Node.js

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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function chilkatExample() {

    var success = false;

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

    var key = new chilkat.SshKey();

    //  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.Password = "myKeyPassword";

    //  LoadText is a convenience method that reads any text file into a string.  It does not itself
    //  load the key.
    var keyStr = key.LoadText("qa_data/putty_private_key.ppk");
    if (key.LastMethodSuccess == false) {
        console.log(key.LastErrorText);
        return;
    }

    success = key.FromPuttyPrivateKey(keyStr);
    if (success == false) {
        console.log(key.LastErrorText);
        return;
    }

    //  Export to an unencrypted OpenSSH key.
    var bEncrypt = false;
    var unencryptedKeyStr = key.ToOpenSshPrivateKey(bEncrypt);
    if (key.LastMethodSuccess == false) {
        console.log(key.LastErrorText);
        return;
    }

    success = key.SaveText(unencryptedKeyStr,"qa_output/unencrypted_openssh.pem");
    if (success == false) {
        console.log(key.LastErrorText);
        return;
    }

    //  Export to an encrypted OpenSSH key.  The Password property supplies the passphrase used to
    //  encrypt the output.
    bEncrypt = true;
    key.Password = "myExportPassword";
    var encryptedKeyStr = key.ToOpenSshPrivateKey(bEncrypt);
    if (key.LastMethodSuccess == false) {
        console.log(key.LastErrorText);
        return;
    }

    success = key.SaveText(encryptedKeyStr,"qa_output/encrypted_openssh.pem");
    if (success == false) {
        console.log(key.LastErrorText);
        return;
    }

    console.log("Done!");

}

chilkatExample();