Swift

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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Swift


func chilkatTest() {
    var success: Bool = false

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

    let key = CkoSshKey()!

    //  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: String? = key.loadText(path: "qa_data/putty_private_key.ppk")
    if key.lastMethodSuccess == false {
        print("\(key.lastErrorText!)")
        return
    }

    success = key.fromPuttyPrivateKey(keyStr: keyStr)
    if success == false {
        print("\(key.lastErrorText!)")
        return
    }

    //  Export to an unencrypted OpenSSH key.
    var bEncrypt: Bool = false
    var unencryptedKeyStr: String? = key.toOpenSshPrivateKey(bEncrypt: bEncrypt)
    if key.lastMethodSuccess == false {
        print("\(key.lastErrorText!)")
        return
    }

    success = key.saveText(strToSave: unencryptedKeyStr, path: "qa_output/unencrypted_openssh.pem")
    if success == false {
        print("\(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: String? = key.toOpenSshPrivateKey(bEncrypt: bEncrypt)
    if key.lastMethodSuccess == false {
        print("\(key.lastErrorText!)")
        return
    }

    success = key.saveText(strToSave: encryptedKeyStr, path: "qa_output/encrypted_openssh.pem")
    if success == false {
        print("\(key.lastErrorText!)")
        return
    }

    print("Done!")

}