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EuroTcl/OpenACS 11 - 12 JULY 2024, VIENNA

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    <dl>
	<dd><b>tls</b> - binding to <b>OpenSSL</b> library
	for socket and I/O channel communications.</dd>
    </dl>
    </dd>
    <dd><a href="#SYNOPSIS">SYNOPSIS</a> </dd>
    <dd><dl>
	    <dd><b>package require Tcl</b> <em>?8.5?</em></dd>
	    <dd><b>package require Tcl</b> <em>?<b>8.5</b>?</em></dd>
	    <dd><b>package require tls</b></dd>
	    <dt>&nbsp;</dt>
	    <dd><b>tls::init</b> <em>?options?</em> </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>?-local? channel</em></dd>
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<h3><a name="NAME">NAME</a></h3>

<p><strong>tls</strong> - binding to <strong>OpenSSL</strong> library
for socket and I/O channel communications.</p>

<h3><a name="SYNOPSIS">SYNOPSIS</a></h3>

<p><b>package require Tcl 8.5</b><br>
<p><b>package require Tcl</b> <em>?<b>8.5</b>?</em><br>
<b>package require tls</b><br>
<br>
<a href="#tls::init"><b>tls::init</b> <i>?options?</i></a><br>
<a href="#tls::socket"><b>tls::socket</b> <i>?options? host port</i><br>
<a href="#tls::socket"><b>tls::socket</b> <i>?-server command? ?options? port</i></a><br>
<a href="#tls::status"><b>tls::status</b> <i>?-local? channel</i></a><br>
<a href="#tls::connection"><b>tls::connection</b> <i>channel</i></a><br>
<a href="#tls::handshake"><b>tls::handshake</b> <i>channel</i></a><br>
<a href="#tls::import"><b>tls::import</b> <i>channel ?options?</i></a><br>
<a href="#tls::unimport"><b>tls::unimport</b> <i>channel</i></a><br>
<br>
<a href="#tls::protocols"><b>tls::protocols</b></a><br>
<a href="#tls::version"><b>tls::version</b></a><br>
</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
<strong>Tcl_StackChannel</strong>
API for Tcl 8.4 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>This extension provides TCL script access to secure socket communications
using the Transport Layer Security (TLS) protocol. It provides a generic
binding to <a href="http://www.openssl.org/">OpenSSL</a>, utilizing the
<strong>Tcl_StackChannel</strong> API in Tcl 8.4 and higher.
These sockets behave exactly the same as channels created using the built-in
<strong>socket</strong> command, along 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
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	<br>
	<br>

	<dl>

	<dt>
	  <strong>error</strong> <em>channel message</em>
	  <strong>error</strong> <em>channelId message</em>
	</dt>
	<dd>
	  This form of callback is invoked whenever an error occurs during the
	  The <em>message</em> argument contains an error message generated
	  by the OpenSSL function <code>ERR_reason_error_string()</code>.
	  initial connection, handshake, or I/O operations. The <em>message</em>
	  argument can be from the Tcl_ErrnoMsg, OpenSSL function
	  <code>ERR_reason_error_string()</code>, or a custom message.
	</dd>

	<br>

	<dt>
	  <strong>info</strong> <em>channel major minor message type</em>
	  <strong>info</strong> <em>channelId major minor message type</em>
	</dt>
	<dd>
	  This form of callback is invoked by the OpenSSL function
	  <code>SSL_CTX_set_info_callback()</code> during connection setup
	  and use.
	  <code>SSL_set_info_callback()</code> during the initial connection
	  and handshake operations. The <em>type</em> argument is new for
	  TLS 1.8. The arguments are:
	  <br>
	  <ul>
	  <li>Possible values for <em>major</em> are:
	  <code>handshake, alert, connect, accept</code>.</li>
	  <li>Possible values for <em>minor</em> are:
	  <code>start, done, read, write, loop, exit</code>.</li>
	  <li>The <em>message</em> argument is a descriptive string which may
	  be generated either by <code>SSL_state_string_long()</code> or by
	  <code>SSL_alert_desc_string_long()</code>, depending on the context.</li>
	  <li>For alerts, the possible values for <em>type</em> are:
	  <code>warning, fatal, and unknown</code>. For others,
	  <code>info</code> is used.</li>
	  </ul>
	</dd>

	<dt>
	  <strong>message</strong> <em>channel direction version content_type data</em>
	  <strong>message</strong> <em>channelId direction version content_type message</em>
	</dt>
	<dd>
	  This form of callback is invoked by the OpenSSL function
	  <code>SSL_set_msg_callback()</code> whenever a message is sent or
	  received during the initial connection, handshake, or I/O operations.
	  received. It is only available when
	  OpenSSL is complied with the <em>enable-ssl-trace</em> option.
	  Where <em>direction</em> is Sent or Received, <em>version</em> is the
	  protocol version, <em>content_type</em> is the message content type,
	  and <em>data</em> is more info on the message from the <code>SSL_trace</code> API.
	  It is only available when OpenSSL is complied with the
	  <em>enable-ssl-trace</em> option. Arguments are: <em>direction</em> 
	  is <b>Sent</b> or <b>Received</b>, <em>version</em> is the protocol
	  version, <em>content_type</em> is the message content type, and
	  <em>message</em> is more info from the <code>SSL_trace</code> API.
	  This callback is new for TLS 1.8.
	</dd>
	<br>

	<dt>
	  <strong>session</strong> <em>channel session_id ticket lifetime</em>
	  <strong>session</strong> <em>channelId session_id ticket lifetime</em>
	</dt>
	<dd>
	  This form of callback is invoked by the OpenSSL function
	  <code>SSL_CTX_sess_set_new_cb()</code>.
	  Where <em>session_id</em> is the current session identifier,
	  <em>ticket</em> is the session ticket info, and <em>lifetime</em>
	  is the the ticket lifetime in seconds.
	  <code>SSL_CTX_sess_set_new_cb()</code> whenever a new session id is
	  sent by the server during the initial connection and handshake, but
	  can also be received later if the <b>-post_handshake</b> option is
	  used. Arguments are: <em>session_id</em> is the current
	  session identifier, <em>ticket</em> is the session ticket info, and
	  <em>lifetime</em> is the the ticket lifetime in seconds.
	  This callback is new for TLS 1.8.
	</dd>
	<br>
	</dl>
    </dd>

    <br>

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	</dt>
	<dd>
	  Invoked when loading or storing a PEM certificate with encryption.
	  Where <em>rwflag</em> is 0 for reading/decryption or 1 for
	  writing/encryption (can prompt user to confirm) and
	  <em>size</em> is the max password length in bytes.
	  The callback should return the password as a string.
	  Both arguments are new for TLS 1.8.
	</dd>
    </dd>

    <br>


    <dt><strong>-validatecommand</strong> <em>callback</em></dt>
    <dd>
	Invokes the specified <em>callback</em> script during handshake in
	order to validate the provided value(s). See below for the possible
	arguments passed to the callback script.
	To reject the value and abort connection, the callback should return 0.
	arguments passed to the callback script. If not specified, OpenSSL
	will accept valid certificates and extensions.
	To reject the value and abort the connection, the callback should return 0.
	To accept the value and continue the connection, it should return 1.
	To reject the value, but continue the connection, it should return 2.

	<br>
	<br>

	<dl>

	<dt>
	  <strong>alpn</strong> <em>channel protocol match</em>
	  <strong>alpn</strong> <em>channelId protocol match</em>
	</dt>
	<dd>
	  For servers, this form of callback is invoked when the client ALPN
	  extension is received. If <em>match</em> is true, <em>protocol</em>
	  is the first <b>-alpn</b> specified protocol common to the both the
	  client and server. If not, the first client specified protocol is
	  used. Called after hello and ALPN callbacks.
	  is the first <b>-alpn</b> option specified protocol common to both
	  the client and server. If not, the first client specified protocol is
	  used. It is called after the hello and ALPN callbacks.
	  This callback is new for TLS 1.8.
	</dd>

	<br>

	<dt>
	  <strong>hello</strong> <em>channel servername</em>
	  <strong>hello</strong> <em>channelId servername</em>
	</dt>
	<dd>
	  For servers, this form of callback is invoked during client hello
	  message processing. The purpose is so the server can select the
	  message processing. It is used to select an appropriate certificate to
	  present, and make other configuration adjustments relevant to that
	  server name and its configuration. Called before SNI and ALPN callbacks.
	  appropriate certificate to present to the client, and to make other
	  configuration adjustments relevant to that server name and its
	  configuration. It is called before the SNI and ALPN callbacks.
	  This callback is new for TLS 1.8.
	</dd>

	<br>

	<dt>
	  <strong>sni</strong> <em>channelId servername</em>
	</dt>
	<dd>
	  For servers, this form of callback is invoked when the Server Name
	  Indication (SNI) extension is received. The <em>servername</em>
	  argument is the client provided server name in the <b>-servername</b>
	  option. The purpose is so when a server supports multiple names, the
	  right certificate can be used. It is called after the hello callback
	  but before the ALPN callback.
	  This callback is new for TLS 1.8.
	</dd>

	<br>

	<dt>
	  <strong>sni</strong> <em>channel servername</em>
	</dt>
	<dd>
	  For servers, this form of callback is invoked when the SNI extension
	  from the client is received. Where <em>servername</em> is the client
	  provided server name from the <b>-servername</b> option. This is
	  used when a server supports multiple names, so the right certificate
	  can be used. Called after hello callback but before ALPN callback.
	</dd>

	<br>

	<dt>
	  <strong>verify</strong> <em>channel depth cert status error</em>
	  <strong>verify</strong> <em>channelId depth cert status error</em>
	</dt>
	<dd>
	  This form of callback is invoked by OpenSSL when a new certificate
	  is received from the peer. It allows the client to check the
	  certificate verification results and choose whether to continue
	  or not. It is called for each certificate in the certificate chain.
	  <ul>
	  <li>The <em>depth</em> argument is an integer representing the
	  current depth on the certificate chain, with
	  <li>The <em>depth</em> argument is the integer depth of the
	  certificate in the certificate chain, where 0 is the peer certificate
	  <code>0</code> as the peer certificate and higher values going
	  up to the Certificate Authority (CA).</li>
	  and higher values going up to the Certificate Authority (CA).</li>
	  <li>The <em>cert</em> argument is a list of key-value pairs similar
	  to those returned by
	  <a href="#tls::status"><strong>tls::status</strong></a>.</li>
	  <li>The <em>status</em> argument is an boolean representing the
	  validity of the current certificate.
	  <li>The <em>status</em> argument is the boolean validity of the
	  current certificate where 0 is invalid and 1 is valid.</li>
	  A value of <code>0</code> means the certificate is deemed invalid.
	  A value of <code>1</code> means the certificate is deemed valid.</li>
	  <li>The <em>error</em> argument supplies the message, if any, generated
	  <li>The <em>error</em> argument is the error message, if any, generated
	  by <code>X509_STORE_CTX_get_error()</code>.</li>
	  </ul>
	</dd>
	<br>
	</dl>
    </dd>
</dl>
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<p>
<em>
The use of the variable <strong>tls::debug</strong> is not recommended.
It may be removed from future releases.
</em>
</p>
<br>
Example #1: Use HTTP package

<p>This example uses the default Unix platform SSL certificates. For standard
installations, -cadir and -cafile should not be needed. Update -cadir or
replace with -cafile if your platform differs.</p>
Example:

<pre><code>
package require http
package require tls
set url "https://www.tcl.tk/"

http::register https 443 [list ::tls::socket -autoservername true -require true -cadir /etc/ssl/certs \
    -command ::tls::callback -password ::tls::password -validatecommand ::tls::validate_command]

# Check for error
set token [http::geturl "https://www.tcl-lang.org/"]
set token [http::geturl $url]
if {[http::status $token] ne "ok"} {
    puts [format "Error %s" [http::status $token]]
}

# Get web page
set data [http::data $token]
puts [string length $data]

# Cleanup
::http::cleanup $token
</code></pre>

Example #2:
Example #2: Use raw socket
<pre><code>
package require tls

set url "www.tcl-lang.org"
set port 443

set ch [tls::socket -autoservername 1 -servername $url -request 1 -require 1 \
    -alpn {http/1.1 h2} -cadir /etc/ssl/certs -command ::tls::callback \
    -alpn {http/1.1} -cadir /etc/ssl/certs -command ::tls::callback \
    -password ::tls::password -validatecommand ::tls::validate_command $url $port]
chan configure $ch -buffersize 65536
tls::handshake $ch

puts $ch "GET / HTTP/1.1"
flush $ch
after 500
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parray conn
parray chan
</code></pre>


<h3><a name="HTTPS EXAMPLE">HTTPS EXAMPLE</a></h3>

<p>This example uses a sample server.pem provided with the TLS release,
courtesy of the <strong>OpenSSL</strong> project.</p>
<p>This example uses the default Unix platform SSL certificates. For standard
installations, -cadir and -cafile should not be needed. Update -cadir or
replace with -cafile if your platform differs.</p>

<pre><code>
package require http
package require tls
set url "https://www.tcl.tk/"

http::register https 443 [list ::tls::socket -autoservername true -require true -cadir /etc/ssl/certs]

# Check for error
set token [http::geturl https://www.tcl.tk/]
set token [http::geturl $url]
if {[http::status $token] ne "ok"} {
    puts [format "Error %s" [http::status $token]]
}

# Get web page
set data [http::data $token]
puts [string length $data]

# Cleanup
::http::cleanup $token
</code></pre>

<h3><a name="SPECIAL CONSIDERATIONS">SPECIAL CONSIDERATIONS</a></h3>

<p>The capabilities of this package can vary enormously based upon how the
linked to OpenSSL library was configured and built. New versions may obsolete