security(keeper): reject non-GET methods on keeper status with 405

services/keeper/README.md

@@ -37,6 +37,8 @@ The status API is served by `npm run serve` (or any process that calls `createSt
 | `GET` | `/healthz` | Liveness probe — cheap, suitable for load balancers |
 | `GET` | `/` | Service info + endpoint list |
 
+All endpoints only accept `GET` requests. Any non-`GET` method (`POST`, `PUT`, `PATCH`, `DELETE`, `HEAD`, `OPTIONS`, etc.) is rejected at the server boundary with HTTP `405 Method Not Allowed`, an `Allow: GET` response header, and a JSON `{ "error": "method not allowed", "method": "<VERB>", "allow": ["GET"], "available": [...] }` body without invoking RPC or Drand readers.
+
 ### Configuration
 
 | Env var | Default | Description |

services/keeper/src/status-server.test.ts

@@ -88,10 +88,11 @@ function makeSource(overrides: Partial<BuildStatusSource> = {}): BuildStatusSour
 async function invokeHandler(
   source: BuildStatusSource,
   path: string,
+  method = "GET",
 ): Promise<{ status: number; headers: Record<string, string>; body: unknown }> {
   const handler = createStatusHandler(source);
   const req = Object.assign(Readable.from([]), {
-    method: "GET",
+    method,
     url: path,
     headers: { host: "localhost" },
   });
@@ -324,3 +325,54 @@ test("GET /status/health returns health shape", async () => {
     assert.ok(["ok", "degraded", "down"].includes(health.drand as string));
   });
 });
+
+test("rejects non-GET methods with 405 and Allow: GET at the server boundary", async () => {
+  const source = makeSource({
+    reader: {
+      getRound: async () => {
+        throw new Error("reader should not be called on non-GET requests");
+      },
+      getBidState: async () => {
+        throw new Error("reader should not be called on non-GET requests");
+      },
+    },
+  });
+
+  for (const method of ["POST", "PUT", "PATCH", "DELETE", "HEAD", "OPTIONS"]) {
+    const direct = await invokeHandler(source, "/status", method);
+    assert.equal(direct.status, 405);
+    assert.equal(direct.headers["allow"], "GET");
+    assert.equal(direct.headers["cache-control"], "no-store");
+    const directBody = direct.body as Record<string, unknown>;
+    assert.equal(directBody.error, "method not allowed");
+    assert.equal(directBody.method, method);
+    assert.deepEqual(directBody.allow, ["GET"]);
+  }
+
+  await withServer(source, async (server) => {
+    const addr = server.address();
+    assert.ok(addr && typeof addr === "object");
+    const baseUrl = `http://127.0.0.1:${addr.port}`;
+
+    for (const [method, path] of [
+      ["POST", "/status"],
+      ["PUT", "/status/rounds/1"],
+      ["DELETE", "/healthz"],
+      ["PATCH", "/status/health"],
+      ["POST", "/"],
+    ] as const) {
+      const res = await fetch(`${baseUrl}${path}`, {
+        method,
+        headers: { "content-type": "application/json" },
+        body: method === "DELETE" ? undefined : JSON.stringify({ probe: true }),
+      });
+      assert.equal(res.status, 405, `expected 405 for ${method} ${path}`);
+      assert.equal(res.headers.get("allow"), "GET");
+      assert.equal(res.headers.get("cache-control"), "no-store");
+      const body = (await res.json()) as Record<string, unknown>;
+      assert.equal(body.error, "method not allowed");
+      assert.equal(body.method, method);
+      assert.deepEqual(body.allow, ["GET"]);
+    }
+  });
+});

services/keeper/src/status-server.ts

@@ -43,9 +43,13 @@ function send(
   res: http.ServerResponse,
   status: number,
   body: unknown,
+  extraHeaders?: Record<string, string>,
 ): void {
   const payload = JSON.stringify(body, bigintReplacer, 2);
-  res.writeHead(status, JSON_CONTENT);
+  res.writeHead(
+    status,
+    extraHeaders ? { ...JSON_CONTENT, ...extraHeaders } : JSON_CONTENT,
+  );
   res.end(payload);
 }
 
@@ -188,7 +192,28 @@ export function createStatusHandler(config: StatusServerConfig): http.RequestLis
       const baseHost = req.headers.host ?? `${host}:${port}`;
       const url = new URL(req.url ?? "/", `http://${baseHost}`);
 
-      if (req.method === "GET" && url.pathname === "/healthz") {
+      if (req.method !== "GET") {
+        req.resume?.();
+        send(
+          res,
+          405,
+          {
+            error: "method not allowed",
+            method: req.method ?? "UNKNOWN",
+            allow: ["GET"],
+            available: [
+              "GET /status",
+              "GET /status/rounds/:id",
+              "GET /healthz",
+              "GET /status/health",
+            ],
+          },
+          { allow: "GET" },
+        );
+        return;
+      }
+
+      if (url.pathname === "/healthz") {
         void fastHealth(url).then((r) => send(res, r.status, r.body));
         return;
       }