Lua

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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Lua

local chilkat = require("chilkat")

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

local key = chilkat.SshKey.new()

-- 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.
local keyStr = key:load_text("qa_data/putty_private_key.ppk")
if not key.last_method_success then
    print(key.last_error_text)
    return
end

local success = key:from_putty_private_key(keyStr)
if not success then
    print(key.last_error_text)
    return
end

-- Export to an unencrypted OpenSSH key.
local bEncrypt = false
local unencryptedKeyStr = key:to_open_ssh_private_key(bEncrypt)
if not key.last_method_success then
    print(key.last_error_text)
    return
end

success = key:save_text(unencryptedKeyStr, "qa_output/unencrypted_openssh.pem")
if not success then
    print(key.last_error_text)
    return
end

-- Export to an encrypted OpenSSH key.  The Password property supplies the passphrase used to
-- encrypt the output.
bEncrypt = true
key.password = "myExportPassword"
local encryptedKeyStr = key:to_open_ssh_private_key(bEncrypt)
if not key.last_method_success then
    print(key.last_error_text)
    return
end

success = key:save_text(encryptedKeyStr, "qa_output/encrypted_openssh.pem")
if not success then
    print(key.last_error_text)
    return
end

print("Done!")