Merge pull request #7 from ubiquibot/check-signature

Check signature

.cspell.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://raw.githubusercontent.com/streetsidesoftware/cspell/main/cspell.schema.json",
   "version": "0.2",
-  "ignorePaths": ["**/*.json", "**/*.css", "node_modules", "**/*.log", "**/*.toml", "src/adapters/supabase/types/database.ts"],
+  "ignorePaths": ["**/*.json", "**/*.css", "node_modules", "**/*.log", "**/*.toml", "**/*.http", "src/adapters/supabase/types/database.ts"],
   "useGitignore": true,
   "language": "en",
   "words": ["dataurl", "devpool", "outdir", "servedir", "supabase", "typebox", "typeguards", "mswjs", "ubiquibot"],

src/types/env.ts

@@ -5,6 +5,7 @@ import "dotenv/config";
 export const envSchema = T.Object({
   SUPABASE_URL: T.String(),
   SUPABASE_KEY: T.String(),
+  UBIQUIBOT_PUBLIC_KEY: T.String(),
 });
 
 export type Env = StaticDecode<typeof envSchema>;

src/worker.ts

@@ -20,8 +20,15 @@ export default {
         });
       }
       const webhookPayload = await request.json();
-      const settings = Value.Decode(assistivePricingSettingsSchema, Value.Default(assistivePricingSettingsSchema, JSON.parse(webhookPayload.settings)));
-      webhookPayload.eventPayload = JSON.parse(webhookPayload.eventPayload);
+      const signature = webhookPayload.signature;
+      delete webhookPayload.signature;
+      if (!(await verifySignature(env.UBIQUIBOT_PUBLIC_KEY, webhookPayload, signature))) {
+        return new Response(JSON.stringify({ error: `Error: Signature verification failed` }), {
+          status: 400,
+          headers: { "content-type": "application/json" },
+        });
+      }
+      const settings = Value.Decode(assistivePricingSettingsSchema, Value.Default(assistivePricingSettingsSchema, webhookPayload.settings));
       webhookPayload.settings = settings;
       await run(webhookPayload, env);
       return new Response(JSON.stringify("OK"), { status: 200, headers: { "content-type": "application/json" } });
@@ -36,3 +43,24 @@ function handleUncaughtError(error: unknown) {
   const status = 500;
   return new Response(JSON.stringify({ error }), { status: status, headers: { "content-type": "application/json" } });
 }
+
+async function verifySignature(publicKeyPem: string, payload: unknown, signature: string) {
+  const pemContents = publicKeyPem.replace("-----BEGIN PUBLIC KEY-----", "").replace("-----END PUBLIC KEY-----", "").trim();
+  const binaryDer = Uint8Array.from(atob(pemContents), (c) => c.charCodeAt(0));
+
+  const publicKey = await crypto.subtle.importKey(
+    "spki",
+    binaryDer.buffer,
+    {
+      name: "RSASSA-PKCS1-v1_5",
+      hash: "SHA-256",
+    },
+    true,
+    ["verify"]
+  );
+
+  const signatureArray = Uint8Array.from(atob(signature), (c) => c.charCodeAt(0));
+  const dataArray = new TextEncoder().encode(JSON.stringify(payload));
+
+  return await crypto.subtle.verify("RSASSA-PKCS1-v1_5", publicKey, signatureArray, dataArray);
+}