Matrix Synapse SAML2 Login

Tutorial on how to use Keycloak with Matrix Synapse Homeserver for authentication of users.


This is a very rough write-up on how to use Keycloak SAML2 with a Matrix Synapse Homeserver for user authentication. Keep in mind that not all points outlined here may 100% work for you and "turning and changing" some parameters may be needed to get it working for your setup.


This blog post is especially made for Keycloak SAML 2.0 SSO with Matrix with the GitHub matrix-org/synapse - Complete the SAML2 implementation #5422, which is based on my draft PR GitHub matrix-org/synapse - SAML2 Improvements and redirect stuff #5316.


Thanks to Helder Ferreira (@wounn Twitter, HelderFSFerreira GitHub) for reaching out to me and updating the configs in this post!

Matrix Syanspe

To get SAML 2.0 working you need to have a Matrix Synapse Homeserver running version at least version 1.1,0.

In addition to that you need to have the pysaml2 Python module installed and xmlsec1 must be installed on the Matrix Synapse homeserver too.

On Debian and CentOS (possibly all RHEL based OSes) the package is called xmlsec1.

Be sure to verify that the path to xmlsec1 is correctly configured in the upcoming /synapse/config/ section. To make sure you have the right path for the pysaml2 config, run which xmlsec1 and use the printed out path for the xmlsec_binary option.


The blog post assumes that the config for the Matrix Synapse Homeserver is located in /synapse/config/ directory, you can simply change this as long as you change it in all files and/ or steps to do.


SAML2 Client

In Keycloak create a new SAML client and set the settings of that client as follows:

Keycloak Client Settings

Two mappers should be created:

  • uid for the username. Keycloak Client Mapper uid Options
    • Mapper Type - User Property
    • Property - Username
    • Friendly Name - uid
    • SAML Attribute Name - uid
    • SAML Attribute NameFormat - URI Reference
  • displayName for the displayed name in Keycloak. Keycloak Client Mapper displayName Options
    • Mapper Type - Javascript Mapper
    • Script
      // Concat First and Last name of user when non-empty
      names = [];
      firstName = user.getFirstName();
      if (firstName.length > 0) {
      lastName = user.getLastName();
      if (lastName.length > 0) {
      exports = names.join(" ");
    • Single Value Attribute - On
    • Friendly Name - displayName
    • SAML Attribute Name - displayName
    • SAML Attribute NameFormat - Basic

In the end it should look like this:

Keycloak Client Mappers List


Thanks to this comment for pointing to the correct attributes to use for Matrix Synapse code to pick'em up!

SAML 2.0 Identity Provider Metadata file

Now download the Keycloak "SAML 2.0 Identity Provider Metadata" file. You can get it when you login to the "Keycloak Admin Console" and then click the "SAML 2.0 Identity Provider Metadata" link in the General tab (selected by default) at the Endpoints list.

Keycloak Realm Settings


Should you not have this button/ link in the Endpoints list, update your Keycloak instance to version 6.0.1 or higher!

If you have a very good reason to not keep your Keycloak uptodate, you can try to get the file from https://YOUR_KEYCLOAK_URL/auth/realms/YOUR_REALM/protocol/saml/descriptor. (Replace the placeholders according to your setup)



Be sure to replace the following strings with your value:

  • - Your Matrix homeserver address.
  • matrix-example-com - The name of the SAML2 Keycloak client you chose during the client creation.

/synapse/config/key.pem and /synapse/config/cert.pem

Certificate and key from Keycloak Client "SAML Keys" tab page. If there is no certificate and key shown, press the Generate new keys button to generate them.

Click the Export button, set the following options before clicking the Download button:

  • Archive Format: PKCS12
  • Key Alias: The name of your Keycloak Client.
  • Key Password: A password which is used later to "decrypt" the PKCS12 cert + key store.
  • Realm Certificate Alias: master
  • Store password: Either another password or the same as for Key Password.

You should get a file named keystore.p12 after pressing the Download button.

Now run the following sequence of commands to extract the key and cert in PEM format (this assumes the file is named keystore.p12 and the password chosen is example123):

$ 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

Two files, key.pem and cert.pem, are now generated in your current directory and now just need to be placed in the /synapse/config/ directory (full paths see section title) on the Matrix Synapse host(s).



If you have already downloaded the "SAML 2.0 Identity Provider Metadata" file as mentioned in the Keycloak - SAML 2.0 Identity Provider Metadata file section, you can just use and copy it to /synapse/config/idp.xml on the Matrix Synapse Homeserver.

You can get it when you login to the "Keycloak Admin Console" and then click the "SAML 2.0 Identity Provider Metadata" link in the General tab (selected by default) at the Endpoints list.

Keycloak Realm Settings


Should you not have this button/ link in the Endpoints list, update your Keycloak instance to version 6.0.1 or higher!

If you have a very good reason to not keep your Keycloak uptodate, you can try to get the file from https://YOUR_KEYCLOAK_URL/auth/realms/YOUR_REALM/protocol/saml/descriptor. (Replace the placeholders according to your setup)

Be sure to copy the downloaded file to /synapse/config/idp.xml on the Matrix Synapse Homeserver.

Example Keycloak SAML 2.0 Identity Provider Metadata file:

<?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
  ~ 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"
    <EntityDescriptor entityID="https://__YOUR_KEYCLOAK_URL__/auth/realms/master">
        <IDPSSODescriptor WantAuthnRequestsSigned="true"
                        <KeyDescriptor use="signing">

                    Location="https://__YOUR_KEYCLOAK_URL__/auth/realms/master/protocol/saml" />
                    Location="https://__YOUR_KEYCLOAK_URL__/auth/realms/master/protocol/saml" />
            <SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
                Location="https://__YOUR_KEYCLOAK_URL__/auth/realms/master/protocol/saml" />
                Location="https://__YOUR_KEYCLOAK_URL__/auth/realms/master/protocol/saml" />
                Location="https://__YOUR_KEYCLOAK_URL__/auth/realms/master/protocol/saml" />


This is the pysaml2 config file. It configures pysaml2 to talk with the Keycloak server and do SAML2 authentication.

Create this file with the following content: (Don't forget to replace the placeholders, see Replacements section)

import saml2
from saml2.saml import NAME_FORMAT_URI

BASE = ""

    "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": "",
    #"contact_person": [{
    #    "given_name": "Example",
    #    "sur_name": "Example",
    #    "email_address": ["[email protected]"],
    #    "contact_type": "technical",
    #    },
    # Make sure to have xmlsec1 installed on your host(s)!
    "xmlsec_binary": "/usr/bin/xmlsec1",
    "name_form": NAME_FORMAT_URI,


This file is your way to map attributes coming from the SSO (/ IDP) service.

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


fro in the above file is not a typo, see pysaml2 Documentation - "Configuration of pySAML2 entities" - attribute_map_dir.

Your Matrix Synapse Homeserver Config YAML file

Add or change the following lines to your Matrix Synapse Homeserver config (make sure you don't duplicate the lines as that may lead to weird server behavior and/ or issues):

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

# Enable registration for new users.
enable_registration: false

  # `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.
  #  # point this to the IdP's metadata. You can use either a local file or
  #  # (preferably) a URL.
  #    #local: ["saml2/idp.xml"]
        - 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: ""
  #    contact_person:
  #      - given_name: Bob
  #        sur_name: "the Sysadmin"
  #        email_address": ["[email protected]"]
  #        contact_type": technical

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

  # 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.
    # 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.
      # 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:
  #template_dir: "res/templates"

   # 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.
   #pepper: "EVEN_MORE_SECRET"


And again a huge thanks to Helder Ferreira (@wounn Twitter, HelderFSFerreira GitHub) for updating the configs in this post!


That should be it, now when you go to your Riot Webapp (and chose your Matrix Homeserver) it should give you a button to login through your (SAML2) SSO.

Riot Webapp SSO Login

If it does not work, make sure your Matrix Synapse Homeserver has the required pysaml2 module installed and check your Synapse Homeserver logs for errors and/ or warnings.

Have Fun!