fix(cors): enforce explicit allowed_origins in production and restrict methods/headers (#24)

src/config.rs

@@ -1,4 +1,4 @@
-use anyhow::{Context, Result};
+use anyhow::{bail, Context, Result};
 use std::env;
 
 /// Central application configuration, loaded once at startup from environment variables.
@@ -152,6 +152,12 @@ impl Config {
             _ => AppEnv::Development,
         };
 
+        if app_env == AppEnv::Production
+            && (allowed_origins.is_empty() || allowed_origins.iter().any(|o| o == "*"))
+        {
+            bail!("ALLOWED_ORIGINS must be set to an explicit, non-wildcard list of origins in production");
+        }
+
         Ok(Self {
             port,
             host,

src/middleware/cors.rs

@@ -1,10 +1,15 @@
+use axum::http::{header, Method};
 use tower_http::cors::{AllowHeaders, AllowMethods, AllowOrigin, CorsLayer};
 
 /// Build the CORS layer from the configured list of allowed origins.
 ///
 /// When `allowed_origins` contains `"*"`, or is empty, every origin is
-/// permitted (suitable for development / public APIs).  In production, supply
+/// permitted (suitable for development / public APIs). In production, supply
 /// an explicit list so that only known origins are whitelisted.
+///
+/// Methods and headers are restricted to the real surface required by the
+/// StellarSend API (GET, POST, OPTIONS, and standard auth/content headers)
+/// with a 1-hour preflight cache max age.
 pub fn build_cors_layer(allowed_origins: &[String]) -> CorsLayer {
     let allow_origin: AllowOrigin = if allowed_origins.iter().any(|o| o == "*")
         || allowed_origins.is_empty()
@@ -20,6 +25,36 @@ pub fn build_cors_layer(allowed_origins: &[String]) -> CorsLayer {
 
     CorsLayer::new()
         .allow_origin(allow_origin)
-        .allow_methods(AllowMethods::any())
-        .allow_headers(AllowHeaders::any())
+        .allow_methods(AllowMethods::list([
+            Method::GET,
+            Method::POST,
+            Method::OPTIONS,
+        ]))
+        .allow_headers(AllowHeaders::list([
+            header::AUTHORIZATION,
+            header::CONTENT_TYPE,
+            header::ACCEPT,
+            header::HeaderName::from_static("x-request-id"),
+        ]))
+        .max_age(std::time::Duration::from_secs(3600))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn build_cors_layer_with_wildcard_works() {
+        let origins = vec!["*".to_string()];
+        let _layer = build_cors_layer(&origins);
+    }
+
+    #[test]
+    fn build_cors_layer_with_explicit_origins_works() {
+        let origins = vec![
+            "https://app.stellarsend.com".to_string(),
+            "https://staging.stellarsend.com".to_string(),
+        ];
+        let _layer = build_cors_layer(&origins);
+    }
 }