much better ssh example

Author: SimonWaldherr

non-std-lib/ssh-client.go

@@ -4,98 +4,129 @@ import (
 	"flag"
 	"fmt"
 	"io/ioutil"
-	"net"
+	"os"
 
 	"golang.org/x/crypto/ssh"
 )
 
-var user string
-var host string
-var port string
-var keyfile string
+var (
+	user    string
+	host    string
+	port    string
+	keyfile string
+)
+
+func init() {
+	flag.StringVar(&user, "u", "root", "SSH user")
+	flag.StringVar(&host, "h", "example.tld", "Host")
+	flag.StringVar(&port, "p", "22", "SSH port")
+	flag.StringVar(&keyfile, "pk", "", "Public key file, e.g.: \"~/.ssh/id_rsa\"")
+}
 
 func main() {
-	flag.StringVar(&user, "u", "root", "ssh user")
-	flag.StringVar(&host, "h", "example.tld", "host")
-	flag.StringVar(&port, "p", "22", "ssh port")
-	flag.StringVar(&keyfile, "pk", "", "public key file, eg.: \"~/.ssh/id_rsa\"")
 	flag.Parse()
 
-	var client *ssh.Client
-	var session *ssh.Session
-	var err error
-
 	if host == "example.tld" {
-		fmt.Println("go run ssh-client.go -h example.tld -p 22 -pk /Users/johndoe/.ssh/id_rsa")
+		fmt.Println("Usage: go run ssh-client.go -h <host> -p <port> -pk <path_to_private_key>")
 		flag.PrintDefaults()
 		return
 	}
 
+	var client *ssh.Client
+	var err error
+
 	if keyfile != "" {
-		client, session, err = connectToHostWithPublickey(user, fmt.Sprintf("%v:%v", host, port), keyfile)
+		client, err = connectToHostWithPublicKey(user, fmt.Sprintf("%v:%v", host, port), keyfile)
 	} else {
-		client, session, err = connectToHost(user, fmt.Sprintf("%v:%v", host, port))
+		client, err = connectToHost(user, fmt.Sprintf("%v:%v", host, port))
 	}
 
 	if err != nil {
-		panic(err)
-	}
-	out, err := session.CombinedOutput("ls -al")
-	if err != nil {
-		panic(err)
+		fmt.Fprintf(os.Stderr, "Failed to connect: %v\n", err)
+		return
 	}
-	fmt.Println(string(out))
-	client.Close()
+	defer client.Close()
+
+	runRemoteCommands(client)
 }
 
-func connectToHost(user, host string) (*ssh.Client, *ssh.Session, error) {
-	var pass string
-	fmt.Print("SSH-Password: ")
-	fmt.Scanf("%s\n", &pass)
+func connectToHost(user, host string) (*ssh.Client, error) {
+	var password string
+	fmt.Print("SSH Password: ")
+	fmt.Scanf("%s\n", &password)
 
 	sshConfig := &ssh.ClientConfig{
 		User: user,
-		Auth: []ssh.AuthMethod{ssh.Password(pass)},
+		Auth: []ssh.AuthMethod{
+			ssh.Password(password),
+		},
+		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
 	}
-	sshConfig.HostKeyCallback = ssh.InsecureIgnoreHostKey()
 
 	client, err := ssh.Dial("tcp", host, sshConfig)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 
-	session, err := client.NewSession()
-	if err != nil {
-		client.Close()
-		return nil, nil, err
-	}
-
-	return client, session, nil
+	return client, nil
 }
 
-func connectToHostWithPublickey(user, host, publickeyfile string) (*ssh.Client, *ssh.Session, error) {
-	key, err := ioutil.ReadFile(publickeyfile)
+func connectToHostWithPublicKey(user, host, publicKeyFile string) (*ssh.Client, error) {
+	key, err := ioutil.ReadFile(publicKeyFile)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
+
 	signer, err := ssh.ParsePrivateKey(key)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
-	client, err := ssh.Dial("tcp", host, &ssh.ClientConfig{
-		User:            user,
-		Auth:            []ssh.AuthMethod{ssh.PublicKeys(signer)},
-		HostKeyCallback: ssh.HostKeyCallback(func(string, net.Addr, ssh.PublicKey) error { return nil }),
-	})
-	if client == nil || err != nil {
-		return nil, nil, err
+
+	sshConfig := &ssh.ClientConfig{
+		User: user,
+		Auth: []ssh.AuthMethod{
+			ssh.PublicKeys(signer),
+		},
+		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
 	}
 
+	client, err := ssh.Dial("tcp", host, sshConfig)
+	if err != nil {
+		return nil, err
+	}
+
+	return client, nil
+}
+
+func runRemoteCommands(client *ssh.Client) {
+	commands := []string{
+		"ls -al",
+		"df -h",
+		"uptime",
+		"whoami",
+	}
+
+	for _, cmd := range commands {
+		output, err := executeRemoteCommand(client, cmd)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Failed to run command '%s': %v\n", cmd, err)
+			continue
+		}
+		fmt.Printf("Output of '%s':\n%s\n", cmd, output)
+	}
+}
+
+func executeRemoteCommand(client *ssh.Client, command string) (string, error) {
 	session, err := client.NewSession()
 	if err != nil {
-		client.Close()
-		return nil, nil, err
+		return "", err
+	}
+	defer session.Close()
+
+	output, err := session.CombinedOutput(command)
+	if err != nil {
+		return "", err
 	}
 
-	return client, session, nil
+	return string(output), nil
 }