Tcl

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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Tcl


load ./chilkat.dll

set success 0

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

set key [new_CkSshKey]

#  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.
CkSshKey_put_Password $key "myKeyPassword"

#  LoadText is a convenience method that reads any text file into a string.  It does not itself
#  load the key.
set keyStr [CkSshKey_loadText $key "qa_data/putty_private_key.ppk"]
if {[CkSshKey_get_LastMethodSuccess $key] == 0} then {
    puts [CkSshKey_lastErrorText $key]
    delete_CkSshKey $key
    exit
}

set success [CkSshKey_FromPuttyPrivateKey $key $keyStr]
if {$success == 0} then {
    puts [CkSshKey_lastErrorText $key]
    delete_CkSshKey $key
    exit
}

#  Export to an unencrypted OpenSSH key.
set bEncrypt 0
set unencryptedKeyStr [CkSshKey_toOpenSshPrivateKey $key $bEncrypt]
if {[CkSshKey_get_LastMethodSuccess $key] == 0} then {
    puts [CkSshKey_lastErrorText $key]
    delete_CkSshKey $key
    exit
}

set success [CkSshKey_SaveText $key $unencryptedKeyStr "qa_output/unencrypted_openssh.pem"]
if {$success == 0} then {
    puts [CkSshKey_lastErrorText $key]
    delete_CkSshKey $key
    exit
}

#  Export to an encrypted OpenSSH key.  The Password property supplies the passphrase used to
#  encrypt the output.
set bEncrypt 1
CkSshKey_put_Password $key "myExportPassword"
set encryptedKeyStr [CkSshKey_toOpenSshPrivateKey $key $bEncrypt]
if {[CkSshKey_get_LastMethodSuccess $key] == 0} then {
    puts [CkSshKey_lastErrorText $key]
    delete_CkSshKey $key
    exit
}

set success [CkSshKey_SaveText $key $encryptedKeyStr "qa_output/encrypted_openssh.pem"]
if {$success == 0} then {
    puts [CkSshKey_lastErrorText $key]
    delete_CkSshKey $key
    exit
}

puts "Done!"

delete_CkSshKey $key