limes 0.4.0

#![warn(
    missing_debug_implementations,
    rust_2018_idioms,
    unreachable_pub,
    clippy::pedantic
)]
#![allow(
    clippy::module_name_repetitions,
    clippy::large_enum_variant,
    clippy::doc_markdown
)]
#![forbid(unsafe_code)]
// #![cfg_attr(docsrs, feature(doc_cfg))]

//! [![License](https://img.shields.io/badge/License-Apache_2.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)
//! [![Tests](https://github.com/vakamo-labs/limes-rs/actions/workflows/ci.yaml/badge.svg)](https://github.com/vakamo-labs/limes-rs/actions/workflows/unittests.yaml)
//!
//! # Limes
//!
//! Limes is a multi-tenant capable Authentication middleware for OAuth2.0 and Open ID Connect with optional support for `axum`.
//! It supports the following [`Authenticator`]s natively:
//!
//! * [`JWKSWebAuthenticator`](`jwks::JWKSWebAuthenticator`) that fetches JWKs keys from a `.well-known/openid-configuration`, refreshes keys regularly, and validates tokens locally.
//! * [`KubernetesAuthenticator`](`kubernetes::KubernetesAuthenticator`) which validates tokens using Kubernetes `TokenReview`.
//! * [`AuthenticatorChain`] holds a collection of [`Authenticator`]s and authenticates the token with the first suitable Authenticator. This is especially useful for multi-tenant setups where tokens from multiple IdPs should be accepted. Each IdP is assigned a unique `idp_id` to provide a globally unique [`Subject`] that identifies a user.
//!
//! Custom Authenticators can easily be added by implementing the [`Authenticator`] trait.
//!
//! # Why the Name?
//! "Limes" is the ancient Roman wall that fortified the ROman Empire. Just like those mighty walls, our Limes library
//! stands guard, protecting your applications from unauthorized access. So, while you won't find any tangy flavors here,
//! you will find robust authentication to keep your digital empire safe. When life gives you Limes, add auth to your
//! crate! Wait a minute ...
//!
//! # Single-Tenant Example
//!
//! ```no_run
//! use axum::{middleware::from_fn_with_state, response::IntoResponse, routing::get, Extension};
//! use limes::{
//!     axum::authentication_middleware, format_subject, jwks::JWKSWebAuthenticator, Authentication,
//! };
//!
//! // Use none for single tenant setups
//! const IDP_SEPARATOR: Option<char> = None;
//!
//! #[tokio::main]
//! async fn main() {
//!     let authenticator = JWKSWebAuthenticator::new(
//!         "https://accounts.google.com", // Must provide ./well-known/openid-configuration
//!         Some(std::time::Duration::from_secs(10 * 60)), // Refresh JWKS keys every 10 minutes
//!     )
//!     .await
//!     .unwrap()
//!     .set_accepted_audiences(vec!["my-app".to_string()]); // Acceptable audiences (optional)
//!
//!     let app = axum::Router::new()
//!         .route("/whoami", get(whoami))
//!         .layer(from_fn_with_state(
//!             authenticator,
//!             authentication_middleware::<JWKSWebAuthenticator>,
//!         ));
//!
//!     let listener = tokio::net::TcpListener::bind("127.0.0.1:3000")
//!         .await
//!         .unwrap();
//!     println!("listening on {}", listener.local_addr().unwrap());
//!     axum::serve(listener, app).await.unwrap();
//! }
//!
//! async fn whoami(Extension(auth): Extension<Authentication>) -> impl IntoResponse {
//!     format!("Hello, {}!", format_subject(auth.subject(), IDP_SEPARATOR))
//! }
//! ```
//!
//! # Multi-Tenant Setup
//! Limes supports the chained Authenticators. As each Authenticator can point to a different IdP, and subject IDs are not  guaranteed to be unique across IdPs, it is important to specify the `idp_id` for each [`Authenticator`] that is used in a [`AuthenticatorChain`].
//!
//! ```no_run
//! use axum::{middleware::from_fn_with_state, response::IntoResponse, routing::get, Extension};
//! use limes::{
//!     axum::authentication_middleware, format_subject, jwks::JWKSWebAuthenticator,
//!     kubernetes::KubernetesAuthenticator, Authentication, AuthenticatorChain, AuthenticatorEnum,
//! };
//!
//! // We recommend using a character that is never used in subject ids
//! const IDP_SEPARATOR: Option<char> = Some('~');
//!
//! #[tokio::main]
//! async fn main() {
//!     let oidc_authenticator = JWKSWebAuthenticator::new(
//!         "https://accounts.google.com", // Must provide ./well-known/openid-configuration
//!         Some(std::time::Duration::from_secs(10 * 60)), // Refresh JWKS keys every 10 minutes
//!     )
//!     .await
//!     .unwrap()
//!     .set_idp_id("oidc") // Unique identifier for this IdP. Must never contain the `IDP_SEPARATOR`
//!     .set_accepted_audiences(vec!["my-app".to_string()]); // Acceptable audiences (optional)
//!
//!     // Uses the default Kubernetes client. Other constructors are available that accept a custom client.
//!     let kubernetes_authenticator = KubernetesAuthenticator::try_new_with_default_client(
//!         Some("kubernetes"), // Unique identifier for this IdP. Must never contain the `IDP_SEPARATOR`
//!         vec![],             // Don't validate the audience
//!     )
//!     .await
//!     .unwrap();
//!
//!     // Chain the authenticators together. Order matters.
//!     // The first authenticator that returns true for `can_handle_token` will be used.
//!     let chain = AuthenticatorChain::<AuthenticatorEnum>::builder()
//!         .add_authenticator(oidc_authenticator)
//!         .add_authenticator(kubernetes_authenticator)
//!         .build();
//!
//!     let app = axum::Router::new()
//!         .route("/whoami", get(whoami))
//!         .layer(from_fn_with_state(
//!             chain,
//!             authentication_middleware::<AuthenticatorChain<AuthenticatorEnum>>,
//!         ));
//!
//!     let listener = tokio::net::TcpListener::bind("127.0.0.1:3000")
//!         .await
//!         .unwrap();
//!     println!("listening on {}", listener.local_addr().unwrap());
//!     axum::serve(listener, app).await.unwrap();
//! }
//!
//! async fn whoami(Extension(auth): Extension<Authentication>) -> impl IntoResponse {
//!     format!("Hello, {}!", format_subject(auth.subject(), IDP_SEPARATOR))
//!     // Would print "oidc~<subject_id>" for google tokens, where oidc is the `idp_id` we set above.
//! }
//! ```
//!
//! # Feature flags
//! Limes uses a set of feature flags to reduce the amount of compiled code.
//! The following feature flags are available:
//!
//! * `all`: Activate all features
//! * `default`: Includes `rustls-tls` and `jwks`.
//! * `kubernetes`: Provides the `KubernetesAuthenticator` implementation which validates tokens using Kubernetes `TokenReview`.
//!   When enabling this feature you must also select a Kubernetes API version by adding a direct
//!   dependency on `k8s-openapi` with a version feature, e.g. `k8s-openapi = { version = "0.28", features = ["v1_32"] }`.
//!   Limes intentionally does not pin a version so the choice is left to your binary crate.
//! * `rustls-tls`: Enable `rustls` for all dependant crates.
//! * `jwks`: Provides the `JWKSWebAuthenticator`
//! * `axum`: Provides axum middleware that performs the Authentication and provides the tokens Payload as extension.

mod authenticator;
mod chain;
pub mod error;
pub mod introspect;
#[cfg(feature = "jwks")]
pub mod jwks;
mod subject;

#[cfg(feature = "kubernetes")]
pub mod kubernetes;

pub use authenticator::{Authentication, Authenticator, PrincipalType};
pub use chain::{AuthenticatorChain, AuthenticatorChainBuilder, AuthenticatorEnum};
pub use subject::Subject;

pub use subject::{format_subject, parse_subject};

#[cfg(feature = "axum")]
pub mod axum;