[paramiko] migrate from Telnet to SSH

[James Bardin]

It seems the transport is being closed after the first command, probably 
by the server.
This isn't the default behavior for openSSH, but it might be on cisco 
devices.

I don't have anything cisco to connect to, so I can't offer much help on 
testing.
I would step through a couple of the demos, and see where things might 
go wrong. You may need to start a new transport for each command if you 
don't want to use an interactive shell. The server may even be closing 
the socket, in which case you'll need to reconnect entirely.

-jim

 

Chris Hallman wrote:
> Thanks! Ok, I was able to get a connection and retrieve the output of one
> command, however when I try a second command, I receive an error:
>
> program:
>
> import paramiko
>
> client = paramiko.SSHClient()
>
> # ignore host keys for the test
> client.set_missing_host_key_policy(paramiko.MissingHostKeyPolicy())
>
> client.connect('rtr3926', 22, 'cworks', '#####')
>
> (stdin, stdout, stderr) = client.exec_command('sh ver | i IOS')
> print stdout.read()
> (stdin, stdout, stderr) = client.exec_command('sh ver | i IOS')
> print stdout.read()
>
> output:
>
>> pythonw -u "sshclient.test.py"
>
>        ********************************************************
>        *                                                      *
>        *       WARNING         WARNING         WARNING        *
>        *                                                      *
>        *       IF YOU ARE NOT AUTHORIZED TO CONNECT TO        *
>        *       THIS SYSTEM, YOU MUST DISCONNECT AT ONCE.      *
>        *       UNAUTHORIZED ACCESS MAY BE PROSECUTED.         *
>        *                                                      *
>        ********************************************************
> Cisco IOS Software, 2800 Software (C2800NM-ADVSECURITYK9-M), Version 
> 12.4(8c),
> RELEASE SOFTWARE (fc3) (output from first command)
>
> Traceback (most recent call last):
>  File "sshclient.test.py", line 12, in <module>
>    (stdin, stdout, stderr) = client.exec_command('sh ver | i IOS')
>  File "c:\python25\Lib\site-packages\paramiko\client.py", line 315, in
> exec_command
>    chan.exec_command(command)
> AttributeError: 'NoneType' object has no attribute 'exec_command'
>> Exit code: 1
>
> What happened? I attached a copy one of my programs that currently uses
> Telnet so that you can get an idea of what I need to do via SSH.
>
>
> On 7/11/07, James Bardin <jbardin at bu.edu> wrote:
>>
>> Hi Chris,
>>
>> Take a look in the SSHClient class (download the most recent version
>> though).  You don't have to use an interactive shell. The SSHClient
>> class also does nice things like handle an ssh-agent if available, and
>> try to use your private keys if they're not encrypted.
>>
>> A *real* basic example:
>>
>> ############################
>> import paramiko
>>
>> client = paramiko.SSHClient()
>>
>> # ignore host keys for the test
>> client.set_missing_host_key_policy(paramiko.MissingHostKeyPolicy())
>>
>> client.connect('hostname', 22, 'username', 'Passw0rd')
>>
>> (stdin, stdout, stderr) = client.exec_command('command')
>> print stdout.read()
>> ############################
>>
>>
>> -jim
>>
>>
>> Chris Hallman wrote:
>> > I've written numerous programs that utilize Telnet to gather data,
>> > reload,
>> > or reconfigure network devices. I didn't use an interactive session
>> > like the
>> > demo SSH scripts use. I had the program issuing the commands.
>> >
>> > We're migrating from Telnet to SSH. I was hoping to find some examples
>> > where
>> > the program is interacting with the remote device but isn't using a
>> > shell.
>> > Does anyone have a program similar to what I described that I could
>> > look at?
>> >
>> >
>> >
>> > Thanks!!
>> >
>>
>>
>
> ------------------------------------------------------------------------
>
> #
> # This script obtains a directory listing, strips the extensions and telnets to the
> # device (which is the filename in the directory). Then it writes the commands in the
> # file to the device, saves config and writes it back to SYSMAN. It can be run using:
> #	python tftp.file.py
> #
> # Note: "os" is imported for future functionality.
> #
> # by:	TCDH
> # on:	10/17/05
> # release#2
> # revised:	10/18/05	TCDH - Added logic to check for offline devices and sign-on failures.
> #		11/17/05	TCDH - Added logic to control the number of threads.
> # 		01/23/06	TCDH - Moved variables and main logic to the bottom of the program.
> #		08/14/06	TCDH - Added tn.close() to properly close telnet sessions.
>
> import os, os.path, random, re, smtplib, socket, string, sys, telnetlib, threading, time
> from time import strftime
> from threading import Thread
>
>
> class SendFile(threading.Thread):
> 	def __init__(self, host):
> 		""" This instantiates the class and tries to open a connection to the device,
> 		with error checking. """
> 		Thread.__init__(self)
> 		self.host = host
> 		self.filename = filename
> 		self.filepath = filepath
> 		self.fileSize = fileSize
> 		try:
> 			self.tn = telnetlib.Telnet(self.host)
> 		except socket.error, err:
> 			if "Operation timed out" in err:
> 				configResult[self.host] = ["connection timed out"]
> 				return
> 			elif "getaddrinfo failed" in err:
> 				configResult[self.host] = ["DNS resolution failed"]
> 				return
> 			elif "No route to host" in err:
> 				configResult[self.host] = ["device unreachable"]
> 				return
> 			elif "Network is unreachable" in err:
> 				configResult[self.host] = ["device unreachable"]
> 				return
> 			else:
> 				configResult[self.host] = ["unspecified network error"]
> 				return
>
> 	def run(self):
> 		""" This function is the main function. It calls the Logon function and the
> 		TFTPfile function."""
> 		connect_status = self.Logon()
> 		if connect_status  == "authfail":
> 			configResult[self.host] = ["authentication failed"]
> 			self.tn.close()
> 			return
> 		transmit = self.TFTPFile()
> 		self.tn.write("exit\n")
> 		self.tn.close()
> 		if transmit == "failed":
> 			return
> 		for x in range(6):
> 			try:
> 				os.remove(self.filepath)
> 			except:
> 				time.sleep(5)
> 				continue
> 			return
>
> 	def Logon(self):
> 		""" This function attempts to logon to the device 3 times."""
> 		for x in range(3):
> 			self.tn.read_until("Username:", 7)
> 			self.tn.write(user + "\n")
> 			(index, match, read) = self.tn.expect(["Password:"], 7)
> 			self.tn.write(pswd + "\n")
> 			(index, match, read) = self.tn.expect([self.host.upper()], 7)
> 			if match:
> 				return
> 			if not match:
> 				if x == 2:
> 					return "authfail"
> 				else:
> 					continue
>
> 	def TFTPFile(self):
> 		""" This functions does all the work. It does a write to make sure the
> 		startup-confg and running-confg are similar and copies the file into running-confg
> 		with error checking. If all is well, then it does a write to save the changes and
> 		does a write net (with error checking)."""
> 		self.tn.write("wr\n")
> 		(index, match, read) = self.tn.expect(["OK"], 15)
> 		if not match:
> 			self.tn.write("yes\n")
> 		time.sleep(random.uniform(0,2))
> 		self.tn.write("copy tf runn\n")
> 		self.tn.read_until("host []?", 7)
> 		time.sleep(random.uniform(0,2))
> 		self.tn.write("192.168.136.51\n")
> 		self.tn.read_until("filename []?", 7)
> 		time.sleep(random.uniform(0,2))
> 		self.tn.write(self.filename +"\n")
> 		time.sleep(random.uniform(0,2))
> 		self.tn.read_until("[running-config]?", 7)
> 		time.sleep(random.uniform(0,2))
> 		self.tn.write("\n")
> 		time.sleep(random.uniform(0,2))
> 		x = self.tn.read_until(self.host.upper() + "#", 35)
> 		if "% Incomplete command before pipe" in x:
> 			configResult[self.host] = ["command authentication failed"]
> 			return "failed"
> 		elif "% Invalid input detected" in x:
> 			configResult[self.host] = ["invalid command syntax"]
> 			return "failed"
> 		elif "^" in x:
> 			configResult[self.host] = ["unexpected command error"]
> 			return "failed"			
> 		else:
> 			if "[OK" not in x:
> 				configResult[self.host] = ["TFTP get failed"]
> 				return "failed"
> 			elif str(self.fileSize) not in x:
> 				configResult[self.host] = ["TFTP filesize mismatch"]
> 				return "failed"
> 			else:
> 				pass
> 		self.tn.write("wr\n")
> 		self.tn.read_until(self.host.upper() + "#", 7)
> 		time.sleep(random.uniform(0,2))
> 		self.tn.write("wr net\n")
> 		self.tn.read_until("]?")
> 		time.sleep(random.uniform(0,2))
> 		self.tn.write("192.168.19.201\n")
> 		self.tn.read_until("]?")
> 		time.sleep(random.uniform(0,2))
> 		self.tn.write(self.host.lower() + "-confg\n")
> 		self.tn.read_until("[confirm]")
> 		time.sleep(random.uniform(0,2))
> 		self.tn.write("\n")
> 		(index, match, read) = self.tn.expect(["OK"], 30)
> 		if "Error opening tftp" in read:
> 			configResult[self.host] = ["write net failed"]
> 			return "failed"
>
> def count_active():
> 	""" This function returns the number of Getter threads that are alive """
> 	num_active = 0
> 	for thread in tlist:
> 		if thread.isAlive():
> 			num_active += 1
> 	return num_active
>
> def emailResult(e, s, r, m):
> 	""" This function send emails based on the input. """
> 	mailServer = smtplib.SMTP(e)
> 	mailServer.sendmail(s, r, m)
> 	mailServer.quit()
>
> configResult = {}
> emailsrvr = "mail.publix.com"
> threads = []
> dirPath = (r"c:\tftp")
> dirList = os.listdir(dirPath)
> Max_Threads = 20
> pswd = "#####"
> receiver_list = ["<chris.hallman at publix.com>"]
> sender = "<tftp.file at publix.com>"
> subject = "TFTP file results"
> text = ""
> tlist = []
> user = "cworks"
> logFile = (r"c:\logs\tftp.file.log")
> output = file(logFile, "a")
> output.write("\ntftp.file script started -" + strftime(" %H:%M:%S %x") + "\n")
> output.flush()
>
> for entry in dirList:
> 	host = entry.replace(".txt", "")
> 	filename = entry.lower()
> 	filepath = (dirPath + "\\" + filename)
> 	fileSize = str(os.path.getsize(filepath)) + " bytes"
> 	while count_active() >= Max_Threads:
> 		time.sleep(1)
> 	threads = SendFile(host)
> 	tlist.append(threads)
> 	threads.start()
>
> for thread in tlist:
> 	thread.join()
>
> configResult_sorted = sorted(configResult.items())
> for x in range(len(configResult_sorted)):
> 	text = text + str(configResult_sorted[x]) + "\n\r"
> text = text.replace("[", "").replace("]", "").replace("'", "").replace("(", "").replace(")", "").replace(",", "\t")
> output.write(text)
> output.flush()
>
> for receiver in receiver_list:
> 	header = "From: %s\r\nTo: %s\r\nSubject: %s\r\n\r\n" % (sender, receiver, subject)
> 	heading = "If this email is blank, then no failures occurred.\r\n\r\n"
> 	msg = header + heading + text
> 	emailResult(emailsrvr, sender, receiver, msg)
>
> output.write("\ntftp.file script completed -" + strftime(" %H:%M:%S %x") + "\n")
> output.flush()
> output.close()
>