Perl

SSH Keyboard-Interactive Authentication

Demonstrates keyboard-interactive authentication with an SSH server. StartKeyboardAuth returns XML describing the server's prompts, and ContinueKeyboardAuth submits each response. Authentication is complete when the returned XML contains either a success or an error node.

Background: Keyboard-interactive is SSH's flexible, prompt-driven method: rather than assuming a single password, the server asks one or more questions — a password, a one-time code, a security question — and the client answers each. This is how SSH supports two-factor and other challenge-response schemes. The prompt XML also indicates whether each response should be echoed, so a client knows when to mask input. A server may issue several rounds, so a robust implementation loops until it sees success or error rather than assuming one exchange is enough.

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Perl

use chilkat();

$success = 0;

#  This example requires the Chilkat API to have been previously unlocked.
#  See Global Unlock Sample for sample code.

#  Demonstrates keyboard-interactive authentication with an SSH server.  The server sends one or
#  more prompts as XML, and the application answers each with ContinueKeyboardAuth.

$ssh = chilkat::CkSsh->new();

$ssh->put_ConnectTimeoutMs(5000);
$ssh->put_ReadTimeoutMs(15000);

$hostname = "ssh.example.com";
$port = 22;
$success = $ssh->Connect($hostname,$port);
if ($success == 0) {
    print $ssh->lastErrorText() . "\r\n";
    exit;
}

#  Begin keyboard-interactive authentication.  The returned XML describes the server's prompts.
$xmlResponse = $ssh->startKeyboardAuth("mySshLogin");
if ($ssh->get_LastMethodSuccess() == 0) {
    print $ssh->lastErrorText() . "\r\n";
    exit;
}

#  If the server sent a user authentication banner, an application may display it before
#  prompting.
print "UserAuthBanner: " . $ssh->userAuthBanner() . "\r\n";

$xml = chilkat::CkXml->new();
$success = $xml->LoadXml($xmlResponse);
if ($success == 0) {
    print $xml->lastErrorText() . "\r\n";
    exit;
}

#  Authentication is complete when the XML contains either a "success" or an "error" node.
if ($xml->HasChildWithTag("success")) {
    print "No password required, already authenticated." . "\r\n";
    exit;
}

if ($xml->HasChildWithTag("error")) {
    print "Authentication failed." . "\r\n";
    exit;
}

#  Normally you would not hard-code the password in source.  You should instead obtain it
#  from an interactive prompt, environment variable, or a secrets vault.
$password = "mySshPassword";

#  Answer the prompt.  Typically one call is enough, but a server may issue several rounds of
#  prompts, so a robust client loops until it sees "success" or "error".
$xmlResponse = $ssh->continueKeyboardAuth($password);
if ($ssh->get_LastMethodSuccess() == 0) {
    print $ssh->lastErrorText() . "\r\n";
    exit;
}

$success = $xml->LoadXml($xmlResponse);
if ($success == 0) {
    print $xml->lastErrorText() . "\r\n";
    exit;
}

if ($xml->HasChildWithTag("success")) {
    print "SSH keyboard-interactive authentication successful." . "\r\n";
    exit;
}

if ($xml->HasChildWithTag("error")) {
    print "Authentication failed." . "\r\n";
}