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<meta name="Copyright" content="1999 Matt Newman.">
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<title>TLS (SSL) Tcl Commands</title>
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<dl>
<dd><a href="#NAME">NAME</a> <dl>
<dd><strong>tls</strong> - binding to <strong>OpenSSL</strong>
toolkit.</dd>
</dl>
</dd>
<dd><a href="#SYNOPSIS">SYNOPSIS</a> </dd>
<dd><dl>
<dd><b>package require tls </b><em>?1.3?</em></dd>
<dt> </dt>
<dd><b>tls::init </b><i>?options?</i> </dd>
<dd><b>tls::socket </b><em>?options? host port</em></dd>
<dd><b>tls::socket</b><em> ?-server command?
?options? port</em></dd>
<dd><b>tls::handshake</b><em> channel</em></dd>
<dd><b>tls::status </b><em>channel</em></dd>
<dd><b>tls::import</b><em> channel ?options?</em></dd>
<dd><b>tls::ciphers </b><em>protocol ?verbose?</em></dd>
</dl>
</dd>
<dd><a href="#COMMANDS">COMMANDS</a></dd>
<dd><a href="#CONFIGURATION OPTIONS">CONFIGURATION OPTIONS</a></dd>
<dd><a href="#HTTPS EXAMPLE">HTTPS EXAMPLE</a></dd>
<dd><a href="#SEE ALSO">SPECIAL CONSIDERATIONS</a></dd>
<dd><a href="#SEE ALSO">SEE ALSO</a></dd>
</dl>
<hr>
<h3><a name="NAME">NAME</a></h3>
<p><strong>tls</strong> - binding to <strong>OpenSSL</strong>
toolkit.</p>
<h3><a name="SYNOPSIS">SYNOPSIS</a></h3>
<p><b>package require tls </b><em>?1.3?</em><br>
<br>
<a href="#tls::init"><b>tls::init </b><i>?options?</i><br>
</a><a href="#tls::socket"><b>tls::socket </b><em>?options? host
port</em><br>
<b>tls::socket</b><em> ?-server command? ?options? port</em><br>
</a><a href="#tls::status"><b>tls::status </b><em>channel</em><br>
</a><a href="#tls::handshake"><b>tls::handshake</b><em> channel</em></a><br>
<br>
<a href="#tls::import"><b>tls::import </b><i>channel ?options?</i></a><br>
<a href="#tls::ciphers protocol ?verbose?"><strong>tls::ciphers</strong>
<em>protocol ?verbose?</em></a></p>
<h3><a name="DESCRIPTION">DESCRIPTION</a></h3>
<p>This extension provides a generic binding to <a
href="http://www.openssl.org/">OpenSSL</a>, utilizing the <a
href="http://www.oche.de/~akupries/soft/trf/index.html">Trf</a>
Channel Stacking patch for Tcl 8.[01] and the new <strong>Tcl_StackChannel</strong>
API for Tcl 8.2 and higher. The sockets behave exactly the same
as channels created using Tcl's built-in <strong>socket</strong>
command with additional options for controlling the SSL session.</p>
<h3><a name="COMMANDS">COMMANDS</a></h3>
<p>Typically one would use the <strong>tls::socket </strong>command
which provides compatibility with the native Tcl <strong>socket</strong>
command. In such cases <strong>tls::import</strong> should not be
used directly.</p>
<dl>
<dt><a name="tls::init"><b>tls::init </b><i>?options?</i></a></dt>
<dd>This routine sets the default options used by <strong>tls::socket</strong>
and is <em>optional</em>. If you call <strong>tls::import</strong>
directly this routine has no effect. Any of the options
that <strong>tls::socket</strong> accepts can be set
using this command, though you should limit your options
to only TLS related ones.</dd>
<dt> </dt>
<dt><a name="tls::socket"><b>tls::socket </b><em>?options?
host port</em></a></dt>
<dt><b>tls::socket</b><em> ?-server command? ?options? port</em></dt>
<dd>This is a helper function that utilizes the underlying
commands (<strong>tls::import</strong>). It behaves
exactly the same as the native Tcl <strong>socket</strong>
command except that the options can include any of the
applicable <a href="#tls::import"><strong>tls:import</strong></a>
options.</dd>
<dt> </dt>
<dt><a name="tls::handshake"><strong>tls::handshake</strong> <em>channel</em></a></dt>
<dd>Forces handshake to take place, and returns 0 if
handshake is still in progress (non-blocking), or 1 if
the handshake was successful. If the handshake failed
this routine will throw an error.</dd>
<dt> </dt>
<dt><a name="tls::status"><strong>tls::status</strong> <em>channel</em></a></dt>
<dd>Returns the current security status of a SSL channel. The
result is a list of key value pairs describing the
connected peer. If the result is an empty list then the
SSL handshake has not yet completed.</dd>
</dl>
<blockquote>
<dl>
<dt><strong>issuer</strong> <em>dn</em></dt>
<dd>The distinguished name (DN) of the certificate
issuer.</dd>
<dt><strong>subject</strong> <em>dn</em></dt>
<dd>The distinguished name (DN) of the certificate
subject.</dd>
<dt><strong>notBefore</strong> <em>date</em></dt>
<dd>The begin date for the validity of the certificate.</dd>
<dt><strong>notAfter</strong> <em>date</em></dt>
<dd>The expiry date for the certificate.</dd>
<dt><strong>serial</strong> <em>n</em></dt>
<dd>The serial number of the certificate.</dd>
<dt><strong>cipher</strong> <em>cipher</em></dt>
<dd>The current cipher in use between the client and
server channels.</dd>
</dl>
</blockquote>
<dl>
<dt><a name="tls::import"><b>tls::import </b><i>channel
?options?</i></a></dt>
<dd>SSL-enable a regular Tcl channel - it need not be a
socket, but must provide bi-directional flow. Also
setting session parameters for SSL handshake.</dd>
</dl>
<blockquote>
<dl>
<dt><strong>-cafile </strong><em>filename</em></dt>
<dd>Provide the CA file.</dd>
<dt>-<strong>cadir</strong> <em>dir</em></dt>
<dd>Provide the directory containing the CA certificates.</dd>
<dt><strong>-certfile</strong> <em>filename</em></dt>
<dd>Provide the certificate to use.</dd>
<dt><strong>-cipher </strong><em>string</em></dt>
<dd>Provide the cipher suites to use. Syntax is as per
OpenSSL.</dd>
<dt><strong>-command</strong><em> callback</em></dt>
<dd>This callback is invoked to pass errors, tracing
information and to allow Tcl scripts to perform
additional verification of the certificate, which can
override the default validation in OpenSSL.</dd>
<dt><strong>-keyfile</strong> <em>filename</em></dt>
<dd>Provide the private key file. (<strong>default</strong>:
value of -certfile)</dd>
<dt><strong>-model</strong> <em>channel</em></dt>
<dd>This will force this channel to share the same <em><strong>SSL_CTX</strong></em>
structure as the specified <em>channel</em>, and
therefore share callbacks etc.</dd>
<dt><strong>-request </strong><em>bool</em></dt>
<dd>Request a certificate from peer during SSL handshake.
(<strong>default</strong>: <em>true</em>)</dd>
<dt><strong>-require</strong> <em>bool</em></dt>
<dd>Require a valid certificate from peer during SSL
handshake. If this is set to true then <strong>-request</strong>
must also be set to true. (<strong>default</strong>: <em>false</em>)</dd>
<dt><strong>-server</strong> <em>bool</em></dt>
<dd>Handshake as server if true, else handshake as
client.(<strong>default</strong>: <em>false</em>) <em>[Not
available to tls::socket]</em></dd>
<dt><strong>-ssl2</strong> <em>bool</em></dt>
<dd>Enable use of SSL v2. (<strong>default</strong>: <em>true</em>
unless -DNO_PATENTS was specified in build)</dd>
<dt><strong>-ssl3 </strong><em>bool</em></dt>
<dd>Enable use of SSL v3. (<strong>default</strong>: <em>true</em>)</dd>
<dt>-<strong>tls1</strong> <em>bool</em></dt>
<dd>Enable use of TLS v1. (<strong>default</strong>: <em>false</em>)</dd>
</dl>
</blockquote>
<dl>
<dt><a name="tls::ciphers protocol ?verbose?"><strong>tls::ciphers</strong>
<em>protocol ?verbose?</em></a></dt>
<dd>Returns list of supported ciphers based on the <em>protocol</em>
you supply, which must be one of <em>ssl2, ssl3, or tls1</em>.
If <em>verbose</em> is specified as true then a verbose,
semi-human readable list is returned providing additional
information on the nature of the cipher support. In each
case the result is a Tcl list.</dd>
</dl>
<h3><a name="CONFIGURATION OPTIONS">CONFIGURATION OPTIONS</a></h3>
<p>In addition to the options listed above you can set the <strong>tls::debug</strong>
flag to a non-zero value to see the output from the default
command callback (<strong>tls::callback</strong>) which shows the
progression of the SSL handshake. Setting this value to greated
than 1 will cause the default verify method in <strong>tls::callback</strong>
to always accept the certificate, even if it is invalid.</p>
<p>In a real-world deployment you should substitute your own
callback in place of <strong>tls::callback</strong>, via the <em>-command
</em>option to <strong>tls::socket</strong> or <strong>tls::import</strong>.</p>
<p>When the TLS layer needs to obtain a password, typically for a
certificate, the software will invoke a Tcl command called <strong>tls::password</strong>,
which should return a string which represents the password to be
used. A default implementation is provided, which simply returns<em>
"secret"</em> - you should redefine this procedure
after issuing the <em>package require tls</em>.</p>
<h3><a name="HTTPS EXAMPLE">HTTPS EXAMPLE</a></h3>
<p>This example requires a patch to the <strong>http</strong>
module that ships with Tcl - this patch has been submitted for
inclusion in Tcl 8.2.1, but is also provided in the tls directory
if needed. A sample server.pem is provided with the TLS release,
courtesy of the <strong>OpenSSL</strong> project.</p>
<pre><code>package require http
package require tls
http::register https 443 [list ::tls::socket -require 1 -cafile ./server.pem]
set tok [http::geturl https://developer.netscape.com/]
</code></pre>
<h3><a name="SPECIAL CONSIDERATIONS">SPECIAL CONSIDERATIONS</a></h3>
<p>The capabilities of this package can vary enormously based
upon how your OpenSSL library was configured and built. At the
most macro-level OpenSSL supports a "no patents" build,
which disables RSA, IDEA, RC(2,4,5) and SSL2 - if your OpenSSL is
configured this way then you will need to build TLS with the
-DNO_PATENTS option - and the resultant module will function
correctly and also support ADH certificate-less encryption,
however you will be unable to utilize this to speak to normal Web
Servers, which typically require RSA support. Please see <a
href="http://www.openssl.org/">http://www.openssl.org/</a> for
more information on the whole issue of patents and US export
restrictions. </p>
<h3><a name="SEE ALSO">SEE ALSO</a></h3>
<p><strong>socket</strong>, <strong>fileevent, </strong><a
href="http://www.openssl.org/"><strong>OpenSSL</strong></a></p>
<hr>
<pre>
Copyright © 1999 Matt Newman.</pre>
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