diff --git a/src/env.ts b/src/env.ts
index 099efc6..fe6c982 100644
--- a/src/env.ts
+++ b/src/env.ts
@@ -3,7 +3,9 @@ import { z } from "zod";
 
 const schema = z.object({
   PORT: z.coerce.number(),
+  GITEA_WEBHOOK_SECRET: z.string(),
 });
+
 const result = schema.safeParse(process.env);
 if (!result.success) {
   console.error("ERROR: Environment variable validation failed:");
diff --git a/src/index.ts b/src/index.ts
index d3ef563..7703ed9 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,4 +1,5 @@
 import express from "express";
+import crypto from "crypto";
 import { z } from "zod";
 import { env } from "./env";
 
@@ -8,12 +9,38 @@ const webhookSchema = z.object({
 
 const app = express();
 
-app.use(express.json());
+app.use(
+  express.raw({
+    inflate: true,
+    limit: "100kb",
+    type: "application/json",
+  }),
+);
 
 app.post("/", async (req, res) => {
-  const result = webhookSchema.safeParse(req.body);
+  const signature = req.headers["x-gitea-signature"] as string | undefined;
+  if (!signature) {
+    console.error("x-gitea-signature missing");
+    res.sendStatus(401);
+    return;
+  }
+
+  const hmac = crypto.createHmac("sha256", env.GITEA_WEBHOOK_SECRET);
+  hmac.update(req.body);
+  const payloadSignature = hmac.digest("hex");
+
+  if (signature !== payloadSignature) {
+    console.error("signature !== payload_signature");
+    res.sendStatus(401);
+    return;
+  }
+
+  const json = JSON.parse(req.body.toString());
+  const result = webhookSchema.safeParse(json);
+
   if (!result.success) {
-    res.sendStatus(200);
+    console.error("Invalid webhook payload:", result.error.issues);
+    res.sendStatus(400);
     return;
   }