stunnel is an open-source multi-platform application used to provide a universal TLS/SSL tunneling service.
stunnel can be used to provide secure encrypted connections for clients or servers that do not speak TLS or SSL natively. It runs on a variety of operating systems, including most Unix-like operating systems and Windows. stunnel relies on the OpenSSL library to implement the underlying TLS or SSL protocol.
stunnel uses public-key cryptography with X.509 digital certificates to secure the SSL connection, and clients can optionally be authenticated via a certificate.
If linked against libwrap, it can be configured to act as a proxy-firewall service as well.
stunnel is maintained by Michał Trojnara and released under the terms of the GNU General Public License (GPL) with OpenSSL exception.
For versions of Ubuntu between 14.04 LTS (Trusty Tahr) and 15.10 (Wily Werewolf), as well as Ubuntu flavours that don’t include snap by default, snap can be installed from the Ubuntu Software Centre by searching for snapd.
Alternatively, snapd can be installed from the command line:
sudo apt update
sudo apt install snapd
Either log out and back in again, or restart your system, to ensure snap’s paths are updated correctly.
To install stunnel5, simply use the following command: