux servers (all linux servers btw).
I enabled detailed logs, and Here is the full error message anonymized:
INFO:paramiko.transport:Authentication (publickey) successful!
DEBUG:paramiko.transport:[chan 0] Max packet in: 32768 bytes
DEBUG:paramiko.transport:[chan 0] Max packet out: 32768 bytes
DEBUG:paramiko.transport:Secsh channel 0 opened.
DEBUG:paramiko.transport:[chan 1] Max packet in: 32768 bytes
DEBUG:paramiko.transport:[chan 1] Max packet out: 32768 bytes
DEBUG:paramiko.transport:Secsh channel 1 opened.
DEBUG:paramiko.transport:[chan 1] Sesch channel 1 request ok
DEBUG:paramiko.transport:[chan 1] Sesch channel 1 request ok
('[SEND ] >>', 'hostname')
('[RECEIVE] <<', u'Last login: Wed Jan 9 19:51:01 2019 from myserver')
('[RECEIVE] <<', u'hostname ; echo CLIENT_EXPECT_CMD_OK')
('[RECEIVE] <<', u'/----- Welcome to proxy jump server ----------')
('[RECEIVE] <<', u'| CentOS release 6.6 (Final)')
('[RECEIVE] <<', u'[mylogin@proxy_jump_server ~]$ hostname ; echo
CLIENT_EXPECT_CMD_OK')
('[RECEIVE] <<', u'proxy_jump_server')
('[SEND ] >>', 'ssh mylogin@final_server hostname')
('[RECEIVE] <<', u'[mylogin@proxy_jump_server ~]$ ssh mylogin@final_server
hostname ; echo CLIENT_EXPECT_CMD_OK')
DEBUG:paramiko.transport:Incoming forward agent connection
DEBUG:paramiko.transport:[chan 2] Max packet in: 32768 bytes
DEBUG:paramiko.transport:[chan 2] Max packet out: 16384 bytes
DEBUG:paramiko.transport:Secsh channel 2 (auth-agent@openssh.com) opened.
Exception in thread Thread-3:
Traceback (most recent call last):
File "/usr/lib64/python2.7/threading.py", line 812, in __bootstrap_inner
self.run()
File "/usr/lib/python2.7/site-packages/paramiko/agent.py", line 122, in run
raise AuthenticationException("Unable to connect to SSH agent")
AuthenticationException: Unable to connect to SSH agent
On final_server login log (looks fine =/ !):
2019-01-09T19:50:12.417066+00:00 final_server sshd[7968]: Accepted
publickey for mylogin from IP port 42360 ssh2
2019-01-09T19:50:12.428465+00:00 final_server sshd[7968]:
pam_unix(sshd:session): session opened for user mylogin by (uid=0)
2019-01-09T19:50:12.521360+00:00 final_server sshd[7968]:
pam_unix(sshd:session): session closed for user mylogin
Full code anonymized ( adapted from DSA key forwarding using Paramiko?):
#!/usr/bin/python2.7
# -*- coding: utf-8 -*-
import paramiko
class SSHSession:
def __init__(self, server_address, user='mylogin', port=22):
self.connected = False
self.server_address = server_address
self.user = user
self.port = port
def connect(self):
try:
k = paramiko.RSAKey.from_private_key_file("/mypath/mykey.ppk",password='blabla')
self.ssh_client = paramiko.SSHClient()
paramiko.common.logging.basicConfig(level=paramiko.common.DEBUG)
self.ssh_client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
self.ssh_client.connect(self.server_address, username=self.user, pkey=k)
self.transport = self.ssh_client.get_transport()
self.agent_channel = self.transport.open_session()
self.agent_handler = paramiko.agent.AgentRequestHandler(self.agent_channel)
self.channel= self.ssh_client.invoke_shell()
except:
self.connected = False
else:
self.connected = True
return self.connected
def exec_command(self, command, newline='\r'):
if not self.connected:
raise Exception('Not connected')
else:
timeout = 31536000 # 365 days in seconds
self.channel.settimeout(timeout)
line_buffer = ''
channel_buffer = ''
end_string = 'CLIENT_EXPECT_CMD_OK'
print('[SEND ] >>', command)
self.channel.send(command + ' ; echo ' + end_string + newline)
while True:
channel_buffer = self.channel.recv(1).decode('UTF-8')
if len(channel_buffer) == 0:
raise Exception('connection lost with server: ' + self.server_address)
break
channel_buffer = channel_buffer.replace('\r', '')
if channel_buffer != '\n':
line_buffer += channel_buffer
else:
if line_buffer == end_string:
break
print('[RECEIVE] <<', line_buffer)
line_buffer = ''
def disconnect(self):
self.ssh_client.close()
def __enter__(self):
self.connect()
return self
def __exit__(self, _type, value, traceback):
self.disconnect()
if __name__ == "__main__":
server_address = 'proxy_jump_server'
ssh_user = 'mylogin'
with SSHSession(server_address) as ssh_session:
ssh_session.exec_command('hostname')
ssh_session.exec_command('ssh mylogin@final_server hostname' )
Any feedback is welcome ! Been stuck for the whole day on that point.
