wasm-oidc-plugin

A plugin for the Envoy-Proxy written in Rust. It is a HTTP Filter, that implements the OIDC 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 request with a 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, 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 OIDC 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. Configuration: Many configuration options are available to customize the plugin to your needs. More are coming ;)
3. 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.
4. 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.
5. 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-wasi --release

Run

Shortcut (make sure to have make installed):

make run

---

Detailed variant

1. Building the plugin:

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

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

docker compose up

3. 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-wasi --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:

Name	Type	Description	Example	Required
config_endpoint	string	The open id configuration endpoint.	https://accounts.google.com/.well-known/openid-configuration	✅
reload_interval_in_hours	u64	The interval in hours, after which the OIDC configuration is reloaded.	24	✅
exclude_hosts	Vec<Regex>	A comma separated list Hosts (in Regex expressions), that are excluded from the filter.	["localhost:10000"]	❌
exclude_paths	Vec<Regex>	A comma separated list of paths (in Regex expressions), that are excluded from the filter.	["/health"]	❌
exclude_urls	Vec<Regex>	A comma separated list of URLs (in Regex expressions), that are excluded from the filter.	["localhost:10000/health"]	❌
access_token_header_name	string	If set, this name will be used to forward the access token to the backend.	X-Access-Token	❌
access_token_header_prefix	string	The prefix of the header, that is used to forward the access token, if empty "" is used.	Bearer	❌
id_token_header_name	string	If set, this name will be used to forward the id token to the backend.	X-Id-Token	❌
id_token_header_prefix	string	The prefix of the header, that is used to forward the id token, if empty "" is used.	Bearer	❌
cookie_name	string	The name of the cookie, that is used to store the session.	oidcSession	✅
`filter_plugin_cookies	bool	Whether to filter the cookies that are managed and controlled by the plugin (namely cookie_name and nonce).	true	✅
cookie_duration	u64	The duration in seconds, after which the session cookie expires.	86400	✅
token_validation	bool	Whether to validate the token or not.	true	✅
aes_key	string	A base64 encoded AES-256 Key: openssl rand -base64 32	SFDUGDbOsRzSZbv+mvnZdu2x6+Hqe2WRaBABvfxmh3Q=	✅
authority	string	The authority of the authorization_endpoint.	accounts.google.com	✅
redirect_uri	string	The redirect URI, that the authorization_endpoint will redirect to.	http://localhost:10000/oidc/callback	✅
client_id	string	The client ID, for getting and exchanging the code.	wasm-oidc-plugin	✅
scope	string	The scope, to validate	openid email	✅
claims	string	The claims, to validate. Make sure to escape quotes with a backslash	{\"id_token\":{\"groups\":null,\"username\":null}}	✅
client_secret	string	The client secret, that is used to authenticate with the authorization_endpoint.	secret	✅
audience	string	The audience, that is used to validate the token.	wasm-oidc-plugin	✅

With these configuration options, the plugin starts and loads more information itself such as the OIDC providers public keys, issuer, etc.

States

For that a state is used, which determines, what to load next. The following states are possible and depending on the outcome, the state is changed or not:

State	Description
Uninitialized	The plugin is not initialized yet.
LoadingConfig	The plugin is loading the configuration from the config_endpoint.
LoadingJwks	The plugin is loading the public keys from the jwks_uri.
Ready	The plugin is ready to handle requests and will reload the configuration after the reload_interval_in_hours has passed.

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 filter 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 has the code parameter 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.
3. 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.
4. 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.

Tools

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

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.