PHP Extension

Convert a PuTTY Private Key (.ppk) to OpenSSH (.pem)

Demonstrates converting a PuTTY format private key to OpenSSH format. The .ppk is imported with FromPuttyPrivateKey and re-exported with ToOpenSshPrivateKey, both unencrypted and encrypted.

Note: The file paths are relative to the application's current working directory. Supply the paths to your own files.

Background: PuTTY and OpenSSH store the same underlying key material in different container formats, so converting between them is a re-encoding rather than a new key — the corresponding public key, and therefore the server-side authorized_keys entry, is unchanged. This matters when moving between Windows tooling built around PuTTY and Unix tooling that expects PEM. Note that the Password property serves double duty: it decrypts the key on import and encrypts it on export, so set it appropriately for each step.

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PHP Extension

<?php

include("chilkat.php");

$success = false;

//  Demonstrates converting a PuTTY format private key (.ppk) to OpenSSH (.pem) format.

$key = new CkSshKey();

//  Set the password before importing an encrypted PuTTY key.  If the key is not encrypted it
//  makes no difference whether Password is set.  This should come from a secure source rather
//  than being hard-coded.
$key->put_Password('myKeyPassword');

//  LoadText is a convenience method that reads any text file into a string.  It does not itself
//  load the key.
$keyStr = $key->loadText('qa_data/putty_private_key.ppk');
if ($key->get_LastMethodSuccess() == false) {
    print $key->lastErrorText() . "\n";
    exit;
}

$success = $key->FromPuttyPrivateKey($keyStr);
if ($success == false) {
    print $key->lastErrorText() . "\n";
    exit;
}

//  Export to an unencrypted OpenSSH key.
$bEncrypt = false;
$unencryptedKeyStr = $key->toOpenSshPrivateKey($bEncrypt);
if ($key->get_LastMethodSuccess() == false) {
    print $key->lastErrorText() . "\n";
    exit;
}

$success = $key->SaveText($unencryptedKeyStr,'qa_output/unencrypted_openssh.pem');
if ($success == false) {
    print $key->lastErrorText() . "\n";
    exit;
}

//  Export to an encrypted OpenSSH key.  The Password property supplies the passphrase used to
//  encrypt the output.
$bEncrypt = true;
$key->put_Password('myExportPassword');
$encryptedKeyStr = $key->toOpenSshPrivateKey($bEncrypt);
if ($key->get_LastMethodSuccess() == false) {
    print $key->lastErrorText() . "\n";
    exit;
}

$success = $key->SaveText($encryptedKeyStr,'qa_output/encrypted_openssh.pem');
if ($success == false) {
    print $key->lastErrorText() . "\n";
    exit;
}

print 'Done!' . "\n";

?>