Function hostHeaderValidation

hostHeaderValidation(allowedHostnames: string[]): RequestHandler
Express middleware for DNS rebinding protection. Validates Host header hostname (port-agnostic) against an allowed list.

This is particularly important for servers without authorization or HTTPS, such as localhost servers or development servers. DNS rebinding attacks can bypass same-origin policy by manipulating DNS to point a domain to a localhost address, allowing malicious websites to access your local server.
Parameters
- allowedHostnames: string[]
  List of allowed hostnames (without ports). For IPv6, provide the address with brackets (e.g., [::1]).
Returns RequestHandler
Express middleware function
Example
```
const middleware = hostHeaderValidation(['localhost', '127.0.0.1', '[::1]']);
app.use(middleware);
```
- Defined in middleware/hostHeaderValidation.ts:23