How to Fix the SharedArrayBuffer and crossOriginIsolated Error for Bolt.diy

How to Fix the SharedArrayBuffer and crossOriginIsolated Error for Bolt.diy

When deploying Bolt.diy, you might encounter the error:

Failed to execute ‘postMessage‘ on ‘Worker’: SharedArrayBuffer transfer requires self.crossOriginIsolated.

I ran into this problem when trying to run the bolt.diy Docker container on my Synology NAS in their container manager where it could not get beyond the message shown in the image above. As it turns out, this error arises because SharedArrayBuffer requires a secure context (crossOriginIsolated).

Setting up the environment properly is critical, especially when your deployment involves private API keys and needs to remain inaccessible to the wider internet. This post will help resolve the issue while keeping your setup private.

Understanding the Error

What is SharedArrayBuffer?

SharedArrayBuffer enables high-performance, memory-sharing features in modern web applications. To use it, the browser enforces strict security measures.

What is crossOriginIsolated?

To ensure security, SharedArrayBuffer requires the application to:

1. Be served in a crossOriginIsolated context.
2. Be accessed over HTTPS or localhost.

Common Causes of the Error

• Accessing the app over HTTP instead of HTTPS.
• Missing Cross-Origin headers.
• Using an IP address instead of localhost.

Solutions to Fix the Error

1. Access via localhost Using SSH Port Forwarding

The simplest solution is to create an SSH tunnel to access the application through localhost, bypassing cross-origin issues entirely.

1. On your local machine, open a terminal and run:
2. ssh -L 5173:127.0.0.1:5173 user@nas-ip
3. Replace:
   • 5173 with the port your app runs on.
   • user with your NAS username.
   • nas-ip with your NAS’s local IP address.
4. Open your browser and access the application at:
5. http://localhost:5173
6. This ensures the browser treats the connection as localhost, satisfying the security requirements without exposing the app to the wider internet.

2. Use Docker in host Network Mode

Docker’s default bridge network can complicate cross-origin setups. Running Docker in host mode allows the container to use the host’s network directly.

1. Start your Docker container with:
2. docker run –network host -d your-image
3. Access the app directly via the NAS’s IP:
4. http://nas-ip:5173
5. This simplifies networking but ensures your NAS remains isolated from external networks.

3. Add Required Headers

If you want to access the application using the NAS’s IP or a local hostname, you must configure the required headers for SharedArrayBuffer.

1. Add the following headers to your server:
   • Cross-Origin-Opener-Policy: same-origin
   • Cross-Origin-Embedder-Policy: require-corp
2. Nginx Configuration Example:
3. server {
4.     listen 5173;
5.     server_name nas-ip;
7.     add_header Cross-Origin-Opener-Policy “same-origin”;
8.     add_header Cross-Origin-Embedder-Policy “require-corp”;
10.     location / {
11.         proxy_pass http://127.0.0.1:5173;
12.     }
13. }
14. Restart your server and test the application.

4. Use a .local Domain for Local Network Access

1. Modify your local hosts file:
   • Windows: C:\Windows\System32\drivers\etc\hosts
   • Linux/macOS: /etc/hosts
2. Add:
3. 192.168.x.x mynas.local
4. Access the site using:
5. http://mynas.local:5173
6. Combine this with the required headers to ensure crossOriginIsolated is satisfied.

5. Keep the Site Private

Since your site uses private API keys, ensure it remains inaccessible to the public:

1. Restrict Firewall Rules:
   • On your NAS, restrict access to the container’s ports to your local network only.
   • Example rule:
     • Allow: 192.168.0.0/24
     • Deny: All others.
2. Disable External DDNS Access:
   • Avoid exposing the app via DDNS or public IP.
3. Use Local Network-Only DNS:
   • Set up a local DNS server (e.g., Pi-hole) to resolve mynas.local for your network.

Troubleshooting

1. Check Headers:
   • Open your browser’s developer tools (F12 > Network > Headers) to verify the Cross-Origin headers.
2. Browser Warnings:
   • For local use, manually trust self-signed certificates if using HTTPS.
3. Performance Issues:
   • Allocate sufficient resources to your Docker container.

Conclusion

Fixing the SharedArrayBuffer and crossOriginIsolated error for Bolt.diy requires ensuring the correct security context while keeping your setup private. For those running Docker, setting up Nginx as a reverse proxy is a powerful solution. By combining it with a private network or VPN, you can securely access your application while maintaining privacy.

If you’re ready to set up Nginx in Docker, check out this comprehensive guide on installing Nginx on a DigitalOcean Droplet to learn more. Adapting these steps for your Docker container will help you implement a robust and secure configuration.