Chris CoutinhoandClaude Opus 4.7
15dbb26349
Pre-launch hardening for the hosted Astrolabe Cloud offering. Addresses all five findings raised in #626 (Tim Kaufmann, code review of v0.65.0). Re-verified against master before fixing. Finding 3 (LLM-controllable user_id) — drop user_id from the public signatures of provision_nextcloud_access, revoke_nextcloud_access, check_provisioning_status, check_logged_in. Tool wrappers now always derive identity from the verified AccessToken; user_id is no longer accepted as MCP input. Adds parameterized CI-guard test that locks the schema. Finding 2 (predictable session cookie) — replace mcp_session=<user_id> cookie with a cryptographically random session_id mapped server-side (new browser_sessions table, alembic 005). Cookie value is opaque, expires, revocable. SessionAuthBackend looks up user_id via the new mapping and additionally requires a refresh token to fail closed. Finding 4 (logout doesn't revoke refresh token) — oauth_logout now calls the IdP revocation_endpoint (RFC 7009) when advertised, deletes the stored refresh token regardless, and clears the browser_sessions row. Cleanup is best-effort: logout always 302s. Finding 1 (unverified ID token decodes) — verify_id_token helper does JWKS signature + issuer + audience + exp + nonce checks per OIDC core 3.1.3.7. Used by both OAuth callback handlers (browser + MCP). Removes the four "verify_signature: False" decodes that previously trusted IdP claims unconditionally. Drops dead-code _validate_token_audience in token_broker. Refactors token_utils + provisioning_decorator to read user_id from the verified AccessToken instead of re-decoding the JWT. Finding 5 (hardcoded Fernet keys in docker-compose.yml) — replace the three inline TOKEN_ENCRYPTION_KEY values with required env var interpolation; document in env.sample. Test coverage: 4 new unit test modules (signature pinning, browser sessions, ID-token verification, logout + revoke + session backend). 693 unit tests pass; ruff/format/ty clean. Migration note: existing browser admin-UI sessions become invalid on rollout (cookies are looked up against the new browser_sessions table, which starts empty). Users re-login. MCP API access is unaffected. Tracked on Astrolabe Cloud POC board card #37. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
99 lines
3.4 KiB
Python
99 lines
3.4 KiB
Python
"""Session-based authentication backend for Starlette routes.
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Provides browser-based authentication for admin UI routes, separate from
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MCP's OAuth authentication flow.
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"""
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import logging
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import os
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from starlette.authentication import (
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AuthCredentials,
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AuthenticationBackend,
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SimpleUser,
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)
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from starlette.requests import HTTPConnection
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logger = logging.getLogger(__name__)
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class SessionAuthBackend(AuthenticationBackend):
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"""Authentication backend using signed session cookies.
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For BasicAuth mode: Always authenticates as the configured user.
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For OAuth mode: Checks for valid session cookie with stored refresh token.
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"""
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def __init__(self, oauth_enabled: bool = False):
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"""Initialize session authentication backend.
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Args:
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oauth_enabled: Whether OAuth mode is enabled
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"""
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self.oauth_enabled = oauth_enabled
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async def authenticate(
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self, conn: HTTPConnection
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) -> tuple[AuthCredentials, SimpleUser] | None:
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"""Authenticate the request based on session cookie or BasicAuth mode.
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This backend is only applied to browser routes (/user/*) via a separate
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Starlette app mount. FastMCP routes use their own OAuth Bearer token
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authentication.
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Args:
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conn: HTTP connection
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Returns:
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Tuple of (credentials, user) if authenticated, None otherwise
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"""
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# BasicAuth mode: Always authenticated as the configured user
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if not self.oauth_enabled:
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username = os.getenv("NEXTCLOUD_USERNAME", "admin")
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return AuthCredentials(["authenticated", "admin"]), SimpleUser(username)
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# OAuth mode: opaque random session_id cookie -> user_id mapping.
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# Replaces the prior `mcp_session=<user_id>` cookie pattern (issue
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# #626 finding 2). The cookie value is no longer the user identity;
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# we look it up server-side and reject unknown / expired sessions.
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session_id = conn.cookies.get("mcp_session")
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if not session_id:
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logger.info("No session cookie found - redirecting to login")
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return None
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oauth_context = getattr(conn.app.state, "oauth_context", None)
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if not oauth_context:
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logger.warning("OAuth context not available in app state")
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return None
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storage = oauth_context.get("storage")
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if not storage:
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logger.warning("OAuth storage not available")
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return None
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try:
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user_id = await storage.get_browser_session_user(session_id)
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if not user_id:
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logger.info(
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"Browser session not found or expired (sid=%s…)", session_id[:8]
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)
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return None
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# Defense-in-depth: only authenticate sessions for users that
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# actually have a refresh token persisted. Logout deletes both,
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# so an expired/revoked user state will fail closed here.
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token_data = await storage.get_refresh_token(user_id)
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if not token_data:
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logger.warning(
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"Session %s… has no refresh token for user %s; rejecting",
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session_id[:8],
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user_id,
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)
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return None
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return AuthCredentials(["authenticated"]), SimpleUser(user_id)
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except Exception as e:
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logger.warning(f"Session validation error: {e}")
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return None
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