SQL Server

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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-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @iTmp0 int
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

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

    DECLARE @key int
    EXEC @hr = sp_OACreate 'Chilkat.SshKey', @key OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    --  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.
    EXEC sp_OASetProperty @key, 'Password', 'myKeyPassword'

    --  LoadText is a convenience method that reads any text file into a string.  It does not itself
    --  load the key.
    DECLARE @keyStr nvarchar(4000)
    EXEC sp_OAMethod @key, 'LoadText', @keyStr OUT, 'qa_data/putty_private_key.ppk'
    EXEC sp_OAGetProperty @key, 'LastMethodSuccess', @iTmp0 OUT
    IF @iTmp0 = 0
      BEGIN
        EXEC sp_OAGetProperty @key, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @key
        RETURN
      END

    EXEC sp_OAMethod @key, 'FromPuttyPrivateKey', @success OUT, @keyStr
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @key, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @key
        RETURN
      END

    --  Export to an unencrypted OpenSSH key.
    DECLARE @bEncrypt int
    SELECT @bEncrypt = 0
    DECLARE @unencryptedKeyStr nvarchar(4000)
    EXEC sp_OAMethod @key, 'ToOpenSshPrivateKey', @unencryptedKeyStr OUT, @bEncrypt
    EXEC sp_OAGetProperty @key, 'LastMethodSuccess', @iTmp0 OUT
    IF @iTmp0 = 0
      BEGIN
        EXEC sp_OAGetProperty @key, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @key
        RETURN
      END

    EXEC sp_OAMethod @key, 'SaveText', @success OUT, @unencryptedKeyStr, 'qa_output/unencrypted_openssh.pem'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @key, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @key
        RETURN
      END

    --  Export to an encrypted OpenSSH key.  The Password property supplies the passphrase used to
    --  encrypt the output.
    SELECT @bEncrypt = 1
    EXEC sp_OASetProperty @key, 'Password', 'myExportPassword'
    DECLARE @encryptedKeyStr nvarchar(4000)
    EXEC sp_OAMethod @key, 'ToOpenSshPrivateKey', @encryptedKeyStr OUT, @bEncrypt
    EXEC sp_OAGetProperty @key, 'LastMethodSuccess', @iTmp0 OUT
    IF @iTmp0 = 0
      BEGIN
        EXEC sp_OAGetProperty @key, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @key
        RETURN
      END

    EXEC sp_OAMethod @key, 'SaveText', @success OUT, @encryptedKeyStr, 'qa_output/encrypted_openssh.pem'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @key, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @key
        RETURN
      END


    PRINT 'Done!'

    EXEC @hr = sp_OADestroy @key


END
GO