Tool Command Language (TCL) Transport Layer Security (TLS) Extension

Intro
=====

This package provides an extension which implements Secure Socket Layer (SSL)
and Transport Layer Security (TLS) encryption over Transmission Control
Protocol (TCP) network communication channels utilizing the OpenSSL library.


Description
===========

This extension works by creating a layered TCL Channel on top of an existing
bi-directional channel created by the TLS socket command. All existing socket
functionality is supported in addition to several new options. Both client and
server modes are supported.


Documentation
=============

See the doc directory for the full usage documentation.


Compatibility
=============

TCL
---

This package requires TCL 8.5 or later. It will also work with TCL 9, but it is
not binary compatible between major TCL versions. This means if this extension
is built with TCL 8.x it will not load into TCL 9 or vice versa. It is best
to compile both separately then install them with the compatible TCL versions.


OpenSSL
-------

This package is compatible with OpenSSL v1.1.1 or later, though 3.2 or later is

preferred. See http://www.openssl.org/. Please note that there are a few API
incompatibilities between OpenSSL 1.1.1 and 3.x, so if this extension is built
against OpenSSL 1.1.1 it is not binary compatible with OpenSSL 3.x or vice
versa.

TCLTLS
------

There were several changes made in the callback command arguments between
versions 1.7 and 2.0. See the doc/tls.html for what changed and library/tls.tcl
for example handler functions that are backwards compatible.


Installation
============

This package uses the TCL Extension Architecture (TEA) to build and install on
any supported Unix, Mac, or MS Windows system. It depends on the OpenSSL

==========

Original TLS Copyright (C) 1997-2000 Matt Newman <matt@novadigm.com>
TLS 1.4.1    Copyright (C) 2000 Ajuba Solutions
TLS 1.6      Copyright (C) 2008 ActiveState Software Inc.
TLS 1.7      Copyright (C) 2016 Matt Newman, Ajuba Solutions, ActiveState
                                Software Inc, Roy Keene <tcltls@rkeene.org>
TLS 1.8-2.0  Copyright (C) 2023-2024 Brian O'Hagan

Acknowledgments
===============

Non-exclusive credits for TLS are:
   Original work: Matt Newman @ Novadigm
   Updates: Jeff Hobbs @ ActiveState

	}
	"session" {
	    lassign $args session_id ticket lifetime

	    log 0 "TLS/$chan: session: lifetime $lifetime"
	}
	"verify" {
	    # Backwards compatible for v1.7
	    return [tls::validate_command $option $chan {*}$args]
	}
	default	{
	    return -code error "bad option \"$option\":\
		    must be one of error, info, message, or session"
	}
    }
}

#
# Sample callback when return value is needed. New for TLS 1.8+.
#
proc tls::validate_command {option chan args} {
    variable debug

    switch -- $option {
	"alpn" {
	    lassign $args protocol match

	}
	if {$cb(handshake) == "done"} {
	    return 1
	}
    }
}

#
# Sample callback to get password when needed. Args are new for TLS 1.8+.
#
proc tls::password {{option password} {rwflag 0} {size 0}} {
    log 0 "TLS/Password: did you forget to set your passwd!"
    # Return the worlds best kept secret password.
    return "secret"
}

proc tls::log {level msg} {