The stunnel program is designed to work as an SSL encryption wrapper
between remote client and local (inetd-startable) or remote server. It can be
used to add SSL functionality to commonly used inetd daemons like POP2, POP3,
and IMAP servers without any changes in the programs‘ code. Stunnel uses
the OpenSSL library
for cryptography, so it supports whatever cryptographic algorithms are compiled
into the library.
Stunnel can benefit
from FIPS
140-2 validation of the OpenSSL FIPS Object Module, as long as
the building process meets its Security
Policy. A scanned FIPS
140-2 Validation Certificate document is available for download
on the NIST web page.
The Windows binary
installer is compiled with FIPS 140-2 support. The FIPS mode of
operation is no longer enabled by default since stunnel
5.00.
Stunnel is a free software authored
by Michal Trojnara.
Although distributed under GNU
GPL version 2 or later with OpenSSL exception, stunnel is not a
community project. We retain the copyright of the source code.
Please contact
us for commercial support or non-GPL licenses. Free,
community-based support is also available via stunnel-users mailing
list.
The obsolete 3.x branch is no longer maintained.
Use stunnel3 perl
script as a drop-in replacement for backward compatibility.
reference from：https://www.stunnel.org/index.html