Serve a content repo's .well-known/ at the site root

Everything a site has to publish for another program to find it lives
under /.well-known/, and portal had no way to put a file there: the
catch-all answered those paths 200 with the app shell, so a client
probing for security.txt or matrix/server got HTML where it expected a
document, and could not tell a missing file from a present one.

The prefix is the one place this is safe to overlay. RFC 8615 reserves
it, and a question's id comes from a file name under questions/, which
cannot begin with a dot - so no file a repo ships can shadow a page. The
path still goes through is_safe_site_path, so it cannot climb out of the
repo either, and a miss is a real 404.

Types: an extensionless file under the prefix is JSON, which is what
matrix/server and nodeinfo are; .mobileconfig is the Apple profile type,
without which iOS downloads a profile instead of offering to install it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015GeH3y8fwTaTudaD88P57o

CHANGELOG.md

@@ -4,6 +4,14 @@ One line per change, grouped by the release that shipped it. Newest
 first. A release is a Cargo.toml bump plus a `v<version>` tag; the
 content repos pin the tag they run (see the end of this file).
 
+## 0.6.21 (2026-10-07)
+
+- A content repo's `.well-known/` is served at the site root (`/.well-known/security.txt`, `/.well-known/assetlinks.json`, `/.well-known/matrix/server`), and a miss there is a 404 instead of the app shell answering 200 with an HTML page. RFC 8615 reserves the prefix and a question's id cannot begin with a dot, so nothing a repo ships can shadow a page. An extensionless file under it is typed as JSON, by the convention those files follow; `.txt`, `.xml`, `.webmanifest` and `.mobileconfig` are typed too, the last so an Apple configuration profile offers to install rather than download.
+
+## 0.6.20 (2026-10-05)
+
+- A releases card lets a platform's file carry an architecture: a Mac visitor is offered the `macos-arm64` file, not sent to TestFlight past it.
+
 ## 0.6.19 (2026-10-05)
 
 - A `kind: url` resource whose JSON is a releases manifest (`latest`, `versions` with per-platform `assets`, `channels` such as a package repo or TestFlight) renders as a download card: the file for the visitor's own platform first, decided in the browser, the rest and the channels folded. Written for redoal's public releases at dl.redoal.com (docs: content-reference, "A releases manifest").

Cargo.lock

@@ -3357,7 +3357,7 @@ dependencies = [
 
 [[package]]
 name = "portal"
-version = "0.6.19"
+version = "0.6.21"
 dependencies = [
  "anyhow",
  "arc-swap",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "portal"
-version = "0.6.19"
+version = "0.6.21"
 edition = "2021"
 
 [lib]

src/app.rs

@@ -2226,7 +2226,8 @@ fn ReleasesCard(manifest: serde_json::Value) -> impl IntoView {
                 let p = platform.get()?;
                 let arch = arch_for_pick.clone();
                 let ios = ios_for_pick.clone();
-                let own = assets_for_pick.iter().find(|(pl, _, _)| pl == p).cloned();
+                // "macos" is satisfied by a "macos-arm64" file, and so on.
+                let own = assets_for_pick.iter().find(|(pl, _, _)| pl == p || pl.starts_with(&format!("{p}-"))).cloned();
                 let pick: Option<AnyView> = match (p, own) {
                     (_, Some((pl, url, _))) => Some(view! {
                         <p><a class="pill" href=url download>{t(&lang().get(), "for_this_device")} ": " {label(&pl)}</a></p>

src/content/handlers.rs

@@ -49,15 +49,56 @@ pub struct GiteaRepoQuery {
 pub async fn site_asset_handler(
     axum::extract::State(state): axum::extract::State<crate::server::AppState>,
     axum::extract::Path(path): axum::extract::Path<String>,
+) -> axum::response::Response {
+    serve_repo_file(&state, &path, false).await
+}
+
+/// `GET /.well-known/{*path}` - the content repo overlaid on the one part
+/// of the URL space that can never collide with a question: RFC 8615
+/// reserves `/.well-known/`, and a question's id is derived from a file
+/// name under `questions/`, which cannot begin with a dot. A repo ships
+/// `.well-known/security.txt`, `.well-known/assetlinks.json`,
+/// `.well-known/matrix/server` and so on at the path they are served at,
+/// and a miss is a real 404 rather than the app shell answering 200 with
+/// an HTML page - which is what a client probing for one of these would
+/// otherwise have to parse.
+///
+/// Paths Caddy claims in front of portal (mail autoconfiguration, the
+/// CalDAV and CardDAV redirects) never reach here.
+#[cfg(feature = "ssr")]
+pub async fn well_known_handler(
+    axum::extract::State(state): axum::extract::State<crate::server::AppState>,
+    axum::extract::Path(path): axum::extract::Path<String>,
+) -> axum::response::Response {
+    serve_repo_file(&state, &format!(".well-known/{path}"), true).await
+}
+
+/// Proxies one repo-relative file from the content repo's default branch.
+/// `well_known` only changes what an extensionless file is typed as: under
+/// `/.well-known/` those are JSON by convention (`matrix/server`,
+/// `nodeinfo`), while elsewhere a file with no extension is an unknown.
+#[cfg(feature = "ssr")]
+async fn serve_repo_file(
+    state: &crate::server::AppState,
+    path: &str,
+    well_known: bool,
 ) -> axum::response::Response {
     use axum::http::{header, StatusCode};
     use axum::response::IntoResponse;
 
-    if !is_safe_site_path(&path) {
+    if !is_safe_site_path(path) {
         return (StatusCode::BAD_REQUEST, "invalid asset path").into_response();
     }
-    let url = format!("{}/{path}?ref={}", state.content_raw_base, state.content_branch);
-    let resp = match crate::http::client().get(&url).send().await.and_then(|r| r.error_for_status()) {
+    let url = format!(
+        "{}/{path}?ref={}",
+        state.content_raw_base, state.content_branch
+    );
+    let resp = match crate::http::client()
+        .get(&url)
+        .send()
+        .await
+        .and_then(|r| r.error_for_status())
+    {
         Ok(r) => r,
         Err(e) => {
             tracing::warn!("site asset {path}: {e}");
@@ -79,12 +120,26 @@ pub async fn site_asset_handler(
         Some("avif") => "image/avif",
         Some("ico") => "image/x-icon",
         Some("woff2") => "font/woff2",
+        Some("txt") => "text/plain; charset=utf-8",
+        Some("xml") => "application/xml; charset=utf-8",
+        Some("webmanifest") => "application/manifest+json",
+        // An Apple configuration profile only offers to install when it
+        // arrives under this type; anything else is just a download.
+        Some("mobileconfig") => "application/x-apple-aspen-config",
+        // A file with no extension at all: rsplit yields the whole name.
+        _ if well_known && !path.rsplit('/').next().unwrap_or_default().contains('.') => {
+            "application/json; charset=utf-8"
+        }
         _ => "application/octet-stream",
     };
     // Photographs are large and do not change under a name, so a
     // browser may keep them for an hour; everything else revalidates,
     // so a content push shows on reload.
-    let cache = if matches!(mime, "image/webp" | "image/avif" | "image/jpeg") { "public, max-age=3600" } else { "no-cache" };
+    let cache = if matches!(mime, "image/webp" | "image/avif" | "image/jpeg") {
+        "public, max-age=3600"
+    } else {
+        "no-cache"
+    };
     (
         [(header::CONTENT_TYPE, mime), (header::CACHE_CONTROL, cache)],
         bytes,
@@ -114,14 +169,22 @@ pub async fn gitea_repo_handler(
                 .all(|c| c.is_ascii_alphanumeric() || c == '-' || c == '_' || c == '.')
     };
     if !is_safe_segment(&query.owner) || !is_safe_segment(&query.repo) {
-        return Err((axum::http::StatusCode::BAD_REQUEST, "invalid owner/repo".to_string()));
+        return Err((
+            axum::http::StatusCode::BAD_REQUEST,
+            "invalid owner/repo".to_string(),
+        ));
     }
     let GiteaRepoQuery { owner, repo } = query;
 
     let api_url = format!("{}/api/v1/repos/{owner}/{repo}", state.gitea_base);
     let body = crate::http::get_text(&api_url, crate::http::GITEA_CAP)
         .await
-        .map_err(|e| (axum::http::StatusCode::BAD_GATEWAY, format!("fetching {api_url}: {e}")))?;
+        .map_err(|e| {
+            (
+                axum::http::StatusCode::BAD_GATEWAY,
+                format!("fetching {api_url}: {e}"),
+            )
+        })?;
     let json: serde_json::Value = serde_json::from_str(&body).map_err(|e| {
         (
             axum::http::StatusCode::BAD_GATEWAY,
@@ -168,27 +231,38 @@ pub async fn automation_kv_handler(
         .and_then(|v| v.strip_prefix("Bearer "))
         .unwrap_or("");
     if expected.is_empty() || presented != expected {
-        return Err((axum::http::StatusCode::UNAUTHORIZED, "unauthorized".to_string()));
+        return Err((
+            axum::http::StatusCode::UNAUTHORIZED,
+            "unauthorized".to_string(),
+        ));
     }
     // The token authenticates the automation service; what it may read
     // is the policy's to say, like every other principal.
     let decision = crate::access::decide_and_publish(
         &state.nats,
         &state.access.load(),
-        &crate::access::Principal::Service { name: "automation".to_string() },
+        &crate::access::Principal::Service {
+            name: "automation".to_string(),
+        },
         crate::access::Action::AutomationRead,
-        &crate::access::Resource::Bucket { name: bucket.clone() },
+        &crate::access::Resource::Bucket {
+            name: bucket.clone(),
+        },
         serde_json::json!({}),
     );
     if !decision.allow {
-        return Err((axum::http::StatusCode::FORBIDDEN, "not authorized".to_string()));
+        return Err((
+            axum::http::StatusCode::FORBIDDEN,
+            "not authorized".to_string(),
+        ));
     }
 
-    let store = state
-        .jetstream
-        .get_key_value(&bucket)
-        .await
-        .map_err(|e| (axum::http::StatusCode::BAD_GATEWAY, format!("bucket unavailable: {e}")))?;
+    let store = state.jetstream.get_key_value(&bucket).await.map_err(|e| {
+        (
+            axum::http::StatusCode::BAD_GATEWAY,
+            format!("bucket unavailable: {e}"),
+        )
+    })?;
 
     use futures::TryStreamExt;
     let keys: Vec<String> = store
@@ -209,3 +283,29 @@ pub async fn automation_kv_handler(
     Ok(axum::Json(serde_json::Value::Array(items)))
 }
 
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// The overlay's whole safety argument: `/.well-known/` is reserved by
+    /// RFC 8615 and a question's id comes from a file under `questions/`, so
+    /// a repo file served at the site root cannot shadow a page - and the
+    /// path it is fetched by still cannot climb out of the repo.
+    #[test]
+    fn well_known_paths_stay_inside_the_repo() {
+        for path in [
+            ".well-known/security.txt",
+            ".well-known/matrix/server",
+            ".well-known/assetlinks.json",
+        ] {
+            assert!(is_safe_site_path(path), "{path} should be servable");
+        }
+        for path in [
+            ".well-known/../questions/index.yaml",
+            ".well-known//escape",
+            "/.well-known/security.txt",
+        ] {
+            assert!(!is_safe_site_path(path), "{path} should be refused");
+        }
+    }
+}

src/main.rs

@@ -27,7 +27,14 @@ async fn main() -> anyhow::Result<()> {
 
 #[cfg(feature = "ssr")]
 async fn serve() -> anyhow::Result<()> {
-    use axum::{body::Body, extract::State, http::Request, response::IntoResponse, routing::{any, get, post}, Router};
+    use axum::{
+        body::Body,
+        extract::State,
+        http::Request,
+        response::IntoResponse,
+        routing::{any, get, post},
+        Router,
+    };
     use leptos::prelude::*;
     use leptos_axum::{generate_route_list, LeptosRoutes};
     use portal::app::{shell, App};
@@ -57,12 +64,15 @@ async fn serve() -> anyhow::Result<()> {
     let gitea_base = content::gitea_api_base(&content_repo)?;
     let content_raw_base = content::gitea_raw_base(&content_repo)?;
     let aggregates = content::load_aggregates_from_gitea(&content_repo, &content_branch).await?;
-    let questions = content::load_questions_from_gitea(&content_repo, &content_branch, "questions").await?;
+    let questions =
+        content::load_questions_from_gitea(&content_repo, &content_branch, "questions").await?;
     content::validate_questions(&questions, &aggregates)?;
     let site = content::load_site_from_gitea(&content_repo, &content_branch).await?;
     let storylines = content::same_arity(questions.arity(), aggregates.arity(), site.arity())?;
     tracing::info!(count = questions.len(), storylines, repo = %content_repo, branch = %content_branch, "loaded content");
-    let access = Arc::new(arc_swap::ArcSwap::from_pointee(portal::access::Policy::from_content(&questions, &aggregates)));
+    let access = Arc::new(arc_swap::ArcSwap::from_pointee(
+        portal::access::Policy::from_content(&questions, &aggregates),
+    ));
     let questions = Arc::new(arc_swap::ArcSwap::from_pointee(questions));
     let aggregates = Arc::new(arc_swap::ArcSwap::from_pointee(aggregates));
     let site = Arc::new(arc_swap::ArcSwap::from_pointee(site));
@@ -128,7 +138,12 @@ async fn serve() -> anyhow::Result<()> {
 
     // The same decisions, answerable by other apps over NATS, for a
     // person named by phone number or address as well as by groups.
-    tokio::spawn(portal::access::serve(state.nats.clone(), site_name_for_subjects(), state.access.clone(), Some(state.clone())));
+    tokio::spawn(portal::access::serve(
+        state.nats.clone(),
+        site_name_for_subjects(),
+        state.access.clone(),
+        Some(state.clone()),
+    ));
     // Announced pages: keep their desk records current, close ended
     // windows (see announce.rs).
     tokio::spawn(portal::announce::run(state.clone()));
@@ -202,17 +217,16 @@ async fn serve() -> anyhow::Result<()> {
     });
     match &governor {
         Some(_) => tracing::info!(rate_per_second, rate_burst, "rate limiting per caller IP"),
-        None => tracing::warn!("rate limiting is off (PORTAL_RATE_PER_SECOND or PORTAL_RATE_BURST is 0)"),
+        None => tracing::warn!(
+            "rate limiting is off (PORTAL_RATE_PER_SECOND or PORTAL_RATE_BURST is 0)"
+        ),
     }
 
     async fn server_fn_handler(
         State(state): State<AppState>,
         request: Request<Body>,
     ) -> impl IntoResponse {
-        leptos_axum::handle_server_fns_with_context(
-            move || provide_context(state.clone()),
-            request,
-        )
+        leptos_axum::handle_server_fns_with_context(move || provide_context(state.clone()), request)
             .await
     }
 
@@ -264,10 +278,7 @@ async fn serve() -> anyhow::Result<()> {
         .route_service("/favicon-light.svg", ServeFile::new(favicon_light_path))
         .route_service("/favicon-dark.svg", ServeFile::new(favicon_dark_path))
         .route_service("/wordmark.svg", ServeFile::new(wordmark_path))
-        .route_service(
-            "/swiper-element-bundle.min.js",
-            ServeFile::new(swiper_path),
-        )
+        .route_service("/swiper-element-bundle.min.js", ServeFile::new(swiper_path))
         // Same name every release, so revalidated like /pkg.
         .route_service(
             "/page-motion.js",
@@ -291,7 +302,9 @@ async fn serve() -> anyhow::Result<()> {
         // with room for the multipart framing.
         .route(
             "/upload",
-            post(upload::upload).layer(axum::extract::DefaultBodyLimit::max(upload::MAX_UPLOAD_BYTES + 64 * 1024)),
+            post(upload::upload).layer(axum::extract::DefaultBodyLimit::max(
+                upload::MAX_UPLOAD_BYTES + 64 * 1024,
+            )),
         )
         .route(
             "/attachment/{bucket}/{record}/{field}",
@@ -302,7 +315,11 @@ async fn serve() -> anyhow::Result<()> {
         .route("/report", get(portal::report::handler))
         // Content-shipped assets (hero module etc.), same-origin.
         .route("/site/{*path}", get(content::site_asset_handler))
-        .route("/automation/kv/{bucket}", get(content::automation_kv_handler))
+        .route("/.well-known/{*path}", get(content::well_known_handler))
+        .route(
+            "/automation/kv/{bucket}",
+            get(content::automation_kv_handler),
+        )
         // Maps, proxied: the browser asks this origin for every tile
         // and every still, so nothing third-party loads in a page and
         // the token stays here (see maps.rs).
@@ -324,7 +341,10 @@ async fn serve() -> anyhow::Result<()> {
         .fallback(leptos_axum::file_and_error_handler::<AppState, _>(shell))
         .layer(session_layer)
         // Which storyline this visitor reads, before anything renders.
-        .layer(axum::middleware::from_fn_with_state(state.clone(), portal::server::storyline::assign));
+        .layer(axum::middleware::from_fn_with_state(
+            state.clone(),
+            portal::server::storyline::assign,
+        ));
     // Outermost, so a caller who is over the limit is turned away
     // before a session is loaded or a handler is entered.
     let app = match governor {
@@ -362,7 +382,17 @@ fn site_name_for_subjects() -> String {
     let raw = std::env::var("SITE_NAME").unwrap_or_else(|_| "portal".to_string());
     let folded: String = raw
         .chars()
-        .map(|c| if c.is_ascii_alphanumeric() || c == '_' || c == '-' { c.to_ascii_lowercase() } else { '_' })
+        .map(|c| {
+            if c.is_ascii_alphanumeric() || c == '_' || c == '-' {
+                c.to_ascii_lowercase()
+            } else {
+                '_'
+            }
+        })
         .collect();
-    if folded.is_empty() { "portal".to_string() } else { folded }
+    if folded.is_empty() {
+        "portal".to_string()
+    } else {
+        folded
+    }
 }