SSH from Golang code successfully but hangs

Question

I used the following go code to open an ssh connection to a remote host

func ssh(keyname string, user string, address string) {
    cmd := exec.Command("ssh", "-tt", user+"@"+address, "-i", "~/"+keyname) 
    cmd.Stderr = os.Stderr
    cmd.Stdout = os.Stdout

    if err := cmd.Run(); err != nil {
        fmt.Println(err.Error())
    }
}

func main() {
    ssh("example.pem", "ubuntu", "192.169.0.1")
}

When i run the code i connect successully to the remote host and get a terminal, but when i type commands it doesn't show any outputs just hangs, tried to ssh normally via my terminal and everything is ok. Not sure if this is from my code or SSH

you're missing the type handler. and you need ssh package(pkg.go.dev/golang.org/x/crypto/ssh) maybe. — Jiang YD
– Jiang YD, Commented Sep 1, 2022 at 13:57
@JiangYD I avoided the ssh package route, because i thought i could do a simple exec. — badman
– badman, Commented Sep 1, 2022 at 16:26

Suyash Medhavi · Accepted Answer · 2022-09-01 14:21:00Z

1

Use following code

package main
import (
    "log"

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

func main() {
    // ssh config
    hostKeyCallback, err := knownhosts.New("/home/debian11/.ssh/known_hosts")
    if err != nil {
        log.Fatal(err)
    }
    config := &ssh.ClientConfig{
        User: "ubuntu",
        Auth: []ssh.AuthMethod{
            ssh.Password("password"),
        },
        HostKeyCallback: hostKeyCallback,
    }
    // connect to ssh server
    conn, err := ssh.Dial("tcp", "192.169.0.1:22", config)
    if err != nil {
        log.Fatal(err)
    }
    defer conn.Close()
}

Above is for password based login. Some changes will be required for certificate based auth.

1 Comment

badman Over a year ago

Is there a reason ssh exec doesn't work as expected?

badman · Accepted Answer · 2022-09-01 16:43:38Z

0

Assigning os.stdin to Stdin solves this problem, subtle

func ssh(keyname string, user string, address string) {
    cmd := exec.Command("ssh", "-tt", user+"@"+address, "-i", "~/"+keyname)

    cmd.Stdin = os.Stdin
    cmd.Stderr = os.Stderr
    cmd.Stdout = os.Stdout

    if err := cmd.Run(); err != nil {
        fmt.Println(err.Error())
    }
}

answered Sep 1, 2022 at 16:43

badman

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