Function hostHeaderValidation

hostHeaderValidation(
allowedHostnames: string[],
): (request: FastifyRequest, reply: FastifyReply) => Promise<void>
Fastify onRequest hook 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 (request: FastifyRequest, reply: FastifyReply) => Promise<void>
Fastify onRequest hook handler
Example
```
app.addHook('onRequest', hostHeaderValidation(['localhost', '127.0.0.1', '[::1]']));
```
- Defined in middleware/hostHeaderValidation.ts:22