Initial working version

main.go

@@ -0,0 +1,138 @@
+package main
+
+import (
+	"github.com/cloudfoundry/socks5-proxy"
+	"github.com/xor-gate/sshfp"
+	"golang.org/x/crypto/ssh"
+	"io"
+	"log"
+	"net"
+	"os"
+	"time"
+)
+
+var fetchedSSHHostPublicKey SSHHostPublicKeyFetcher
+var sshfpResolver *sshfp.Resolver
+
+type SSHHostPublicKeyFetcher struct {
+	ssh.PublicKey
+}
+
+func (f *SSHHostPublicKeyFetcher) Get(username, privateKey, serverURL string) (ssh.PublicKey, error) {
+	return f.PublicKey, nil
+}
+
+func readSSHPrivateKey(filename string, privateKey []byte) (string, ssh.Signer, error) {
+	if filename != "" {
+		file, err := os.Open(filename)
+		if err != nil {
+			return "", nil, err
+		}
+
+		defer file.Close()
+
+		privateKey, err = io.ReadAll(file)
+		if err != nil {
+			return "", nil, err
+		}
+	}
+
+	signer, err := ssh.ParsePrivateKey([]byte(privateKey))
+	if err != nil {
+		return "", nil, err
+	}
+
+	return string(privateKey), signer, err
+}
+
+// logHostKeyCallback logs the host key and performs the actual verification
+func fetchSSHHostKeyCallback(hostname string, remote net.Addr, key ssh.PublicKey) error {
+	err := sshfpResolver.HostKeyCallback(hostname, remote, key)
+	if err != nil {
+		if err == sshfp.ErrNoHostKeyFound {
+			log.Println("WARNING: No SSHFP present in DNS")
+			if cfg.SSHVerifyValidSSHFP {
+				log.Fatalln("ERROR: SSHVerifyValidSSHFP = true")
+			}
+		}
+		log.Println("SSHFP check failed:", err)
+	} else {
+		log.Println("SSH server succesfully verified using DNS")
+	}
+
+	fetchedSSHHostPublicKey.PublicKey = key
+
+	return nil
+}
+
+func getSSHHostKeyFromServer(signer ssh.Signer, userName, serverURL string) {
+	// Establish a connection to the SSH server
+	conn, err := ssh.Dial("tcp", serverURL, &ssh.ClientConfig{
+		User: userName,
+		Auth: []ssh.AuthMethod{
+			ssh.PublicKeys(signer),
+		},
+		HostKeyCallback: fetchSSHHostKeyCallback,
+	})
+	if err != nil {
+		log.Fatal(err)
+		return
+	}
+
+	defer conn.Close()
+
+	if err != nil {
+		log.Fatalf("Failed to dial: %s", err)
+		return
+	}
+
+	log.Println("SSH host key fetched", userName, "@", serverURL)
+}
+
+func main() {
+	var err error
+	var signer ssh.Signer
+	var privateKey string
+
+	dnsServers := sshfp.WithDNSClientConfigFromReader(cfg.DNSServersResolvConf)
+
+	sshfpResolver, err = sshfp.NewResolver(dnsServers)
+	if err != nil {
+		log.Println(err)
+		return
+	}
+
+	if resourceSSHPrivateKey != "" {
+		privateKey, signer, err = readSSHPrivateKey("", []byte(resourceSSHPrivateKey))
+		log.Println("Using embedded private key")
+	} else {
+		privateKey, signer, err = readSSHPrivateKey(cfg.SSHPrivateKeyFile, nil)
+	}
+
+	if err != nil {
+		log.Println(err)
+		return
+	}
+
+	getSSHHostKeyFromServer(signer, cfg.SSHServerUserName, cfg.SSHServerURL)
+
+	sshSocks5Proxy := proxy.NewSocks5Proxy(&fetchedSSHHostPublicKey, nil, time.Minute)
+	sshSocks5Proxy.SetListenPort(cfg.SOCKS5ListenPort)
+	err = sshSocks5Proxy.Start("tunnel", privateKey, cfg.SSHServerURL)
+	if err != nil {
+		log.Println(err)
+		return
+	}
+
+	time.Sleep(time.Second)
+
+	proxyServerURL, err := sshSocks5Proxy.Addr()
+	if err != nil {
+		log.Println(err)
+	}
+
+	log.Println("SOCKS5 Addr", proxyServerURL)
+
+	for {
+	}
+}