<p>tls - binding to the OpenSSL library for encrypted socket and I/O channel communications</p>
</div>
<div id="toc" class="doctools_section"><h2><a name="toc">Table Of Contents</a></h2>
<ul class="doctools_toc">
<li class="doctools_section"><a href="#toc">Table Of Contents</a></li>
<li class="doctools_section"><a href="#synopsis">Synopsis</a></li>
<li class="doctools_section"><a href="#section1">Description</a></li>
<li class="doctools_section"><a href="#section2">Compatibility</a></li>
<li class="doctools_section"><a href="#section3">Commands</a></li>
<li class="doctools_section"><a href="#section4">Certificate Validation</a>
<ul>
<li class="doctools_subsection"><a href="#subsection1">PKI and Certificates</a></li>
<li class="doctools_subsection"><a href="#subsection2">Summary of command line options</a></li>
<li class="doctools_subsection"><a href="#subsection3">When are command line options needed?</a></li>
</ul>
</li>
<li class="doctools_section"><a href="#section5">Callback Options</a>
<ul>
<li class="doctools_subsection"><a href="#subsection4">Values for Command Callback</a></li>
<li class="doctools_subsection"><a href="#subsection5">Values for Password Callback</a></li>
<li class="doctools_subsection"><a href="#subsection6">Values for Validate Command Callback</a></li>
</ul>
</li>
<li class="doctools_section"><a href="#section6">Debug</a></li>
<li class="doctools_section"><a href="#section7">Examples</a></li>
<li class="doctools_section"><a href="#section8">Special Considerations</a></li>
<li class="doctools_section"><a href="#see-also">See Also</a></li>
<li class="doctools_section"><a href="#keywords">Keywords</a></li>
<li class="doctools_section"><a href="#category">Category</a></li>
<li class="doctools_section"><a href="#copyright">Copyright</a></li>
</ul>
</div>
<div id="synopsis" class="doctools_section"><h2><a name="synopsis">Synopsis</a></h2>

using the Transport Layer Security (TLS) protocol. It provides a generic
binding to <a href="https://www.openssl.org/">OpenSSL</a>, utilizing the
<b class="syscmd">Tcl_StackChannel</b> API in TCL 8.4 and higher.
These sockets behave exactly the same as channels created using the built-in
<b class="syscmd">socket</b> command, but provide additional options for controlling
the SSL/TLS session.</p>
</div>
<div id="section2" class="doctools_section"><h2><a name="section2">Compatibility</a></h2>
<p>This extension is compatible with OpenSSL 1.1.1 or later. It requires Tcl
version 8.5 or later and will work with Tcl 9.0.</p>
</div>
<div id="section3" class="doctools_section"><h2><a name="section3">Commands</a></h2>
<p>The following are the commands provided by the TcLTLS package. See the
<span class="sectref"><a href="#section7">Examples</a></span> for example usage and the &quot;<b class="file">demos</b>&quot; directory for
more example usage.</p>
<dl class="doctools_definitions">
<dt><a name="1"><b class="cmd">tls::init</b> <span class="opt">?<i class="arg">-option</i>?</span> <span class="opt">?<i class="arg">value</i>?</span> <span class="opt">?<i class="arg">-option value ...</i>?</span></a></dt>
<dd><p>Optional function to set the default options used by <b class="cmd">tls::socket</b>. If you
call <b class="cmd">tls::import</b> directly, the values set by this command have no effect.
This command supports all of the same options as the <b class="cmd">tls::socket</b> command,
though you should limit your options to only TLS related ones.</p></dd>

<dd><p>List of protocols to offer during Application-Layer Protocol Negotiation
(ALPN). For example: <b class="const">h2</b> and <b class="const">http/1.1</b>, but not <b class="const">h3</b> or
<b class="const">quic</b>. This option is new for TclTLS 1.8.</p></dd>
<dt><b class="option">-cadir</b> <i class="arg">directory</i></dt>
<dd><p>Specifies the directory where the Certificate Authority (CA) certificates are
stored. The default is platform specific and can be set at compile time. The
default location can be overridden by the <b class="variable">SSL_CERT_DIR</b> environment
variable. See <span class="sectref"><a href="#section4">Certificate Validation</a></span> for more details.</p></dd>
<dt><b class="option">-cafile</b> <i class="arg">filename</i></dt>
<dd><p>Specifies the file with the Certificate Authority (CA) certificates to use in
<b class="const">PEM</b> file format. The default is &quot;<b class="file">cert.pem</b>&quot;, in the OpenSSL
directory. The default file can be overridden by the <b class="variable">SSL_CERT_FILE</b> environment
variable. See <span class="sectref"><a href="#section4">Certificate Validation</a></span> for more details.</p></dd>
<dt><b class="option">-castore</b> <i class="arg">URI</i></dt>
<dd><p>Specifies the Uniform Resource Identifier (URI) for the Certificate Authority
(CA) store, which may be a single container or a catalog of containers.
Starting with OpenSSL 3.2 on MS Windows, set to &quot;<b class="const">org.openssl.winstore://</b>&quot;
to use the built-in MS Windows Certificate Store.
See <span class="sectref"><a href="#section4">Certificate Validation</a></span> for more details.
This option is new for TclTLS 1.8.</p></dd>
<dt><b class="option">-certfile</b> <i class="arg">filename</i></dt>
<dd><p>Specifies the name of the file with the certificate to use in PEM format
as the local (client or server) certificate. It also contains the public key.</p></dd>
<dt><b class="option">-cert</b> <i class="arg">string</i></dt>
<dd><p>Specifies the certificate to use as a DER encoded string (X.509 DER).</p></dd>
<dt><b class="option">-cipher</b> <i class="arg">string</i></dt>

&quot;<b class="const">:</b>&quot; separated list of cipher suite names. See the
<a href="https://docs.openssl.org/master/man1/openssl-ciphers/#options">OpenSSL</a>
documentation for the full list of valid values.
This option is new for TclTLS 1.8.</p></dd>
<dt><b class="option">-command</b> <i class="arg">callback</i></dt>
<dd><p>Specifies the callback command to be invoked at several points during the
handshake to pass errors, tracing information, and protocol messages.
See <span class="sectref"><a href="#section5">Callback Options</a></span> for more info.</p></dd>
<dt><b class="option">-dhparams</b> <i class="arg">filename</i></dt>
<dd><p>Specifies the Diffie-Hellman (DH) parameters file.</p></dd>
<dt><b class="option">-keyfile</b> <i class="arg">filename</i></dt>
<dd><p>Specifies the private key file. The default is to use the file
specified by the <i class="arg">-certfile</i> option.</p></dd>
<dt><b class="option">-key</b> <i class="arg">string</i></dt>
<dd><p>Specifies the private key to use as a DER encoded string (PKCS#1 DER).</p></dd>
<dt><b class="option">-model</b> <i class="arg">channel</i></dt>
<dd><p>Force this channel to share the same <i class="term">SSL_CTX</i> structure as the
specified <i class="arg">channel</i>, and therefore share config, callbacks, etc.</p></dd>
<dt><b class="option">-password</b> <i class="arg">callback</i></dt>
<dd><p>Specifies the callback command to invoke when OpenSSL needs to obtain a
password. This is typically used to unlock the private key of a certificate.
The callback should return a password string. This option has changed for
TclTLS 1.8. See <span class="sectref"><a href="#section5">Callback Options</a></span> for more info.</p></dd>
<dt><b class="option">-post_handshake</b> <i class="arg">bool</i></dt>
<dd><p>Allow post-handshake session ticket updates. This option is new for TclTLS 1.8.</p></dd>
<dt><b class="option">-request</b> <i class="arg">bool</i></dt>
<dd><p>Request a certificate from the peer during the SSL handshake. This is needed
to do Certificate Validation. Starting in TclTLS 1.8, the default is
<b class="const">true</b>. Starting in TclTLS 2.0, If set to <b class="const">false</b> and
<b class="option">-require</b> is <b class="const">true</b>, then this will be overridden to <b class="const">true</b>.
See <span class="sectref"><a href="#section4">Certificate Validation</a></span> for more details.</p></dd>
<dt><b class="option">-require</b> <i class="arg">bool</i></dt>
<dd><p>Require a valid certificate from the peer during the SSL handshake. If this is
set to true, then <b class="option">-request</b> must also be set to true and a either
<b class="option">-cadir</b>, <b class="option">-cafile</b>, <b class="option">-castore</b>, or a platform default
must be provided in order to validate against. The default in TclTLS 1.8 and
earlier versions is <b class="const">false</b> since not all platforms have certificates to
validate against in a form compatible with OpenSSL. Starting in TclTLS 2.0,
the default is <b class="const">true</b>.
See <span class="sectref"><a href="#section4">Certificate Validation</a></span> for more details.</p></dd>
<dt><b class="option">-security_level</b> <i class="arg">integer</i></dt>
<dd><p>Specifies the security level (value from 0 to 5). The security level affects
the allowed cipher suite encryption algorithms, supported ECC curves,
supported signature algorithms, DH parameter sizes, certificate key sizes
and signature algorithms. The default is 1 prior to OpenSSL 3.2 and 2
thereafter. Level 3 and higher disable support for session tickets and
only accept cipher suites that provide forward secrecy.

<dd><p>Enable use of TLS v1.3. The default is <b class="const">true</b>. This is only available
starting with OpenSSL 1.1.1 and TclTLS 1.7.</p></dd>
<dt><b class="option">-validatecommand</b> <i class="arg">callback</i></dt>
<dd><p>Specifies the callback command to invoke to validate the peer certificates
and other config info during the protocol negotiation phase. This can be used
by TCL scripts to perform their own Certificate Validation to supplement the
default validation provided by OpenSSL. The script must return a boolean true
to continue the negotiation. See <span class="sectref"><a href="#section5">Callback Options</a></span> for more info.
This option is new for TclTLS 1.8.</p></dd>
</dl></dd>
<dt><a name="5"><b class="cmd">tls::unimport</b> <i class="arg">channel</i></a></dt>
<dd><p>Compliment to <b class="cmd">tls::import</b>. Used to remove the top level stacked channel
from <i class="arg">channel</i>. This unstacks the encryption of a regular TCL channel. An
error is thrown if TLS is not the top stacked channel type.</p></dd>
<dt><a name="6"><b class="cmd">tls::handshake</b> <i class="arg">channel</i></a></dt>

<b class="const">ssl2</b>, <b class="const">ssl3</b>, <b class="const">tls1</b>, <b class="const">tls1.1</b>, <b class="const">tls1.2</b>, and
<b class="const">tls1.3</b>. Exact list depends on OpenSSL version and compile time flags.
This command is new for TclTLS 1.8.</p></dd>
<dt><a name="11"><b class="cmd">tls::version</b></a></dt>
<dd><p>Returns the OpenSSL version string.</p></dd>
</dl>
</div>
<div id="section4" class="doctools_section"><h2><a name="section4">Certificate Validation</a></h2>
<div id="subsection1" class="doctools_subsection"><h3><a name="subsection1">PKI and Certificates</a></h3>
<p>Using the Public Key Infrastructure (PKI), each user creates a private key that
only they know about and a public key they can exchange with others for use in
encrypting and decrypting data. The process is the sender encrypts their data
using their private key and the receiver's public key. The data is then sent
to the receiver. In a similar manner, the receiver uses their private key and
the sender's public key to decrypt the data. This provides data integrity, to

<dt><b class="option">-castore</b> <i class="arg">URI</i></dt>
<dd><p>Specifies the Uniform Resource Identifier (URI) for the Certificate Authority
(CA) store, which may be a single container or a catalog of containers.
Starting with OpenSSL 3.2 on MS Windows, set to &quot;<b class="const">org.openssl.winstore://</b>&quot;
to use the built-in MS Windows Certificate Store. Starting in TclTLS 2.0, this
is the default if <b class="option">-cadir</b>, <b class="option">-cadir</b>, and <b class="option">-castore</b> are
not specified. This store only supports root certificate stores. See
<span class="sectref"><a href="#section4">Certificate Validation</a></span> for more details.</p></dd>
<dt><b class="option">-request</b> <i class="arg">bool</i></dt>
<dd><p>Request a certificate from the peer during the SSL handshake. This is needed
to do Certificate Validation. Starting in TclTLS 1.8, the default is
<b class="const">true</b>. Starting in TclTLS 2.0, If set to <b class="const">false</b> and
<b class="option">-require</b> is <b class="const">true</b>, then this will be overridden to <b class="const">true</b>.
In addition, the client can manually inspect and accept or reject
each certificate using the <i class="arg">-validatecommand</i> option.</p></dd>

from Mozilla</a> in the &quot;<b class="file">cacert.pem</b>&quot; file. You must then either set the
<b class="variable">SSL_CERT_DIR</b> and/or <b class="variable">SSL_CERT_FILE</b> environment variables or the
<b class="option">-cadir</b> or <b class="option">-cafile</b> options to the CA cert file's install
location. It is your responsibility to keep this file up to date.</p></li>
</ul>
</div>
</div>
<div id="section5" class="doctools_section"><h2><a name="section5">Callback Options</a></h2>
<p>As previously described, each channel can be given their own callbacks
to handle intermediate processing by the OpenSSL library, using the
<b class="option">-command</b>, <b class="option">-password</b>, and <b class="option">-validate_command</b> options
passed to either of <b class="cmd">tls::socket</b> or <b class="cmd">tls::import</b>.
Unlike previous versions of TclTLS, only if the callback generates an error,
will the <b class="syscmd">bgerror</b> command be invoked with the error information.</p>
<div id="subsection4" class="doctools_subsection"><h3><a name="subsection4">Values for Command Callback</a></h3>

attempting to call <b class="cmd">tls::password</b>. The difference between these two
behaviors is a consequence of maintaining compatibility with earlier
implementations.</p>
<p><em>The use of the reference callbacks <b class="cmd">tls::callback</b>, <b class="cmd">tls::password</b>,
and <b class="cmd">tls::validate_command</b> is not recommended. They may be removed from future releases.</em></p>
</div>
</div>
<div id="section6" class="doctools_section"><h2><a name="section6">Debug</a></h2>
<p>For most debugging needs, the <b class="option">-callback</b> option can be used to provide
sufficient insight and information on the TLS handshake and progress. If
further troubleshooting insight is needed, the compile time option
<b class="option">--enable-debug</b> can be used to get detailed execution flow status.</p>
<p>TLS key logging can be enabled by setting the environment variable
<b class="variable">SSLKEYLOGFILE</b> to the name of the file to log to. Then whenever TLS key
material is generated or received it will be logged to the file. This is useful
for logging key data for network logging tools to use to decrypt the data.</p>
<p>The <b class="variable">tls::debug</b> variable provides some additional control over the
debug logging in the <b class="cmd">tls::callback</b>, <b class="cmd">tls::password</b>, and
<b class="cmd">tls::validate_command</b> default handlers in &quot;<b class="file">tls.tcl</b>&quot;.
The default value is 0 with higher values producing more diagnostic output,
and will also force the verify method in <b class="cmd">tls::callback</b> to accept the
certificate, even if it is invalid when the <b class="option">-validatecommand</b>
option is set to <b class="cmd">tls::validate_command</b>.</p>
<p><em>The use of the variable <b class="variable">tls::debug</b> is not recommended.
It may be removed from future releases.</em></p>
</div>
<div id="section7" class="doctools_section"><h2><a name="section7">Examples</a></h2>
<p>The following are example scripts to download a webpage and file using the
http package. See <span class="sectref"><a href="#section4">Certificate Validation</a></span> for when the
<b class="option">-cadir</b>, <b class="option">-cafile</b>, and <b class="option">-castore</b> options are also
needed. See the &quot;<b class="file">demos</b>&quot; directory for more example scripts.</p>
<p>Example #1: Download a web page</p>
<pre class="doctools_example">
package require http
package require tls
set url &quot;https://www.tcl.tk/&quot;

    puts [format "Error %s" [http::status $token]]
}
# Cleanup
close $ch
::http::cleanup $token
</pre>
</div>
<div id="section8" class="doctools_section"><h2><a name="section8">Special Considerations</a></h2>
<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
older protocol versions, add or remove ciphers, change default values, etc.
Use the <b class="cmd">tls::protocols</b> commands to obtain the supported
protocol versions.</p>
</div>
<div id="see-also" class="doctools_section"><h2><a name="see-also">See Also</a></h2>

using the Transport Layer Security (TLS) protocol. It provides a generic
binding to [uri "https://www.openssl.org/" OpenSSL], utilizing the
[syscmd Tcl_StackChannel] API in TCL 8.4 and higher.
These sockets behave exactly the same as channels created using the built-in
[syscmd socket] command, but provide additional options for controlling
the SSL/TLS session.

[section Compatibility]
This extension is compatible with OpenSSL 1.1.1 or later. It requires Tcl
version 8.5 or later and will work with Tcl 9.0.

[section Commands]

The following are the commands provided by the TcLTLS package. See the
[sectref Examples] for example usage and the [file demos] directory for
more example usage.

[list_begin definitions]

This extension provides TCL script access to secure socket communications
using the Transport Layer Security (TLS) protocol\&. It provides a generic
binding to \fIOpenSSL\fR [https://www\&.openssl\&.org/], utilizing the
\fBTcl_StackChannel\fR API in TCL 8\&.4 and higher\&.
These sockets behave exactly the same as channels created using the built-in
\fBsocket\fR command, but provide additional options for controlling
the SSL/TLS session\&.
.SH COMPATIBILITY
This extension is compatible with OpenSSL 1\&.1\&.1 or later\&. It requires Tcl
version 8\&.5 or later and will work with Tcl 9\&.0\&.
.SH COMMANDS
The following are the commands provided by the TcLTLS package\&. See the
\fBExamples\fR for example usage and the "\fIdemos\fR" directory for
more example usage\&.
.TP
\fBtls::init\fR ?\fI-option\fR? ?\fIvalue\fR? ?\fI-option value \&.\&.\&.\fR?
Optional function to set the default options used by \fBtls::socket\fR\&. If you