# Authentication

Metra currently supports authentication exclusively through **Keycloak**.

Supported:

* **OIDC Authorization Code Flow**
* **Keycloak Realm configured for Canton Network users**

Future Support:

* Other OAuth/OIDC Identity Providers (Azure AD, Auth0, Ping Identity, etc.).

***

### Keycloak Configuration

Metra uses OIDC claims to determine access and the corresponding party identity of a user.

#### 3.1 Create an OIDC Client for Metra

In your Canton Keycloak realm:

1. Go to **Clients** → **Create**.
2. Select type: **OpenID Connect**.
3. Set:
   * Client ID: `metra`
   * Access Type: `confidential`
   * Standard Flow Enabled: **ON**.
4. Save the client.

#### 3.2 Configure the Callback URL

Under **Client → Settings → Valid Redirect URIs**, add:

```
https://metra.YOUR_DOMAIN/auth/callback
```

Or if running locally:

```
http://localhost:3000/auth/callback
```

#### 3.3 Add Required User Attributes

Each Keycloak user who can access Metra **must have a party identifier**:

1. Go to **Users → {User} → Attributes**.
2. Add:
   * Key: `party_id`
   * Value: `{Canton Party ID Hint}`\
     Example: `party1::issuer-xyz`

This allows Metra to know which party the user represents on Canton network.

#### 3.4 Add Attribute Mapper to Tokens

Under **Client → Mappers → Create**:

* Name: `party_id`
* Mapper Type: **User Attribute**
* User Attribute: `party_id`
* Token Claim Name: `party_id`
* Claim JSON Type: `String`
* Add to ID token: **ON**
* Add to Access token: **ON**

This ensures `party_id` flows through OIDC tokens.


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