kellnr-http 7.0.0

use axum::extract::{Request, State};
use axum::http::header::{CONTENT_LENGTH, CONTENT_TYPE};
use axum::http::{HeaderValue, StatusCode};
use axum::middleware::Next;
use axum::response::{IntoResponse, Response};
use tracing::warn;

use crate::error::{ApiError, KeepPlainText};
use crate::identity::{Accepts, identify};
use crate::state::AppStateData;

/// Middleware that rejects requests without a login of one of the accepted
/// methods when `settings.registry.auth_required` is `true`.
///
/// Endpoints for cargo answer with a `WWW-Authenticate` header. Cargo and
/// other registry clients retry with credentials after a 401, so `/config.json`
/// is not public even if `auth_required` is `true`. See:
/// - <https://github.com/kellnr/kellnr/pull/773#discussion_r2300752458>
/// - <https://doc.rust-lang.org/cargo/reference/registry-index.html#sparse-authentication>
///
/// If both methods are accepted, every failed login is a 401.
pub async fn auth_when_required(
    State((state, accepts)): State<(AppStateData, Accepts)>,
    request: Request,
    next: Next,
) -> Response {
    if !state.settings.registry.auth_required {
        return next.run(request).await;
    }

    let (mut parts, body) = request.into_parts();
    match identify(&mut parts, &state, accepts).await {
        Ok(_) => next.run(Request::from_parts(parts, body)).await,
        Err(status) => {
            warn!("Authentication required, but failed: {status}");
            rejection(status, accepts)
        }
    }
}

fn rejection(status: StatusCode, accepts: Accepts) -> Response {
    let status = match accepts {
        Accepts::TokenOrSession => StatusCode::UNAUTHORIZED,
        Accepts::Token | Accepts::Session => status,
    };
    let mut response = ApiError::from(status).into_response();
    if accepts != Accepts::Session {
        // See: https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/WWW-Authenticate
        response.headers_mut().insert(
            "WWW-Authenticate",
            HeaderValue::from_static("Basic, Bearer"),
        );
    }
    response
}

/// Largest body of an error response that [`errors_as_json`] reads.
const MAX_ERROR_BODY: usize = 64 * 1024;

/// Turns error responses that are not JSON yet, like the rejections of axum's
/// extractors, into the error format of all Kellnr endpoints. Their text
/// becomes the detail; other headers are kept. A
/// [`PlainTextError`](crate::error::PlainTextError) stays as it is.
pub async fn errors_as_json(request: Request, next: Next) -> Response {
    let response = next.run(request).await;
    let status = response.status();
    let is_json = response
        .headers()
        .get(CONTENT_TYPE)
        .is_some_and(|v| v.as_bytes().starts_with(b"application/json"));
    let keep = response.extensions().get::<KeepPlainText>().is_some();
    if !(status.is_client_error() || status.is_server_error()) || is_json || keep {
        return response;
    }

    let (parts, body) = response.into_parts();
    let detail = axum::body::to_bytes(body, MAX_ERROR_BODY)
        .await
        .map(|b| String::from_utf8_lossy(&b).trim().to_string())
        .unwrap_or_default();
    let error = if detail.is_empty() {
        ApiError::from(status)
    } else {
        ApiError::new(&detail, status)
    };
    let mut response = error.into_response();
    for (name, value) in &parts.headers {
        if name != CONTENT_TYPE && name != CONTENT_LENGTH {
            response.headers_mut().insert(name, value.clone());
        }
    }
    response
}

#[cfg(test)]
mod auth_when_required_tests {
    use std::sync::Arc;

    use axum::Router;
    use axum::body::Body;
    use axum::http::header;
    use axum::middleware::from_fn_with_state;
    use axum::routing::get;
    use kellnr_db::UserFlags;
    use kellnr_db::test_utils::test_drop_table;
    use kellnr_settings::constants::COOKIE_SESSION_ID;
    use kellnr_test_db::TestDb;
    use tower::ServiceExt;

    use super::*;
    use crate::test_support::{encode_cookies, session_cookie, sqlite_test_state, test_state};

    type Result<T = ()> = std::result::Result<T, Box<dyn std::error::Error>>;

    /// Router with `/guarded` behind the middleware and `/not_guarded` without.
    fn app(state: AppStateData, auth_required: bool, accepts: Accepts) -> Router {
        let mut settings = (*state.settings).clone();
        settings.registry.auth_required = auth_required;
        let state = AppStateData {
            settings: Arc::new(settings),
            ..state
        };
        Router::new()
            .route("/guarded", get(StatusCode::OK))
            .route_layer(from_fn_with_state(
                (state.clone(), accepts),
                auth_when_required,
            ))
            .route("/not_guarded", get(StatusCode::OK))
            .with_state(state)
    }

    /// App on a database that holds `admin` with the cargo token `token`.
    async fn db_app(accepts: Accepts) -> (Router, TestDb) {
        let (state, db) = sqlite_test_state().await;
        (app(state, true, accepts), db)
    }

    async fn guest_session(db: &TestDb) -> String {
        session_cookie(db, "guest", UserFlags::default()).await
    }

    fn unknown_session() -> String {
        encode_cookies([(COOKIE_SESSION_ID, "1234")])
    }

    async fn send(app: Router, uri: &str, cookie: Option<String>) -> Result<Response> {
        let mut request = Request::get(uri);
        if let Some(cookie) = cookie {
            request = request.header(header::COOKIE, cookie);
        }
        Ok(app.oneshot(request.body(Body::empty())?).await?)
    }

    async fn send_token(app: Router, token: &str) -> Result<Response> {
        let request = Request::get("/guarded").header(header::AUTHORIZATION, token);
        Ok(app.oneshot(request.body(Body::empty())?).await?)
    }

    #[tokio::test]
    async fn guarded_route_with_valid_token() -> Result {
        let (app, _db) = db_app(Accepts::Token).await;
        let r = send_token(app, "token").await?;
        assert_eq!(r.status(), StatusCode::OK);
        Ok(())
    }

    #[tokio::test]
    async fn guarded_route_with_invalid_token() -> Result {
        let (app, _db) = db_app(Accepts::Token).await;
        let r = send_token(app, "wrong_token").await?;
        assert_eq!(r.status(), StatusCode::FORBIDDEN);
        Ok(())
    }

    #[tokio::test]
    async fn guarded_route_without_token() -> Result {
        let r = send(app(test_state(), true, Accepts::Token), "/guarded", None).await?;
        assert_eq!(r.status(), StatusCode::UNAUTHORIZED);
        Ok(())
    }

    #[tokio::test]
    async fn guarded_route_with_valid_cookie() -> Result {
        let (app, db) = db_app(Accepts::Session).await;
        let r = send(app, "/guarded", Some(guest_session(&db).await)).await?;
        assert_eq!(r.status(), StatusCode::OK);
        Ok(())
    }

    #[tokio::test]
    async fn guarded_route_with_invalid_cookie() -> Result {
        let (app, _db) = db_app(Accepts::Session).await;
        let r = send(app, "/guarded", Some(unknown_session())).await?;
        assert_eq!(r.status(), StatusCode::UNAUTHORIZED);
        assert!(!r.headers().contains_key("WWW-Authenticate"));
        Ok(())
    }

    /// A failing database is not a missing login.
    #[tokio::test]
    async fn guarded_route_with_database_error() -> Result {
        let (app, db) = db_app(Accepts::Session).await;
        let cookie = guest_session(&db).await;
        test_drop_table(&db, "session").await?;
        let r = send(app, "/guarded", Some(cookie)).await?;
        assert_eq!(r.status(), StatusCode::INTERNAL_SERVER_ERROR);
        Ok(())
    }

    #[tokio::test]
    async fn guarded_route_without_cookie() -> Result {
        let r = send(app(test_state(), true, Accepts::Session), "/guarded", None).await?;
        assert_eq!(r.status(), StatusCode::UNAUTHORIZED);
        Ok(())
    }

    #[tokio::test]
    async fn not_guarded_route_without_cookie() -> Result {
        let r = send(
            app(test_state(), true, Accepts::Session),
            "/not_guarded",
            None,
        )
        .await?;
        assert_eq!(r.status(), StatusCode::OK);
        Ok(())
    }

    #[tokio::test]
    async fn app_not_required_auth_with_guarded_route() -> Result {
        let r = send(app(test_state(), false, Accepts::Session), "/guarded", None).await?;
        assert_eq!(r.status(), StatusCode::OK);
        Ok(())
    }

    #[tokio::test]
    async fn token_or_session_accepts_session() -> Result {
        let (app, db) = db_app(Accepts::TokenOrSession).await;
        let r = send(app, "/guarded", Some(guest_session(&db).await)).await?;
        assert_eq!(r.status(), StatusCode::OK);
        Ok(())
    }

    /// Cargo retries with credentials after a 401, so every failed login is
    /// one, also a failing database.
    #[tokio::test]
    async fn token_or_session_answers_every_failure_with_401() -> Result {
        let (app, db) = db_app(Accepts::TokenOrSession).await;
        let cookie = guest_session(&db).await;
        test_drop_table(&db, "session").await?;
        let r = send(app, "/guarded", Some(cookie)).await?;
        assert_eq!(r.status(), StatusCode::UNAUTHORIZED);
        assert_eq!(r.headers()["WWW-Authenticate"], "Basic, Bearer");
        Ok(())
    }
}

#[cfg(test)]
mod errors_as_json_tests {
    use axum::Router;
    use axum::body::Body;
    use axum::http::header;
    use axum::routing::{get, post};
    use tower::ServiceExt;

    use super::*;
    use crate::error::{ErrorDetails, PlainTextError};

    async fn json_body() -> Result<(), ApiError> {
        Err(ApiError::conflict("already there"))
    }

    async fn parse(_body: axum::Json<u32>) {}

    fn app() -> Router {
        Router::new()
            .route("/json", get(json_body))
            .route("/bare", get(|| async { StatusCode::NOT_FOUND }))
            .route(
                "/text",
                get(|| async {
                    (
                        StatusCode::BAD_REQUEST,
                        [(header::ALLOW, "GET")],
                        "invalid input",
                    )
                }),
            )
            .route(
                "/plain",
                get(|| async { PlainTextError::new(StatusCode::FORBIDDEN, "denied") }),
            )
            .route("/parse", post(parse))
            .route("/ok", get(|| async { "fine" }))
            .layer(axum::middleware::from_fn(errors_as_json))
    }

    async fn send(request: Request<Body>) -> (StatusCode, axum::http::HeaderMap, String) {
        let response = app().oneshot(request).await.unwrap();
        let status = response.status();
        let headers = response.headers().clone();
        let body = axum::body::to_bytes(response.into_body(), usize::MAX)
            .await
            .unwrap();
        (status, headers, String::from_utf8(body.to_vec()).unwrap())
    }

    fn detail(body: &str) -> String {
        let details: ErrorDetails = serde_json::from_str(body).unwrap();
        details.errors[0].detail.clone()
    }

    #[tokio::test]
    async fn json_errors_are_kept() {
        let (status, _, body) = send(Request::get("/json").body(Body::empty()).unwrap()).await;
        assert_eq!(status, StatusCode::CONFLICT);
        assert_eq!(detail(&body), "ERROR: already there");
    }

    #[tokio::test]
    async fn bare_status_gets_its_reason_as_detail() {
        let (status, _, body) = send(Request::get("/bare").body(Body::empty()).unwrap()).await;
        assert_eq!(status, StatusCode::NOT_FOUND);
        assert_eq!(detail(&body), "ERROR: Not Found");
    }

    #[tokio::test]
    async fn text_becomes_the_detail_and_headers_are_kept() {
        let (status, headers, body) =
            send(Request::get("/text").body(Body::empty()).unwrap()).await;
        assert_eq!(status, StatusCode::BAD_REQUEST);
        assert_eq!(detail(&body), "ERROR: invalid input");
        assert_eq!(headers[header::ALLOW], "GET");
        assert_eq!(headers[CONTENT_TYPE], "application/json");
    }

    #[tokio::test]
    async fn plain_text_errors_are_kept() {
        let (status, _, body) = send(Request::get("/plain").body(Body::empty()).unwrap()).await;
        assert_eq!((status, body.as_str()), (StatusCode::FORBIDDEN, "denied"));
    }

    #[tokio::test]
    async fn extractor_rejections_become_json() {
        let request = Request::post("/parse")
            .header(CONTENT_TYPE, "application/json")
            .body(Body::from("\"no number\""))
            .unwrap();
        let (status, _, body) = send(request).await;
        assert_eq!(status, StatusCode::UNPROCESSABLE_ENTITY);
        assert!(detail(&body).starts_with("ERROR: "), "{body}");
    }

    #[tokio::test]
    async fn success_is_untouched() {
        let (status, _, body) = send(Request::get("/ok").body(Body::empty()).unwrap()).await;
        assert_eq!((status, body.as_str()), (StatusCode::OK, "fine"));
    }
}