wasm-oidc-plugin

A Wasm-plugin for the Envoy-Proxy written in Rust acting as an HTTP Filter, that implements the OpenID Authorization Code Flow. Requests sent to the filter are checked for the presence of a valid session cookie. If the cookie is not present, the user is redirected to the authorization_endpoint to authenticate. After successful authentication, the user is redirected back to the original path with the authorization code in the URL query. The plugin then exchanges the code for a token using the token_endpoint and stores the token in the session. If the cookie is present and decryptable, the plugin validates the token and passes the request to the backend, if the token is valid (optional).

Demo

Go to demo-page to see the plugin in action. Auth0 is used as the OpenID provider. Simply create an account or login with Google. The plugin has been configured to show httpbin.org as the upstream. Then open the developer tools and check the cookies or use the httpbin cookie inspector. You will see a cookie called oidcSession-0. This is the session, that holds the authorization state. If you delete the cookie and refresh the page, you will be redirected to the authorization_endpoint to authenticate again.

Why this repo?

This repo is the result of a bachelor thesis in Information Systems. It is inspired by two other projects: oidc-filter & wasm-oauth-filter. This project has several advantages and improvements:

1. Encryption: The session in which the authorization state is stored is encrypted using AES-256, by providing a Key in the config and a session-based nonce. This prevents the session from being read by the user and potentially modified. If the user tries to modify the session, the decryption fails and the user is redirected to the authorization_endpoint to authenticate again.
2. Multiple OpenID Providers: The plugin can be configured with multiple OpenID providers. This is useful if you have multiple services that are protected by different OpenID providers. The user can then choose which provider to authenticate with on some auth page.
3. Configuration: Many configuration options are available to customize the plugin to your needs. More are coming ;)
4. Stability: The plugin aims to be stable and ready for production. All forceful value unwraps are expected to be valid. If the value may be invalid or in the wrong format, error handling is in place.
5. Optional validation: The plugin can be configured to validate the token or not. If the validation is disabled, the plugin only checks for the presence of the token and passes the request to the backend. This is because the validation is taking a considerable amount of time. This time becomes worse with the length of the signing key. Cryptographic support is not fully mature in WASM yet, but there is hope.
6. Documentation and comments: The code is documented and commented, so that it is easy to understand and extend.

Install

Install Toolchain for WASM in Rust

For developing the Rust Toolchain has to be installed and the WASM target has to be enabled. E.g. for Ubuntu this can be achieved by:

# Install Build essentials
apt install build-essential
# Install Rustup
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
# Enable WASM compilation target
cargo build --target wasm32-wasip1 --release

Run

Shortcut (make sure to have make installed):

make run

---

Detailed variant

1. Building the plugin:

cargo build --target wasm32-wasip1 --release
# or
make build

1. Testing locally with Envoy (docker and docker-compose are needed):

docker compose up

1. Requests to the locally running envoy with the plugin enabled:

curl localhost:10000

Deploy to Kubernetes

To deploy the plugin to production, the following steps are needed (either manually or via a CI/CD pipeline):

1. Build the plugin

   1.1 with cargo build --target wasm32-wasip1 --release - this can be done in a initContainer (see k8s folder) and then copy the binary to the path /etc/envoy/proxy-wasm-plugins/ in the envoy container.

   1.2 by using the pre-built Docker image antonengelhardt/wasm-oidc-plugin.

2. Run envoy as a container with the envoy.yaml file mounted through the ConfigMap as a volume.

3. Set up Service, Certificate, Ingress to expose the Envoy to the internet.

For reference, see the k8s folder.

Documentation

To generate a detailed documentation, run (also hosted on GitHub Pages):

cargo doc --document-private-items --open

Configuration

The plugin is configured via the envoy.yaml-file. The following configuration options are required:

OpenIdConfig

claims

The claims are defined as a map of strings.

claims:
  id_token:
    groups: null
    username: null

Migrating from the legacy single-provider config

Legacy configs (provider fields at the root) still work and are converted at runtime with a deprecation warning. Prefer migrating to open_id_configs.

Set upstream_cluster to an Envoy cluster name that actually exists — auto-derivation from authority is often wrong.

# Requires PyYAML. Accepts a bare plugin config or a full Envoy/ConfigMap YAML.
python3 scripts/migrate-config.py envoy-legacy.yaml -o envoy-migrated.yaml

States

A state determines what to load next. The following states are possible and depending on the outcome, the state is changed or not:

Below is a state diagram for one single OpenID Provider

stateDiagram-v2
    [*] --> LoadingConfig: on_configure() creates resolvers

    note right of LoadingConfig
        Plugin config loaded + getting OpenIDConfig
    end note

    LoadingConfig --> LoadingJwks: OpenID config response received

    note right of LoadingJwks
        Getting Keys from Endpoint
    end note

    LoadingJwks --> Ready: JWKS response received

    note right of Ready
        Keys stored, providers created, queued requests resumed
    end note

    Ready --> LoadingConfig: [every reload_interval_in_h]
    Ready --> Ready: Process HTTP requests

Handling a request

When a new request arrives, the root context creates a new http context with the information that has been loaded previously.

Then, one of the following cases is handled:

1. The plugin is not configured yet and still loading the configuration. The request is paused and queued until the configuration is loaded. Then, the RootContext resumes the request and the Request is redirected in order to create a new context.
2. The request is excluded from the filter. The request is passed to the backend without any further checks.
3. The request has the authorization code in the URL query. This means that the user has been redirected back from the authorization_endpoint after successful authentication. The plugin exchanges the code for a token using the token_endpoint and stores the token in the session. Then, the user is redirected back to the original request.
4. The request has a valid session cookie. The plugin decoded, decrypts and then validates the cookie and passes the request depending on the outcome of the validation of the token.
5. The request has no valid session cookie. The plugin redirects the user to the authorization_endpoint to authenticate. Once, the user returns, the second case is handled. If multiple OpenID providers are configured, the user is redirected to a page where they can select the provider to authenticate with.

sequenceDiagram
    participant User
    participant Plugin
    participant Auth as Auth-Endpoint
    participant Token as Token-Endpoint
    participant App as App/Backend

    Note over User, App: [No Cookies Present]
    User->>Plugin: Tries to Access App/Backend
    Plugin-->>User: Redirect to Auth-Endpoint
    User->>Auth: User authenticates
    Auth-->>Plugin: Authorization Code
    Plugin->>Token: Exchange Code for Tokens
    Token-->>Plugin: Tokens
    Plugin-->>User: Reply with Cookies and redirect to Original Path

    Note over User, App: [Cookies Present]
    User->>Plugin: Tries to Access App/Backend

    critical [Validation]
        Plugin->>Plugin: Validate Cookie with keys
    end

    alt [Valid]
        Plugin->>App: Allow Request
    else [Invalid]
        Plugin-->>User: Redirect to Auth-Endpoint
    end

Tools

Git Cliff

Git-Cliff automates the generation of changelogs, when following conventional commit messages

Gitleaks

We are using Gitleaks to protect from unwanted secret leaking and prevent security incidents by detecting passwords, secrets, API keys, tokens and more in git repos.

To run gitleaks, install it first and then run:

gitleaks protect

# To get the list of leaks
gitleaks protect --verbose

If you want to install a pre-commit hook - you should - install pre-commit and run (from the root of the project):

pre-commit install

The pre-commit hook will also check for a clean code style, formatting best practices and enforce clippy lints.

Cargo-Deny

Cargo-deny checks all dependencies for security vulnerabilities and license issues.

Install cargo-deny:

cargo install --locked cargo-deny

And then run:

cargo-deny check licenses
cargo-deny check advisories

These commands are also run in the CI pipeline.

FAQ

My OpenID provider uses different hosts for discovery, JWKS, and token exchange (e.g. Google). How can I configure this?

Google publishes:

{
  "authorization_endpoint": "https://accounts.google.com/o/oauth2/v2/auth",
  "token_endpoint": "https://oauth2.googleapis.com/token",
  "jwks_uri": "https://www.googleapis.com/oauth2/v3/certs"
}

Add all three hosts to the Envoy cluster and enable auto_sni so TLS SNI matches the :authority used for each call:

- name: google
  connect_timeout: 5s
  type: STRICT_DNS
  dns_lookup_family: V4_ONLY
  typed_extension_protocol_options:
    envoy.extensions.upstreams.http.v3.HttpProtocolOptions:
      "@type": type.googleapis.com/envoy.extensions.upstreams.http.v3.HttpProtocolOptions
      explicit_http_config:
        http_protocol_options: {}
      upstream_http_protocol_options:
        auto_sni: true
  load_assignment:
    cluster_name: google
    endpoints:
      - lb_endpoints:
          - endpoint:
              address:
                socket_address:
                  address: accounts.google.com
                  port_value: 443
          - endpoint:
              address:
                socket_address:
                  address: www.googleapis.com
                  port_value: 443
          - endpoint:
              address:
                socket_address:
                  address: oauth2.googleapis.com
                  port_value: 443
  transport_socket:
    name: envoy.transport_sockets.tls
    typed_config:
      "@type": type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.UpstreamTlsContext

Keep authority as accounts.google.com for discovery; the plugin uses the token/JWKS URL host for those calls.

Also ensure the Google OAuth client has your redirect_uri (e.g. http://localhost:10000/oidc/callback) allowlisted.