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Wonderwall (sidecar for authentication)

Wonderwall is an application that implements an OpenID Connect (OIDC) Relying Party (client) in a way that makes it easy to plug into Kubernetes as a sidecar.

Abstract

Wonderwall functions as a reverse proxy that intercepts and proxies requests to your application. It provides endpoints to perform logins and logouts for end users, along with session management - so that your application does not have to.

All HTTP requests to the application will be intercepted by Wonderwall, which is attached to your application's pod as a sidecar.

If the user does not have a valid local session with the sidecar, the request will be proxied as-is without modifications to the application container.

In order to obtain a local session, the user must be redirected to the /oauth2/login endpoint, which performs the OpenID Connect Authorization Code Flow.

If the user successfully completed the login flow, the sidecar creates and stores a session. A corresponding session cookie is created and set before finally redirecting user agent to the application. All requests that are forwarded to the application container will now contain an Authorization header with the user's access_token:

Authorization: Bearer <JWT_ACCESS_TOKEN>

Your application is responsible for validating the access_token.

Availability

This feature is only available in dev-gcp and prod-gcp.

Overview

The diagram below shows the overall architecture of an application when using Wonderwall as a sidecar:

flowchart TB
    accTitle: System Architecture
    accDescr: The architectural diagram shows the browser sending a request into the Kubernetes container, requesting the ingress https://&ltapp&gt.nav.no, requesting the service https://&ltapp&gt.&ltnamespace&gt, sending it to the pod, which contains the sidecar. The sidecar sends a proxy request to the app, in addition to triggering and handling the Open ID Connect Auth Code Flow to the identity provider. The identity provider is outside the Kubernetes environment.

    idp(Identity Provider)
    Browser -- 1. initial request --> k8s
    Browser -- 2. redirected by Wonderwall --> idp
    idp -- 3. performs OpenID Connect Auth Code flow --> Browser

    subgraph k8s [Kubernetes]
        direction LR
        Ingress(Ingress<br>https://&ltapp&gt.nav.no) --> Service(Service<br>http://&ltapp&gt.&ltnamespace&gt) --> Wonderwall
        subgraph Pod
            direction TB
            Wonderwall -- 4. proxy request with access token --> Application
            Application -- 5. return response --> Wonderwall
        end
    end

The sequence diagram below shows the default behavior of the sidecar:

sequenceDiagram
    accTitle: Sequence Diagram
    accDescr: The sequence diagram shows the default behaviour of the sidecar, depending on whether the user already has a session or not. If the user does have a session, the sequence is as follows: 1. The user visits a path, that requests the ingress.  2. The request is forwarded to wonderwall 3. Wonderwall checks for a session in session storage. 4. Wonderwall attaches Authorization header and proxies request and sends it to the application. 5. The application returns a response to Wonderwall. 6. Wonderwall returns the response to the user. If the user does not have a session, the sequence is as follows: 1. The user visits a path, that requests the ingress.  2. The request is forwarded to wonderwall 3. Wonderwall checks for a session in session storage. 4. Wonderwall proxies the request as-is and sends it to the application. 5. The application returns a response to Wonderwall. 6. Wonderwall returns the response to the user.

    actor User
    User->>Ingress: visits /path
    Ingress-->>Wonderwall: forwards request
    activate Wonderwall
    Wonderwall-->>Session Storage: checks for session
    alt has session
        Session Storage-->>Wonderwall: session found
        activate Wonderwall
        Wonderwall-->>Application: attaches Authorization header and proxies request
        Application-->>Wonderwall: returns response
        Wonderwall->>User: returns response
        deactivate Wonderwall
    else does not have session
        Session Storage-->>Wonderwall: no session found
        activate Wonderwall
        Wonderwall-->>Application: proxies request as-is
        Application-->>Wonderwall: returns response
        Wonderwall->>User: returns response
        deactivate Wonderwall
    end

Generally speaking, the recommended approach when using the Wonderwall sidecar is to put it in front of your backend-for-frontend server that serves your frontend. Otherwise, you might run into issues with the cookie configuration and allowed redirects - these are both effectively restricted to only match the domain and path for your application's ingress.

Endpoints

The sidecar provides these endpoints under your application's ingress:

Path Description Note
GET /oauth2/login Initiates the OpenID Connect Authorization Code flow
GET /oauth2/logout Performs local logout and redirects the user to global/single-logout
GET /oauth2/logout/local Performs local logout only Only for Azure AD
GET /oauth2/session Returns the current user's session metadata
POST /oauth2/session/refresh Refreshes the tokens and returns the session metadata for the current user Only for Azure AD

Usage

Overview

The contract for usage of the sidecar is fairly simple.

For any endpoint that requires authentication:

  1. Validate the Authorization header as specified in the application guidelines.
  2. If the Authorization header is missing, redirect the user to the login endpoint.
  3. If the JWT access_token in the Authorization header is invalid or expired, redirect the user to the login endpoint.
  4. If you need to log out a user, redirect the user to the logout endpoint.

Providers

Refer to the specific identity provider documentation for additional details that apply to the given provider:

1. Initiate Login

When you must authenticate a user, redirect to the user to:

https://<ingress>/oauth2/login

The user will be sent to the identity provider for authentication and then back to the sidecar's callback endpoint.

1.1. Redirect after Login

After the callback is handled and the user is successfully authenticated, the user will be redirected in this priority:

  1. The URL or absolute path set in the query parameter redirect in the initial login request, e.g: 

    https://<ingress>/oauth2/login?redirect=/some/path
    If you include query parameters, ensure that they are URL encoded. The host and scheme (if provided) are stripped from the redirect URL, which effectively only allows redirects to paths within your own ingress.

  2. The root context path for your application's ingress. E.g. / for https://<app>.nav.no, or /path for https://nav.no/path.

1.2. Autologin

If enabled, the autoLogin option will configure Wonderwall to automatically redirect HTTP GET requests to the login endpoint if the user does not have a session. It will set the redirect parameter for logins to the URL for the original request so that the user is redirected back to their intended location after login.

You should still check the Authorization header for a token and validate the token within as specified in the application guidelines. This is especially important as auto-logins will NOT trigger for HTTP requests that are not GET requests, such as POST or PUT.

To ensure smooth end-user experiences whenever their session expires, your application must thus actively validate and properly handle such requests. For example, your application might respond with an HTTP 401 to allow frontends to cache or store payloads before redirecting them to the login endpoint.

Example configuration:

spec:
  idporten:
    sidecar:
      autoLogin: true

spec:
  azure:
    sidecar:
      autoLogin: true

This will match for all paths for your application's ingresses, except the following:

You can also define additional paths or patterns to be excluded: 

spec:
  idporten:
    sidecar:
      autoLogin: true
      autoLoginIgnorePaths:
        - /internal/*
        - /some/public/path
        - /static/stylesheet.css

spec:
  azure:
    sidecar:
      autoLogin: true
      autoLoginIgnorePaths:
        - /internal/*
        - /some/public/path
        - /static/stylesheet.css

The paths must be absolute paths. The match patterns use glob-style matching.

Example match patterns
  • /allowed or /allowed/
    • Trailing slashes in paths and patterns are effectively ignored during matching.
    • ✅ matches:
      • /allowed
      • /allowed/
    • ❌ does not match:
      • /allowed/nope
      • /allowed/nope/
  • /public/*
    • A single asterisk after a path means any subpath directly below the path, excluding itself and any nested paths.
    • ✅ matches:
      • /public/a
    • ❌ does not match:
      • /public
      • /public/a/b
  • /public/**
    • Double asterisks means any subpath below the path, including itself and any nested paths.
    • ✅ matches:
      • /public
      • /public/a
      • /public/a/b
    • ❌ does not match:
      • /not/public
      • /not/public/a
  • /any*
    • ✅ matches:
      • /any
      • /anything
      • /anywho
    • ❌ does not match:
      • /any/thing
      • /anywho/mst/ve
  • /a/*/*
    • ✅ matches:
      • /a/b/c
      • /a/bee/cee
    • ❌ does not match:
      • /a
      • /a/b
      • /a/b/c/d
  • /static/**/*.js
    • ✅ matches:
      • /static/bundle.js
      • /static/min/bundle.js
      • /static/vendor/min/bundle.js
    • ❌ does not match:
      • /static
      • /static/some.css
      • /static/min
      • /static/min/some.css
      • /static/vendor/min/some.css

2. Initiate Logout

When you must log a user out, redirect to the user to:

https://<ingress>/oauth2/logout

The user's session with the sidecar will be cleared, and the user will be redirected to the identity provider for global/single-logout, if logged in with SSO (single sign-on) at the identity provider.

2.1 Local Logout

Limited Availability

This feature is only available for Azure AD

If you only want to perform a local logout for the user, perform a GET request from the user's browser / user agent:

https://<ingress>/oauth2/logout/local

This will only clear the user's local session (i.e. remove the cookies) with the sidecar, without performing global logout at the identity provider. The endpoint responds with a HTTP 204 after successful logout. It will not respond with a redirect.

A local logout is useful for scenarios where users frequently switch between multiple accounts. This means that they do not have to re-enter their credentials (e.g. username, password, 2FA) between each local logout, as they still have an SSO-session logged in with the identity provider. If the user is using a shared device with other users, only performing a local logout is thus a security risk.

Ensure you understand the difference in intentions between the two logout endpoints. If you're unsure, use /oauth2/logout.

3. Token Validation

Secure your endpoints

Your application is responsible for securing its own endpoints.

  • If a request does not contain an Authorization header, the request should be considered unauthenticated and access should be denied.
  • If a request has an Authorization header that contains a JWT, the token must be validated before access is granted.

Your application should validate the claims and signature for the JWT Bearer access_token attached by the sidecar in the Authorization header.

Each provider may have some differences in claims and values; see their specific page for details:

4. Resource Requirements

The sidecar container is set up with some default resource requirements. This can be customized to your needs. Defaults shown below:

spec:
  idporten:
    sidecar:
      resources:
        limits:
          cpu: 2
          memory: 256Mi
        requests:
          cpu: 20m
          memory: 32Mi

spec:
  azure:
    sidecar:
      resources:
        limits:
          cpu: 2
          memory: 256Mi
        requests:
          cpu: 20m
          memory: 32Mi

5. Sessions

Sessions are stored server-side; we only store a session identifier at the end-user's user agent.

The session lifetime depends on the identity provider:

Identity Provider Session Lifetime
Azure AD 10 hours
ID-porten 1 hour

After the session has expired, the user must be redirected to the /oauth2/login endpoint again.

For convenience, we also offer an endpoint that returns metadata about the user's session as a JSON object at GET /oauth2/session. This endpoint will respond with HTTP status codes on errors:

  • HTTP 401 Unauthorized - no session cookie or matching session found (e.g. user is not authenticated, or has logged out)
  • HTTP 500 Internal Server Error - the session store is unavailable, or Wonderwall wasn't able to process the request

Otherwise, an HTTP 200 OK is returned with the metadata with the application/json as the Content-Type.

Example

Request:

GET /oauth2/session

Response:

HTTP/2 200 OK
Content-Type: application/json

{
  "session": {
    "created_at": "2022-08-31T06:58:38.724717899Z", 
    "ends_at": "2022-08-31T16:58:38.724717899Z",
    "ends_in_seconds": 14658
  },
  "tokens": {
    "expire_at": "2022-08-31T14:03:47.318251953Z",
    "refreshed_at": "2022-08-31T12:53:58.318251953Z",
    "expire_in_seconds": 4166
  }
}

Most of these fields should be self-explanatory, but we'll be explicit with their description:

Field Description
session.created_at The timestamp that denotes when the session was first created.
session.ends_at The timestamp that denotes when the session will end.
session.ends_in_seconds The number of seconds until the session ends.
tokens.expire_at The timestamp that denotes when the tokens within the session will expire.
tokens.refreshed_at The timestamp that denotes when the tokens within the session was last refreshed.
tokens.expire_in_seconds The number of seconds until the tokens expire.

5.1. Refresh Tokens

Limited Availability

This feature is currently only available for Azure AD

Tokens within the session will usually expire before the session itself. To avoid redirecting end-users to the /oauth2/login endpoint whenever the access tokens have expired, we can use refresh tokens to silently get new tokens.

This is enabled by default for applications using Wonderwall with Azure AD.

Tokens will at the earliest be automatically renewed 5 minutes before they expire. If the token already has expired, but the session is still exists and is active, a refresh attempt is automatically triggered as long as the session has not ended. This happens whenever the end-user visits any path that belongs to the application.

If you want to manually trigger token refreshes, you can make use of a new endpoint:

  • POST /oauth2/session/refresh - manually refreshes the tokens for the user's session, and returns the metadata like in /oauth2/session described previously
Example

Request:

POST /oauth2/session/refresh

Response:

HTTP/2 200 OK
Content-Type: application/json

{
  "session": {
    "created_at": "2022-08-31T06:58:38.724717899Z", 
    "ends_at": "2022-08-31T16:58:38.724717899Z",
    "ends_in_seconds": 14658
  },
  "tokens": {
    "expire_at": "2022-08-31T14:03:47.318251953Z",
    "refreshed_at": "2022-08-31T12:53:58.318251953Z",
    "expire_in_seconds": 4166,
    "next_auto_refresh_in_seconds": 3866,
    "refresh_cooldown": true,
    "refresh_cooldown_seconds": 37
  }
}

Additionally, the metadata object returned by both the /oauth2/session and /oauth2/session/refresh endpoints now contain some new fields in addition to the previous fields:

Field Description
tokens.next_auto_refresh_in_seconds The number of seconds until the earliest time where the tokens will automatically be refreshed.
tokens.refresh_cooldown A boolean indicating whether or not the refresh operation is on cooldown or not.
tokens.refresh_cooldown_seconds The number of seconds until the refresh operation is no longer on cooldown.

Note that the refresh operation has a default cooldown period of 1 minute, which may be shorter depending on the token lifetime of the tokens returned by the identity provider. In other words, a refresh is only triggered if tokens.refresh_cooldown is false.

Responsibilities & Guarantees

The sidecar:

  • Adds the Authorization header with the user's JWT access token to the original request if the user has a valid session.
  • Proxies the original request unmodified to your application, if the user does not have a valid session.
  • Owns the /oauth2 endpoints defined above and intercepts all HTTP requests to these. They will never be forwarded to your application.
  • Is safe to enable and use with multiple replicas of your application.
  • Stores session data to a highly available Redis service on Aiven.
  • Validates the id_token acquired from this flow in accordance with the OpenID Connect specifications.

The sidecar does not:

  • Secure your application's endpoints in any way.
  • Validate the user's access_token set in the Authorization header. The token may be invalid or expired by the time your application receives it.

Development

Wonderwall can be fired up locally if you so desire. See the README on GitHub for an example setup with Docker Compose.

Next Steps

The access token that Wonderwall provides should only be accepted and used by your application.

In order to access other applications, you should exchange the token in order to get a new token that is correctly scoped to access a given application.

See the respective identity provider pages for details:

Last update: 2023-04-25
Created: 2022-05-02