structured_proxy/auth/
forward.rs

1//! Forward-auth verification endpoint.
2//!
3//! Exposes `forward_auth.path` (default `/auth/verify`) so a fronting reverse
4//! proxy (nginx `auth_request`, Traefik `forwardAuth`) can delegate auth to this
5//! proxy: it validates the request's `Bearer` token against the configured route
6//! policies and answers 200 (with the verified claim headers) or 401/403.
7
8use std::sync::Arc;
9
10use axum::extract::Request;
11use axum::http::header::{HeaderValue, LOCATION};
12use axum::http::{HeaderMap, StatusCode};
13use axum::response::{IntoResponse, Response};
14use axum::routing::any;
15use axum::Router;
16
17use super::{forbidden, unauthorized, Auth, AuthDecision};
18use crate::config::AuthConfig;
19
20/// A verification endpoint backed by the shared [`Auth`] machinery.
21pub struct ForwardAuth {
22    auth: Arc<Auth>,
23    path: String,
24    login_url: Option<String>,
25}
26
27impl ForwardAuth {
28    /// Build the endpoint, or `None` when forward-auth is disabled.
29    ///
30    /// Shares the already-built [`Auth`], so the verify endpoint and the JWT
31    /// middleware evaluate identical keys and policies.
32    pub fn build(config: &AuthConfig, auth: Arc<Auth>) -> Option<Arc<Self>> {
33        let fa = config.forward_auth.as_ref()?;
34        if !fa.enabled {
35            return None;
36        }
37        Some(Arc::new(Self {
38            auth,
39            path: fa.path.clone(),
40            login_url: fa.login_url.clone(),
41        }))
42    }
43
44    /// The verification route, mounted at `forward_auth.path`.
45    pub fn routes<S>(self: &Arc<Self>) -> Router<S>
46    where
47        S: Clone + Send + Sync + 'static,
48    {
49        let fa = self.clone();
50        // Any method: the fronting proxy issues its own sub-request verb; the
51        // original verb arrives via the forwarding headers.
52        Router::new().route(
53            &self.path,
54            any(move |req: Request| {
55                let fa = fa.clone();
56                async move { fa.verify(req).await }
57            }),
58        )
59    }
60
61    async fn verify(&self, request: Request) -> Response {
62        let headers = request.headers();
63        let method = original_method(headers)
64            .unwrap_or_else(|| request.method().as_str().to_ascii_uppercase());
65        let path = original_path(headers).unwrap_or_else(|| request.uri().path().to_string());
66
67        match self.auth.decide(headers, &path, &method).await {
68            // 200 carries the verified claim headers for the fronting proxy to
69            // copy upstream.
70            AuthDecision::Allow(claim_headers, _) => {
71                (StatusCode::OK, claim_headers).into_response()
72            }
73            AuthDecision::Unauthenticated(msg) => self.deny(msg),
74            AuthDecision::Forbidden(msg) => forbidden(msg),
75        }
76    }
77
78    /// A 401, adding `Location: login_url` when configured so a fronting proxy
79    /// can drive an error-page redirect to the login flow.
80    fn deny(&self, msg: &'static str) -> Response {
81        let mut response = unauthorized(msg);
82        if let Some(url) = &self.login_url {
83            if let Ok(value) = HeaderValue::try_from(url.as_str()) {
84                response.headers_mut().insert(LOCATION, value);
85            }
86        }
87        response
88    }
89}
90
91/// The original request method, from the fronting proxy's forwarding headers.
92fn original_method(headers: &HeaderMap) -> Option<String> {
93    forwarded(headers, &["x-forwarded-method", "x-original-method"]).map(|m| m.to_ascii_uppercase())
94}
95
96/// The original request path (query stripped), from the forwarding headers.
97fn original_path(headers: &HeaderMap) -> Option<String> {
98    let raw = forwarded(headers, &["x-forwarded-uri", "x-original-uri"])?;
99    let path = raw.split_once('?').map_or(raw.as_str(), |(p, _)| p);
100    Some(path.to_string())
101}
102
103/// First non-empty value among `names`.
104fn forwarded(headers: &HeaderMap, names: &[&str]) -> Option<String> {
105    names
106        .iter()
107        .filter_map(|n| headers.get(*n).and_then(|v| v.to_str().ok()))
108        .find(|v| !v.is_empty())
109        .map(str::to_string)
110}
111
112// The endpoint is exercised end to end against the built-in verifier, so these
113// tests need a crypto backend; the `Auth` seam itself is covered in `tests.rs`.
114#[cfg(all(test, feature = "builtin_jwt"))]
115mod tests;
structured_proxy/auth/forward.rs

structured_proxy/auth/
forward.rs
