Lexoffice.login <FHD 2026>

Future work could explore automated refresh token handling and background token refresh in SPAs using Web Workers. The principles outlined here are transferable to any OAuth2‑protected financial API. [1] lexoffice API Documentation. Authentication . Retrieved from https://developers.lexoffice.io/docs/#authentication [2] IETF RFC 6749 – The OAuth 2.0 Authorization Framework. [3] IETF RFC 7636 – Proof Key for Code Exchange (PKCE). [4] OWASP. OAuth 2.0 Security Cheat Sheet . [5] lexoffice OpenID Configuration – https://login.lexoffice.io/.well-known/openid-configuration Appendix – Full Token Response Example

def handle_callback(self, callback_url): """Parse callback, verify state, exchange code for tokens.""" parsed = urlparse(callback_url) query = parse_qs(parsed.query) if "state" not in query or query["state"][0] != self.state: raise ValueError("Invalid state parameter – possible CSRF attack") if "code" not in query: raise ValueError("No authorization code received") auth_code = query["code"][0] lexoffice.login

import hashlib import secrets import requests from urllib.parse import urlencode, urlparse, parse_qs class LexofficeLogin: AUTH_URL = "https://login.lexoffice.io/connect/authorize" TOKEN_URL = "https://login.lexoffice.io/connect/token" Future work could explore automated refresh token handling

"access_token": "eyJhbGciOiJSUzI1NiIs...", "token_type": "Bearer", "expires_in": 3600, "refresh_token": "8xLOxBtZp8...", "scope": "invoice.read contact.read openid profile" Authentication

def _generate_pkce_pair(self): """Generate code_verifier and code_challenge (S256).""" self.code_verifier = secrets.token_urlsafe(64)[:128] code_challenge = hashlib.sha256(self.code_verifier.encode()).digest() # Base64url encode without padding code_challenge = secrets.token_urlsafe(32) # simplified; use proper base64url # For correctness, implement: import base64 code_challenge = base64.urlsafe_b64encode( hashlib.sha256(self.code_verifier.encode()).digest() ).decode().rstrip("=") return code_challenge