I plan to write a PHP script that makes an SSH connection. I've investigated how to do this and this looks the most promising solution: https://github.com/phpseclib/phpseclib My only issue is how to handle the fact that my SSH key has a passphrase, and I don't want to have to enter it every time I run the script. For every day SSH use I have ssh-agent running in the background, and it's configured to use pinentry. This makes it so that I don't have to enter my passphrase EVERY time. Any ideas as to how I could get PHP and ssh-agent to talk to each other? My only clue is that ssh-agent sets an environment variable, SSH_AUTH_SOCK, pointing to a socket file.
While the documentation for phpseclib addresses this issue, its answer is silly (just put the passphrase in the code): http://phpseclib.sourceforge.net/ssh/2.0/auth.html#encrsakey
UPDATE: I've looked more into phpseclib and written my own simple wrapper class. However, I cannot get it to login either through ssh-agent or by supplying my RSA key. Only password-based authentication works, contrary to my experiences logging in directly with the ssh command. Here is my code:
<?php
// src/Connection.php
declare(strict_types=1);
namespace MyNamespace\PhpSsh;
use phpseclib\System\SSH\Agent;
use phpseclib\Net\SSH2;
use phpseclib\Crypt\RSA;
use Exception;
class Connection
{
private SSH2 $client;
private string $host;
private int $port;
private string $username;
/**
* @param string $host
* @param int $port
* @param string $username
*
* @return void
*/
public function __construct(string $host, int $port,
string $username)
{
$this->host = $host;
$this->port = $port;
$this->username = $username;
$this->client = new SSH2($host, $port);
}
/**
* @return bool
*/
public function connectUsingAgent(): bool
{
$agent = new Agent();
$agent->startSSHForwarding($this->client);
return $this->client->login($this->username, $agent);
}
/**
* @param string $key_path
* @param string $passphrase
*
* @return bool
* @throws Exception
*/
public function connectUsingKey(string $key_path, string $passphrase = ''): bool
{
if (!file_exists($key_path)) {
throw new Exception(sprintf('Key file does not exist: %1$s', $key_path));
}
if (is_dir($key_path)) {
throw new Exception(sprintf('Key path is a directory: %1$s', $key_path));
}
if (!is_readable($key_path)) {
throw new Exception(sprintf('Key file is not readable: %1$s', $key_path));
}
$key = new RSA();
if ($passphrase) {
$key->setPassword($passphrase);
}
$key->loadKey(file_get_contents($key_path));
return $this->client->login($this->username, $key);
}
/**
* @param string $password
*
* @return bool
*/
public function connectUsingPassword(string $password): bool
{
return $this->client->login($this->username, $password);
}
/**
* @return void
*/
public function disconnect(): void
{
$this->client->disconnect();
}
/**
* @param string $command
* @param callable $callback
*
* @return string|false
*/
public function exec(string $command, callable $callback = null)
{
return $this->client->exec($command, $callback);
}
/**
* @return string[]
*/
public function getErrors(): array {
return $this->client->getErrors();
}
}
And:
<?php
// test.php
use MyNamespace\PhpSsh\Connection;
require_once(__DIR__ . '/vendor/autoload.php');
(function() {
$host = '0.0.0.0'; // Fake, obviously
$username = 'user'; // Fake, obviously
$connection = new Connection($host, 22, $username);
$connection_method = 'AGENT'; // or 'KEY', or 'PASSWORD'
switch($connection_method) {
case 'AGENT':
$connected = $connection->connectUsingAgent();
break;
case 'KEY':
$key_path = getenv( 'HOME' ) . '/.ssh/id_rsa.pub';
$passphrase = trim(fgets(STDIN)); // Pass this in on command line via < key_passphrase.txt
$connected = $connection->connectUsingKey($key_path, $passphrase);
break;
case 'PASSWORD':
default:
$password = trim(fgets(STDIN)); // Pass this in on command line via < password.txt
$connected = $connection->connectUsingPassword($password);
break;
}
if (!$connected) {
fwrite(STDERR, "Failed to connect to server!" . PHP_EOL);
$errors = implode(PHP_EOL, $connection->getErrors());
fwrite(STDERR, $errors . PHP_EOL);
exit(1);
}
$command = 'whoami';
$result = $connection->exec($command);
echo sprintf('Output of command "%1$s:"', $command) . PHP_EOL;
echo $result . PHP_EOL;
$command = 'pwd';
$result = $connection->exec($command);
echo sprintf('Output of command "%1$s:"', $command) . PHP_EOL;
echo $result . PHP_EOL;
$connection->disconnect();
})();
The SSH2 class has a getErrors() method, unfortunately it wasn't logging any in my case. I had to debug the class. I found that, whether using ssh-agent or passing in my key, it always reached this spot (https://github.com/phpseclib/phpseclib/blob/2.0.23/phpseclib/Net/SSH2.php#L2624):
<?php
// vendor/phpseclib/phpseclib/phpseclib/Net/SSH2.php: line 2624
extract(unpack('Ctype', $this->_string_shift($response, 1)));
switch ($type) {
case NET_SSH2_MSG_USERAUTH_FAILURE:
// either the login is bad or the server employs multi-factor authentication
return false;
case NET_SSH2_MSG_USERAUTH_SUCCESS:
$this->bitmap |= self::MASK_LOGIN;
return true;
}
Obviously the response being returned is of type NET_SSH2_MSG_USERAUTH_FAILURE. There's nothing wrong with the login, of that I'm sure, so per the comment in the code that means the host (Digital Ocean) must use multi-factor authentication. Here's where I'm stumped. What other means of authentication am I lacking? This is where my understanding of SSH fails me.
