deer-flow/backend/app/gateway/auth_middleware.py

"""Global authentication middleware — fail-closed safety net.

Rejects unauthenticated requests to non-public paths with 401. When a
request passes the cookie check, resolves the JWT payload to a real
``User`` object and stamps it into both ``request.state.user`` and the
``deerflow.runtime.user_context`` contextvar so that repository-layer
owner filtering works automatically via the sentinel pattern.

Fine-grained permission checks remain in authz.py decorators.
"""

from collections.abc import Callable

from fastapi import HTTPException, Request, Response
from starlette.middleware.base import BaseHTTPMiddleware
from starlette.responses import JSONResponse
from starlette.types import ASGIApp

from app.gateway.auth.errors import AuthErrorCode, AuthErrorResponse
from app.gateway.auth_disabled import (
    AUTH_SOURCE_AUTH_DISABLED,
    AUTH_SOURCE_INTERNAL,
    AUTH_SOURCE_PAT,
    AUTH_SOURCE_SESSION,
    get_auth_disabled_user,
    is_auth_disabled,
)
from app.gateway.authz import AuthContext, resolve_route_permissions
from app.gateway.internal_auth import INTERNAL_AUTH_HEADER_NAME, get_internal_user, is_valid_internal_auth_token
from app.gateway.request_path import get_request_route_path
from deerflow.runtime.user_context import reset_current_user, set_current_user

# Paths that never require authentication.
_PUBLIC_PATH_PREFIXES: tuple[str, ...] = (
    "/health",
    "/docs",
    "/redoc",
    "/openapi.json",
    "/api/v1/auth/oauth/",
    "/api/v1/auth/callback/",
    # Inbound webhooks authenticate themselves via provider-specific signatures
    # (e.g. GitHub's X-Hub-Signature-256), not session cookies.
    "/api/webhooks/",
)

# Exact auth paths that are public (login/register/status check).
# /api/v1/auth/me, /api/v1/auth/change-password etc. are NOT public.
_PUBLIC_EXACT_PATHS: frozenset[str] = frozenset(
    {
        "/api/v1/auth/login/local",
        "/api/v1/auth/register",
        "/api/v1/auth/logout",
        "/api/v1/auth/setup-status",
        "/api/v1/auth/initialize",
        "/api/v1/auth/providers",
    }
)


def _is_public(path: str) -> bool:
    stripped = path.rstrip("/")
    if stripped in _PUBLIC_EXACT_PATHS:
        return True
    return any(path.startswith(prefix) for prefix in _PUBLIC_PATH_PREFIXES)


class AuthMiddleware(BaseHTTPMiddleware):
    """Strict auth gate: reject requests without a valid session.

    Two-stage check for non-public paths:

    1. Cookie presence — return 401 NOT_AUTHENTICATED if missing
    2. JWT validation via ``get_optional_user_from_request`` — return 401
       TOKEN_INVALID if the token is absent, malformed, expired, or the
       signed user does not exist / is stale

    On success, stamps ``request.state.user`` and the
    ``deerflow.runtime.user_context`` contextvar so that repository-layer
    owner filters work downstream without every route needing a
    ``@require_auth`` decorator. Routes that need per-resource
    authorization (e.g. "user A cannot read user B's thread by guessing
    the URL") should additionally use ``@require_permission(...,
    owner_check=True)`` for explicit enforcement — but authentication
    itself is fully handled here.
    """

    def __init__(self, app: ASGIApp) -> None:
        super().__init__(app)

    async def dispatch(self, request: Request, call_next: Callable) -> Response:
        if _is_public(get_request_route_path(request)):
            return await call_next(request)

        internal_user = None
        if is_valid_internal_auth_token(request.headers.get(INTERNAL_AUTH_HEADER_NAME)):
            # Extract the channel owner user ID from the trusted header.
            # When present, the synthetic internal user carries the actual
            # owner identity so that get_effective_user_id() and per-user
            # filesystem paths (custom skills, memory, thread data) resolve
            # to the IM channel user instead of falling back to "default".
            from app.gateway.internal_auth import INTERNAL_OWNER_USER_ID_HEADER_NAME

            owner_user_id = request.headers.get(INTERNAL_OWNER_USER_ID_HEADER_NAME)
            if owner_user_id:
                owner_user_id = owner_user_id.strip()
            internal_user = get_internal_user(owner_user_id=owner_user_id or None)

        auth_source = AUTH_SOURCE_SESSION
        access_token = request.cookies.get("access_token")
        authorization = request.headers.get("authorization")
        pat_scopes: frozenset[str] = frozenset()

        # Non-public path: require session cookie
        if internal_user is not None:
            user = internal_user
            auth_source = AUTH_SOURCE_INTERNAL
        elif authorization is not None and not is_auth_disabled():
            # Bearer (PAT) credential precedence (#4849): a present-but-invalid
            # Authorization header is a hard 401 and never silently falls back
            # to the session cookie. This is also what makes the CSRF
            # middleware's Bearer skip safe — a cross-site attacker cannot ride
            # a victim's cookie by padding the request with a garbage Bearer
            # header, because the request dies here before any route runs.
            # Auth-disabled mode is an operator override of all authentication,
            # so it stays ahead of the Bearer check (a stray Authorization
            # header from a proxy must not 401 an E2E sandbox).
            from app.gateway.auth.pat import authenticate_pat, is_pat_allowed_route

            try:
                user, pat_scopes = await authenticate_pat(request.app, authorization)
            except HTTPException as exc:
                return JSONResponse(status_code=exc.status_code, content={"detail": exc.detail})
            # Default-deny route boundary (#5041 review P1-1): scopes only
            # constrain @require_permission routes, so any route outside the
            # explicit PAT policy is closed to PAT callers outright — an
            # all-scopes token must not reach undecorated mutation routes.
            if not is_pat_allowed_route(request.method, get_request_route_path(request)):
                return JSONResponse(
                    status_code=403,
                    content={"detail": "PAT credentials are not permitted on this route"},
                )
            auth_source = AUTH_SOURCE_PAT
        elif access_token:
            # Strict JWT validation: reject junk/expired tokens with 401
            # right here instead of silently passing through. This closes
            # the "junk cookie bypass" gap (AUTH_TEST_PLAN test 7.5.8):
            # without this, non-isolation routes like /api/models would
            # accept any cookie-shaped string as authentication.
            #
            # We call the *strict* resolver so that fine-grained error
            # codes (token_expired, token_invalid, user_not_found, …)
            # propagate from AuthErrorCode, not get flattened into one
            # generic code. BaseHTTPMiddleware doesn't let HTTPException
            # bubble up, so we catch and render it as JSONResponse here.
            from app.gateway.deps import get_current_user_from_request

            try:
                user = await get_current_user_from_request(request)
            except HTTPException as exc:
                if not is_auth_disabled():
                    return JSONResponse(status_code=exc.status_code, content={"detail": exc.detail})
                user = get_auth_disabled_user()
                auth_source = AUTH_SOURCE_AUTH_DISABLED
        elif is_auth_disabled():
            user = get_auth_disabled_user()
            auth_source = AUTH_SOURCE_AUTH_DISABLED
        else:
            return JSONResponse(
                status_code=401,
                content={
                    "detail": AuthErrorResponse(
                        code=AuthErrorCode.NOT_AUTHENTICATED,
                        message="Authentication required",
                    ).model_dump()
                },
            )

        # Stamp both request.state.user (for the contextvar pattern)
        # and request.state.auth (so @require_permission's "auth is
        # None" branch short-circuits instead of running the entire
        # JWT-decode + DB-lookup pipeline a second time per request).
        request.state.user = user
        request.state.auth_source = auth_source
        permissions = await resolve_route_permissions(
            user,
            is_internal=auth_source == AUTH_SOURCE_INTERNAL,
        )
        if auth_source == AUTH_SOURCE_PAT:
            # A PAT can only narrow its owning user's permissions: the stored
            # scopes intersect the resolved route permissions, never widen
            # them, and role changes / authorization policy stay authoritative
            # because they were resolved fresh from the owning user above.
            permissions = [permission for permission in permissions if permission in pat_scopes]
        request.state.auth = AuthContext(user=user, permissions=permissions)
        token = set_current_user(user)
        try:
            return await call_next(request)
        finally:
            reset_current_user(token)