feat(caretaker): implement Cloud Run webhook ingestion service by chadd28 · Pull Request #28015 · google-gemini/gemini-cli

chadd28 · 2026-06-18T17:50:43Z

Summary

Implements the Cloud Run Webhook Ingestion Service for the Caretaker Agent. The service acts as an entry point for GitHub webhooks, verifies incoming payload signatures, stores new issue entries using Firestore transactions, and publishes sanitized issue metadata to a GCP Pub/Sub topic for downstream processing.

Details

Server (server.ts): The main Express server (to be hosted on Cloud Run) that receives GitHub issues.opened events, validates their signature, adds the issue to Firestore, and publishes the issue details to Pub/Sub.
Auth Verification (auth/github.ts): HMAC SHA-256 signature verification helper using node:crypto and a secure timing-safe equality check.
Store (db/issuesStore.ts): Initializes new issues in Firestore using a transaction.
Tests: Added issuesStore.test.ts (Firestore mock tests) and github.test.ts (HMAC signature verification tests).

How to Validate

Run unit tests in the service directory:

cd tools/caretaker-agent/cloudrun/ingestion-service
npm install
npx vitest run

Pre-Merge Checklist

@galz10

…tion

github-actions · 2026-06-18T17:50:55Z

📊 PR Size: size/L

Lines changed: 441
Additions: +441
Deletions: -0
Files changed: 9

gemini-code-assist · 2026-06-18T19:45:06Z

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new ingestion service for the Caretaker Agent, designed to run on Cloud Run. The service acts as a secure gateway for GitHub webhooks, handling event validation, deduplication via Firestore transactions, and message queuing through Pub/Sub. This infrastructure enables automated downstream triage workflows for incoming GitHub issues.

Highlights

Webhook Ingestion Service: Implemented a new Express-based service to receive and process GitHub 'issues.opened' webhooks.
Security & Verification: Added HMAC SHA-256 signature verification using timing-safe equality checks to ensure payload authenticity.
Data Persistence: Integrated Firestore transactions to reliably store issue metadata and prevent duplicate entries.
Downstream Integration: Configured Pub/Sub publishing to forward sanitized issue data for further processing.

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gemini-code-assist

Code Review

This pull request introduces a new Express-based ingestion service for a triage worker, featuring GitHub webhook signature verification, Firestore storage for tracking issues, and Pub/Sub integration. The review feedback highlights three critical security and reliability improvements: validating the signature length and payload type in the GitHub auth module to prevent crashes and DoS attacks, escaping the issue body to mitigate prompt injection vulnerabilities, and checking the return value of the issue creation transaction to prevent duplicate Pub/Sub messages.

gemini-code-assist · 2026-06-18T19:47:26Z

+  }
+
+  // Payload preprocessing
+  const sanitizedBody = `<untrusted_context>\n${payload.issue?.body || ''}\n</untrusted_context>`;


Wrapping untrusted user input directly in <untrusted_context> tags without escaping or sanitizing the input makes the system vulnerable to prompt injection. An attacker could include </untrusted_context> in their issue body to escape the context block and inject malicious instructions.

Sanitize or escape any occurrences of </untrusted_context> in the issue body before wrapping it.

const rawBody = payload.issue?.body || ''; const escapedBody = rawBody.replace(/<\/untrusted_context>/g, '[escaped_untrusted_context_tag]'); const sanitizedBody = `\<untrusted_context\>\n\${escapedBody}\n\</untrusted_context\>`;

…timing attacks

galz10 · 2026-06-22T21:54:31Z

+COPY . .
+EXPOSE 8080
+CMD ["npx", "tsx", "server.ts"]
+


[P1] Production anti-pattern.
Running tsx (or ts-node) in a production container introduces significant memory overhead and startup latency. Add a "build": "tsc" script to package.json and run the compiled JavaScript here instead.

Suggested change

RUN npm run build

CMD ["node", "dist/server.js"]

galz10 · 2026-06-22T21:56:40Z

+
+    // Publish to Pub/Sub
+    const dataBuffer = Buffer.from(JSON.stringify(processedData));
+    const messageId = await topic.publishMessage({ data: dataBuffer });


[P0] Dual-write failure state permanently drops retried webhooks.
If the Firestore write succeeds but the Pub/Sub publish fails, the server returns a 500 error, and GitHub will retry. On the retry, createIssue returns false (since the document already exists), causing the endpoint to return 200 early and skip the Pub/Sub publish entirely. The issue will never be processed downstream. You should publish to Pub/Sub even if the DB document exists (assuming downstream is idempotent) or rely entirely on Pub/Sub and let the downstream worker deduplicate.

galz10 · 2026-06-22T21:57:01Z

+});
+
+app.post('/webhook', async (req, res) => {
+  const signature = req.headers['x-hub-signature-256'] as string | undefined;


[P2] Unsafe header cast.
Express headers can be an array (string[]) if multiple headers with the same name are sent. If an array is passed, downstream checks like signature.length will evaluate the array length rather than string length.

Suggested change

const signature = req.headers['x-hub-signature-256'] as string | undefined;

const header = req.headers['x-hub-signature-256'];

const signature = Array.isArray(header) ? header[0] : header;

galz10 · 2026-06-22T21:57:01Z

+} from '@google-cloud/firestore';
+
+export class IssuesStore {
+  private db: Firestore;


[P3] Missing readonly modifier.
These properties are only set in the constructor. Mark them as readonly to enforce immutability.

Suggested change

private db: Firestore;

private readonly db: Firestore;

private readonly collectionName: string;

galz10 · 2026-06-22T21:57:01Z

+const issuesStore = new IssuesStore(db, collectionName);
+
+// Middleware: read incoming JSON payloads as raw Buffer bytes
+app.use(express.raw({ type: 'application/json' }));


[P3] Missing payload limit.
While GitHub webhooks are generally small, setting an explicit limit is best practice for documenting expectations and preventing payload-based denial of service.

Suggested change

app.use(express.raw({ type: 'application/json' }));

app.use(express.raw({ type: 'application/json', limit: '1mb' }));

galz10 · 2026-06-22T21:57:01Z

+  let payload: GitHubWebhookPayload;
+  try {
+    payload = JSON.parse(req.body.toString()) as GitHubWebhookPayload;
+  } catch {


[P2] Blind type casting.
The explicit cast as GitHubWebhookPayload bypasses runtime safety. At minimum, we should validate the presence of payload.issue.number and payload.repository.full_name before assuming the structure exists to avoid unexpected undefined errors downstream.

galz10 · 2026-06-22T21:57:01Z

+
+  // Payload preprocessing
+  const sanitizedBody = `<untrusted_context>\n${payload.issue?.body || ''}\n</untrusted_context>`;
+  const processedData = {


[P2] Misleading variable name / Missing sanitization.
This is not actually sanitized. If a user maliciously includes </untrusted_context> in their GitHub issue description, they will break out of the LLM context wrapper downstream. Rename this to wrappedBody to be accurate, or implement actual tag escaping/stripping.

galz10

[P0] Missing core unit tests.
The PR introduces complex routing, orchestrating validation, DB writes, and Pub/Sub publishing in server.ts without a corresponding server.test.ts. This violates the testing standard criteria. Please add tests that mock the Firestore and Pub/Sub clients to verify the endpoint behavior.

chadd28 added 5 commits June 17, 2026 17:19

chore(ingestion): initialize project setup and environment configuration

8d23977

feat(ingestion): implement Firestore IssuesStore for new documents

c9cbd86

feat(ingestion): add GitHub webhook HMAC signature verification

2d09842

feat(ingestion): create Express server and webhook ingestion route

a6ef7a9

test(ingestion): add unit tests for GitHub webhook signature verifica…

40c59c1

…tion

github-actions Bot added the size/l A large sized PR label Jun 18, 2026

chadd28 marked this pull request as ready for review June 18, 2026 19:38

chadd28 requested a review from a team as a code owner June 18, 2026 19:38

gemini-code-assist Bot reviewed Jun 18, 2026

View reviewed changes

gemini-cli Bot added the status/need-issue Pull requests that need to have an associated issue. label Jun 18, 2026

feat(ingestion): skip Pub/Sub publishing for duplicate issues

a8a0fe8

This was referenced Jun 19, 2026

📊 AI CLI 工具社区动态日报 2026-06-19 zx0828/big_model_radar#146

Open

📊 AI CLI 工具社区动态日报 2026-06-19 96loveslife/big_model_radar#33

Open

fix(ingestion): secure GitHub signature verification against DoS and …

5650049

…timing attacks

chadd28 force-pushed the feature/caretaker-agent branch from ef27d32 to 5650049 Compare June 22, 2026 21:51

galz10 reviewed Jun 22, 2026

View reviewed changes

github-actions Bot mentioned this pull request Jun 23, 2026

📊 AI CLI 工具社区动态日报 2026-06-23 litang9/big_model_radar#109

Open

	const signature = req.headers['x-hub-signature-256'] as string \| undefined;
	const header = req.headers['x-hub-signature-256'];
	const signature = Array.isArray(header) ? header[0] : header;

	private db: Firestore;
	private readonly db: Firestore;
	private readonly collectionName: string;

	app.use(express.raw({ type: 'application/json' }));
	app.use(express.raw({ type: 'application/json', limit: '1mb' }));

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chadd28 commented Jun 18, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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chadd28 commented Jun 18, 2026 •

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