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SFTP in Python? (platform independent)

Posted by: admin November 1, 2017 Leave a comment

Questions:

I’m working on a simple tool that transfers files to a hard-coded location with the password also hard-coded. I’m a python novice, but thanks to ftplib, it was easy:

import ftplib

info= ('someuser', 'password')    #hard-coded

def putfile(file, site, dir, user=(), verbose=True):
    """
    upload a file by ftp to a site/directory
    login hard-coded, binary transfer
    """
    if verbose: print 'Uploading', file
    local = open(file, 'rb')    
    remote = ftplib.FTP(site)   
    remote.login(*user)         
    remote.cwd(dir)
    remote.storbinary('STOR ' + file, local, 1024)
    remote.quit()
    local.close()
    if verbose: print 'Upload done.'

if __name__ == '__main__':
    site = 'somewhere.com'            #hard-coded
    dir = './uploads/'                #hard-coded
    import sys, getpass
    putfile(sys.argv[1], site, dir, user=info)

The problem is that I can’t find any library that supports sFTP. What’s the normal way to do something like this securely?

Edit: Thanks to the answers here, I’ve gotten it working with Paramiko and this was the syntax.

import paramiko

host = "THEHOST.com"                    #hard-coded
port = 22
transport = paramiko.Transport((host, port))

password = "THEPASSWORD"                #hard-coded
username = "THEUSERNAME"                #hard-coded
transport.connect(username = username, password = password)

sftp = paramiko.SFTPClient.from_transport(transport)

import sys
path = './THETARGETDIRECTORY/' + sys.argv[1]    #hard-coded
localpath = sys.argv[1]
sftp.put(localpath, path)

sftp.close()
transport.close()
print 'Upload done.'

Thanks again!

Answers:

Paramiko supports SFTP. I’ve used it, and I’ve used Twisted. Both have their place, but you might find it easier to start with Paramiko.

Questions:
Answers:

You should check out pysftp https://pypi.python.org/pypi/pysftp it depends on paramiko, but wraps most common use cases to just a few lines of code.

import pysftp
import sys

path = './THETARGETDIRECTORY/' + sys.argv[1]    #hard-coded
localpath = sys.argv[1]

host = "THEHOST.com"                    #hard-coded
password = "THEPASSWORD"                #hard-coded
username = "THEUSERNAME"                #hard-coded

with pysftp.Connection(host, username=username, password=password) as sftp:
    sftp.put(localpath, path)

print 'Upload done.'

Questions:
Answers:

If you want easy and simple, you might also want to look at Fabric. It’s an automated deployment tool like Ruby’s Capistrano, but simpler and ofc ourse for Python. It’s build on top of Paramiko.

You might not want to do ‘automated deployment’ but Fabric would suit your use case perfectly none the less. To show you how simple Fabric is: the fab file and command for your script would look like this (not tested, but 99% sure it will work):

fab_putfile.py:

from fabric.api import *

env.hosts = ['THEHOST.com']
env.user = 'THEUSER'
env.password = 'THEPASSWORD'

def put_file(file):
    put(file, './THETARGETDIRECTORY/') # it's copied into the target directory

Then run the file with the fab command:

fab -f fab_putfile.py put_file:file=./path/to/my/file

And you’re done! 🙂

Questions:
Answers:

I’d stick with a pure Python solution, but it’s not true that there aren’t Windows ssh options. Cygwin has one, for example, and there are plenty more.

Questions:
Answers:

Here is a sample using pysftp and a private key.

import pysftp

def upload_file(file_path):

    private_key = "~/.ssh/your-key.pem"  # can use password keyword in Connection instead
    srv = pysftp.Connection(host="your-host", username="user-name", private_key=private_key)
    srv.chdir('/var/web/public_files/media/uploads')  # change directory on remote server
    srv.put(file_path)  # To download a file, replace put with get
    srv.close()  # Close connection

pysftp is an easy to use sftp module that utilizes paramiko and pycrypto. It provides a simple interface to sftp.. Other things that you can do with pysftp which are quite useful:

data = srv.listdir()  # Get the directory and file listing in a list
srv.get(file_path)  # Download a file from remote server
srv.execute('pwd') # Execute a command on the server

More commands and about PySFTP here.

Questions:
Answers:

Twisted can help you with what you are doing, check out their documentation, there are plenty of examples. Also it is a mature product with a big developer/user community behind it.

Questions:
Answers:

You can use the pexpect module

Here is a good intro post

child = pexpect.spawn ('/usr/bin/sftp ' + [email protected] )
child.expect ('.* password:')
child.sendline (your_password)
child.expect ('sftp> ')
child.sendline ('dir')
child.expect ('sftp> ')
file_list = child.before
child.sendline ('bye')

I haven’t tested this but it should work

Questions:
Answers:

There are a bunch of answers that mention pysftp, so in the event that you want a context manager wrapper around pysftp, here is a solution that is even less code that ends up looking like the following when used

path = "sftp://user:[email protected]@test.com/path/to/file.txt"

# Read a file
with open_sftp(path) as f:
    s = f.read() 
print s

# Write to a file
with open_sftp(path, mode='w') as f:
    f.write("Some content.") 

The (fuller) example: http://www.prschmid.com/2016/09/simple-opensftp-context-manager-for.html

This context manager happens to have auto-retry logic baked in in the event you can’t connect the first time around (which surprisingly happens more often than you’d expect in a production environment…)

The context manager gist for open_sftp: https://gist.github.com/prschmid/80a19c22012e42d4d6e791c1e4eb8515

Questions:
Answers:

Paramiko is so slow. Use subprocess and shell, here is an example:

remote_file_name = "filename"
remotedir = "/remote/dir"
localpath = "/local/file/dir"
    ftp_cmd_p = """
    #!/bin/sh
    lftp -u username,password sftp://ip:port <<EOF
    cd {remotedir}
    lcd {localpath}
    get {filename}
    EOF
    """
subprocess.call(ftp_cmd_p.format(remotedir=remotedir,
                                 localpath=localpath,
                                 filename=remote_file_name 
                                 ), 
                shell=True, stdout=sys.stdout, stderr=sys.stderr)

Questions:
Answers:

With RSA Key then refer here

Snippet:

import pysftp
import paramiko
from base64 import decodebytes

keydata = b"""L+WsiL5VL51ecJi3LVjmblkAdUTU+xbmXmUArIU5+8N6ua76jO/+T""" 
key = paramiko.RSAKey(data=decodebytes(keydata)) 
cnopts = pysftp.CnOpts()
cnopts.hostkeys.add(host, 'ssh-rsa', key)


with pysftp.Connection(host=host, username=username, password=password, cnopts=cnopts) as sftp:   
  with sftp.cd(directory):
    sftp.put(file_to_sent_to_ftp)