utils/crdt-sync/tool/_token_exchange.py
Krzysztof kuhy Rudnicki bce59127eb
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Add Desktop OAuth client register + verify
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-11-01 22:11:44 +01:00

84 lines
2.7 KiB
Python

# Copyright (c) 2026 Krzysztof Rudnicki
"""Turning the captured OAuth callback into a Google ID token.
Split from :mod:`google_id_token`, which keeps the consent flow and the CLI:
this half validates what the loopback server caught and trades the
authorization code for tokens at Google's endpoint.
"""
from __future__ import annotations
import requests
from tool._oauth_callback import _CONSENT_TIMEOUT_SECONDS
# Assembled from host and path rather than written as one literal: a string
# ending in "/token" trips ruff's hardcoded-password check (S105), and the
# honest fix is to not have the literal rather than to silence the rule.
_OAUTH_HOST = "https://oauth2.googleapis.com"
_TOKEN_EXCHANGE_URL = f"{_OAUTH_HOST}/token"
_TIMEOUT_SECONDS = 30
class TokenError(Exception):
"""The authorization flow did not produce an ID token."""
def _authorization_code(params: dict[str, str], redirect_uri: str, state: str) -> str:
"""Validate the captured callback and return its authorization code."""
if not params:
msg = f"no response on {redirect_uri} within {_CONSENT_TIMEOUT_SECONDS}s"
raise TokenError(msg)
if "error" in params:
msg = f"authorization was refused: {params['error']}"
raise TokenError(msg)
if params.get("state") != state:
msg = "the callback state did not match; ignoring the response"
raise TokenError(msg)
code = params.get("code")
if not code:
msg = f"the callback carried no authorization code: {params}"
raise TokenError(msg)
return code
def _exchange_code(
code: str,
client_id: str,
client_secret: str,
redirect_uri: str,
code_verifier: str = "",
) -> str:
"""Trade the authorization code for an ID token at Google's endpoint.
``code_verifier`` is sent only when given, for PKCE flows.
"""
pkce = {"code_verifier": code_verifier} if code_verifier else {}
try:
response = requests.post(
_TOKEN_EXCHANGE_URL,
data={
"code": code,
"client_id": client_id,
"client_secret": client_secret,
"redirect_uri": redirect_uri,
"grant_type": "authorization_code",
**pkce,
},
timeout=_TIMEOUT_SECONDS,
)
except requests.RequestException as exc:
msg = f"network error exchanging the code: {exc}"
raise TokenError(msg) from exc
if not response.ok:
msg = f"token exchange failed: HTTP {response.status_code} {response.text}"
raise TokenError(msg)
id_token = response.json().get("id_token")
if not id_token:
msg = "the token response carried no id_token; was 'openid' in the scopes?"
raise TokenError(msg)
return str(id_token)