Integrate login using OIDC

OpenID Connect (OIDC) is one of the most common identity authentication protocols used by SaaS products today. OIDC extends the authentication and authorization mechanisms of OAuth 2.0 with identity-focused security features like ID tokens and user profiles.

Transmit supports an OIDC-based integration option for adding hosted login to your website. This includes login using secure FIDO2 WebAuthn biometrics, and social providers like Google, Facebook, Apple, and LINE. If you've already implemented OIDC for other providers, this provides a faster and easier way to kick off your integration. For more, see our OIDC API Reference.

How it works

Transmit supports the OIDC authorization code flow for user authentication and the OIDC RP-initiated logout for logout.

Here's an example of a login flow that can be implemented using the steps in this guide. Transmit APIs are shown in pink along with the relevant integration step, described below. Note that refreshing tokens and logout aren't shown.

1. The user requests to log in and your app sends an authorization request to Transmit ( Step 3 ).
2. Transmit redirects to the hosted login experience to authenticate the user.
3. If successful, Transmit redirects back to your app with an authorization code.
4. Your app exchanges the authorization code for user tokens in the backend ( Step 4 ).
5. After validating the user tokens, your app logs in the user ( Step 5 ).
6. If needed, your app refreshes the user access token and continues working while user if offline ( Step 6 ).
7. Upon local session expiration or user logout, your app logs out the user from Transmit ( Step 7 ).

Step 1: Set up login method

Before you add login to your application, set up the login method you plan to use by completing the provider-specific setup, as described in these dedicated guides:

• Google : Set up Google credentials and consent screen using steps 1-3
• Apple : Set up Apple credentials using steps 1-2
• Facebook : Set up Facebook credentials using steps 1-2
• LINE : Set up LINE credentials using steps 1-2

Step 2: Add redirect URI to app

After the authentication is completed, the authentication result is returned to your redirect URI. This URI should be registered in your application settings in Transmit Admin Portal. From the Admin Portal under Applications, click your application to enter its settings and add this URI under Redirect URIs. If you don't already have an application, you'll need to create one first (see Create application).

Step 3: Authorize user

Authorize the user by sending a GET request to /oidc/auth, which initiates an OIDC authorization code flow. This returns an authorization code to your redirect URI upon successful authentication; otherwise, an error.

Here are some basic parameters of the OIDC authorization request (see OIDC API Reference):

Below is a sample request to login with Google. It obtains the relevant user consents and doesn't re-authenticate the user if there's a valid session (since prompt doesn't include login). Based on the scope, the ID token will include the user's email address and the access token can be refreshed. In addition, since createNewUser is true, a new user will be automatically created if no user is found for the email address used in the Google authentication.

curl -i -X GET \
  'https://api.transmitsecurity.io/cis/oidc/auth?client_id=CLIENT_ID&scope=openid%20email%20offline_access&response_type=code&redirect_uri=REDIRECT_URI&prompt=consent&acr_values=urn:transmit:google_direct&createNewUser=true'

Step 4: Get user tokens

The authorization code returned to your redirect URI upon successful authentication should be passed to your app backend. Your server can exchange this code for an ID and access token by sending a POST request like the one below to the /oidc/token endpoint, along with the following parameters:

curl -i -X POST \
  https://api.transmitsecurity.io/oidc/token \
  -H 'Content-Type: application/x-www-form-urlencoded' \
  -d client_id=CLIENT_ID \
  -d client_secret=CLIENT_SECRET \
  -d code=CODE \
  -d grant_type=authorization_code \
  -d redirect_uri=REDIRECT_URI

Step 5: Validate tokens

The /oidc/token response includes an ID token with user profile data, and a user access token. These tokens must be validated as described here. Validate the token signatures using the public key retrieved from this request:

curl -i -X GET \
  'https://api.transmitsecurity.io/cis/oidc/jwks'

Step 6: Refresh access tokens

If the app has to keep operating on the user's behalf after the user has left, you can obtain a user access token using the refresh token, i.e., to extend access of logged-in users when the access token has expired. Both of these tokens are returned upon successful authentication (if offline_access is requested). To do this, send a POST request to the /oidc/token endpoint, along with the following parameters:

curl -i -X POST \
https://api.transmitsecurity.io/oidc/token \
-H 'Content-Type: application/x-www-form-urlencoded' \
-d grant_type=refresh_token \
-d client_id=CLIENT_ID \
-d client_secret=CLIENT_SECRET \
-d refresh_token=REFRESH_TOKEN

Step 7: Log out user

Once the user is authenticated, a new session is created and these tokens are returned: ID token, access token, and refresh token (if offline_access was requested). If the authorization request doesn't force re-authentication (by passing prompt=login), the user won't be re-authenticated if there's a valid session.

If the user requests to logout, redirect the User Agent to the /oidc/session/end endpoint below (defined by OIDC), which will terminate all the user's sessions for this tenant. We recommend specifying your client ID and the URI to which the user will be redirected once the sessions are terminated. If these parameters aren't passed, our default logout success page will be shown instead.

https://api.transmitsecurity.io/cis/oidc/session/end?post_logout_redirect_uri=LOGOUT_URI&client_id=CLIENT_ID

To complete the logout, revoke both their access token and refresh token so they can no longer gain access to your resources without authenticating. This is done by sending the POST /oidc/token/revocation request below (defined by OAuth) from your backend, along with the token you want to revoke and your client credentials.

curl -i -X POST \
https://api.transmitsecurity.io/oidc/token/revocation \
-H 'Content-Type: application/x-www-form-urlencoded' \
-d client_id=CLIENT_ID \
-d client_secret=CLIENT_SECRET \
-d token=TOKEN

Discovery

If needed, information for configuring Transmit as an OIDC IDP is available using the discovery endpoint, including Transmit OIDC endpoints and supported parameters. Send the following request:

curl -i -X GET \
  'https://api.transmitsecurity.io/cis/oidc/.well-known/openid-configuration'