On Tue, 2016-05-17 11:13:26 +0000, David Faizulaev wrote:

I see, I have a keystore file for the server, can it be set as KEY ? can I convert keystore to PEM?

I don't know.

Some key/certificate repositories don't allow to export private keys. Maybe there is a PKCS11 plug-in for OpenSSL to access the keystore. If this is the case, you don't have to export your private key. But again, I don't know.

Additionally, I've thought about configuring Stunnel in client mode. Here is the configuration: [..]

Running stunnel in client or server mode makes no difference w.r.t. certificate and key files. As long as stunnel is not able to access your private key, the client mode won't work either.

HTH,

Ludolf