Setting up Delegated Authentication with SAML on Microsoft Azure

Before setting up the installer, you have to configure Microsoft Azure Active Directory.

You need to create an App registration.
You have to select Redirect URI (optional) and set it to https://matrix.your-domain.com/_synapse/client/oidc/callback

For the bridge to be able to operate correctly, navigate to API permissions, add Microsoft Graph APIs, choose Delegated Permissions and add

Remember to grant the admin consent for those.

To setup the installer, you'll need

Add an OIDC provider in the 'Synapse' configuration after enabling Delegated Auth and set the following fields in the installer:

Allow Existing Users: if checked, it allows a user logging in via OIDC to match a pre-existing account instead of failing. This could be used if switching from password logins to OIDC.
Authorization Endpoint: the oauth2 authorization endpoint. Required if provider discovery is disabled.
https://login.microsoftonline.com/<Directory (tenant) ID>/oauth2/v2.0/authorize
Backchannel Logout Enabled: Synapse supports receiving OpenID Connect Back-Channel Logout notifications. This lets the OpenID Connect Provider notify Synapse when a user logs out, so that Synapse can end that user session. This property has to bet set to https://your-domain/_synapse/client/oidc/backchannel_logoutin your identity provider

Client Auth Method: auth method to use when exchanging the token. Set it to Client Secret Post or any method supported by your Idp
Client ID: your Application (client) ID
Discover: enable/disable the use of the OIDC discovery mechanism to discover endpoints
Idp Brand: an optional brand for this identity provider, allowing clients to style the login flow according to the identity provider in question
Idp ID: a string identifying your identity provider in your configuration
Idp Name: A user-facing name for this identity provider, which is used to offer the user a choice of login mechanisms in the Element UI. In the screenshot bellow, Idp Name is set to Azure AD

Issuer: the OIDC issuer. Used to validate tokens and (if discovery is enabled) to discover the provider's endpoints
https://login.microsoftonline.com/<Directory (tenant) ID>/v2.0
Token Endpoint: the oauth2 authorization endpoint. Required if provider discovery is disabled.
Client Secret: your secret value defined under "Certificates and secrets"

Scopes: add every scope on a different line
- The openid scope is required which translates to the Sign you in permission in the consent UI
- You might also include other scopes in this request for requesting consent.

User Mapping Provider: Configuration for how attributes returned from a OIDC provider are mapped onto a matrix user.
- Localpart Template: Jinja2 template for the localpart of the MXID. Set it to {{ user.preferred_username.split('@')[0] }} for Azure AD
- Display Name Template: Jinja2 template for the display name to set on first login. If unset, no displayname will be set. Set it to {{ user.name }}for Azure AD
Other configurations are documented here.

With an account with enough rights, go to : Enterprise Applications Portal

Click on New Application
Click on Create your own application on the top left corner
Choose a name for it, and select Integrate any other application you don't find in the gallery
Click on "Create"
Select Set up single sign on
Select SAML
Edit on Basic SAML Configuration
In Identifier , add the following URL : https://<synapse fqdn>/_synapse/client/saml2/metadata.xml
Remove the default URL
In Reply URL , add the following URL : https://<synapse fqdn>/_synapse/client/saml2/authn_response
Click on Save
Edit on Attributes & Claims
Remove all defaults additional claims
Click on Add new claim to add the following claims. The UID will be used as the MXID, the
value here is mostly a suggestion :

Name: uid , Transformation : ExtractMailPrefix , Parameter 1 :user.userprincipalname
Name: email , Source attribute : user.mail