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Iframes support

While iframes have various security challenges and are not supported for regular BankID, it is part of the 3d secure standard and has become an expectation in ecommerce to preserve context to avoid losing the customer in case of errors.

Providing a dedicated iframes solution is a controlled way of moving user interaction from the iframe to other more secure channels while we balance security and usability concerns along the way.

Steps

1. Register a client with BankID OIDC

If you don't have a client registered with BankID OIDC yet, you'll need to register one. Follow the instructions here to register your application and obtain the necessary client credentials (client_id and client_secret).

Info

Ensure that your client has the permissions/client and permissions/iframe scope available.

2. Get the BankID OIDC Configuration

To ensure seamless integration with BankID OIDC and avoid hardcoding specific endpoints in your application, follow these steps to dynamically fetch the OpenID Connect configuration:

  1. Determine the appropriate configuration URL based on the environment:

    Environment Url
    Production https://auth.bankid.no/auth/realms/prod/.well-known/openid-configuration
    Current (public test environment) https://auth.current.bankid.no/auth/realms/current/.well-known/openid-configuration

  2. Send an HTTP GET request to the respective configuration URL using your preferred programming language or API tool.

  3. Capture the response which will contain a JSON document with the configuration. By dynamically fetching the OIDC configuration, your application remains flexible, allowing for future changes or updates to the endpoints without requiring modifications to your code.

Example response from Current (relevant fields only)

{
  ...
  "token_endpoint": "https://auth.current.bankid.no/auth/realms/current/protocol/openid-connect/token",
  ...
}

This is a sample response. The actual response may differ.

3. Get an access token from BankID OIDC

To obtain an access token from OIDC, follow these steps:

  1. Retrieve the token endpoint URL token_endpoint dynamically from the OIDC configuration.

  2. Call the token endpoint URL with your client credentials.

    You can find more detailed information about acquiring access tokens in the BankID OIDC documentation.

  3. In the scope field, include the following: permissions/client, and permissions/iframe. This field specifies the scope of access granted to the token.

Here's an example of a valid request in the current environment:

POST /auth/realms/current/protocol/openid-connect/token HTTP/1.1
Host: auth.current.bankid.no
Content-Type: application/x-www-form-urlencoded
Authorization: Basic <Base64-encoded client id:client secret>

grant_type=client_credentials&scope=openid%20permissions%2Fclient%20permissions%2Fiframe

Make sure to replace the <Base64-encoded client id:client secret> placeholder in the Authorization header with your actual client credentials.

4. Get the BankID with biometrics OIDC configuration

Note

The BankID with biometrics OIDC configuration is a separate configuration from the BankID OIDC configuration.

To ensure seamless integration and avoid hardcoding specific endpoints in your application, follow these steps to dynamically fetch the BankID with biometrics OpenID Connect configuration:

  1. Determine the appropriate configuration URL based on the environment:

    Environment Url
    Production https://app.bankid.no/.well-known/openid-configuration
    Current (public test environment) https://current.aletheia-test.idtech.no/.well-known/openid-configuration

  2. Send an HTTP GET request to the respective configuration URL using your preferred programming language or API tool.

  3. Capture the response which will contain a JSON document with the configuration. By dynamically fetching the OIDC configuration, your application remains flexible, allowing for future changes or updates to the endpoints without requiring modifications to your code.
  4. To enhance the reliability and performance of your integration, we strongly advise implementing response caching for the OIDC configuration.

5. Register the permission upfront

To register a permission, follow these steps:

  1. Construct a permission statement. See the permissions API for detailed information of how to construct the different permissions. Encode the permission statement using URL safe Base64 encoding. Below is an example of a permission statement for a payment:

    const permissionStatement = {
    "nonce": "dW5pcXVlIHZhbHVl", // Must be unique
    "id": "YmFza2V0IGlk", // Your reference
    "payments": [
        {
            "paymentId": "cGF5bWVudCBpZA", // Your reference
            "amount": "123.45",
            "currency": "NOK",
            "creditorName": "Scrooge McDuck"
        }
    ]
}

// Example implementation of a b64 URL Safe Encoder
function b64URLSafeEncode(stringData) {
    return btoa(stringData)
        .replace(/\+/g, "-")
        .replace(/\//g, "_")
        .replace(/=/g, "");
}

b64URLSafeEncode(
    JSON.stringify(
        permissionStatement
    )
);
// -> "eyJub25jZSI6ImRXNXBjWFZsSUhaaGJIVmwiLCJpZCI6IlltRnphMlYwSUdsayIsInBheW1lbnRzIjpbeyJwYXltZW50SWQiOiJjR0Y1YldWdWRDQnBaQSIsImFtb3VudCI6IjEyMy40NSIsImN1cnJlbmN5IjoiTk9LIiwiY3JlZGl0b3JOYW1lIjoiU2Nyb29nZSBNY0R1Y2sifV19"

    Note

    • The nonce must be a unique value for each permission you register.
    • Use id (basket ID) and paymentId as references to the payment(s) in your systems. These will not be shown to the end user.
    • The amount is a decimal amount represented as a string and must use the dot as the decimal separator.

  2. Send a POST request to the permissions endpoint, providing the access token received in the first step as a bearer token. Include the permission, which is the URL safe Base64 encoding of the permission statement object.

    Login hint is optional but highly recommended to simplify user interaction in the iframe.

    POST /permissions/v1/ HTTP/1.1
Host: api.current.aletheia-test.idtech.no
Content-Type: application/json
Authorization: Bearer <access token from step 1>

{
  "type": "payment.v1",
  "iat": 1617091752,
  "exp": 1617092652,
  "permission": < URL safe b64 encoded permission statement from step 2a >,
  "intents": [
    "iframe"
  ],
  "loginHint": [
    {
      "scheme": "nnin",
      "value": "<nnin_as_string>"
    }
  ]
}

    Note

    iat and exp are timestamps in seconds since the UNIX epoch. iat can be at most 1 minute into the past. exp sets the maximum time by which the permission must be granted and should normally be set just a few minutes into the future.

  3. On a successful request, you will receive a response body containing a permission ID, a permission token and a binding message:

    {
  "id": "1.BY.MEKrA-00GVtmvWOCDYQko_fSg93LO5n2rBnlj-X4MQg.BiDEl_CgfakqahcXjLrFet_GGpEkR_W8D-RK4hORBO0",
  "permissionToken": "eyJhbGciOiJIUzI1NiIsImtpZCI6IjB5Z3hDX3UzQlpPWXlKZ0Y3eDJ0eWtQaTRCTml2cG9KMDBmYjFzTGliUVUiLCJ0eXAiOiJKV1QifQ.eyJleHAiOjE2MTcwOTU3NDQsImlhdCI6MTYxNzA5MjE0NCwicyI6IjA6LTEjOTIzIiwicCI6IkJpREVsX0NnZmFrcWFoY1hqTHJGZXRfR0dwRWtSX1c4RC1SSzRoT1JCTzAiLCJuYmYiOjE2MTcwOTIxNDh9.39GWvNjNMSKKhKOF4t4HcDnZGNJmLmPT3f612z1VKko",
  "bindingMessage":"Farlig frakk"
}

6. Create Code Verifier and Code Challenge for PKCE

The iframe flow requires the use of PKCE (Proof Key for Code Exchange by OAuth Public Clients) to protect against authorization code interception attacks. You will need to create a code verifier and code challenge to use in the next steps.

For more detailed information and reasoning, please see RFC 7636.

Steps for Implementing PKCE

  1. Create a Code Verifier:
    • Generate a code_verifier. The verifier should be a high-entropy cryptographic random string.
    • Character Set: Use unreserved characters [A-Z] / [a-z] / [0-9] / "-" / "." / "_" / "~".
    • Length: The length should be between 43 and 128 characters.
    • The Code Verifier will be included when exchanging the authorization code for an access token.
  2. Create the Code Challenge:
    • Create a code_challenge from the code_verifier as follows:
      • code_challenge = BASE64URL-ENCODE(SHA256(ASCII(code_verifier))).
    • Note: The S256 transformation method is mandatory according to FAPI 2.0, thus the plain transformation is not supported.
    • The Code Challenge will be included when getting an iframe URL with iframe-authorize.

7. Get iframe URL

  1. Make a POST request to the iframe-authorize endpoint.
    • Include the permissionToken from step 4 as the login_hint_token in the iframe-authorize endpoint.
    • In the scope, include the following scopes:
    • Required:
      • openid
    • Optional:
      • profile - to get the user's profile information.
        • Claims: name, given_name, family_name,birthdate, updated_at
      • sub_nnin - to get the user's national identity number (NNIN).
        • Claims: sub_nnin
        • Note: This is only available for clients with explicit access!
      • sub_bankid - to get the user's BankID PID.
        • Claims: sub_bankid
    • Provide redirect_uri as the URL to which the user will be redirected after the authentication is completed.
    • Provide state to protect against cross-site request forgery (CSRF) attacks.
    • Provide nonce to associate the OIDC Client session with an ID Token, and to prevent replay attacks.
    • Provide code_challenge generated as described in the PKCE section.
    • Provide code_challenge_method to indicate which method was used to derive the challenge. Currently, only S256 is supported.
    • Provide frame_ancestor to specify which domain is allowed to embed the iframe. This is a security measure to prevent clickjacking.

Below is an example of a request to the iframe-authorize endpoint:

POST /iframe-authorize HTTP/1.1
Host: oidc.current.aletheia-test.idtech.no
Content-Type: application/x-www-form-urlencoded
Authorization: Bearer <access token from step 1>

login_hint_token=string
&scope=openid+permissions%2Fiframe
&state=string
&nonce=string
&code_challenge=string
&code_challenge_method=S256
&redirect_uri=https%3A%2F%2Fexample.com%2Fcallback
&frame_ancestor=https%3A%2F%2Fexample.com

Note: Ensure to replace the string placeholder values with actual data and provide appropriate values for other fields.

After calling the iframe-authorize endpoint, you will receive the following response:

{
    "authorize_uri": "stringstring", 
    "expires_in": 60
}

8. Open url in iframe

Open the authorize_uri from the /iframe-authorize response in a new iframe to start the auth code flow.

Referrer policies

As a security measure, we will match the document.referrer as reported by our client against the frame_ancestor you provided in step 7. The client will error on origin mismatch. This means that you cannot use any Referrer-Policy header that would prevent us from reading the referrer origin on the page that opens the iframe.

If you must use a Referrer-Policy header on your embedding page, in order for the referrer to be readable by us, the value must be one of: no-referrer-when-downgrade, origin, origin-when-cross-origin or unsafe-url.

Read more about referrer policies here.

9. Listen for analytics events (optional)

Events are sent to the embedding page (window.parent) using postMessage. The intention is to allow insights into the funnel. The analytics event is a JSON object with the following shape:

{
    "type": "analytics",
    "event": "string"
}

Refer to the below tables for possible event values:

Initialization events

event Description
initialization_pending The session is initializing.
initialization_completed The initialization completed.
initialization_errored The initialization errored.

Authorization events

event Description
authorization_pending The authorization is in progress, possibly awaiting user consent or additional credentials.
authorization_granted The user has been successfully authorized.
authorization_denied The user or system denied the authorization.
authorization_timeout The authorization timed out.
authorization_errored The authorization errored.

Additional events

event Description
awaiting_user_identity_input Waiting for the user to provide user identity input.
awaiting_delegated_authentication Waiting for a delegated authentication to be completed.
redirecting_to_merchant The user is being redirected to the callback url.

A listener for these events can be implemented using this example code:

window.addEventListener("message", (event) => {
  if (event.origin !== "https://app.bankid.no") return; // Verify sender

  try{
    const message = JSON.parse(event.data);

    if(message.type !== "analytics") return;

    console.debug(messageData.event) // "initializing"
  }
  catch(err) {}
})

10. Handle callback and exchange code for tokens

After the user has authenticated or encountered an error, they will be redirected to the callback URI specified in the redirect_uri parameter, with the state, code and error query parameters present according to the outcome of the authentication.

From this callback, you can either:

  • Make a backend call from inside the iframe
  • Transport the data out to the parent frame, for example using window.parent.postMessage and make a backend call from there

Steps to handle the callback and exchange the code for tokens

  1. Retrieve the code parameter from the callback request.
  2. Build the token request by including the following parameters:
    • grant_type=authorization_code: Indicates the usage of the Authorization Code Flow.
    • redirect_uri: The same callback URI used in the authorization request.
    • code: The authorization code received in the callback.
    • code_verifier: Include the code_verifier used to generate the code_challenge in step 6.
  3. Make a POST request to the token endpoint. Obtain the token_endpoint from the BankID with biometrics OIDC configuration, not the BankID OIDC configuration. You will use the same access token you received from BankID OIDC in step 3 to authenticate the token request. You only need to request a new token if the old has expired.

Here's an example of a valid request:

POST /oidc/v1/token HTTP/1.1
Host: oidc.current.aletheia-test.idtech.no
Content-Type: application/x-www-form-urlencoded
Authorization: Bearer <access token retrieved from BankID OIDC  in step 3>

grant_type=authorization_code
&redirect_uri=https://localhost:3000/api/auth/callback/bid
&code=AUTHORIZATION_CODE
&code_verifier=code_verifier

11. Verify the token

To ensure the authenticity and integrity of the received token, perform the following verifications:

  • Verify that the nonce claim in the received ID token corresponds to the nonce value belonging to the same session (i.e. the nonce associated with the state).
  • Verify that the acr claim include LOA=3 (Level of Assurance 3). This indicating the desired level of trust in the authentication process.
  • Verify that the token is signed by JWKS (JSON Web Key Set) document from the endpoint provided in the BankID OIDC configuration.

If any of the above verifications fail, it indicates a failed authentication process.

12. Get the signed permission (optional)

To get the signed permission you can send in a GET request to the permissionId/grant endpoint. The permissionId you use is the one that you got from your permissions POST request. Be aware that it can return a 404 error code (permission not yet granted) but as mentioned in the api specification you can set up a polling request on the permissionId/grant endpoint until your initial permission has been signed.

If your permission has been successfully granted you will receive this response:

{
  "gv": 1,
  "pt": "string",
  "type": "string",
  "rpId": "bankid-app",
  "sv": "2020-10-30@deadbeef",
  "iat": 1800000000,
  "iss": "string",
  "nonce": "string",
  "proofKeyId": "string",
  "sub": "nnin:010112345",
  "permissionId": "string",
  "digest": "string"
}

The grant is a JWT token that can be validated as follows:

  • In the BankID with biometrics OIDC configuration (as mentioned here) get the Grant JWK set from the URI pointed to by the jwks_uri_grants property in this document.
  • Check that the JWT token is signed by one of the keys in the Grant JWK set. You can find a suitable library for performing this verification at https://jwt.io/libraries.
  • Check that the nonce claim inside the token payload is equal to the nonce in the permission statement created in step 2.