Visual FoxPro

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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LOCAL lnSuccess
LOCAL loKey
LOCAL lcKeyStr
LOCAL lnBEncrypt
LOCAL lcUnencryptedKeyStr
LOCAL lcEncryptedKeyStr

lnSuccess = 0

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

loKey = CreateObject('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.
loKey.Password = "myKeyPassword"

*  LoadText is a convenience method that reads any text file into a string.  It does not itself
*  load the key.
lcKeyStr = loKey.LoadText("qa_data/putty_private_key.ppk")
IF (loKey.LastMethodSuccess = 0) THEN
    ? loKey.LastErrorText
    RELEASE loKey
    CANCEL
ENDIF

lnSuccess = loKey.FromPuttyPrivateKey(lcKeyStr)
IF (lnSuccess = 0) THEN
    ? loKey.LastErrorText
    RELEASE loKey
    CANCEL
ENDIF

*  Export to an unencrypted OpenSSH key.
lnBEncrypt = 0
lcUnencryptedKeyStr = loKey.ToOpenSshPrivateKey(lnBEncrypt)
IF (loKey.LastMethodSuccess = 0) THEN
    ? loKey.LastErrorText
    RELEASE loKey
    CANCEL
ENDIF

lnSuccess = loKey.SaveText(lcUnencryptedKeyStr,"qa_output/unencrypted_openssh.pem")
IF (lnSuccess = 0) THEN
    ? loKey.LastErrorText
    RELEASE loKey
    CANCEL
ENDIF

*  Export to an encrypted OpenSSH key.  The Password property supplies the passphrase used to
*  encrypt the output.
lnBEncrypt = 1
loKey.Password = "myExportPassword"
lcEncryptedKeyStr = loKey.ToOpenSshPrivateKey(lnBEncrypt)
IF (loKey.LastMethodSuccess = 0) THEN
    ? loKey.LastErrorText
    RELEASE loKey
    CANCEL
ENDIF

lnSuccess = loKey.SaveText(lcEncryptedKeyStr,"qa_output/encrypted_openssh.pem")
IF (lnSuccess = 0) THEN
    ? loKey.LastErrorText
    RELEASE loKey
    CANCEL
ENDIF

? "Done!"

RELEASE loKey