How to Establish SSH Connections with Keys Using Go\'s ssh Package?

Establish SSH Connection with Key Using Go's ssh Package

Connecting to a remote server via SSH with a key is an essential task in systems administration and DevOps. The Go programming language provides the ssh package for handling SSH connections. However, navigating its documentation can be challenging.

The question arises: Can we connect to an SSH server using a key file or a private key with the Go ssh package?

The documentation states that only the "password" authentication method is currently supported. Fret not, because it is entirely possible to establish a connection using a key file or a private key.

The key to unlocking this functionality lies in converting the key file into an ssh.Signer and then embedding it within ssh.AuthMethod.PublicKeys. Here's a sample code snippet to elaborate on the process:

<code class="go">import (
    "crypto/ecdsa"
    "crypto/x509"
    "encoding/pem"
    "fmt"
    "io/ioutil"
    "log"
    "net"

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

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

    block, _ := pem.Decode(pemBytes)
    privKey, err := x509.ParseECPrivateKey(block.Bytes)
    if err != nil {
        log.Fatal(err)
    }

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

    auths := []ssh.AuthMethod{ssh.PublicKeys(signer)}

    cfg := &ssh.ClientConfig{
        User: "username",
        Auth: auths,
    }
    cfg.SetDefaults()

    client, err := ssh.Dial("tcp", "aws-hostname:22", cfg)
    if err != nil {
        log.Fatal(err)
    }

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

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

    fmt.Println(string(stdout))
}</code>

This enhanced code handles both key files and private keys, providing a more comprehensive solution. In the example, an ecdsa key is used, but the concept applies to any type of private key.

Conclusion:

The Go ssh package allows for establishing SSH connections using keys. Understandably, the documentation might appear intricate. By utilizing ssh.PublicKeys and converting the key into the appropriate format using ssh.Signer, it becomes possible to connect seamlessly and perform essential system tasks.

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