<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>
	    <dd><b>tls::connection </b> <em>channel</em></dd>
	    <dd><b>tls::import</b> <em>channel ?options?</em></dd>
	    <dd><b>tls::unimport</b> <em>channel</em></dd>
	    <dt>&nbsp;</dt>
	    <dd><b>tls::cipher</b> <em>name</em></dd>
	    <dd><b>tls::ciphers</b> <em>?protocol? ?verbose? ?supported?</em></dd>
	    <dd><b>tls::digests</b> <em>?name?</em></dd>
	    <dd><b>tls::macs</b></dd>
	    <dd><b>tls::protocols</b></dd>
	    <dd><b>tls::version</b></dd>
	    <dt>&nbsp;</dt>
	    <dd><b>tls::digest</b> <b>-digest</b> <em>name ?options?</em></dd>
	    <dd><b>tls::cmac</b> <b>-cipher</b> <em>name</em> <b>-key</b> <em>key ?options?</em></dd>
	    <dd><b>tls::hmac</b> <b>-digest</b> <em>name</em> <b>-key</b> <em>key ?options?</em></dd>
	    <dd><b>tls::md4</b> <em>data</em></dd>
	    <dd><b>tls::md5</b> <em>data</em></dd>
	    <dd><b>tls::sha1</b> <em>data</em></dd>
	    <dd><b>tls::sha256</b> <em>data</em></dd>
	    <dd><b>tls::sha512</b> <em>data</em></dd>
	</dl>
    </dd>
    <dd><a href="#COMMANDS">COMMANDS</a></dd>
    <dd><a href="#CALLBACK OPTIONS">CALLBACK 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 Tcl 8.5</b><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::cipher"><b>tls::cipher</b> <i>name</i></a><br>
<a href="#tls::ciphers"><b>tls::ciphers</b> <i>?protocol? ?verbose? ?supported?</i></a><br>
<a href="#tls::digests"><b>tls::digests</b> <i>?name?</i></a><br>
<a href="#tls::macs"><b>tls::macs</b></a><br>
<a href="#tls::protocols"><b>tls::protocols</b></a><br>
<a href="#tls::version"><b>tls::version</b></a><br>
<br>
<a href="#tls::digest"><b>tls::digest</b> <b>-digest</b> <i>name ?options?</i></a><br>
<a href="#tls::cmac"><b>tls::cmac</b> <b>-cipher</b> <i>name</i> <b>-key</b> <i>key ?options?</i></a><br>
<a href="#tls::hmac"><b>tls::hmac</b> <b>-digest</b> <i>name</i> <b>-key</b> <i>key ?options?</i></a><br>
<a href="#tls::md4"><b>tls::md4</b> <i>data</i></a><br>
<a href="#tls::md5"><b>tls::md5</b> <i>data</i></a><br>
<a href="#tls::sha1"><b>tls::sha1</b> <i>data</i></a><br>
<a href="#tls::sha256"><b>tls::sha256</b> <i>data</i></a><br>
<a href="#tls::sha512"><b>tls::sha512</b> <i>data</i></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>

	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 with one additional option:</dd>
<blockquote>
    <dl>
	<dt><strong>-autoservername</strong> <em>bool</em></dt>
	<dd>Automatically send the -servername as the <em>host</em> argument
	    (default is <em>false</em>)</dd>
    </dl>
</blockquote>

	<dt><strong>-request </strong><em>bool</em></dt>
	<dd>Request a certificate from peer during SSL handshake.
	    (default is <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. (default is <em>false</em>)</dd>
	<dt><strong>-security_level</strong> <em>integer</em></dt>
	<dd>Set security level. Must be 0 to 5. The security level affects
	    cipher suite encryption algorithms, supported ECC curves,
	    supported signature algorithms, DH parameter sizes, certificate
	    key sizes and signature algorithms. The default is 1.
	    Level 3 and higher disable support for session tickets and only
	    accept cipher suites that provide forward secrecy.</dd>
	<dt><strong>-server</strong> <em>bool</em></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>&nbsp;</dt>
    <dt><a name="tls::status"><strong>tls::status</strong>
    <em>?</em><b>-local</b><em>? channel</em></a></dt>
    <dd>Returns the current status of the certificate for an SSL
	channel. The result is a list of key-value pairs describing

	the certificate. If the SSL handshake has not yet completed,
	an empty list is returned. If <b>-local</b> is
	specified, then the local certificate is used.</dd>
<blockquote>
	<b>SSL Status</b>
    <dl>
	<dt><strong>alpn</strong> <em>protocol</em></dt>
	<dd>The protocol selected after Application-Layer Protocol
	    Negotiation (ALPN).</dd>

	<dt><strong>state</strong> <em>state</em></dt>
	<dd>State of the connection.</dd>
	<dt><strong>servername</strong> <em>name</em></dt>
	<dd>The name of the connected to server.</dd>
	<dt><strong>protocol</strong> <em>version</em></dt>
	<dd>The protocol version used for the connection:
	    SSL2, SSL3, TLS1, TLS1.1, TLS1.2, TLS1.3, or unknown.</dd>
	<dt><strong>renegotiation_allowed</strong> <em>boolean</em></dt>
	<dd>Whether protocol renegotiation is supported or not.</dd>
	<dt><strong>security_level</strong> <em>level</em></dt>
	<dd>The security level used for selection of ciphers, key size, etc.</dd>
	<dt><strong>session_reused</strong> <em>boolean</em></dt>
	<dd>Whether the session has been reused or not.</dd>
	<dt><strong>is_server</strong> <em>boolean</em></dt>
	<dd>Whether the connection is configured as a server (1) or client (0).</dd>
	<dt><strong>compression</strong> <em>mode</em></dt>
	<dd>Compression method.</dd>
	<dt><strong>expansion</strong> <em>mode</em></dt>
	<dd>Expansion method.</dd>
	<dt><strong>caList</strong> <em>list</em></dt>
	<dd>List of Certificate Authorities (CA) for X.509 certificate.</dd>
    </dl>
</blockquote>
<blockquote>
	<b>Cipher Info</b>
    <dl>
	<dt><strong>cipher</strong> <em>cipher</em></dt>
	<dd>The current cipher in use for the connection.</dd>
	<dt><strong>standard_name</strong> <em>name</em></dt>
	<dd>The standard RFC name of cipher.</dd>
	<dt><strong>algorithm_bits</strong> <em>n</em></dt>
	<dd>The number of processed bits used for cipher.</dd>
	<dt><strong>secret_bits</strong> <em>n</em></dt>
	<dd>The number of secret bits used for cipher.</dd>
	<dt><strong>min_version</strong> <em>version</em></dt>
	<dd>The minimum protocol version for cipher.</dd>
	<dt><strong>cipher_is_aead</strong> <em>boolean</em></dt>
	<dd>Whether the cipher is Authenticated encryption with associated
	data (AEAD).</dd>
	<dt><strong>cipher_id</strong> <em>id</em></dt>
	<dd>The OpenSSL cipher id.</dd>
	<dt><strong>description</strong> <em>string</em></dt>
	<dd>A text description of the cipher.</dd>
	<dt><strong>handshake_digest</strong> <em>boolean</em></dt>
	<dd>Digest used during handshake.</dd>
    </dl>
</blockquote>
<blockquote>
	<b>Session Info</b>
    <dl>
	<dt><strong>alpn</strong> <em>protocol</em></dt>
	<dd>The protocol selected after Application-Layer Protocol

	<dd>Unique session ticket application data.</dd>
	<dt><strong>master_key</strong> <em>binary_string</em></dt>
	<dd>Unique session master key.</dd>
	<dt><strong>session_cache_mode</strong> <em>mode</em></dt>
	<dd>Server cache mode (client, server, or both).</dd>
    </dl>
</blockquote>

    <dt><a name="tls::cipher"><strong>tls::cipher</strong> <em>name</em></a></dt>
    <dd>Return a list of property names and values describing cipher
	<i>name</i>. Properties include name, description, block_size,
	key_length, iv_length, type, and mode list.</dd>

    <dt><a name="tls::ciphers"><strong>tls::ciphers</strong>
    <em>?protocol? ?verbose? ?supported?</em></a></dt>
    <dd>Without any args, returns a list of all ciphers. With <em>protocol</em>,
	only the ciphers supported for that protocol are returned. See
	<b>tls::protocols</b> command for the supported protocols. If

	<em>verbose</em> is specified as true then a verbose, human readable
	list is returned with additional information on the cipher. If
	<em>supported</em> is specified as true, then only the ciphers
	supported for protocol will be listed.</dd>

    <dt><a name="tls::digests"><strong>tls::digests</strong> <em>?name?</em></a></dt>
    <dd>Without <em>name</em>, returns a list of the supported hash algorithms
	for <b>tls::digest</b> command. With <em>name</em>, returns a list of
	property names and values describing digest <i>name</i>. Properties
	include name, description, size, block_size, type, and flags list.</dd>

    <dt><a name="tls::macs"><strong>tls::macs</strong></a></dt>
    <dd>Returns a list of the available Message Authentication Codes (MAC) for
	the <b>tls::digest</b> command.</dd>

    <dt><a name="tls::protocols"><strong>tls::protocols</strong></a></dt>
    <dd>Returns a list of supported protocols. Valid values are:
	<b>ssl2</b>, <b>ssl3</b>, <b>tls1</b>, <b>tls1.1</b>, <b>tls1.2</b>,
	and <b>tls1.3</b>. Exact list depends on OpenSSL version and
	compile time flags.</dd>

    <dt><a name="tls::version"><strong>tls::version</strong></a></dt>
    <dd>Returns the OpenSSL version string.</dd>

    <br>
    <dt><a name="tls::digest"><strong>tls::digest</strong> <b>-digest</b>
	<em>name ?</em><b>-bin</b>|<b>-hex</b><em>? [</em><b>-file</b> <em>filename | </em><b>-command</b> <em>cmdName |
	</em><b>-chan</b> <em>channelId | </em><b>-data</b> <em>data]</em></a></dt>
    <dd>Calculate the message digest (MD) of data using <em>name</em> hash
	function and return the resulting hash value as a hex string (default)
	or as a binary value with <b>-bin</b> or <b>-binary</b> option. MDs
	are used to ensure the integrity of data. The hash function can be any
	supported OpenSSL algorithm such as <b>md4</b>, <b>md5</b>, <b>sha1</b>,
	<b>sha256</b>, <b>sha512</b>, <b>sha3-256</b>, etc. See
	<b>tls::digests</b> command for a full list. In OpenSSL 3.0+, older
	algorithms may reside in the legacy provider.
	<br>
	Using the <b>-data</b> option will immediately return the message
	digest for <em>data</em> in the specified format. Example code:
<blockquote><code>
		set md [::tls::digest sha256 "Some example data."]<br>
</code></blockquote>
	Using the <b>-file</b> or <b>-filename</b> option will open file
	<em>filename</em>, read the file data, close the file, and return the
	message digest in the specified format. This uses the TCL APIs, so VFS
	files are supported. Example code:
<blockquote><code>
		set md [::tls::digest -digest sha256 -file test_file.txt]<br>
</code></blockquote>
	Using the <b>-chan</b> or <b>-channel</b> option, a stacked channel is
	created for <em>channelId</em> and data read from the channel is used
	to calculate a message digest with the result returned with the last
	read operation before EOF. Channel is automatically set to binary mode.
	Example code:
<blockquote><code>
		set ch [open test_file.txt r]<br>
		::tls::digest -digest sha256 -chan $ch<br>
		while {![eof $ch]} {set md [read $ch 4096]}<br>
		close $ch
</code></blockquote>
	Using the <b>-command</b> option, a new command <em>cmdName</em> is
	created and returned. To add data to the hash function, call
	&quot;<em>cmdName</em> <b>update</b> <em>data</em>&quot;, where data is
	the data to add. When done, call &quot;<em>cmdName</em> <b>finalize</b>&quot;
	to return the message digest. Example code:
<blockquote><code>
		set cmd [::tls::digest -digest sha256 -command ::tls::temp]<br>
		$cmd update "Some data. "<br>
		$cmd update "More data."<br>
		set md [$cmd finalize]
</code></blockquote>
	</dd>

    <dt><a name="tls::cmac"><strong>tls::cmac</strong> <b>-cipher</b> <em>name</em>
	<b>-key</b> <em>key ?</em><b>-bin</b>|<b>-hex</b><em>? [</em><b>-file</b> <em>filename | </em><b>-command</b> <em>cmdName |
	</em><b>-chan</b> <em>channelId | </em><b>-data</b> <em>data]</em></a></dt>
    <dd>Calculate the Cipher-based Message Authentication Code (CMAC). MACs
	are used to ensure authenticity and the integrity of data. It uses the
	same options as <b>tls::digest</b>, plus the additional option
	<b>-cipher</b> to specify the cipher to use and for certain ciphers,
	<b>-key</b> to specify the key.</dd>

    <dt><a name="tls::hmac"><strong>tls::hmac</strong> <b>-digest</b> <em>name</em>
	<b>-key</b> <em>key ?</em><b>-bin</b>|<b>-hex</b><em>? [</em><b>-file</b> <em>filename | </em><b>-command</b> <em>cmdName |
	</em><b>-chan</b> <em>channelId | </em><b>-data</b> <em>data]</em></a></dt>
    <dd>Calculate the Hash-based Message Authentication Code (HMAC). HMACs are
	used to ensure the data integrity and authenticity of a message using a
	shared secret key. The cryptographic strength depends upon the size of
	the key and the security of the hash function used. It uses the same
	options as <b>tls::digest</b>, plus additional option <b>-key</b> to
	specify the key to use. To salt a password, append or prepend the salt
	data to the password.</dd>

    <dt><a name="tls::md4"><strong>tls::md4</strong> <em>data</em></a></dt>
    <dd>Returns the MD4 message-digest for <em>data</em> as a hex string.</dd>

    <dt><a name="tls::md5"><strong>tls::md5</strong> <em>data</em></a></dt>
    <dd>Returns the MD5 message-digest for <em>data</em> as a hex string.</dd>

    <dt><a name="tls::sha1"><strong>tls::sha1</strong> <em>data</em></a></dt>
    <dd>Returns the SHA1 secure hash algorithm digest for <em>data</em> as a hex string.</dd>

    <dt><a name="tls::sha256"><strong>tls::sha256</strong> <em>data</em></a></dt>
    <dd>Returns the SHA-2 SHA256 secure hash algorithm digest for <em>data</em> as a hex string.</dd>

    <dt><a name="tls::sha512"><strong>tls::sha512</strong> <em>data</em></a></dt>
    <dd>Returns the SHA-2 SHA512 secure hash algorithm digest for <em>data</em> as a hex string.</dd>
</dl>

<h3><a name="CALLBACK OPTIONS">CALLBACK OPTIONS</a></h3>

<p>
As indicated above, individual channels can be given their own callbacks
to handle intermediate processing by the OpenSSL library, using the