Matrix Synapse SAML2 Login

$ export KEYSTORE_PW="example123"
$ openssl pkcs12 -in keystore.p12 -password "pass:${KEYSTORE_PW}" -nocerts -nodes | openssl rsa -out key.pem
writing RSA key
$ openssl pkcs12 -in keystore.p12 -password "pass:${KEYSTORE_PW}" -nodes | openssl x509 -out cert.pem

<?xml version="1.0" encoding="UTF-8"?>
<!--
  ~ Copyright 2016 Red Hat, Inc. and/or its affiliates
  ~ and other contributors as indicated by the @author tags.
  ~
  ~ 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.
  -->

<EntitiesDescriptor Name="urn:keycloak" xmlns="urn:oasis:names:tc:SAML:2.0:metadata"
                    xmlns:dsig="http://www.w3.org/2000/09/xmldsig#">
    <EntityDescriptor entityID="https://__YOUR_KEYCLOAK_URL__/auth/realms/master">
        <IDPSSODescriptor WantAuthnRequestsSigned="true"
            protocolSupportEnumeration="urn:oasis:names:tc:SAML:2.0:protocol">
                        <KeyDescriptor use="signing">
                          <dsig:KeyInfo>
                            <dsig:KeyName>[REDACTED]</dsig:KeyName>
                            <dsig:X509Data>
                              <dsig:X509Certificate>[REDACTED]</dsig:X509Certificate>
                            </dsig:X509Data>
                          </dsig:KeyInfo>
                        </KeyDescriptor>

            <SingleLogoutService
                    Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
                    Location="https://__YOUR_KEYCLOAK_URL__/auth/realms/master/protocol/saml" />
            <SingleLogoutService
                    Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect"
                    Location="https://__YOUR_KEYCLOAK_URL__/auth/realms/master/protocol/saml" />
            <NameIDFormat>urn:oasis:names:tc:SAML:2.0:nameid-format:persistent</NameIDFormat>
            <NameIDFormat>urn:oasis:names:tc:SAML:2.0:nameid-format:transient</NameIDFormat>
            <NameIDFormat>urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified</NameIDFormat>
            <NameIDFormat>urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress</NameIDFormat>
            <SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
                Location="https://__YOUR_KEYCLOAK_URL__/auth/realms/master/protocol/saml" />
            <SingleSignOnService
                Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect"
                Location="https://__YOUR_KEYCLOAK_URL__/auth/realms/master/protocol/saml" />
            <SingleSignOnService
                Binding="urn:oasis:names:tc:SAML:2.0:bindings:SOAP"
                Location="https://__YOUR_KEYCLOAK_URL__/auth/realms/master/protocol/saml" />
        </IDPSSODescriptor>
    </EntityDescriptor>
</EntitiesDescriptor>

import saml2
from saml2.saml import NAME_FORMAT_URI

BASE = "https://matrix.example.com/"

CONFIG = {
    "entityid": "matrix-example-com",
    "description": "Matrix Server",
    "service": {
        "sp": {
            "name": "matrix-login",
            "endpoints": {
                "single_sign_on_service": [
                    (BASE + "_matrix/saml2/authn_response", saml2.BINDING_HTTP_POST),
                ],
                "assertion_consumer_service": [
                    (BASE + "_matrix/saml2/authn_response", saml2.BINDING_HTTP_POST),
                ],
                #"single_logout_service": [
                #    (BASE + "_matrix/saml2/logout", saml2.BINDING_HTTP_POST),
                #],
            },
            "required_attributes": ["uid",],
            "optional_attributes": ["displayName"],
            "sign_assertion": True,
            "sign_response": True,
        }
    },
    "debug": 0,
    "key_file": "/synapse/config/key.pem",
    "cert_file": "/synapse/config/cert.pem",
    "encryption_keypairs": [
        {
            "key_file": "/synapse/config/key.pem",
            "cert_file": "/synapse/config/cert.pem",
        }
    ],
    "attribute_map_dir": "/synapse/saml2_attribute_maps/",
    "metadata": {
        "local": ["/synapse/config/idp.xml"]
    },
    # If you want to have organization and contact_person for the pysaml2 config
    #"organization": {
    #    "name": "Example AB",
    #    "display_name": [("Example AB", "se"), ("Example Co.", "en")],
    #    "url": "http://example.com/roland",
    #},
    #"contact_person": [{
    #    "given_name": "Example",
    #    "sur_name": "Example",
    #    "email_address": ["example@example.com"],
    #    "contact_type": "technical",
    #    },
    #],
    # Make sure to have xmlsec1 installed on your host(s)!
    "xmlsec_binary": "/usr/bin/xmlsec1",
    "name_form": NAME_FORMAT_URI,
}

MAP = {
    "identifier": "urn:oasis:names:tc:SAML:2.0:attrname-format:uri",
    "fro": {
        'uid': 'uid',
        'displayName': 'displayName',
    },
    "to": {
        'uid': 'uid',
        'displayName': 'displayName',
    }
}

[...]
## Registration ##
#
# Registration can be rate-limited using the parameters in the "Ratelimiting"
# section of this file.

# Enable registration for new users.
#
enable_registration: false


saml2_config:
  # `sp_config` is the configuration for the pysaml2 Service Provider.
  # See pysaml2 docs for format of config.
  #
  # Default values will be used for the 'entityid' and 'service' settings,
  # so it is not normally necessary to specify them unless you need to
  # override them.
  #
  sp_config:
  #  # point this to the IdP's metadata. You can use either a local file or
  #  # (preferably) a URL.
    metadata:
  #    #local: ["saml2/idp.xml"]
      remote:
        - url: https://YOUR_KEYCLOAK_URL/auth/realms/YOUR_REALM/protocol/saml/descriptor
  #
  #    # By default, the user has to go to our login page first. If you'd like
  #    # to allow IdP-initiated login, set 'allow_unsolicited: true' in a
  #    # 'service.sp' section:
  #    #
  #    #service:
  #    #  sp:
  #    #    allow_unsolicited: true
  #
  #    # The examples below are just used to generate our metadata xml, and you
  #    # may well not need them, depending on your setup. Alternatively you
  #    # may need a whole lot more detail - see the pysaml2 docs!
  #
  #    description: ["My awesome SP", "en"]
  #    name: ["Test SP", "en"]
  #
  #    organization:
  #      name: Example com
  #      display_name:
  #        - ["Example co", "en"]
  #      display_name:
  #        - ["Example co", "en"]
  #      url: "http://example.com"
  #
  #    contact_person:
  #      - given_name: Bob
  #        sur_name: "the Sysadmin"
  #        email_address": ["admin@example.com"]
  #        contact_type": technical

  # Instead of putting the config inline as above, you can specify a
  # separate pysaml2 configuration file:
  #
  config_path: "/data/sp_conf.py"
  # Or for container envs:
  config_path: "/synapse/config/sp_conf.py"

  # The lifetime of a SAML session. This defines how long a user has to
  # complete the authentication process, if allow_unsolicited is unset.
  # The default is 5 minutes.
  #
  #saml_session_lifetime: 5m

  # An external module can be provided here as a custom solution to
  # mapping attributes returned from a saml provider onto a matrix user.
  #
  user_mapping_provider:
    # The custom module's class. Uncomment to use a custom module.
    #
    #module: mapping_provider.SamlMappingProvider

    # Custom configuration values for the module. Below options are
    # intended for the built-in provider, they should be changed if
    # using a custom module. This section will be passed as a Python
    # dictionary to the module's `parse_config` method.
    #
    config:
      # The SAML attribute (after mapping via the attribute maps) to use
      # to derive the Matrix ID from. 'uid' by default.
      #
      # Note: This used to be configured by the
      # saml2_config.mxid_source_attribute option. If that is still
      # defined, its value will be used instead.
      #
      #mxid_source_attribute: displayName

      # The mapping system to use for mapping the saml attribute onto a
      # matrix ID.
      #
      # Options include:
      #  * 'hexencode' (which maps unpermitted characters to '=xx')
      #  * 'dotreplace' (which replaces unpermitted characters with
      #     '.').
      # The default is 'hexencode'.
      #
      # Note: This used to be configured by the
      # saml2_config.mxid_mapping option. If that is still defined, its
      # value will be used instead.
      #
      #mxid_mapping: dotreplace

  # In previous versions of synapse, the mapping from SAML attribute to
  # MXID was always calculated dynamically rather than stored in a
  # table. For backwards- compatibility, we will look for user_ids
  # matching such a pattern before creating a new account.
  #
  # This setting controls the SAML attribute which will be used for this
  # backwards-compatibility lookup. Typically it should be 'uid', but if
  # the attribute maps are changed, it may be necessary to change it.
  #
  # The default is 'uid'.
  #
  #grandfathered_mxid_source_attribute: upn

  # Directory in which Synapse will try to find the template files below.
  # If not set, default templates from within the Synapse package will be used.
  #
  # DO NOT UNCOMMENT THIS SETTING unless you want to customise the templates.
  # If you *do* uncomment it, you will need to make sure that all the templates
  # below are in the directory.
  #
  # Synapse will look for the following templates in this directory:
  #
  # * HTML page to display to users if something goes wrong during the
  #   authentication process: 'saml_error.html'.
  #
  #   This template doesn't currently need any variable to render.
  #
  # You can see the default templates at:
  # https://github.com/matrix-org/synapse/tree/master/synapse/res/templates
  #
  #template_dir: "res/templates"

password_config:
   # Uncomment to disable password login
   #
   enabled: false

   # Uncomment to disable authentication against the local password
   # database. This is ignored if `enabled` is false, and is only useful
   # if you have other password_providers.
   #
   #localdb_enabled: false

   # Uncomment and change to a secret random string for extra security.
   # DO NOT CHANGE THIS AFTER INITIAL SETUP!
   #
   #pepper: "EVEN_MORE_SECRET"
[...]