Merge pull request #367 from matrix-org/rav/document_cas_login
document CAS login and m.login.token loginpull/368/head
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# Copyright 2016 OpenMarket 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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swagger: '2.0'
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info:
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title: "Matrix Client-Server CAS Login API"
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version: "1.0.0"
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host: localhost:8008
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schemes:
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- https
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- http
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basePath: /_matrix/client/%CLIENT_MAJOR_VERSION%
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paths:
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"/login/cas/redirect":
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get:
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summary: Redirect the user's browser to the CAS interface.
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description: |-
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A web-based Matrix client should instruct the user's browser to
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navigate to this endpoint in order to log in via CAS.
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The server MUST respond with an HTTP redirect to the CAS interface. The
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URI MUST include a ``service`` parameter giving the path of the
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|/login/cas/ticket|_ endpoint (including the ``redirectUrl`` query
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parameter).
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For example, if the endpoint is called with
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``redirectUrl=https://client.example.com/?q=p``, it might redirect to
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``https://cas.example.com/?service=https%3A%2F%2Fserver.example.com%2F_matrix%2Fclient%2F%CLIENT_MAJOR_VERSION%%2Flogin%2Fcas%2Fticket%3FredirectUrl%3Dhttps%253A%252F%252Fclient.example.com%252F%253Fq%253Dp``.
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parameters:
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- in: query
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type: string
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name: redirectUrl
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description: |-
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URI to which the user will be redirected after the homeserver has
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authenticated the user with CAS.
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required: true
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responses:
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302:
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description: A redirect to the CAS interface.
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headers:
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Location:
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type: "string"
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# Copyright 2016 OpenMarket 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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swagger: '2.0'
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info:
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title: "Matrix Client-Server CAS Login API"
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version: "1.0.0"
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host: localhost:8008
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schemes:
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- https
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- http
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basePath: /_matrix/client/%CLIENT_MAJOR_VERSION%
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paths:
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"/login/cas/ticket":
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get:
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summary: Receive and validate a CAS login ticket.
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description: |-
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Once the CAS server has authenticated the user, it will redirect the
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browser to this endpoint (assuming |/login/cas/redirect|_ gave it the
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correct ``service`` parameter).
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The server MUST call ``/proxyValidate`` on the CAS server, to validate
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the ticket supplied by the browser.
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If validation is successful, the server must generate a Matrix login
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token. It must then respond with an HTTP redirect to the URI given in
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the ``redirectUrl`` parameter, adding a ``loginToken`` query parameter
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giving the generated token.
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If validation is unsuccessful, the server should respond with a ``401
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Unauthorized`` error, the body of which will be displayed to the user.
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parameters:
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- in: query
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type: string
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name: redirectUrl
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description: |-
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The ``redirectUrl`` originally provided by the client to
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|/login/cas/redirect|_.
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required: true
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- in: query
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type: string
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name: ticket
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description: |-
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CAS authentication ticket.
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required: true
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responses:
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302:
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description: A redirect to the Matrix client.
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headers:
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Location:
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type: "string"
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x-example: |-
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https://client.example.com/?q=p&loginToken=secrettoken
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401:
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description: The server was unable to validate the CAS ticket.
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.. Copyright 2016 OpenMarket 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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CAS-based client login
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======================
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.. _module:cas_login:
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`Central Authentication Service
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<https://github.com/apereo/cas/blob/master/cas-server-documentation/protocol/CAS-Protocol-Specification.md>`_
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(CAS) is a web-based single sign-on protocol.
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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/cas/redirect|_ endpoint on the user's homeserver.
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2. The homeserver responds with an HTTP redirect to the CAS user interface,
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which the browser follows.
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3. The CAS system authenticates the user.
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4. The CAS server responds to the user's browser with a redirect back to the
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|/login/cas/ticket|_ endpoint on the homeserver, which the browser
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follows. A 'ticket' identifier is passed as a query parameter in the
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redirect.
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5. The homeserver receives the ticket ID from the user's browser, and makes a
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request to the CAS server to validate the ticket.
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6. Having validated the ticket, the homeserver responds to the browser with a
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third HTTP redirect, back to the Matrix client application. A login token
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is passed as a query parameter in the redirect.
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7. The Matrix client receives the login token and passes it to the |/login|_
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API.
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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/cas/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/cas/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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{{cas_login_redirect_cs_http_api}}
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{{cas_login_ticket_cs_http_api}}
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Server behaviour
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----------------
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The URI for the CAS system to be used should be configured on the server by the
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server administrator.
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Handling the redirect endpoint
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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When responding to the ``/login/cas/redirect`` endpoint, the server must
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generate a URI for the CAS login page. The server should take the base CAS URI
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described above, and add a ``service`` query parameter. This parameter MUST be
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the URI of the ``/login/cas/ticket`` endpoint, including the ``redirectUrl``
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query parameter. Because the homeserver may not know its base URI, this may
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also require manual configuration.
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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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When responding to the ``/login/cas/ticket`` endpoint, the server MUST make a
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request to the CAS server to validate the provided ticket. The server MAY also
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check for certain user attributes in the response. Any required attributes
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should be configured by the server administrator.
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Once the ticket has been validated, the server MUST map the CAS ``user_id``
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to a valid `Matrix user identifier <../intro.html#user-identifiers>`_. The
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guidance in `Mapping from other character sets
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<../intro.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.
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.. |/login| replace:: ``/login``
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.. _/login: #post-matrix-client-%CLIENT_MAJOR_VERSION%-login
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.. |/login/cas/redirect| replace:: ``/login/cas/redirect``
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.. _/login/cas/redirect: #get-matrix-client-%CLIENT_MAJOR_VERSION%-login-cas-redirect
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.. |/login/cas/ticket| replace:: ``/login/cas/ticket``
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.. _/login/cas/ticket: #get-matrix-client-%CLIENT_MAJOR_VERSION%-login-cas-ticket
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