I need to securely store a username and password in Python, what are my options?

Question

I'm writing a small Python script which will periodically pull information from a 3rd party service using a username and password combo. I don't need to create something that is 100% bulletproof (does 100% even exist?), but I would like to involve a good measure of security so at the very least it would take a long time for someone to break it.

This script won't have a GUI and will be run periodically by cron, so entering a password each time it's run to decrypt things won't really work, and I'll have to store the username and password in either an encrypted file or encrypted in a SQLite database, which would be preferable as I'll be using SQLite anyway, and I might need to edit the password at some point. In addition, I'll probably be wrapping the whole program in an EXE, as it's exclusively for Windows at this point.

How can I securely store the username and password combo to be used periodically via a cron job?

Answer 1

The python keyring library integrates with the CryptProtectData API on Windows (along with relevant API's on Mac and Linux) which encrypts data with the user's logon credentials.

Simple usage:

import keyring

# the service is just a namespace for your app
service_id = 'IM_YOUR_APP!'

keyring.set_password(service_id, 'dustin', 'my secret password')
password = keyring.get_password(service_id, 'dustin') # retrieve password

Usage if you want to store the username on the keyring:

import keyring

MAGIC_USERNAME_KEY = 'im_the_magic_username_key'

# the service is just a namespace for your app
service_id = 'IM_YOUR_APP!'  

username = 'dustin'

# save password
keyring.set_password(service_id, username, "password")

# optionally, abuse `set_password` to save username onto keyring
# we're just using some known magic string in the username field
keyring.set_password(service_id, MAGIC_USERNAME_KEY, username)

Later to get your info from the keyring

# again, abusing `get_password` to get the username.
# after all, the keyring is just a key-value store
username = keyring.get_password(service_id, MAGIC_USERNAME_KEY)
password = keyring.get_password(service_id, username)  

Items are encrypted with the user's operating system credentials, thus other applications running in your user account would be able to access the password.

To obscure that vulnerability a bit you could encrypt/obfuscate the password in some manner before storing it on the keyring. Of course, anyone who was targeting your script would just be able to look at the source and figure out how to unencrypt/unobfuscate the password, but you'd at least prevent some application vacuuming up all passwords in the vault and getting yours as well.