fix: ignore stray oauth callback requests

src/auth/oauth.ts

@@ -29,6 +29,7 @@ type TokenResponse = {
 };
 
 const CALLBACK_HOST = "127.0.0.1";
+const CALLBACK_PATH = "/callback";
 const DEFAULT_CALLBACK_PORT = 53682;
 const OAUTH_CALLBACK_PORT_ENV_KEY = "OPENWIKI_OAUTH_CALLBACK_PORT";
 const HTTPS_OAUTH_REDIRECT_URI_ENV_KEY = "OPENWIKI_HTTPS_OAUTH_REDIRECT_URI";
@@ -404,6 +405,13 @@ export async function createCallbackServer(
       request.url ?? "/",
       `http://${CALLBACK_HOST}:${callbackPort}`,
     );
+
+    if (requestUrl.pathname !== CALLBACK_PATH) {
+      response.writeHead(404, getCallbackResponseHeaders());
+      response.end("OpenWiki OAuth callback server is waiting for /callback.");
+      return;
+    }
+
     const code = requestUrl.searchParams.get("code");
     const state = requestUrl.searchParams.get("state");
     const error = requestUrl.searchParams.get("error");
@@ -438,7 +446,7 @@ export async function createCallbackServer(
   if (!address || typeof address === "string") {
     throw new Error("Could not start OAuth callback server.");
   }
-  const localRedirectUri = `http://${CALLBACK_HOST}:${address.port}/callback`;
+  const localRedirectUri = `http://${CALLBACK_HOST}:${address.port}${CALLBACK_PATH}`;
 
   return {
     close: () => closeCallbackServer(server),
@@ -524,7 +532,7 @@ function getProviderRedirectUri(
 
   const url = new URL(override);
 
-  if (url.pathname !== "/callback") {
+  if (url.pathname !== CALLBACK_PATH) {
     throw new Error(
       `${HTTPS_OAUTH_REDIRECT_URI_ENV_KEY} must end with /callback.`,
     );

test/oauth-callback-server.test.ts

@@ -46,6 +46,8 @@ describe("createCallbackServer", () => {
     const callback = await createCallbackServer(getAuthProvider("gmail"));
 
     try {
+      expect(callback.redirectUri).toBe(`http://127.0.0.1:${port}/callback`);
+
       const codePromise = callback.waitForCode("expected-state");
       const redirect = await fetch(
         `http://127.0.0.1:${port}/callback?code=test-code&state=expected-state`,
@@ -58,6 +60,61 @@ describe("createCallbackServer", () => {
     }
   });
 
+  test("ignores non-callback requests without rejecting the pending flow", async () => {
+    const callback = await createCallbackServer(getAuthProvider("gmail"));
+
+    try {
+      const codePromise = callback.waitForCode("expected-state");
+      const strayRequest = await fetch(`http://127.0.0.1:${port}/favicon.ico`);
+
+      expect(strayRequest.status).toBe(404);
+      await expect(
+        fetch(
+          `http://127.0.0.1:${port}/callback?code=test-code&state=expected-state`,
+        ),
+      ).resolves.toMatchObject({ status: 200 });
+      await expect(codePromise).resolves.toBe("test-code");
+    } finally {
+      await callback.close();
+    }
+  });
+
+  test("rejects a callback request that is missing code or state", async () => {
+    const callback = await createCallbackServer(getAuthProvider("gmail"));
+
+    try {
+      const codePromise = callback.waitForCode("expected-state");
+      const codeRejection = expect(codePromise).rejects.toThrow(
+        "OAuth callback was missing code or state.",
+      );
+      const redirect = await fetch(`http://127.0.0.1:${port}/callback`);
+
+      expect(redirect.status).toBe(400);
+      await codeRejection;
+    } finally {
+      await callback.close();
+    }
+  });
+
+  test("rejects a callback request with a provider error", async () => {
+    const callback = await createCallbackServer(getAuthProvider("gmail"));
+
+    try {
+      const codePromise = callback.waitForCode("expected-state");
+      const codeRejection = expect(codePromise).rejects.toThrow(
+        "OAuth provider returned error: access_denied",
+      );
+      const redirect = await fetch(
+        `http://127.0.0.1:${port}/callback?error=access_denied`,
+      );
+
+      expect(redirect.status).toBe(400);
+      await codeRejection;
+    } finally {
+      await callback.close();
+    }
+  });
+
   test("answers a trailing request that arrives while the server is closing", async () => {
     const callback = await createCallbackServer(getAuthProvider("gmail"));
     const codePromise = callback.waitForCode("expected-state");
@@ -83,7 +140,7 @@ describe("createCallbackServer", () => {
     await closePromise;
 
     const response = Buffer.concat(chunks).toString();
-    expect(response).toMatch(/^HTTP\/1\.1 400 /);
-    expect(response).toContain("missing required data");
+    expect(response).toMatch(/^HTTP\/1\.1 404 /);
+    expect(response).toContain("waiting for /callback");
   });
 });