usethatapp 0.3.0

For use in your UseThatApp Web Apps

usethatapp

A small utility library for UseThatApp web applications providing helpers to verify signatures and decrypt RSA/OAEP-encrypted messages.

Features

• Verify PSS/SHA256 signatures
• Decrypt OAEP/SHA256 encrypted messages
• Helpers to load RSA keys from files or PEM strings

Install

From PyPI:

pip install usethatapp

Requirements

• Python >= 3.8
• cryptography>=46.0.5,<47

Quick usage

The package exposes a simple API in usethatapp.webapps and helpers in usethatapp.encryption.

Example: verify signature and decrypt message from a requestAccessLevel() envelope

from usethatapp.webapps import get_version

# The envelope returned by requestAccessLevel() via postMessage
envelope = {
    "type": "level",
    "responseTo": "<request-id>",
    "message": {
        "contents": "0x...",
        "signature": "0xdeadbeef..."
    }
}
public_key_path = "./keys/public.pem"
private_key_path = "./keys/private.pem"

try:
    version = get_version(envelope, public_key_path, private_key_path)
except ValueError as e:
    print(f"Error: {e}")
else:
    if version.lower() == 'pro':
        # expose pro features
        print('Pro version detected!')
    else:
        # hide pro features
        print('Free version detected.')

Loading keys directly

You can also use the Keys helper from usethatapp.encryption to load keys from PEM strings or files:

from usethatapp.encryption import Keys

pub = Keys.read_public_key_from_file('keys/public.pem')
priv = Keys.read_private_key_from_file('keys/private.pem')

API reference

• usethatapp.webapps.get_version(envelope, public_key_path, private_key_path, encoding='utf-8')

  • envelope: dict or JSON string — the full postMessage envelope returned by requestAccessLevel(). Must have type ("level"), responseTo, and a message dict containing contents and signature (hex strings, optionally prefixed with 0x). Envelopes with type "error" raise a ValueError.
  • public_key_path / private_key_path: paths to PEM key files
  • encoding: attempt to decode decrypted bytes (defaults to 'utf-8')
  • returns: decoded string or raw bytes

• usethatapp.encryption.decrypt_message(private_key, encrypted_message) -> bytes

• usethatapp.encryption.verify_signature(public_key, signature, message) -> bool

• usethatapp.encryption.Keys: convenience class with these methods:

  • read_public_key_from_string(pem_str)
  • read_public_key_from_file(file_path)
  • read_private_key_from_string(pem_str)
  • read_private_key_from_file(file_path)

License

This project is licensed under the MIT License. details.

Links

• Homepage: https://github.com/UseThatApp/python
• Documentation: https://docs.usethatapp.com
• Changelog: https://github.com/UseThatApp/python/blob/main/CHANGELOG.md

Contact

For support: [e-mail]