package main

import (
	"fmt"
	"log"
	"net"

	"golang.org/x/crypto/ssh"
)

func main() {
	private, err := ssh.ParsePrivateKey([]byte(testServerKey))
	if err != nil {
		log.Fatalf("failed to parse private key: %v", err)
	}

	config := &ssh.ServerConfig{NoClientAuth: false}
	config.AddHostKey(private)
	config.PublicKeyCallback = func(conn ssh.ConnMetadata, key ssh.PublicKey) (*ssh.Permissions, error) {
		// No keys are accepted — force failure to test multiple attempts.
		fmt.Println("Key attempt from:", conn.User())
		return nil, fmt.Errorf("unauthorized")
	}

	listener, err := net.Listen("tcp", ":2222")
	if err != nil {
		log.Fatalf("failed to listen on 2222: %v", err)
	}
	log.Println("Listening on :2222")

	for {
		conn, err := listener.Accept()
		if err != nil {
			log.Fatalf("failed to accept incoming connection: %v", err)
		}
		go func(c net.Conn) {
			_, chans, reqs, err := ssh.NewServerConn(c, config)
			if err != nil {
				log.Printf("handshake failed: %v", err)
				return
			}
			go ssh.DiscardRequests(reqs)
			for ch := range chans {
				ch.Reject(ssh.Prohibited, "no channels accepted")
			}
		}(conn)
	}
}

const testServerKey = `-----BEGIN RSA PRIVATE KEY-----
MIIBOgIBAAJBANlfqF8A3gBzgU6bEqkG6nRzrtNdEPr+HMX3/fOjYbt5tI/gA2w7
s+pu5PxtjLMToCbMSqXnsRUtCTy3s+N3LfkCAwEAAQJAAOso8bEqBuYkqWolHpw3
s1+Zp0xDZklnwQkk+blO2f4VokFHVf0EheG45KkQAfIZK0GnxK5v5X9vQb6PtX2z
wQIhAPM7hpE0DwHHZbT+zG8cEoVazDNZdPpjU1wJ7HKrPu2DAiEA3ZyxB7KhSvn1
bA9UURccYmn7ppHJ3FQogZhTY7v8sokCIQDaxl00GV4g8ow6HxWfVHtLgQYVyxGi
gFRcHyPuPGvTiQIhAIAvdfmXoiAEAKLyH2VG9r5L6fDZzOVlK3kU4IJK1ahJAiBZ
3Ghuo1VGeF2hHpiFci0JHk3akGczRGwQ9+QXJFx+0g==
-----END RSA PRIVATE KEY-----`