fix: Verify SNS URL before sending fetch request

apps/api/src/controllers/Webhooks.ts

@@ -34,11 +34,35 @@ export class Webhooks {
       // Handle SNS subscription confirmation FIRST (before parsing Message field)
       if (req.body.Type === 'SubscriptionConfirmation') {
         signale.info('SNS Subscription Confirmation received');
-        signale.info('Subscribe URL:', req.body.SubscribeURL);
+
+        // Validate SubscribeURL to prevent SSRF: must be HTTPS and from an official AWS SNS host.
+        // Legitimate URLs look like:
+        //   https://sns.<region>.amazonaws.com/?Action=ConfirmSubscription&...
+        const subscribeURL: unknown = req.body.SubscribeURL;
+        if (typeof subscribeURL !== 'string') {
+          signale.warn('SNS SubscriptionConfirmation missing SubscribeURL');
+          return res.status(400).json({success: false, message: 'Invalid SubscribeURL'});
+        }
+
+        let parsedURL: URL;
+        try {
+          parsedURL = new URL(subscribeURL);
+        } catch {
+          signale.warn('SNS SubscriptionConfirmation has unparseable SubscribeURL');
+          return res.status(400).json({success: false, message: 'Invalid SubscribeURL'});
+        }
+
+        // Only allow HTTPS requests to official AWS SNS endpoints.
+        // The hostname must be exactly sns.<region>.amazonaws.com.
+        const SNS_HOST_RE = /^sns\.[a-z0-9-]+\.amazonaws\.com$/;
+        if (parsedURL.protocol !== 'https:' || !SNS_HOST_RE.test(parsedURL.hostname)) {
+          signale.warn(`SNS SubscriptionConfirmation rejected — disallowed SubscribeURL host: ${parsedURL.hostname}`);
+          return res.status(400).json({success: false, message: 'Invalid SubscribeURL'});
+        }
 
         // Automatically confirm the subscription
         try {
-          const confirmResponse = await fetch(req.body.SubscribeURL);
+          const confirmResponse = await fetch(subscribeURL);
           if (confirmResponse.ok) {
             signale.success('SNS subscription confirmed successfully');
             return res.status(200).json({
@@ -50,7 +74,6 @@ export class Webhooks {
             return res.status(200).json({
               success: false,
               message: 'Failed to confirm subscription',
-              subscribeURL: req.body.SubscribeURL,
             });
           }
         } catch (confirmError) {
@@ -58,7 +81,6 @@ export class Webhooks {
           return res.status(200).json({
             success: false,
             message: 'Error confirming subscription',
-            subscribeURL: req.body.SubscribeURL,
           });
         }
       }