omnium

A set of extensions for building web applications on axum.

Unstable: This crate is not ready for use. The author is building out these extensions to iterate on a proof of concept, and the surface may change frequently.

Responses

The api::responses module provides a set of response conventions for axum handlers, implementing axum's IntoResponse trait for typical use cases.

A handler returns JsonResult<T>:

// ...
use omnium::api::{JsonResult, JsonResponse, JsonStatus};

async fn handler() -> JsonResult<JsonStatus> {
    let result = try_do_or_err().await;
    match result {
        Ok => JsonResponse::of_status(StatusCode::ACCEPTED).into()
        Err => JsonResponse::of_status(StatusCode::CONFLICT).into()
    }
}

You can build responses using JsonResponse<T>, which implements Into<JsonResult>, as well as axum's IntoResponse.

For clarity, you can use the provided respond! macro instead of calling .into().

A handler can return a JSON response for any serializable body, with a default OK status:

async fn handler() -> JsonResult<SomeBodyType> {
    respond!(JsonResponse::of_json(body));
}

Another status code can be set on the response:

async fn handler() -> JsonResult<JsonStatus> {
    respond!(JsonResponse::of_json(body).with_status(StatusCode::IM_A_TEAPOT));
}

A handler can return a simple JsonStatus status response, implicitly deriving the response body as appropriate for the status:

async fn handler() -> JsonResult<JsonStatus> {
    respond!(JsonResponse::of_status(StatusCode::OK));
}

An additional detail message can be added to the JsonStatus:

async fn handler() -> JsonResult<JsonStatus> {
    respond!(JsonResponse::of_status(StatusCode::OK).with_detail("Additional detail"));
}

Errors

A status response can be returned on the Err arm of JsonResult, regardless of the happy path response type.

async fn handler() -> JsonResult<()> {
    Err(JsonResponse::of_status(StatusCode::OK).with_detail("Additional detail"))
}

An arbitrary error propagated to the top of a handler is treated as an internal server error, and is rendered with an opaque INTERNAL_SERVER_ERROR response that masks any error details from the caller.

async fn handler() -> JsonResult<()> {
    let success = try_do_or_err().await?;
    // ...
}

Depending on whether you are in a function returning anyhow::Result or JsonResult, you can return errors using anyhow::bail! or respond_err!, respectively. In both cases, you can propagate an arbitrary error to be handled as an internal server error, or you can provide a JsonResult status response.

async fn handler() -> anyhow::Result<()> {
    anyhow::bail!("Internal error!");
    // ...
}

async fn handler() -> JsonResult<()> {
    respond_err!("Internal error!");
    // ...
}

Authentication

The security module provides JWT-based authentication middleware, with utilities for a cookie-based credential exchange or the authorization header for browser-based or programmatic authentication.

Create a service secret:

let service_secret = create_service_secret();

Configure authentication middleware:

#[derive(Clone)]
struct AppAccount {}

struct AppState {
    pub service_secret: ServiceSecret,
}

impl SessionManager<AppAccount> for Arc<AppState> {
    async fn get_service_secret(&self) -> anyhow::Result<&ServiceSecret> {
        // Return secret from application secret manager:
        Ok(&self.service_secret)
    }


    async fn get_account(&self, _account_id: String) -> anyhow::Result<Option<AppAccount>> {
        // Return account from application database:
        Ok(Some(AppAccount {}))
    }

    fn extract_credential(&self, request: &Request, _cookies: &CookieJar) -> Option<Credential> {
        // Extract credential from request:
        Credential::from_authorization_header(&request)
    }
}

Attach authentication middleware:

fn app(state: Arc<AppState>) -> Router {
    Router::new()
        .route("/api/account", get(|| async { "Hello, caller!" }))
        .layer(from_fn_with_state(
            state.clone(),
            authenticate::<AppAccount, Arc<AppState>>,
        ))
         .layer(from_fn_with_state(
            state.clone(),
            decorate::<AppAccount, Arc<AppState>>,
        ))
        .with_state(state)
}

Note that the authentication middleware is attached in two parts: 1) decorating the authenticated account on the request, and 2) enforcing authentication for the request.

Create the account session:

create_session(
    "some-account-id",
    &EncodingKey::from_secret(state.service_secret.value.as_bytes()),
    Duration::from_secs(60),
);

With Credential::from_authorization_header, a client may pass the session as the authorization header. With Credential::from_cookie, a client may pass the session as the __Host-omn-sess cookie. For a simple, user-facing web application, you can set the __Host-omn-sess cookie when the account signs in, in order to authenticate requests to the service running on the same origin. If the application shares a session across multiple services on different origins, it can expose the session for use by the client in the authorization header for programmatic, cross-origin requests. You can plug in your own handling for extracting credentials from requests with a custom extract_credential handler.

Requests from an unauthenticated caller will reject with a 401 response.

For an authenticated caller, the account object from account_lookup can be retrieved from request state to avoid redundant lookup in handlers:

pub async fn handler(
    Extension(caller): Extension<AppAccount>,
) {
    println!("Caller is: {}", caller);
}

Because a variety of data may need to be passed and verified between an application and its callers, encode_claims and decode_claims may also be used for other purposes other than authentication. Note that claims are signed but not encrypted.

In addition to claims-based utilities, this crate wraps aes_gcm to provide utilties encrypt_string_aes256_gcm and decrypt_string_aes256_gcm. A secret created by create_service_secret can also be used with these encryption utilities.