Sending a password over SSH or SCP with subprocess.Popen
Sending a password over SSH or SCP with subprocess.Popen
I’m trying to run an scp (secure copy) command using subprocess.Popen . The login requires that I send a password:
from subprocess import Popen, PIPE proc = Popen(['scp', "[email protected]:/foo/bar/somefile.txt", "."], stdin = PIPE) proc.stdin.write(b'mypassword') proc.stdin.flush() This immediately returns an error:
[email protected]'s password: Permission denied, please try again. I’m certain the password is correct. I easily verify it by manually invoking scp on the shell. So why doesn’t this work?
Note, there are many similar questions to this, asking about subprocess.Popen and sending a password for automated SSH or FTP login:
The answer(s) to these questions don’t work and/or don’t apply because I am using Python 3.
Solution – 1
The second answer you linked suggests you use Pexpect (which is usually the right way to go about interacting with command line programs that expect input).
Solution – 2
Here’s a function to ssh with a password using pexpect :
import pexpect import tempfile def ssh(host, cmd, user, password, timeout=30, bg_run=False): """SSH'es to a host using the supplied credentials and executes a command. Throws an exception if the command doesn't return 0. bgrun: run command in the background""" fname = tempfile.mktemp() fout = open(fname, 'w') options = '-q -oStrictHostKeyChecking=no -oUserKnownHostsFile=/dev/null -oPubkeyAuthentication=no' if bg_run: options += ' -f' ssh_cmd = 'ssh %s@%s %s "%s"' % (user, host, options, cmd) child = pexpect.spawn(ssh_cmd, timeout=timeout) #spawnu for Python 3 child.expect(['[pP]assword: ']) child.sendline(password) child.logfile = fout child.expect(pexpect.EOF) child.close() fout.close() fin = open(fname, 'r') stdout = fin.read() fin.close() if 0 != child.exitstatus: raise Exception(stdout) return stdout Something similar should be possible using scp .
Solution – 3
Pexpect has a library for exactly this: pxssh
import pxssh import getpass try: s = pxssh.pxssh() hostname = raw_input('hostname: ') username = raw_input('username: ') password = getpass.getpass('password: ') s.login(hostname, username, password) s.sendline('uptime') # run a command s.prompt() # match the prompt print(s.before) # print everything before the prompt. s.logout() except pxssh.ExceptionPxssh as e: print("pxssh failed on login.") print(e) Solution – 4
I guess some applications interact with the user using stdin and some applications interact using terminal. In this case when we write the password using PIPE we are writing to stdin. But SCP application reads the password from terminal. As subprocess cannot interact with user using terminal but can only interact using stdin we cannot use the subprocess module and we must use pexpect for copying the file using scp.
Feel free for corrections.
Solution – 5
The OpenSSH scp utility invokes the ssh program to make the SSH connection to the remote host, and the ssh process handles authentication. The ssh utility doesn’t accept a password on the command line or on its standard input. I believe this is a deliberate decision on the part of the OpenSSH developers, because they feel that people should be using more secure mechanisms like key-based authentication. Any solution for invoking ssh is going to follow one of these approaches:
- Use an SSH key for authentication, instead of a password.
- Use sshpass, expect, or a similar tool to automate responding to the password prompt.
- Use (abuse) the SSH_ASKPASS feature to get ssh to get the password by invoking another command, described here or here, or in some of the answers here.
- Get the SSH server administrator to enable host-based authentication and use that. Note that host-based authentication is only suitable for certain network environments. See additional notes here and here.
- Write your own ssh client using perl, python, java, or your favorite language. There are ssh client libraries available for most modern programming languages, and you’d have full control over how the client gets the password.
- Download the ssh source code and build a modified version of ssh that works the way you want.
- Use a different ssh client. There are other ssh clients available, both free and commercial. One of them might suit your needs better than the OpenSSH client.
In this particular case, given that you’re already invoking scp from a python script, it seems that one of these would be the most reasonable approach:
- Use pexpect, the python expect module, to invoke scp and feed the password to it.
- Use paramiko, the python ssh implementation, to do this ssh task instead of invoking an outside program.
Solution – 6
Here is my scp function based on pexpect. It can handle wildcards (i.e. multiple file transfer), in addition to the password.
To handle multiple file transfer (i.e. wildcards), we need to issue a command via a shell. Refer to pexpect FAQ.
import pexpect def scp(src,user2,host2,tgt,pwd,opts='',timeout=30): ''' Performs the scp command. Transfers file(s) from local host to remote host ''' cmd = f'''/bin/bash -c "scp @:"''' print("Executing the following cmd:",cmd,sep='n') tmpFl = '/tmp/scp.log' fp = open(tmpFl,'wb') childP = pexpect.spawn(cmd,timeout=timeout) try: childP.sendline(cmd) childP.expect([f"@'s password:"]) childP.sendline(pwd) childP.logfile = fp childP.expect(pexpect.EOF) childP.close() fp.close() fp = open(tmpFl,'r') stdout = fp.read() fp.close() if childP.exitstatus != 0: raise Exception(stdout) except KeyboardInterrupt: childP.close() fp.close() return print(stdout) Solution – 7
This is a rewrite I did from the code posted by @Kobayashi and @sjbx but for the purposes of doing scp requests, so credit to those two.
def scp(host, user, password, from_dir, to_dir, timeout=300, recursive=False): fname = tempfile.mktemp() fout = open(fname, 'w') scp_cmd = 'scp' if recursive: scp_cmd += ' -r' scp_cmd += f' @: ' child = pexpect.spawnu(scp_cmd, timeout=timeout) child.expect(['[pP]assword: ']) child.sendline(str(password)) child.logfile = fout child.expect(pexpect.EOF) child.close() fout.close() fin = open(fname, 'r') stdout = fin.read() fin.close() if 0 != child.exitstatus: raise Exception(stdout) return stdout SCP in python by using password
I also tried other ways that people suggest and seems that none of them works. Does anybody have a suggestion that really works? p.s. I have to use password not the key if your answer depends on that.
You’ve copied an example from a question, and not the answer. Take another look at the post you based your example on.
2 Answers 2
The scp.py GitHub page has the following example that uses itself with the paramiko library for handling SSL:
from paramiko import SSHClient from scp import SCPClient ssh = SSHClient() ssh.load_system_host_keys() ssh.connect(hostname='ip', port = 'port', username='username', password='password', pkey='load_key_if_relevant') # SCPCLient takes a paramiko transport as its only argument scp = SCPClient(ssh.get_transport()) scp.put('file_path_on_local_machine', 'file_path_on_remote_machine') scp.get('file_path_on_remote_machine', 'file_path_on_local_machine') scp.close() So the actual type you want it is scp.SCPClient .
This is working as Jan 2019:
Install required Python packages:
pip install scp pip install paramiko Include library in the code:
from paramiko import SSHClient from scp import SCPClient # SSH/SCP Directory Recursively def ssh_scp_files(ssh_host, ssh_user, ssh_password, ssh_port, source_volume, destination_volume): logging.info("In ssh_scp_files()method, to copy the files to the server") ssh = SSHClient() ssh.load_system_host_keys() ssh.connect(ssh_host, username=ssh_user, password=ssh_password, look_for_keys=False) with SCPClient(ssh.get_transport()) as scp: scp.put(source_volume, recursive=True, remote_path=destination_volume) Now call it anywhere you want in the code:
ssh_scp_files(ssh_host, ssh_user, ssh_password, ssh_port, source_volume, destination_volume)
If all above implemented correctly, you will see the the successful messages in the console/logs like this: