auth/key.go

/* Copyright (c) 2020 Bram Vandenbogaerde
 * You may use, distribute or modify this code under the
 * terms of the Mozilla Public License 2.0, which is distributed
 * along with the source code.
 */
package auth

import (
	"io/ioutil"
	"net"
	"os"

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

// PrivateKey Loads a private and public key from "path" and returns a SSH ClientConfig to authenticate with the server
func PrivateKey(username string, path string, keyCallBack ssh.HostKeyCallback) (ssh.ClientConfig, error) {
	privateKey, err := ioutil.ReadFile(path)

	if err != nil {
		return ssh.ClientConfig{}, err
	}

	signer, err := ssh.ParsePrivateKey(privateKey)

	if err != nil {
		return ssh.ClientConfig{}, err
	}

	return ssh.ClientConfig{
		User: username,
		Auth: []ssh.AuthMethod{
			ssh.PublicKeys(signer),
		},
		HostKeyCallback: keyCallBack,
	}, nil
}

// Creates the configuration for a client that authenticates with a password protected private key
func PrivateKeyWithPassphrase(username string, passpharase []byte, path string, keyCallBack ssh.HostKeyCallback) (ssh.ClientConfig, error) {
	privateKey, err := ioutil.ReadFile(path)

	if err != nil {
		return ssh.ClientConfig{}, err
	}
	signer, err := ssh.ParsePrivateKeyWithPassphrase(privateKey, passpharase)

	if err != nil {
		return ssh.ClientConfig{}, err
	}

	return ssh.ClientConfig{
		User: username,
		Auth: []ssh.AuthMethod{
			ssh.PublicKeys(signer),
		},
		HostKeyCallback: keyCallBack,
	}, nil
}

// Creates a configuration for a client that fetches public-private key from the SSH agent for authentication
func SshAgent(username string, keyCallBack ssh.HostKeyCallback) (ssh.ClientConfig, error) {
	socket := os.Getenv("SSH_AUTH_SOCK")
	conn, err := net.Dial("unix", socket)
	if err != nil {
		return ssh.ClientConfig{}, err
	}

	agentClient := agent.NewClient(conn)
	return ssh.ClientConfig{
		User: username,
		Auth: []ssh.AuthMethod{
			ssh.PublicKeysCallback(agentClient.Signers),
		},
		HostKeyCallback: keyCallBack,
	}, nil
}

// Creates a configuration for a client that authenticates using username and password
func PasswordKey(username string, password string, keyCallBack ssh.HostKeyCallback) (ssh.ClientConfig, error) {

	return ssh.ClientConfig{
		User: username,
		Auth: []ssh.AuthMethod{
			ssh.Password(password),
		},
		HostKeyCallback: keyCallBack,
	}, nil
}