Develop Reference

python subprocess and wget ask-password

I'm running the following python code:
import subprocess
host = "ftp://localhost:2121"
p = subprocess.Popen(
['wget', '-P', '/tmp/output', '-N', '-r', '-l', 'inf', '--ask-password', '--user', 'anonymous', host],
stdin=subprocess.PIPE)
p.communicate("password\n")
if p.returncode != 0:
raise RuntimeError('wget command failed with return code: %d' % p.returncode)
It appears that password is not sent to wget since the script will hang showing:
Password for user ‘anonymous’:
Pressing enter causes wget to exit with an error code of '1'
Pressing keys then pressing enter causes wget to begin downloading as expected.
The ftp server is local and has anonymous access enabled. Python version is 2.7.8

Try adding this before p.communicate:
p.stdin.write('password\n')
p.stdin.flush()
stdout, stderr = p.communicate()

It appears that wget reads the password from the tty rather than stdin. These are not the same!
The sudo command allows you to switch to stdin
also
Certain programs read directly from /dev/tty, not stdin. "passwd" for example. So it's difficult to script them. Expect is one way around that - it can trick the program by providing input to them:
One way to achieve reading the password from stdin is to construct a url containing the user & pass:
ftp://user:password#ftp.server.com/link.txt
And using the -l - switch to pass the link into wget via stdin. This is suggested here

How can I use Python to automate setting a password using the Unix pass command line program

I'm trying to automate setting new passwords using the Unix pass program.
I understand that there is a Python library, pexpect, that might help, but I would like to avoid using third-party libraries.
When using a terminal, the flow looks like this:
$ pass insert --force gmail
>> Enter password for gmail: <type in password using masked prompt>
>> Retype password for gmail: <reenter password>
What I would like my function to do:
Run the command pass insert --force {entry_name}
Capture the output (and echo it for testing)
Check output for the presence of 'password for gmail', and if True
write '{password}\n' to stdin
write '{password}\n' to stdin again
Echo any errors or messages for testing
Issues:
I'm stuck on step 2. The subprocess either hangs indefinitely, times out with an error, or produces no output.
Attempts:
I've tried configurations of Popen(), using both stdin.write() and communicate().
I've set wait() calls at various points.
I've tried both the shell=True and shell=False options (prefer False for security reasons)
Code:
def set_pass_password(entry_name, password):
from subprocess import Popen, PIPE
command = ['pass', 'insert', '--force', entry_name]
sub = Popen(command, stdin=PIPE, stdout=PIPE, stderr=PIPE, universal_newlines=True)
# At this point I assume that the command has run, and that there is an "Enter password..." message
message = sub.stdout.read() # also tried readline() and readlines()
print(message) # never happens, because process hangs on stdout.read()
if 'password for {}'.format(entry_name) in message:
err, msg = sub.communicate(input='{p}\n{p}\n'.format(p=password))
print('errors: {}\nmessage: {}'.format(err, msg))

Edit: the original answer was about passwd, which is what's used to set passwords. I noticed late that you use pass, which is a keystore (doesn't actually change the Unix password). The pass program works differently and will not print a prompt if stdin is not a tty. Therefore the following very simple program works:
def set_pass_password(entry_name, password):
from subprocess import Popen, PIPE
command = ['pass', 'insert', '--force', entry_name]
sub = Popen(command, bufsize=0, stdin=PIPE, stdout=PIPE, stderr=PIPE)
err, msg = sub.communicate(input='{p}\n{p}\n'.format(p=password))
print('errors: {}\nmessage: {}'.format(err, msg))
if __name__ == "__main__":
set_pass_password("ttt", "ttt123asdqwe")
(you will see that both stderr and stdout are empty, if the command succeeded).
For the passwd command:
FYI: the passwd command outputs the prompt to stderr, not stdout.
NOTE: rather than sending the password twice in the same 'write', you might need to wait for the second prompt before sending the password again.
For this simple case, code similar to yours should work, but in general you should use select on all the pipes and send/receive data when the other side is ready, so you don't get deadlocks.

Connect to gce instance and run command

I have a simple request. I want to connect to an already existing google compute engine instance, run a command, and close the connection.
I have used the great sample code here for instance creation and deletion.
Additionally, I have a startup script running which works perfectly.
Now I am reading this article to use paramiko to connect to my instance. This may or may not be the best thing to do, so please correct me if I am going down the wrong path.
I have the following sample code:
import paramiko
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(
paramiko.AutoAddPolicy())
ssh.connect('35.***.***.**',username='user',password='pass')
stdin, stdout, stderr = ssh.exec_command("sudo su -")
stdin, stdout, stderr = ssh.exec_command("ls -l")
stdout.readlines()
Now - I am not sure which username or password I am supposed to use.
When I run this code, I do not get the list of files and directories in my root as I want, but I do get a list of files and directories in the default user account's home - so it is connecting.
My goal is to connect to a gce instance, run a command, and that is it! For some reason it is trickier than I anticipated. Am I doing something wrong here?

If you are facing a similar use case you can explore gcloud ssh. It worked for me, but I cannot comment if this is best practice or not.
My solution here was something like the following:
import subprocess
def check_for_completion(instance_name = ""):
cmd = "gcloud compute ssh %s --zone=us-east1-b --command=\"sudo -S -i -u root -p '' ls /root/temp/ \""%(instance_name)
try:
res = subprocess.check_output(cmd, shell=True)
items = str(res).split('\n')
return {'response':items,'complete':False}
except:
return {'response':None,'complete':True}

Subprocess on remote server

I am using this code for executing command on remote server.
import subprocess
import sys
COMMAND="ls"
ssh = subprocess.Popen(["ssh", "%s" % HOST, COMMAND],
shell=False,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
result = ssh.stdout.readlines()
if result == []:
error = ssh.stderr.readlines()
print >>sys.stderr, "ERROR: %s" % error
else:
print result
When I try to execute this script, I get prompt for password. Is there any way I could avoid it, for example, can I enter password in script somehow? Also, password should be encrypted somehow so that people who have access to the script cannot see it.

Why make it so complicated? Here's what I suggest:
1) Create a ssh config section in your ~/.ssh/config file:
Host myserver
HostName 50.50.50.12 (fill in with your server's ip)
Port xxxx (optional)
User me (your username for server)
2) If you have generated your ssh keypair do it now (with ssh-keygen). Then upload with:
$ ssh-copy-id myserver
3) Now you can use subprocess with ssh. For example, to capture output, I call:
result = subprocess.check_output(['ssh', 'myserver', 'cat', 'somefile'])
Simple, robust, and the only time a password is needed is when you copy the public key to the server.
BTW, you code will probably work just fine as well using these steps.

One way is to create a public key, put it on the server, and do ssh -i /path/to/pub/key user#host or use paramiko like this:
import paramiko
import getpass
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
p = getpass.getpass()
ssh.connect('hostname', username='user', password=p)
stdin, stdout, stderr = ssh.exec_command('ls')
print stdout.readlines()
ssh.close()

You should use pexpect or paramiko to connect to remote machine,then spawn a child ,and then run subprocess to achieve what you want.

Here's what I did when encountering this issue before:
Set up your ssh keys for access to the server.
Set up an alias for the server you're accessing. Below I'll call it remote_server.
Put the following two lines at the end of ~/.bash_profile.
eval $(ssh-agent -s)
ssh-add
Now every time you start your shell, you will be prompted for a passphrase. By entering it, you will authenticate your ssh keys and put them 'in hand' at the start of your bash session. For the remainder of your session you will be able to run commands like
ssh remote_server ls
without being prompted for a passphrase. Here ls will run on the remote server and return the results to you. Likewise your python script should run without password prompt interruption if you execute it from the shell.
You'll also be able to ssh to the server just by typing ssh remote_server without having to enter your username or password every time.
The upside to doing it this way is that you should be doing this anyway to avoid password annoyances and remembering funky server names :) Also you don't have to worry about having passwords saved anywhere in your script. The only potential downside is that if you want to share the python script with others, they'll have to do this configuring as well (which they should anyway).

You don't really need something like pexpect to handle this. SSH keys already provide a very good and secure solution to this sort of issue.
The simplest way to get the results you want would probably be to generate an ssh key and place it in the .ssh folder of your device. I believe github has a pretty good guide to doing that, if you look into it. Once you set up the keys correctly on both systems, you won't actually have to add a single line to your code. When you don't specify a password it will automatically use the key to authenticate you.

While subprocess.Popen might work for wrapping ssh access, this is not the preferred way to do so.
I recommend using paramiko.
import paramiko
ssh_client = paramiko.SSHClient()
ssh_client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh_client.connect(server, username=user,password=password)
...
ssh_client.close()
And If you want to simulate a terminal, as if a user was typing:
chan=ssh_client.invoke_shell()
def exec_cmd(cmd):
"""Gets ssh command(s), execute them, and returns the output"""
prompt='bash $' # the command line prompt in the ssh terminal
buff=''
chan.send(str(cmd)+'\n')
while not chan.recv_ready():
time.sleep(1)
while not buff.endswith(prompt):
buff+=ssh_client.chan.recv(1024)
return buff[:len(prompt)]
Example usage: exec_cmd('pwd')
If you don't know the prompt in advance, you can set it with:
chan.send('PS1="python-ssh:"\n')

You could use following.
import subprocess
import sys
COMMAND="ls"
ssh = subprocess.Popen("powershell putty.exe user#HOST -pw "password", stdout=PIPE, stdin=PIPE, stderr=STDOUT)
result = ssh.stdout.readlines()
if result == []:
error = ssh.stderr.readlines()
print >>sys.stderr, "ERROR: %s" % error
else:
print result

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', "user#10.0.1.12:/foo/bar/somefile.txt", "."], stdin = PIPE)
proc.stdin.write(b'mypassword')
proc.stdin.flush()
This immediately returns an error:
user#10.0.1.12'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:
How can I set a users password in linux from a python script?
Use subprocess to send a password
The answer(s) to these questions don't work and/or don't apply because I am using Python 3.

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.

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.

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).

Pexpect has a library for exactly this: pxssh
http://pexpect.readthedocs.org/en/stable/api/pxssh.html
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)

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.

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 {opts} {src} {user2}#{host2}:{tgt}"'''
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"{user2}#{host2}'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)
It can be used this way:
params = {
'src': '/home/src/*.txt',
'user2': 'userName',
'host2': '192.168.1.300',
'tgt': '/home/userName/',
'pwd': myPwd(),
'opts': '',
}
scp(**params)

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' {user}#{host}:{from_dir} {to_dir}'
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