Python Paramiko reports "EOF in transport thread" after logging in and closes ssh session

Question

I'm writing a script that should log into some network devices, execute commands and collect some files. Now I seem to be stuck with an issue that just after logging in and without executing anything or doing anything on the remote host, the ssh connection gets closed. After checking the debug messages from paramiko I see following message: "EOF in transport thread". I have tried it with password and PSK, from Windows and from Linux, also tried Spur, always get the same EOF. So far I have this issue only with Session Border Controllers with different software versions but can't debug anything on them, while running debug can't even see the SSH connection happening, probably it's happening somewhere in the background where I have no access.

Here the debug messages:

Trying to connect to 10.xxx.xxx.xxx (1/3)
starting thread (client mode): 0x57f09d0L
Local version/idstring: SSH-2.0-paramiko_2.1.1
Remote version/idstring: SSH-2.0-Mocana SSH
Connected (version 2.0, client Mocana)
kex algos:[u'diffie-hellman-group14-sha1', u'diffie-hellman-group1-sha1'] server key:[u'ssh-dss', u'ssh-rsa'] client encrypt:[u'aes256-cbc', u'rijndael256-cbc', u'aes192-cbc', u'rijndael192-cbc', u'aes128-cbc', u'rijndael128-cbc', u'3des-cbc', u'arcfour'] server encrypt:[u'aes256-cbc', u'rijndael256-cbc', u'aes192-cbc', u'rijndael192-cbc', u'aes128-cbc', u'rijndael128-cbc', u'3des-cbc', u'arcfour'] client mac:[u'hmac-sha1', u'hmac-sha1-96', u'hmac-md5', u'hmac-md5-96'] server mac:[u'hmac-sha1', u'hmac-sha1-96', u'hmac-md5', u'hmac-md5-96'] client compress:[u'none'] server compress:[u'none'] client lang:[u''] server lang:[u''] kex follows?False
Kex agreed: diffie-hellman-group1-sha1
Cipher agreed: aes128-cbc
MAC agreed: hmac-md5
Compression agreed: none
kex engine KexGroup1 specified hash_algo <built-in function openssl_sha1>
Switch to new keys ...
Adding ssh-rsa host key for 10.xxx.xxx.xxx: e3afa50cb2380e75cbbd535fb6ceb3fc
userauth is OK
Authentication (password) successful!
Connected to 10.xxx.xxx.xxx
EOF in transport thread

And here is the script, nothing there, just the login:

import paramiko
import time
import sys
import logging

logging.getLogger("paramiko").setLevel(logging.DEBUG) 


host = '10.xxx.xxx.xxx'
username = 'username'
password = 'password'
i = 1

while True:
    print ("Trying to connect to %s (%i/3)" % (host, i))

    try:
        paramiko.common.logging.basicConfig(level=paramiko.common.DEBUG)
        ssh = paramiko.SSHClient()
        ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
        ssh.connect(host,username=username,password=password)
        print "Connected to %s" % host
        break
    except paramiko.AuthenticationException:
        print "Authentication failed when connecting to %s" % host
        sys.exit(1)
    except:
        print "Could not SSH to %s, waiting for it to start" % host
        i += 1
        time.sleep(2)

    # If we could not connect within time limit
    if i == 3:
        print "Could not connect to %s. Giving up" % host
        sys.exit(1)

Any idea how this could be further investigated or what could be the root cause?

Answer 1

It looks like this was caused by the fact that the devices I'm trying to access only allow interactive shells, so I had to use paramiko's invoke_shell, for me it basically worked like this:

ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(host,username=username,password=password)
channel = ssh.invoke_shell()
channel.send('uname -a\n' )

buff=''
while not buff.endswith('# '): # Checking for returned prompt
    resp = channel.recv(4096)
    buff += resp
print resp

Answer 2

After the break statement, the script terminates... So add the work you need to do.