Stunnel is a wrapper for network connections. It can be used to tunnel an
unencrypted network connection over a secure connection (encrypted using
SSL or TLS) or to provide a secure means of connecting to services that do
not natively support encryption.
When configured to listen for incoming connections (instead of being
invoked by xinetd), stunnel can be configured to either start a thread or a
child process to handle each new connection. If Stunnel is configured to
start a new child process to handle each connection, it will receive a
SIGCHLD signal when that child exits.
Stunnel versions prior to 4.04 would perform tasks in the SIGCHLD signal
handler which, if interrupted by another SIGCHLD signal, could be unsafe.
This could lead to a denial of service.
