Jun. 17, 2013

Python Secure FTP module

Overview

In the previous post we covered the ftplib module in Python, which you can read
more about here. In this post we will cover the pysftp module.

SFTP (Secure File Transfer Protocol) is used for securely exchanging files
over the Internet. 

What is it?

pysftp is an easy to use sftp module that utilizes paramiko and pycrypto. 

It provides a simple interface to sftp.

Some of the features are:
Gracefully handles both RSA and DSS private key files automatically

Supports encrypted private key files.

Logging can now be enabled/disabled

Why should I use it?

When you want to securely exchange files over the Internet. 

How do I install it?

pysftp is listed on PyPi and can be installed using pip.
# Search for pysftp
pip search pysftp

pysftp                    # - A friendly face on SFTP

#Install pysftp
pip install pysftp

How do I use it?

Using pysftp is easy and we will show some examples on how you can use it

List a remote directory

To connect to our FTP server, we first have to import the pysftp module and
specify (if applicable) server, username and password credentials.

After running this program, you should see all the files and directories of
the current directory of your FTP server.
import pysftp

srv = pysftp.Connection(host="your_FTP_server", username="your_username",
password="your_password")

# Get the directory and file listing
data = srv.listdir()

# Closes the connection
srv.close()

# Prints out the directories and files, line by line
for i in data:
    print i

Connection parameters

Arguments that are not given are guessed from the environment.
Parameter	Description
host	 	The Hostname of the remote machine.
username	Your username at the remote machine.(None)
private_key	Your private key file.(None)
password	Your password at the remote machine.(None)
port	 	The SSH port of the remote machine.(22)
private_key_pass password to use if your private_key is encrypted(None)
log	 	log connection/handshake details (False)

Download / Upload a remote file

As in the previous example we first import the pysftp module and specify
(if applicable) server, username and password credentials. 

We also import the sys module, since we want the user to specify the file to
download / upload. 
import pysftp
import sys

# Defines the name of the file for download / upload
remote_file = sys.argv[1]

srv = pysftp.Connection(host="your_FTP_server", username="your_username",
password="your_password")

# Download the file from the remote server
srv.get(remote_file)

# To upload the file, simple replace get with put. 
srv.put(remote_file)

# Closes the connection
srv.close()

What's the next step?

Play around with the script, change things and see what happens. 

Try add error handling to it. What happens if no argument is passed?

Add some interaction to the program by prompting for input. 
Sources
https://code.google.com/p/pysftp/
http://en.wikipedia.org/wiki/SSH_File_Transfer_Protocol

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