Delphi ActiveX

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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var
success: Integer;
key: TChilkatSshKey;
keyStr: WideString;
bEncrypt: Integer;
unencryptedKeyStr: WideString;
encryptedKeyStr: WideString;

begin
success := 0;

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

key := TChilkatSshKey.Create(Self);

//  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.
keyStr := key.LoadText('qa_data/putty_private_key.ppk');
if (key.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(key.LastErrorText);
    Exit;
  end;

success := key.FromPuttyPrivateKey(keyStr);
if (success = 0) then
  begin
    Memo1.Lines.Add(key.LastErrorText);
    Exit;
  end;

//  Export to an unencrypted OpenSSH key.
bEncrypt := 0;
unencryptedKeyStr := key.ToOpenSshPrivateKey(bEncrypt);
if (key.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(key.LastErrorText);
    Exit;
  end;

success := key.SaveText(unencryptedKeyStr,'qa_output/unencrypted_openssh.pem');
if (success = 0) then
  begin
    Memo1.Lines.Add(key.LastErrorText);
    Exit;
  end;

//  Export to an encrypted OpenSSH key.  The Password property supplies the passphrase used to
//  encrypt the output.
bEncrypt := 1;
key.Password := 'myExportPassword';
encryptedKeyStr := key.ToOpenSshPrivateKey(bEncrypt);
if (key.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(key.LastErrorText);
    Exit;
  end;

success := key.SaveText(encryptedKeyStr,'qa_output/encrypted_openssh.pem');
if (success = 0) then
  begin
    Memo1.Lines.Add(key.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('Done!');