Golang SSH to Cisco Wireless Controller and Run Commands - go

Question

I am trying to SSH to a Cisco wireless controller through Go, using Go's golang.org/x/crypto/ssh library, to programmatically configure access points. The problem I'm running into is correctly parsing the controller CLI in Go. For example, this is the typical SSH login to the controller:
$ ssh <controller_ip>
(Cisco Controller)
User: username
Password:****************
(Cisco Controller) >
I am trying to figure out how to send the username and then the password after the SSH session is established in Go. So far, I am able to successfully SSH to the controller, but the program exits at the username prompt, like this:
$ go run main.go
(Cisco Controller)
User:
How would I go about sending the username when prompted, then repeating that for the password prompt?
No errors are being thrown or exit codes are being given, so I'm not sure why the program is exiting immediately at the username prompt. But Even if it wasn't exiting that way, I'm still unsure of how to send the username and password when the controller's CLI is expecting it.
Here is my code:
package main
import (
"golang.org/x/crypto/ssh"
"log"
"io/ioutil"
"os"
"strings"
"path/filepath"
"bufio"
"fmt"
"errors"
"time"
)
const (
HOST = "host"
)
func main() {
hostKey, err := checkHostKey(HOST)
if err != nil {
log.Fatal(err)
}
key, err := ioutil.ReadFile("/Users/user/.ssh/id_rsa")
if err != nil {
log.Fatalf("unable to read private key: %v", err)
}
// Create the Signer for this private key.
signer, err := ssh.ParsePrivateKey(key)
if err != nil {
log.Fatalf("unable to parse private key: %v", err)
}
// Create client config
config := &ssh.ClientConfig{
User: "username",
Auth: []ssh.AuthMethod{
ssh.Password("password"),
// Use the PublicKeys method for remote authentication.
ssh.PublicKeys(signer),
},
HostKeyCallback: ssh.FixedHostKey(hostKey),
Timeout: time.Second * 5,
}
// Connect to the remote server and perform the SSH handshake.
client, err := ssh.Dial("tcp", HOST+":22", config)
if err != nil {
log.Fatalf("unable to connect: %v", err)
}
defer client.Close()
// Create a session
session, err := client.NewSession()
if err != nil {
log.Fatal("Failed to create session: ", err)
}
defer session.Close()
stdin, err := session.StdinPipe()
if err != nil {
log.Fatal(err)
}
stdout, err := session.StdoutPipe()
if err != nil {
log.Fatal(err)
}
modes := ssh.TerminalModes{
ssh.ECHO: 0,
ssh.TTY_OP_ISPEED: 9600,
ssh.TTY_OP_OSPEED: 9600,
}
if err := session.RequestPty("xterm", 0, 200, modes); err != nil {
log.Fatal(err)
}
if err := session.Shell(); err != nil {
log.Fatal(err)
}
buf := make([]byte, 1000)
n, err := stdout.Read(buf) //this reads the ssh terminal welcome message
loadStr := ""
if err == nil {
loadStr = string(buf[:n])
}
for (err == nil) && (!strings.Contains(loadStr, "(Cisco Controller)")) {
n, err = stdout.Read(buf)
loadStr += string(buf[:n])
}
fmt.Println(loadStr)
if _, err := stdin.Write([]byte("show ap summary\r")); err != nil {
panic("Failed to run: " + err.Error())
}
}
func checkHostKey(host string) (ssh.PublicKey, error) {
file, err := os.Open(filepath.Join(os.Getenv("HOME"), ".ssh", "known_hosts"))
if err != nil {
return nil, err
}
defer file.Close()
scanner := bufio.NewScanner(file)
var hostKey ssh.PublicKey
for scanner.Scan() {
fields := strings.Split(scanner.Text(), " ")
if len(fields) != 3 {
continue
}
if strings.Contains(fields[0], host) {
hostKey, _, _, _, err = ssh.ParseAuthorizedKey(scanner.Bytes())
if err != nil {
return nil, errors.New(fmt.Sprintf("error parsing %q: %v", fields[2], err))
}
break
}
}
if hostKey == nil {
return nil, errors.New(fmt.Sprintf("no hostkey for %s", host))
}
return hostKey, nil
}

Answer 1

Finally got it working. Here is my new code inspired by this post:
package main
import (
"golang.org/x/crypto/ssh"
"log"
"io/ioutil"
"os"
"strings"
"path/filepath"
"bufio"
"fmt"
"errors"
"time"
)
func main() {
client, err := authenticate("10.4.112.11", "mwalto7", "lion$Tiger$Bear$")
if err != nil {
log.Fatalf("unable to connect: %v", err)
}
defer client.Close()
// Create a session
session, err := client.NewSession()
if err != nil {
log.Fatal("Failed to create session: ", err)
}
defer session.Close()
stdin, err := session.StdinPipe()
if err != nil {
log.Fatal(err)
}
session.Stdout = os.Stdout
session.Stderr = os.Stderr
if err := session.Shell(); err != nil {
log.Fatal(err)
}
for _, cmd := range os.Args[1:] {
stdin.Write([]byte(cmd + "\n"))
}
stdin.Write([]byte("logout\n"))
stdin.Write([]byte("N\n"))
session.Wait()
}
func authenticate(host, username, password string) (ssh.Client, error) {
hostKey, err := checkHostKey(host)
if err != nil {
log.Fatal(err)
}
key, err := ioutil.ReadFile(filepath.Join(os.Getenv("HOME"), ".ssh", "id_rsa"))
if err != nil {
log.Fatalf("unable to read private key: %v", err)
}
// Create the Signer for this private key.
signer, err := ssh.ParsePrivateKey(key)
if err != nil {
log.Fatalf("unable to parse private key: %v", err)
}
// Create client config
config := &ssh.ClientConfig{
User: username,
Auth: []ssh.AuthMethod{
ssh.Password(password),
// Use the PublicKeys method for remote authentication.
ssh.PublicKeys(signer),
},
HostKeyCallback: ssh.FixedHostKey(hostKey),
Timeout: time.Second * 5,
}
// Connect to the remote server and perform the SSH handshake.
client, err := ssh.Dial("tcp", host+":22", config)
return *client, err
}
func checkHostKey(host string) (ssh.PublicKey, error) {
file, err := os.Open(filepath.Join(os.Getenv("HOME"), ".ssh", "known_hosts"))
if err != nil {
return nil, err
}
defer file.Close()
scanner := bufio.NewScanner(file)
var hostKey ssh.PublicKey
for scanner.Scan() {
fields := strings.Split(scanner.Text(), " ")
if len(fields) != 3 {
continue
}
if strings.Contains(fields[0], host) {
hostKey, _, _, _, err = ssh.ParseAuthorizedKey(scanner.Bytes())
if err != nil {
return nil, errors.New(fmt.Sprintf("error parsing %q: %v", fields[2], err))
}
break
}
}
if hostKey == nil {
return nil, errors.New(fmt.Sprintf("no hostkey for %s", host))
}
return hostKey, nil
}