114 lines
4.8 KiB
ReStructuredText
114 lines
4.8 KiB
ReStructuredText
.. Copyright 2019 New Vector Ltd
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..
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.. Licensed under the Apache License, Version 2.0 (the "License");
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.. you may not use this file except in compliance with the License.
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.. You may obtain a copy of the License at
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..
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.. http://www.apache.org/licenses/LICENSE-2.0
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..
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.. Unless required by applicable law or agreed to in writing, software
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.. distributed under the License is distributed on an "AS IS" BASIS,
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.. WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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.. See the License for the specific language governing permissions and
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.. limitations under the License.
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SSO client login
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================
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.. _module:sso_login:
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Single Sign-On (SSO) is a generic term which refers to protocols which allow
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users to log into applications via a single web-based authentication portal.
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Examples include "Central Authentication Service" (CAS) and SAML.
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An overview of the process, as used in Matrix, is as follows:
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1. The Matrix client instructs the user's browser to navigate to the
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|/login/sso/redirect|_ endpoint on the user's homeserver.
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2. The homeserver responds with an HTTP redirect to the SSO user interface,
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which the browser follows.
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3. The SSO system authenticates the user.
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4. The SSO server and the homeserver interact to verify the user's identity
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and other authentication information, potentially using a number of redirects.
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5. The browser is directed to the ``redirectUrl`` provided by the client with
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a ``loginToken`` query parameter for the client to log in with.
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.. Note::
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In the older `r0.4.0 version <https://matrix.org/docs/spec/client_server/r0.4.0.html#cas-based-client-login>`_
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of this specification it was possible to authenticate via CAS when the server
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provides a ``m.login.cas`` login flow. This specification deprecates the use
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of ``m.login.cas`` to instead prefer ``m.login.sso``, which is the same process
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with the only change being which redirect endpoint to use: for ``m.login.cas``, use
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``/cas/redirect`` and for ``m.login.sso`` use ``/sso/redirect`` (described below).
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The endpoints are otherwise the same.
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Client behaviour
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----------------
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The client starts the process by instructing the browser to navigate to
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|/login/sso/redirect|_ with an appropriate ``redirectUrl``. Once authentication
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is successful, the browser will be redirected to that ``redirectUrl``.
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.. TODO-spec
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Should we recommend some sort of CSRF protection here (specifically, we
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should guard against people accidentally logging in by sending them a link
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to ``/login/sso/redirect``.
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Maybe we should recommend that the ``redirectUrl`` should contain a CSRF
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token which the client should then check before sending the login token to
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``/login``?
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{{sso_login_redirect_cs_http_api}}
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Server behaviour
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----------------
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The URI for the SSO system to be used should be configured on the server by the
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server administrator. The server is expected to set up any endpoints required to
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interact with that SSO system. For example, for CAS authentication the homeserver
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should provide a means for the administrator to configure where the CAS server is
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and the REST endpoints which consume the ticket. A good reference for how CAS could
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be implemented is available in the older `r0.4.0 version <https://matrix.org/docs/spec/client_server/r0.4.0.html#cas-based-client-login>`_
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of this specification.
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Handling the redirect endpoint
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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When responding to the ``/login/sso/redirect`` endpoint, the server must
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generate a URI for the SSO login page with any appropriate parameters.
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.. TODO-spec:
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It might be nice if the server did some validation of the ``redirectUrl``
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parameter, so that we could check that aren't going to redirect to a non-TLS
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endpoint, and to give more meaningful errors in the case of
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faulty/poorly-configured clients.
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Handling the authentication endpoint
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Once the homeserver has verified the user's identity with the SSO system, it
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MUST map the user ID to a valid `Matrix user identifier <../index.html#user-identifiers>`_.
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The guidance in `Mapping from other character sets
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<../index.html#mapping-from-other-character-sets>`_ may be useful.
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If the generated user identifier represents a new user, it should be registered
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as a new user.
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Finally, the server should generate a short-term login token. The generated
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token should be a macaroon, suitable for use with the ``m.login.token`` type of
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the |/login|_ API, and `token-based interactive login <#token-based>`_. The
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lifetime of this token SHOULD be limited to around five seconds. This token is
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given to the client via the ``loginToken`` query parameter previously mentioned.
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.. |/login| replace:: ``/login``
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.. _/login: #post-matrix-client-%CLIENT_MAJOR_VERSION%-login
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.. |/login/sso/redirect| replace:: ``/login/sso/redirect``
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.. _/login/sso/redirect: #get-matrix-client-%CLIENT_MAJOR_VERSION%-login-sso-redirect
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