Stunnel – An Open Source Program For TLS / SSL Tunneling


The architecture of the Stunnel program is optimized for portability, security and scalability and thus making it useful for deployments that are large. Stunnel is used for clients or servers who do not have secured encryption connections and those who do not use TLS or SSL. Stunnel does run on various operating systems, which includes Windows and Unix too.

A separate library is used by Stunnel which includes OpenSSL or SSLeay for implementing SSL or TSL protocol. For cryptography, Stunnel does use OpenSSL library so that algorithms that are cryptographic could be compiled into a library. It could benefit from the validation of FIPS 140-2 of the object module of OpenSSL as long as the process of building meets the security policy. Stunnel does use public key cryptography such as X.509 digital certificate that is used to secure the connection of SSL. Clients could even be authenticated by a certificate too.

It could be used a proxy wall if it is linked by libwrap.  Stunnel was created by Michael Trojan a and was released as Gnu General Public License having Open SSL exception. The latest version used is Stunnel 3 which is used as a replacement for backward compatibility. Stunnel is used to add functionality in SSL and used to add functionality to used daemons like POP-2,3 and servers like IMAP, other daemons that could be as standalone such as SMTP, NNTP and HTTP and without changing the source code, PPP is tunneled over various sockets of the network.

Each section of the configuration does start with a name of the service that is given in a square bracket. The name of the service for libwrap known as TCP Wrappers does give access to control and gives you distinguished stunnel services in the files for logs.

Stunnel used public key cryptography that has X.509 certificate that is digital to get the SSL connection secured. Clients could be authenticated by a certificate too. The easiest way to get a certificate and a key is to generate them  with a package of OpenSSL. Information related to them is available on different websites that are useful. Stunnel is also considered as one of the most demandable product online too.

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