I'm writing a script with Paramiko and I would like to handle network error if it happens during exec_command.
With the sample code below, if there is a network error from the beginning, it works well. The function is trying to execute itself until the connection is established.
But if the error happens in the middle of the function, it doesn't raise an exception and returns an empty string instead.
def execute(command, connection):
try:
client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
client.connect(connection.host, username=connection.username, password=connection.password)
log("Command: "+command, YELLOW)
dummy_stdin, stdout, stderr = client.exec_command("source ~/.bash_profile > \
/dev/null; "+command)
err = stderr.read()
res = stdout.read()
client.close()
if err.strip() == "OK":
log(err.strip(), BLANK)
return err.strip()
elif err != '':
log(err.strip(), RED)
sys.exit()
else:
log(res.strip(), BLANK)
return res.strip()
except:
log("Network failure. Trying again ...", RED)
return execute(command, connection)
Thanks for your help!
Test for an active connection after you finish reading a command output:
client.get_transport().is_active()
Related
I've been trying to run commands on an Overture Box using paramiko to establish the SSH connection.
My script does connect properly to the box, no issues are seen, the problem comes when the script runs the exec_command(cmd) method:
Traceback (most recent call last):
File "test.py", line 39, in <module>
stdin, stdout, stderr = ssh.exec_command("version")
File "/opt/csw/lib/python2.7/site-packages/paramiko/client.py", line 345, in exec_command
chan.exec_command(command)
File "/opt/csw/lib/python2.7/site-packages/paramiko/channel.py", line 60, in _check
return func(self, *args, **kwds)
File "/opt/csw/lib/python2.7/site-packages/paramiko/channel.py", line 229, in exec_command
self._wait_for_event()
File "/opt/csw/lib/python2.7/site-packages/paramiko/channel.py", line 1086, in _wait_for_event
raise e
paramiko.ssh_exception.SSHException: Channel closed.
Same script using a Linux Box as the target host yields the proper results
The code is borrowed, I just found the snippet Googling:
import sys
import time
import select
import paramiko
host = raw_input("Hostname?: ")
i = 1
password = raw_input("Password?: ")
#
# Try to connect to the host.
# Retry a few times if it fails.
#
while True:
print "Trying to connect to %s (%i/30)" % (host, i)
try:
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(host, port=22, 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 == 30:
print "Could not connect to %s. Giving up" % host
sys.exit(1)
# Send the command (non-blocking)
stdin, stdout, stderr = ssh.exec_command("version")
# Wait for the command to terminate
while not stdout.channel.exit_status_ready():
# Only print data if there is data to read in the channel
if stdout.channel.recv_ready():
rl, wl, xl = select.select([stdout.channel], [], [], 0.0)
if len(rl) > 0:
# Print data from stdout
print stdout.channel.recv(1024),
#
# Disconnect from the host
#
print "Command done, closing SSH connection"
ssh.close()
I found other questions where it's said that the issue might be related to the SFTP settings in the host, but I'm able to do:
sftp username#hostname
I've Googled for a while but I can't find anything helpful so far.
Thanks in advance for your help.
EDIT: Almost forgot, I know the issue is exactly at:
stdin, stdout, stderr = ssh.exec_command("version")
I've run the whole script interactively and it breaks when I run that line.
Could be that the Overture does not support the SSH exec_command request.
I have needed to use transport.open_session(), and session.get_pty() and session.invoke_shell() to setup an interactive shell session, then use session.send() and session.recv() to write/read to the shell session for Cisco switches and other network appliances, when exec_command() is not available.
here is a workaround for this,
get a transport for your connection.
open a session.
then exec_command(command) and thenrecv()`, no need for sleep.
client.connect("host", port=22, username="user",password= "pass",look_for_keys=False, allow_agent=False)
transport=client.get_transport()
channel = t.open_session()
channel.exec_command(command)
out = channel.recv(-1)
print(out.decode())
Lately, I've developed an interest in penetration testing. I decided to try and learn how to write some scripts before investing in a full blown course. Currently I'm working my way through the book Black Hat Python book by Justin Seitz.
I'm in the section on SSH using Paramiko and two of the scripts have me stumped. They both run without errors but nothing gets shown on screen. In Windows and Linux the terminal (or DOS prompt) just returns immediately to the prompt. I have gone over the scripts several times and can't find the issue. The code for both scripts is shown in full below.
Script #1 bh_sshserver.py (The purpose of this script is to create an ssh server)
import socket
import paramiko
import threading
import sys
class Server (paramiko.ServerInterface):
def _init_(self):
self.event = threading.Event()
def check_channel_request(self, kind, chanid):
if kind == 'session':
return
paramiko.OPEN_SUCCEEDED
return
paramiko.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED
def check_auth_password(self, username, password):
if (username == 'root') and (password == '12345'):
return paramiko.AUTH_SUCCESSFUL
return paramiko.AUTH_FAILED
server = sys.argv[1]
ssh_port = sys.argv[2]
try:
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind((server, ssh_port))
sock.listen(100)
print '[+] Listening for connection...'
client, addr = sock.accept()
except Exception, e:
print ' [-] Listen Failed: ' + str(e)
sys.exit(1)
print '[+] Got a connection'
try:
bhSession = paramiko.Transport(client)
bhSession.add_server_key(host_key)
server = Server()
try:
bhSession.start_server(server=server)
except paramiko.SSHException, x:
print '[-] SSH Negotiation Failed'
chan = bhSession.accept(20)
print '[+] Authenticated!'
print chan.recv(1024)
chan.send ('Welcome to bh_ssh')
while True:
try:
command= raw_input("Enter command: ").strip('\n')
if command != 'exit':
chan.send(command)
print chan.recv(1024) + '\n'
else:
chan.send('exit')
print 'exiting'
bhSession.close()
raise Exception ('exit')
except KeyboardInterrupt:
bhSession.close()
except Exception, e:
print '[-] Caught exception: ' + str(e)
try:
bhSession.close()
except:
pass
sys.exit(1)
Script #2 bh_sshRcmd.py (The purpose of this script is to create a command receiver for the ssh server to connect to)
import threading
import paramiko
import subprocess
def ssh_command(ip, user, passwd, command):
client = paramiko.SSHClient()
#client.load host keys ('/home/root/.ssh/known_hosts')
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
client.connect(ip, username=user, password=passwd)
ssh_session = client.get_transport().open_session()
if ssh_session.active:
ssh_session.exec_command(command)
print ssh_session.recv(1024)
# Read the banner
while True:
command = ssh_session.recv(1024)
# Get Command from SSH Server
try:
cmd_output = subprocess.check_output(command, shell=True)
ssh_session.send(cmd_output)
except Exception, e:
ssh_session.send(str(e))
client.close()
return
ssh_command('192.168.1.26', 'Admin', '12345', 'ClientConnected')
Both of these scripts were written in Windows and so do not need the shebang statement (ie #!/usr/bin/python) at the top. I copied them over to a Linux VM and added that statement, plus made them executable using chmod +x. Still, nothing shows on screen when the scripts run. The IP addresses are from a VMware virtual network which has never given me problems before.
It is likely that there is an error connecting to your server. Try adding more print statements to cover the conditionals like so:
import threading
import paramiko
import subprocess
def ssh_command(ip, user, passwd, command):
print 'running ssh_command with ip: {ip} user: {user} passwd: {passwd}, command: {command}'.format(ip=ip,user=user,passwd=passwd,command=command)
client = paramiko.SSHClient()
#client.load host keys ('/home/root/.ssh/known_hosts')
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
client.connect(ip, username=user, password=passwd)
ssh_session = client.get_transport().open_session()
if ssh_session.active:
print 'ssh_session is active'
ssh_session.exec_command(command)
print ssh_session.recv(1024)
# Read the banner
while True:
print 'recv-ing'
command = ssh_session.recv(1024)
# Get Command from SSH Server
try:
cmd_output = subprocess.check_output(command, shell=True)
ssh_session.send(cmd_output)
except Exception, e:
ssh_session.send(str(e))
client.close()
return
else:
print 'ssh_session is not active'
ssh_command('192.168.1.26', 'Admin', '12345', 'ClientConnected')
As for bh_sshserver.py, if you ran python bh_sshserver.py, nothing would happen. This is because you don't have any statements in the main scope. If you wanted to start the server you could add code to the bottom of the script with no indentation.
You should call your server from the terminal using command-line arguments like this:
python scriptname.py server_adress port
Change indentation on the last line of client script - it should call your function
Server adresses in the terminal and in the client function should be the same
That's pretty much all
I can provide you with these two scripts that are working for me, if you need it.
Thanks to everyone who replied. In the end I found some Paramiko demo files from github that included a sample SSH server. It turns out the script is much more complicated than the author makes it out to be. I was missing a ton of code, which is why the server was not working. As soon as I made my script a rough match to the sample it worked perfectly so did my client.
In case anyone comes across a similar problem, here is the link to the Paramiko demo files:
https://github.com/paramiko/paramiko/tree/master/demos
I am writing a script in Python for login to ssh and read the output of commands just executed. I am using paramiko package for this. I am trying to execute command "top" and get its output printed on the console. However, I am not able to do this. Please find the snippet:
import sys
import time
import select
import paramiko
host = 'localhost'
i = 1
#
# Try to connect to the host.
# Retry a few times if it fails.
#
while True:
print 'Trying to connect to %s (%i/30)' % (host, i)
try:
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(host, port=22, username='dummy', password='dummy')
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 == 30:
print "Could not connect to %s. Giving up" % host
sys.exit(1)
# Send the command (non-blocking)
stdin, stdout, stderr = ssh.exec_command("uname")
# Wait for the command to terminate
while not stdout.channel.exit_status_ready():
# Only print data if there is data to read in the channel
if stdout.channel.recv_ready():
rl, wl, xl = select.select([stdout.channel], [], [], 0.0)
if len(rl) > 0:
# Print data from stdout
print '-------------------------------'
print stdout.channel.recv(1024)
print '-------------------------------'
# Send the command (non-blocking)
stdin, stdout, stderr = ssh.exec_command("top -n 1")
# Wait for the command to terminate
while not stdout.channel.exit_status_ready():
# Only print data if there is data to read in the channel
if stdout.channel.recv_ready():
rl, wl, xl = select.select([stdout.channel], [], [], 0.0)
if len(rl) > 0:
# Print data from stdout
print '-------------------------------'
print stdout.channel.recv(1024)
print '-------------------------------'
# Send the command (non-blocking)
stdin, stdout, stderr = ssh.exec_command("uname")
# Wait for the command to terminate
while not stdout.channel.exit_status_ready():
# Only print data if there is data to read in the channel
if stdout.channel.recv_ready():
rl, wl, xl = select.select([stdout.channel], [], [], 0.0)
if len(rl) > 0:
# Print data from stdout
print '-------------------------------'
print stdout.channel.recv(1024)
print '-------------------------------'
#
# Disconnect from the host
#
print "Command done, closing SSH connection"
ssh.close()
Output:
Trying to connect to localhost (1/30)
Connected to localhost
Linux
-------------------------------
Linux
Command done, closing SSH connection
I am not sure, where I am doing wrong. I am able to get output of other linux commands though. But not sure, why top command's output is not getting printed.
as Jason S pointed out
stdin, stdout, stderr = ssh.exec_command("top -b -n1")
print stdout.read()
works just fine.
top normally uses curses for display rather than just printing. Try the -b for batch option along with the -n 1 you have (top options vary by platform, check the manpage). And in the future, try isolating the problem more - if you were to invoke top via ssh on the command line without your script you would still have an issue.
so I was working with paramiko for some basic SSH testing and I'm not getting any output into stdout. Heres my code.
import paramiko
client=paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
com="ls ~/desktop"
client.connect('MyIPAddress',MyPortNumber, username='username', password='password')
output=""
stdin, stdout, stderr = client.exec_command(com)
print "ssh succuessful. Closing connection"
client.close()
print "Connection closed"
stdout=stdout.readlines()
print stdout
print com
for line in stdout:
output=output+line
if output!="":
print output
else:
print "There was no output for this command"
So whenever I run this, the command is executed (as seen by if I do something like a cp, the file is copied), but I always get "There was no output for this command". When stdout=stdout.readlines() is printed, [] is the output. In addition, if I add a print statement into the for loop, it never gets run. Could someone help me out here? Thanks!
You have closed the connection before reading lines:
import paramiko
client=paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
com="ls ~/desktop"
client.connect('MyIPAddress',MyPortNumber, username='username', password='password')
output=""
stdin, stdout, stderr = client.exec_command(com)
print "ssh succuessful. Closing connection"
stdout=stdout.readlines()
client.close()
print "Connection closed"
print stdout
print com
for line in stdout:
output=output+line
if output!="":
print output
else:
print "There was no output for this command"
The code in the accepted answer may hang, if the command produces also an error output. See Paramiko ssh die/hang with big output.
An easy solution, if you do not mind merging stdout and stderr, is to combine them into one stream using Channel.set_combine_stderr:
stdin, stdout, stderr = client.exec_command(command)
stdout.channel.set_combine_stderr(True)
output = stdout.readlines()
If you need to read the outputs separately, see Run multiple commands in different SSH servers in parallel using Python Paramiko.
*Interactive example ：
====Part 1， this show the sh output in server ，at the end of is ">"
need some input to continual or exit ======
selilsosx045:uecontrol-CXC_173_6456-R32A01 lteue$ ./uecontrol.sh -host localhost
UE Control:Start UE control using:
UE Control:java -Dlogdir= -Duecontrol.configdir=./etc -jar ./server/server-R32A01.jar -host localhost
Loading properties from file /Users/lteue/Downloads/uecontrol-CXC_173_6456-R32A01/etc/uecontrol.properties
Starting remote CLI towards host localhost
Enter the command Q to exit the CLI, or the command HELP
to get information on available commands.
The CLI is ready for input.
uec>
===========Pyhton code with peramiko ============*
Try below method ： while not stdout.channel.exit_status_ready():
def shCommand(server_list):
server_IP = server_list[0]
username = server_list[1]
password = server_list[2]
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(server_IP,22,username, password)strong text
commandList = ['list \n']
alldata = getUeInfo(ssh,commandList)
ssh.close()
def getUeInfo(ssh,commandList):
data_buffer = ""
num_of_input = 0
stdin, stdout, stderr = ssh.exec_command('cmd')
while not stdout.channel.exit_status_ready():
solo_line = ""
if stdout.channel.recv_ready():
solo_line = stdout.channel.recv(1024) # Retrieve the first 1024 bytes
data_buffer += solo_line
if(cmp(solo_line,'uec> ') ==0 ): #len of solo should be 5 ,
if num_of_input == 0 :
data_buffer = ""
for cmd in commandList :
#print cmd
stdin.channel.send(cmd)
num_of_input += 1
if num_of_input == 1 :
stdin.channel.send('q \n')
num_of_input += 1
return data_buffer
As #jabaldonedo said you closed your SSHClient connection before reading the stdout. SSHClient can be used as a context manager. Using the SSHClient as a context manager helps prevent you from trying to access stdout and stderr after the ssh connection is closed. The resulting code in Python3 syntax looks like:
from paramiko import AutoAddPolicy, SSHClient
with SSHClient() as client:
client.set_missing_host_key_policy(AutoAddPolicy)
client.connect(
'MyIPAddress',
MyPortNumber,
username='username',
password='password'
)
com = "ls ~/desktop"
stdin, stdout, stderr = client.exec_command(com)
output = ''
for line in stdout.readlines()
output += line
if output:
print(output)
else:
print("There was no output for this command")
# Program to print the output in console/interpreter/shell in runtime without using stdout.
import paramiko
import xlrd
import time
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
loc = ('/Users/harshgow/Documents/PYTHON_WORK/labcred.xlsx')
wo = xlrd.open_workbook(loc)
sheet = wo.sheet_by_index(0)
Host = sheet.cell_value(0, 1)
Port = int(sheet.cell_value(3, 1))
User = sheet.cell_value(1, 1)
Pass = sheet.cell_value(2, 1)
def details(Host, Port, User, Pass):
time.sleep(2)
ssh.connect(Host, Port, User, Pass)
print('connected to ip ', Host)
stdin = ssh.exec_command("")
remote_conn = ssh.invoke_shell()
print("Interactive SSH session established")
output = remote_conn.recv(1000)
remote_conn.send("\n")
remote_conn.send("xstatus Cameras\n")
time.sleep(5)
output = remote_conn.recv(10000)
print(output)
details(Host, Port, User, Pass)
client = paramiko.SSHClient()
stdin, stdout, stderr = client.exec_command(command)
Is there any way to get the command return code?
It's hard to parse all stdout/stderr and know whether the command finished successfully or not.
A much easier example that doesn't involve invoking the "lower level" channel class directly (i.e. - NOT using the client.get_transport().open_session() command):
import paramiko
client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
client.connect('blahblah.com')
stdin, stdout, stderr = client.exec_command("uptime")
print stdout.channel.recv_exit_status() # status is 0
stdin, stdout, stderr = client.exec_command("oauwhduawhd")
print stdout.channel.recv_exit_status() # status is 127
SSHClient is a simple wrapper class around the more lower-level functionality in Paramiko. The API documentation lists a recv_exit_status() method on the Channel class.
A very simple demonstration script:
import paramiko
import getpass
pw = getpass.getpass()
client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.WarningPolicy())
client.connect('127.0.0.1', password=pw)
while True:
cmd = raw_input("Command to run: ")
if cmd == "":
break
chan = client.get_transport().open_session()
print "running '%s'" % cmd
chan.exec_command(cmd)
print "exit status: %s" % chan.recv_exit_status()
client.close()
Example of its execution:
$ python sshtest.py
Password:
Command to run: true
running 'true'
exit status: 0
Command to run: false
running 'false'
exit status: 1
Command to run:
$
Thanks for JanC, I added some modification for the example and tested in Python3, it really useful for me.
import paramiko
import getpass
pw = getpass.getpass()
client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.WarningPolicy())
#client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
def start():
try :
client.connect('127.0.0.1', port=22, username='ubuntu', password=pw)
return True
except Exception as e:
#client.close()
print(e)
return False
while start():
key = True
cmd = input("Command to run: ")
if cmd == "":
break
chan = client.get_transport().open_session()
print("running '%s'" % cmd)
chan.exec_command(cmd)
while key:
if chan.recv_ready():
print("recv:\n%s" % chan.recv(4096).decode('ascii'))
if chan.recv_stderr_ready():
print("error:\n%s" % chan.recv_stderr(4096).decode('ascii'))
if chan.exit_status_ready():
print("exit status: %s" % chan.recv_exit_status())
key = False
client.close()
client.close()
In my case, output buffering was the problem. Because of buffering, the outputs from the application doesn't come out non-blocking way. You can find the answer about how to print output without buffering in here: Disable output buffering. For short, just run python with -u option like this:
> python -u script.py