I'm looking for advice on how to implement password-based encryption and decryption within a PowerShell script. I have a utility that makes API calls that require a token, but currently, this token is stored in plaintext within the script. Since I need to share this script with potentially untrusted users, I'd like to encrypt the token. My goal is for the user running the script to enter a password so that they can decrypt and access the token. I need a solution that works solely in PowerShell version 5.1. I feel like this should be straightforward, but I couldn't find a way to do it online. Are there better methods to obfuscate the token or handle authorization for the script? Any help would be greatly appreciated!
4 Answers
Before you proceed, what's the primary goal of encrypting the token? Is it to prevent untrusted users from misusing it? Keep in mind, any encrypted information given to users can be potentially decrypted if they have access to the script. It's all about how well you can secure it. You could consider these options: 1) Limit the token's permissions to the minimum necessary; even with it in plaintext, it can be safe this way. 2) Create individual tokens for each user, allowing for more oversight and accountability. 3) If you really can’t trust the users, consider setting up a job runner service that interacts with your API instead; this way, the token remains secure on your server.
I went through a similar challenge a while back. What worked for me was using the .NET AesCryptoServiceProvider to handle string encryption and decryption with a 256-bit key. I derived the key from a password using the PBKDF2 method (Security.Cryptography.Rfc2898DeriveBytes). If you're interested, you can check out my implementation on GitHub: [ProtectStrings](https://github.com/grey0ut/ProtectStrings). You could condense what I've done into three functions: one for converting a password into a 256-bit key, one for encrypting text, and another for decrypting it!
I use DPAPI to manage this type of situation. You can securely transfer the password to users, who can then update their local DPAPI files. Just remember that DPAPI is user-specific, which might not fit your scenario if multiple users manage the same script.
But keep in mind, DPAPI might not be the best fit for your needs in this case!
You can use SecureString cmdlets which accept an AES key. Here's a quick way to do it: First, generate a key and store it, then use it to encrypt your token. After encrypting your token, save both the key and encrypted data in separate PS1 files. Just remember to exclude them from any version control with a .gitignore. Dot-sourcing is great for managing these files efficiently. While it's not as secure as using a dedicated vault service, it can work in certain scenarios.
Just ensure that you securely transfer the password so they update their DPAPI correctly.