Xbase++

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 nSuccess
LOCAL oKey
LOCAL cKeyStr
LOCAL nBEncrypt
LOCAL cUnencryptedKeyStr
LOCAL cEncryptedKeyStr

nSuccess := 0

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

oKey := 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.
oKey:Password := "myKeyPassword"

//  LoadText is a convenience method that reads any text file into a string.  It does not itself
//  load the key.
cKeyStr := oKey:LoadText("qa_data/putty_private_key.ppk")
IF (oKey:LastMethodSuccess == 0)
    ? oKey:LastErrorText
    oKey:destroy()
    RETURN
ENDIF

nSuccess := oKey:FromPuttyPrivateKey(cKeyStr)
IF (nSuccess == 0)
    ? oKey:LastErrorText
    oKey:destroy()
    RETURN
ENDIF

//  Export to an unencrypted OpenSSH key.
nBEncrypt := 0
cUnencryptedKeyStr := oKey:ToOpenSshPrivateKey(nBEncrypt)
IF (oKey:LastMethodSuccess == 0)
    ? oKey:LastErrorText
    oKey:destroy()
    RETURN
ENDIF

nSuccess := oKey:SaveText(cUnencryptedKeyStr, "qa_output/unencrypted_openssh.pem")
IF (nSuccess == 0)
    ? oKey:LastErrorText
    oKey:destroy()
    RETURN
ENDIF

//  Export to an encrypted OpenSSH key.  The Password property supplies the passphrase used to
//  encrypt the output.
nBEncrypt := 1
oKey:Password := "myExportPassword"
cEncryptedKeyStr := oKey:ToOpenSshPrivateKey(nBEncrypt)
IF (oKey:LastMethodSuccess == 0)
    ? oKey:LastErrorText
    oKey:destroy()
    RETURN
ENDIF

nSuccess := oKey:SaveText(cEncryptedKeyStr, "qa_output/encrypted_openssh.pem")
IF (nSuccess == 0)
    ? oKey:LastErrorText
    oKey:destroy()
    RETURN
ENDIF

? "Done!"

oKey:destroy()