fix(install): send a default User-Agent with app-source downloads (#2842)

packages/provision-kit/src/install-source-download.test.ts

@@ -51,6 +51,43 @@ test('download redirects revalidate destinations and strip sensitive cross-origi
   }
 });
 
+test('download sends a default user-agent that a caller header replaces', async () => {
+  const tempRoot = await mkdtempForTest('agent-device-download-user-agent-');
+  const lookup = vi
+    .spyOn(dns, 'lookup')
+    .mockImplementation(
+      async () =>
+        [{ address: '93.184.216.34', family: 4 }] as unknown as Awaited<
+          ReturnType<typeof dns.lookup>
+        >,
+    );
+  const requestMock = vi
+    .spyOn(networkTransport, 'requestApprovedUrl')
+    .mockImplementation(async () => response(200, Buffer.from('apk')));
+  try {
+    await downloadInstallSource({
+      tempDir: tempRoot,
+      url: 'https://example.com/default.apk',
+      signal: new AbortController().signal,
+    });
+    await downloadInstallSource({
+      tempDir: tempRoot,
+      url: 'https://example.com/custom.apk',
+      headers: { 'User-Agent': 'caller-agent' },
+      signal: new AbortController().signal,
+    });
+    const defaultHeaders = requestMock.mock.calls[0]![0].headers;
+    const customHeaders = requestMock.mock.calls[1]![0].headers;
+    assert.equal(defaultHeaders['user-agent'], 'agent-device');
+    assert.equal(customHeaders['User-Agent'], 'caller-agent');
+    assert.equal(customHeaders['user-agent'], undefined);
+  } finally {
+    requestMock.mockRestore();
+    lookup.mockRestore();
+    await fs.rm(tempRoot, { recursive: true, force: true });
+  }
+});
+
 test('download errors do not disclose URL credentials or query values', async () => {
   const tempRoot = await mkdtempForTest('agent-device-download-redaction-');
   const lookup = vi

packages/provision-kit/src/install-source-download.ts

@@ -11,6 +11,7 @@ import { approveDownloadSourceUrl } from './install-source-network.ts';
 import * as networkTransport from './install-source-network-transport.ts';
 
 const MAX_REDIRECTS = 5;
+const DEFAULT_USER_AGENT = 'agent-device';
 const REDIRECT_STATUSES = new Set([301, 302, 303, 307, 308]);
 const FORBIDDEN_HEADERS = new Set([
   'accept-encoding',
@@ -33,7 +34,7 @@ export async function downloadInstallSource(params: {
   signal: AbortSignal;
 }): Promise<string> {
   let currentUrl = parseSourceUrl(params.url);
-  let headers = sanitizeHeaders(params.headers);
+  let headers = withDefaultUserAgent(sanitizeHeaders(params.headers));
   for (let redirectCount = 0; ; redirectCount += 1) {
     const response = await requestHop(currentUrl, headers, params.signal);
     try {
@@ -159,6 +160,11 @@ function sanitizeHeaders(input: Record<string, string> | undefined): Record<stri
   );
 }
 
+function withDefaultUserAgent(headers: Record<string, string>): Record<string, string> {
+  if (Object.keys(headers).some((name) => name.toLowerCase() === 'user-agent')) return headers;
+  return { ...headers, 'user-agent': DEFAULT_USER_AGENT };
+}
+
 function crossOriginHeaders(headers: Record<string, string>): Record<string, string> {
   return Object.fromEntries(
     Object.entries(headers).filter(([name]) =>