Repair Redirect, Proxy & Routing Failures

I have analyzed the Nginx configuration and the Next.js middleware. The redirect loop is caused by the application failing to recognize the X-Forwarded-Proto header, leading it to attempt a redirect to HTTPS which the proxy then terminates and passes back as HTTP.

Proxy and Middleware Repair

# Updated Nginx Location Block
location / {
    proxy_pass http://nextjs_upstream;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection 'upgrade';
    proxy_set_header Host $host;
    proxy_cache_bypass $http_upgrade;
    
    # Ensure these headers are explicitly set for the application
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
}

// middleware.ts or next.config.js Trust Logic
// Ensure the application trusts the proxy headers to determine the protocol
export function middleware(request) {
  const proto = request.headers.get('x-forwarded-proto');
  const host = request.headers.get('host');
  
  // Logic to prevent internal loops
  if (proto === 'http' && process.env.NODE_ENV === 'production') {
    return NextResponse.redirect(`https://${host}${request.nextUrl.pathname}`, 301);
  }
}

Next steps

1. Apply the Nginx configuration changes and reload the service using nginx -s reload.
2. Deploy the updated middleware to your staging environment.
3. Verify the fix by running curl -I -H "X-Forwarded-Proto: http" https://yourdomain.com/dashboard to ensure only one redirect occurs.