# Copyright 2014-2021 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import logging
import re
from typing import (
    TYPE_CHECKING,
    Any,
    Awaitable,
    Callable,
    Dict,
    List,
    Optional,
    Tuple,
    Union,
)

from typing_extensions import TypedDict

from synapse.api.constants import ApprovalNoticeMedium
from synapse.api.errors import (
    Codes,
    InvalidClientTokenError,
    LoginError,
    NotApprovedError,
    SynapseError,
    UserDeactivatedError,
)
from synapse.api.ratelimiting import Ratelimiter
from synapse.api.urls import CLIENT_API_PREFIX
from synapse.appservice import ApplicationService
from synapse.handlers.sso import SsoIdentityProvider
from synapse.http import get_request_uri
from synapse.http.server import HttpServer, finish_request
from synapse.http.servlet import (
    RestServlet,
    assert_params_in_dict,
    parse_bytes_from_args,
    parse_json_object_from_request,
    parse_string,
)
from synapse.http.site import RequestInfo, SynapseRequest
from synapse.rest.client._base import client_patterns
from synapse.rest.well_known import WellKnownBuilder
from synapse.types import JsonDict, UserID

if TYPE_CHECKING:
    from synapse.server import HomeServer

logger = logging.getLogger(__name__)


class LoginResponse(TypedDict, total=False):
    user_id: str
    access_token: Optional[str]
    home_server: str
    expires_in_ms: Optional[int]
    refresh_token: Optional[str]
    device_id: Optional[str]
    well_known: Optional[Dict[str, Any]]


class LoginRestServlet(RestServlet):
    PATTERNS = client_patterns("/login$", v1=True)
    CATEGORY = "Registration/login requests"

    CAS_TYPE = "m.login.cas"
    SSO_TYPE = "m.login.sso"
    TOKEN_TYPE = "m.login.token"
    JWT_TYPE = "org.matrix.login.jwt"
    APPSERVICE_TYPE = "m.login.application_service"
    REFRESH_TOKEN_PARAM = "refresh_token"

    def __init__(self, hs: "HomeServer"):
        super().__init__()
        self.hs = hs
        self._main_store = hs.get_datastores().main

        # JWT configuration variables.
        self.jwt_enabled = hs.config.jwt.jwt_enabled

        # SSO configuration.
        self.saml2_enabled = hs.config.saml2.saml2_enabled
        self.cas_enabled = hs.config.cas.cas_enabled
        self.oidc_enabled = hs.config.oidc.oidc_enabled
        self._refresh_tokens_enabled = (
            hs.config.registration.refreshable_access_token_lifetime is not None
        )

        # Whether we need to check if the user has been approved or not.
        self._require_approval = (
            hs.config.experimental.msc3866.enabled
            and hs.config.experimental.msc3866.require_approval_for_new_accounts
        )

        # Whether get login token is enabled.
        self._get_login_token_enabled = hs.config.auth.login_via_existing_enabled

        self.auth = hs.get_auth()

        self.clock = hs.get_clock()

        self.auth_handler = self.hs.get_auth_handler()
        self.registration_handler = hs.get_registration_handler()
        self._sso_handler = hs.get_sso_handler()
        self._spam_checker = hs.get_module_api_callbacks().spam_checker
        self._account_validity_handler = hs.get_account_validity_handler()

        self._well_known_builder = WellKnownBuilder(hs)
        self._address_ratelimiter = Ratelimiter(
            store=self._main_store,
            clock=hs.get_clock(),
            cfg=self.hs.config.ratelimiting.rc_login_address,
        )
        self._account_ratelimiter = Ratelimiter(
            store=self._main_store,
            clock=hs.get_clock(),
            cfg=self.hs.config.ratelimiting.rc_login_account,
        )

        # ensure the CAS/SAML/OIDC handlers are loaded on this worker instance.
        # The reason for this is to ensure that the auth_provider_ids are registered
        # with SsoHandler, which in turn ensures that the login/registration prometheus
        # counters are initialised for the auth_provider_ids.
        _load_sso_handlers(hs)

    def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
        flows: List[JsonDict] = []
        if self.jwt_enabled:
            flows.append({"type": LoginRestServlet.JWT_TYPE})

        if self.cas_enabled:
            # we advertise CAS for backwards compat, though MSC1721 renamed it
            # to SSO.
            flows.append({"type": LoginRestServlet.CAS_TYPE})

        # The login token flow requires m.login.token to be advertised.
        support_login_token_flow = self._get_login_token_enabled

        if self.cas_enabled or self.saml2_enabled or self.oidc_enabled:
            flows.append(
                {
                    "type": LoginRestServlet.SSO_TYPE,
                    "identity_providers": [
                        _get_auth_flow_dict_for_idp(idp)
                        for idp in self._sso_handler.get_identity_providers().values()
                    ],
                }
            )

            # SSO requires a login token to be generated, so we need to advertise that flow
            support_login_token_flow = True

        # While it's valid for us to advertise this login type generally,
        # synapse currently only gives out these tokens as part of the
        # SSO login flow or as part of login via an existing session.
        #
        # Generally we don't want to advertise login flows that clients
        # don't know how to implement, since they (currently) will always
        # fall back to the fallback API if they don't understand one of the
        # login flow types returned.
        if support_login_token_flow:
            tokenTypeFlow: Dict[str, Any] = {"type": LoginRestServlet.TOKEN_TYPE}
            # If the login token flow is enabled advertise the get_login_token flag.
            if self._get_login_token_enabled:
                tokenTypeFlow["get_login_token"] = True
            flows.append(tokenTypeFlow)

        flows.extend({"type": t} for t in self.auth_handler.get_supported_login_types())

        flows.append({"type": LoginRestServlet.APPSERVICE_TYPE})

        return 200, {"flows": flows}

    async def on_POST(self, request: SynapseRequest) -> Tuple[int, LoginResponse]:
        login_submission = parse_json_object_from_request(request)

        # Check to see if the client requested a refresh token.
        client_requested_refresh_token = login_submission.get(
            LoginRestServlet.REFRESH_TOKEN_PARAM, False
        )
        if not isinstance(client_requested_refresh_token, bool):
            raise SynapseError(400, "`refresh_token` should be true or false.")

        should_issue_refresh_token = (
            self._refresh_tokens_enabled and client_requested_refresh_token
        )

        request_info = request.request_info()

        try:
            if login_submission["type"] == LoginRestServlet.APPSERVICE_TYPE:
                requester = await self.auth.get_user_by_req(request)
                appservice = requester.app_service

                if appservice is None:
                    raise InvalidClientTokenError(
                        "This login method is only valid for application services"
                    )

                if appservice.is_rate_limited():
                    await self._address_ratelimiter.ratelimit(
                        None, request.getClientAddress().host
                    )

                result = await self._do_appservice_login(
                    login_submission,
                    appservice,
                    should_issue_refresh_token=should_issue_refresh_token,
                    request_info=request_info,
                )
            elif (
                self.jwt_enabled
                and login_submission["type"] == LoginRestServlet.JWT_TYPE
            ):
                await self._address_ratelimiter.ratelimit(
                    None, request.getClientAddress().host
                )
                result = await self._do_jwt_login(
                    login_submission,
                    should_issue_refresh_token=should_issue_refresh_token,
                    request_info=request_info,
                )
            elif login_submission["type"] == LoginRestServlet.TOKEN_TYPE:
                await self._address_ratelimiter.ratelimit(
                    None, request.getClientAddress().host
                )
                result = await self._do_token_login(
                    login_submission,
                    should_issue_refresh_token=should_issue_refresh_token,
                    request_info=request_info,
                )
            else:
                await self._address_ratelimiter.ratelimit(
                    None, request.getClientAddress().host
                )
                result = await self._do_other_login(
                    login_submission,
                    should_issue_refresh_token=should_issue_refresh_token,
                    request_info=request_info,
                )
        except KeyError:
            raise SynapseError(400, "Missing JSON keys.")

        if self._require_approval:
            approved = await self.auth_handler.is_user_approved(result["user_id"])
            if not approved:
                raise NotApprovedError(
                    msg="This account is pending approval by a server administrator.",
                    approval_notice_medium=ApprovalNoticeMedium.NONE,
                )

        well_known_data = self._well_known_builder.get_well_known()
        if well_known_data:
            result["well_known"] = well_known_data
        return 200, result

    async def _do_appservice_login(
        self,
        login_submission: JsonDict,
        appservice: ApplicationService,
        should_issue_refresh_token: bool = False,
        *,
        request_info: RequestInfo,
    ) -> LoginResponse:
        identifier = login_submission.get("identifier")
        logger.info("Got appservice login request with identifier: %r", identifier)

        if not isinstance(identifier, dict):
            raise SynapseError(
                400, "Invalid identifier in login submission", Codes.INVALID_PARAM
            )

        # this login flow only supports identifiers of type "m.id.user".
        if identifier.get("type") != "m.id.user":
            raise SynapseError(
                400, "Unknown login identifier type", Codes.INVALID_PARAM
            )

        user = identifier.get("user")
        if not isinstance(user, str):
            raise SynapseError(400, "Invalid user in identifier", Codes.INVALID_PARAM)

        if user.startswith("@"):
            qualified_user_id = user
        else:
            qualified_user_id = UserID(user, self.hs.hostname).to_string()

        if not appservice.is_interested_in_user(qualified_user_id):
            raise LoginError(403, "Invalid access_token", errcode=Codes.FORBIDDEN)

        return await self._complete_login(
            qualified_user_id,
            login_submission,
            ratelimit=appservice.is_rate_limited(),
            should_issue_refresh_token=should_issue_refresh_token,
            # The user represented by an appservice's configured sender_localpart
            # is not actually created in Synapse.
            should_check_deactivated=qualified_user_id != appservice.sender,
            request_info=request_info,
        )

    async def _do_other_login(
        self,
        login_submission: JsonDict,
        should_issue_refresh_token: bool = False,
        *,
        request_info: RequestInfo,
    ) -> LoginResponse:
        """Handle non-token/saml/jwt logins

        Args:
            login_submission:
            should_issue_refresh_token: True if this login should issue
                a refresh token alongside the access token.

        Returns:
            HTTP response
        """
        # Log the request we got, but only certain fields to minimise the chance of
        # logging someone's password (even if they accidentally put it in the wrong
        # field)
        logger.info(
            "Got login request with identifier: %r, medium: %r, address: %r, user: %r",
            login_submission.get("identifier"),
            login_submission.get("medium"),
            login_submission.get("address"),
            login_submission.get("user"),
        )
        canonical_user_id, callback = await self.auth_handler.validate_login(
            login_submission, ratelimit=True
        )
        result = await self._complete_login(
            canonical_user_id,
            login_submission,
            callback,
            should_issue_refresh_token=should_issue_refresh_token,
            request_info=request_info,
        )
        return result

    async def _complete_login(
        self,
        user_id: str,
        login_submission: JsonDict,
        callback: Optional[Callable[[LoginResponse], Awaitable[None]]] = None,
        create_non_existent_users: bool = False,
        ratelimit: bool = True,
        auth_provider_id: Optional[str] = None,
        should_issue_refresh_token: bool = False,
        auth_provider_session_id: Optional[str] = None,
        should_check_deactivated: bool = True,
        *,
        request_info: RequestInfo,
    ) -> LoginResponse:
        """Called when we've successfully authed the user and now need to
        actually login them in (e.g. create devices). This gets called on
        all successful logins.

        Applies the ratelimiting for successful login attempts against an
        account.

        Args:
            user_id: ID of the user to register.
            login_submission: Dictionary of login information.
            callback: Callback function to run after login.
            create_non_existent_users: Whether to create the user if they don't
                exist. Defaults to False.
            ratelimit: Whether to ratelimit the login request.
            auth_provider_id: The SSO IdP the user used, if any.
            should_issue_refresh_token: True if this login should issue
                a refresh token alongside the access token.
            auth_provider_session_id: The session ID got during login from the SSO IdP.
            should_check_deactivated: True if the user should be checked for
                deactivation status before logging in.

                This exists purely for appservice's configured sender_localpart
                which doesn't have an associated user in the database.
            request_info: The user agent/IP address of the user.

        Returns:
            Dictionary of account information after successful login.
        """

        # Before we actually log them in we check if they've already logged in
        # too often. This happens here rather than before as we don't
        # necessarily know the user before now.
        if ratelimit:
            await self._account_ratelimiter.ratelimit(None, user_id.lower())

        if create_non_existent_users:
            canonical_uid = await self.auth_handler.check_user_exists(user_id)
            if not canonical_uid:
                canonical_uid = await self.registration_handler.register_user(
                    localpart=UserID.from_string(user_id).localpart
                )
            user_id = canonical_uid

        # If the account has been deactivated, do not proceed with the login.
        if should_check_deactivated:
            deactivated = await self._main_store.get_user_deactivated_status(user_id)
            if deactivated:
                raise UserDeactivatedError("This account has been deactivated")

        device_id = login_submission.get("device_id")

        # If device_id is present, check that device_id is not longer than a reasonable 512 characters
        if device_id and len(device_id) > 512:
            raise LoginError(
                400,
                "device_id cannot be longer than 512 characters.",
                errcode=Codes.INVALID_PARAM,
            )

        if self._require_approval:
            approved = await self.auth_handler.is_user_approved(user_id)
            if not approved:
                # If the user isn't approved (and needs to be) we won't allow them to
                # actually log in, so we don't want to create a device/access token.
                return LoginResponse(
                    user_id=user_id,
                    home_server=self.hs.hostname,
                )

        initial_display_name = login_submission.get("initial_device_display_name")
        spam_check = await self._spam_checker.check_login_for_spam(
            user_id,
            device_id=device_id,
            initial_display_name=initial_display_name,
            request_info=[(request_info.user_agent, request_info.ip)],
            auth_provider_id=auth_provider_id,
        )
        if spam_check != self._spam_checker.NOT_SPAM:
            logger.info("Blocking login due to spam checker")
            raise SynapseError(
                403,
                msg="Login was blocked by the server",
                errcode=spam_check[0],
                additional_fields=spam_check[1],
            )

        (
            device_id,
            access_token,
            valid_until_ms,
            refresh_token,
        ) = await self.registration_handler.register_device(
            user_id,
            device_id,
            initial_display_name,
            auth_provider_id=auth_provider_id,
            should_issue_refresh_token=should_issue_refresh_token,
            auth_provider_session_id=auth_provider_session_id,
        )

        result = LoginResponse(
            user_id=user_id,
            access_token=access_token,
            home_server=self.hs.hostname,
            device_id=device_id,
        )

        # execute the callback
        await self._account_validity_handler.on_user_login(
            user_id,
            auth_provider_type=login_submission.get("type"),
            auth_provider_id=auth_provider_id,
        )

        if valid_until_ms is not None:
            expires_in_ms = valid_until_ms - self.clock.time_msec()
            result["expires_in_ms"] = expires_in_ms

        if refresh_token is not None:
            result["refresh_token"] = refresh_token

        if callback is not None:
            await callback(result)

        return result

    async def _do_token_login(
        self,
        login_submission: JsonDict,
        should_issue_refresh_token: bool = False,
        *,
        request_info: RequestInfo,
    ) -> LoginResponse:
        """
        Handle token login.

        Args:
            login_submission: The JSON request body.
            should_issue_refresh_token: True if this login should issue
                a refresh token alongside the access token.

        Returns:
            The body of the JSON response.
        """
        token = login_submission["token"]
        res = await self.auth_handler.consume_login_token(token)

        return await self._complete_login(
            res.user_id,
            login_submission,
            self.auth_handler._sso_login_callback,
            auth_provider_id=res.auth_provider_id,
            should_issue_refresh_token=should_issue_refresh_token,
            auth_provider_session_id=res.auth_provider_session_id,
            request_info=request_info,
        )

    async def _do_jwt_login(
        self,
        login_submission: JsonDict,
        should_issue_refresh_token: bool = False,
        *,
        request_info: RequestInfo,
    ) -> LoginResponse:
        """
        Handle the custom JWT login.

        Args:
            login_submission: The JSON request body.
            should_issue_refresh_token: True if this login should issue
                a refresh token alongside the access token.

        Returns:
            The body of the JSON response.
        """
        user_id = self.hs.get_jwt_handler().validate_login(login_submission)
        return await self._complete_login(
            user_id,
            login_submission,
            create_non_existent_users=True,
            should_issue_refresh_token=should_issue_refresh_token,
            request_info=request_info,
        )


def _get_auth_flow_dict_for_idp(idp: SsoIdentityProvider) -> JsonDict:
    """Return an entry for the login flow dict

    Returns an entry suitable for inclusion in "identity_providers" in the
    response to GET /_matrix/client/r0/login

    Args:
        idp: the identity provider to describe
    """
    e: JsonDict = {"id": idp.idp_id, "name": idp.idp_name}
    if idp.idp_icon:
        e["icon"] = idp.idp_icon
    if idp.idp_brand:
        e["brand"] = idp.idp_brand
    return e


class RefreshTokenServlet(RestServlet):
    PATTERNS = client_patterns("/refresh$")
    CATEGORY = "Registration/login requests"

    def __init__(self, hs: "HomeServer"):
        self._auth_handler = hs.get_auth_handler()
        self._clock = hs.get_clock()
        self.refreshable_access_token_lifetime = (
            hs.config.registration.refreshable_access_token_lifetime
        )
        self.refresh_token_lifetime = hs.config.registration.refresh_token_lifetime

    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
        refresh_submission = parse_json_object_from_request(request)

        assert_params_in_dict(refresh_submission, ["refresh_token"])
        token = refresh_submission["refresh_token"]
        if not isinstance(token, str):
            raise SynapseError(400, "Invalid param: refresh_token", Codes.INVALID_PARAM)

        now = self._clock.time_msec()
        access_valid_until_ms = None
        if self.refreshable_access_token_lifetime is not None:
            access_valid_until_ms = now + self.refreshable_access_token_lifetime
        refresh_valid_until_ms = None
        if self.refresh_token_lifetime is not None:
            refresh_valid_until_ms = now + self.refresh_token_lifetime

        (
            access_token,
            refresh_token,
            actual_access_token_expiry,
        ) = await self._auth_handler.refresh_token(
            token, access_valid_until_ms, refresh_valid_until_ms
        )

        response: Dict[str, Union[str, int]] = {
            "access_token": access_token,
            "refresh_token": refresh_token,
        }

        # expires_in_ms is only present if the token expires
        if actual_access_token_expiry is not None:
            response["expires_in_ms"] = actual_access_token_expiry - now

        return 200, response


class SsoRedirectServlet(RestServlet):
    PATTERNS = list(client_patterns("/login/(cas|sso)/redirect$", v1=True)) + [
        re.compile(
            "^"
            + CLIENT_API_PREFIX
            + "/(r0|v3)/login/sso/redirect/(?P<idp_id>[A-Za-z0-9_.~-]+)$"
        )
    ]
    CATEGORY = "SSO requests needed for all SSO providers"

    def __init__(self, hs: "HomeServer"):
        # make sure that the relevant handlers are instantiated, so that they
        # register themselves with the main SSOHandler.
        _load_sso_handlers(hs)
        self._sso_handler = hs.get_sso_handler()
        self._public_baseurl = hs.config.server.public_baseurl

    async def on_GET(
        self, request: SynapseRequest, idp_id: Optional[str] = None
    ) -> None:
        if not self._public_baseurl:
            raise SynapseError(400, "SSO requires a valid public_baseurl")

        # if this isn't the expected hostname, redirect to the right one, so that we
        # get our cookies back.
        requested_uri = get_request_uri(request)
        baseurl_bytes = self._public_baseurl.encode("utf-8")
        if not requested_uri.startswith(baseurl_bytes):
            # swap out the incorrect base URL for the right one.
            #
            # The idea here is to redirect from
            #    https://foo.bar/whatever/_matrix/...
            # to
            #    https://public.baseurl/_matrix/...
            #
            i = requested_uri.index(b"/_matrix")
            new_uri = baseurl_bytes[:-1] + requested_uri[i:]
            logger.info(
                "Requested URI %s is not canonical: redirecting to %s",
                requested_uri.decode("utf-8", errors="replace"),
                new_uri.decode("utf-8", errors="replace"),
            )
            request.redirect(new_uri)
            finish_request(request)
            return

        args: Dict[bytes, List[bytes]] = request.args  # type: ignore
        client_redirect_url = parse_bytes_from_args(args, "redirectUrl", required=True)
        sso_url = await self._sso_handler.handle_redirect_request(
            request,
            client_redirect_url,
            idp_id,
        )
        logger.info("Redirecting to %s", sso_url)
        request.redirect(sso_url)
        finish_request(request)


class CasTicketServlet(RestServlet):
    PATTERNS = client_patterns("/login/cas/ticket", v1=True)

    def __init__(self, hs: "HomeServer"):
        super().__init__()
        self._cas_handler = hs.get_cas_handler()

    async def on_GET(self, request: SynapseRequest) -> None:
        client_redirect_url = parse_string(request, "redirectUrl")
        ticket = parse_string(request, "ticket", required=True)

        # Maybe get a session ID (if this ticket is from user interactive
        # authentication).
        session = parse_string(request, "session")

        # Either client_redirect_url or session must be provided.
        if not client_redirect_url and not session:
            message = "Missing string query parameter redirectUrl or session"
            raise SynapseError(400, message, errcode=Codes.MISSING_PARAM)

        await self._cas_handler.handle_ticket(
            request, ticket, client_redirect_url, session
        )


def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
    if hs.config.experimental.msc3861.enabled:
        return

    LoginRestServlet(hs).register(http_server)
    if (
        hs.config.worker.worker_app is None
        and hs.config.registration.refreshable_access_token_lifetime is not None
    ):
        RefreshTokenServlet(hs).register(http_server)
    if (
        hs.config.cas.cas_enabled
        or hs.config.saml2.saml2_enabled
        or hs.config.oidc.oidc_enabled
    ):
        SsoRedirectServlet(hs).register(http_server)
    if hs.config.cas.cas_enabled:
        CasTicketServlet(hs).register(http_server)


def _load_sso_handlers(hs: "HomeServer") -> None:
    """Ensure that the SSO handlers are loaded, if they are enabled by configuration.

    This is mostly useful to ensure that the CAS/SAML/OIDC handlers register themselves
    with the main SsoHandler.

    It's safe to call this multiple times.
    """
    if hs.config.cas.cas_enabled:
        hs.get_cas_handler()
    if hs.config.saml2.saml2_enabled:
        hs.get_saml_handler()
    if hs.config.oidc.oidc_enabled:
        hs.get_oidc_handler()