Handle malformed feed path encoding

apps/commandboard-api/src/contract.test.ts

@@ -100,6 +100,14 @@ describe("CommandBoard API contracts", () => {
     expect(opmlBody).toContain("<opml");
   });
 
+  it("rejects malformed encoded feed discovery paths as client errors", async () => {
+    const response = await fetch(`${baseUrl}/rss/discover/%E0%A4%A.xml`);
+    const body = await response.json() as { error: string };
+
+    expect(response.status).toBe(400);
+    expect(body).toEqual({ error: "Invalid path encoding" });
+  });
+
   it("exposes sh1pt project and action contracts", async () => {
     const projectsResponse = await fetch(`${baseUrl}/api/plugins/sh1pt/projects`);
     const projectsBody = await projectsResponse.json() as { projects: Array<{ id: string; board: string; status: string; actions: number }> };

apps/commandboard-api/src/index.ts

@@ -172,6 +172,11 @@ async function route(request: IncomingMessage, response: ServerResponse) {
 
   const formattedDiscover = matchFormattedDiscoverPath(url.pathname);
   if (request.method === "GET" && formattedDiscover) {
+    if (formattedDiscover.format === "invalid-encoding") {
+      json(response, 400, { error: "Invalid path encoding" });
+      return;
+    }
+
     const result = await discoverFeeds({
       q: formattedDiscover.keyword,
       type: "all",
@@ -312,23 +317,34 @@ function listParam(value: string | null) {
 function matchFormattedDiscoverPath(pathname: string) {
   const rss = /^\/rss\/discover\/(.+)\.xml$/.exec(pathname);
   if (rss) {
-    return { format: "rss" as const, keyword: decodeURIComponent(rss[1]) };
+    return formattedDiscoverMatch("rss", rss[1]);
   }
   const opml = /^\/opml\/discover\/(.+)\.xml$/.exec(pathname) ?? /^\/rss\/discover\/(.+)\.opml$/.exec(pathname);
   if (opml) {
-    return { format: "opml" as const, keyword: decodeURIComponent(opml[1]) };
+    return formattedDiscoverMatch("opml", opml[1]);
   }
   const atom = /^\/atom\/discover\/(.+)\.xml$/.exec(pathname);
   if (atom) {
-    return { format: "atom" as const, keyword: decodeURIComponent(atom[1]) };
+    return formattedDiscoverMatch("atom", atom[1]);
   }
   const jsonFeed = /^\/json-feed\/discover\/(.+)\.json$/.exec(pathname);
   if (jsonFeed) {
-    return { format: "json-feed" as const, keyword: decodeURIComponent(jsonFeed[1]) };
+    return formattedDiscoverMatch("json-feed", jsonFeed[1]);
   }
   return undefined;
 }
 
+function formattedDiscoverMatch(format: "rss" | "opml" | "atom" | "json-feed", encodedKeyword: string) {
+  try {
+    return { format, keyword: decodeURIComponent(encodedKeyword) };
+  } catch (error) {
+    if (error instanceof URIError) {
+      return { format: "invalid-encoding" as const };
+    }
+    throw error;
+  }
+}
+
 export function startCommandBoardServer(port = Number(process.env.PORT ?? 4010)) {
   const server = createCommandBoardServer();
   server.listen(port, () => {