How to Connect to a Server Using SSH and a PEM Key in Go?

Connect to a Server using SSH and a PEM / Key with Go

Connecting to a remote server securely using SSH is a common task in system administration and automation. When dealing with Linux servers, SSH key authentication is often preferred over password authentication for its increased security. This article demonstrates how to establish an SSH connection to a remote server using a PEM (Privacy Enhanced Mail) key in Go.

The ssh package in Go provides support for SSH connections. To connect using a PEM key, we need to first parse the key into an ssh.Signer object. We can use the ssh.ParsePrivateKey function for this purpose. Once we have a ssh.Signer, we can create an ssh.AuthMethod object using ssh.PublicKeys. This ssh.AuthMethod will be used to authenticate with the server.

With the ssh.AuthMethod ready, we can now configure the ssh.ClientConfig object. We specify the username, authentication method, and other necessary parameters in this config. Once the config is set up, we use the ssh.Dial function to establish the connection. We can then create a new session using ssh.NewSession and execute commands on the remote server.

Here's an example code snippet that outlines the steps:

<code class="go">import (
    "io"
    "log"
    "net"
    "os"

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

func main() {
    pemBytes, err := os.ReadFile("my_key.pem")
    if err != nil {
        log.Fatal(err)
    }

    signer, err := ssh.ParsePrivateKey(pemBytes)
    if err != nil {
        log.Fatal(err)
    }

    auths := []ssh.AuthMethod{ssh.PublicKeys(signer)}
    cfg := &ssh.ClientConfig{
        User: "my_user",
        Auth: auths,
    }

    conn, err := ssh.Dial("tcp", "remote_host:22", cfg)
    if err != nil {
        log.Fatal(err)
    }
    defer conn.Close()

    session, err := conn.NewSession()
    if err != nil {
        log.Fatal(err)
    }
    defer session.Close()

    stdout, err := session.StdoutPipe()
    if err != nil {
        log.Fatal(err)
    }
    if err := session.Run("whoami"); err != nil {
        log.Fatal(err)
    }

    if _, err := io.ReadAll(stdout); err != nil {
        log.Fatal(err)
    }
}</code>

By following these steps and using the provided code snippet, you can establish a secure SSH connection to a remote server using a PEM key in your Go programs.

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