tls.html at [92ad9d0c97]
EuroTcl/OpenACS 11 - 12 JULY 2024, VIENNA

File doc/tls.html artifact 5d085814d9 part of check-in 92ad9d0c97


<!doctype html public "-//W3C//DTD HTML 4.0 Transitional//EN">

<html>

<head>
<meta http-equiv="Content-Type"
content="text/html; charset=iso-8859-1">
<meta name="Copyright" content="1999 Matt Newman / 2004 Starfish Systems">
<title>TLS (SSL) Tcl Commands</title>
</head>

<body bgcolor="#FFFFFF">

<dl>
    <dd><a href="#NAME">NAME</a>
    <dl>
	<dd><b>tls</b> - binding to <b>OpenSSL</b> toolkit.</dd>
    </dl>
    </dd>
    <dd><a href="#SYNOPSIS">SYNOPSIS</a> </dd>
    <dd><dl>
	    <dd><b>package require Tcl</b> <em>?8.4?</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>
	    <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::ciphers</b> <em>?protocol? ?verbose? ?supported?</em></dd>
	    <dd><b>tls::protocols</b></dd>
	    <dd><b>tls::version</b></dd>
	    <dt>&nbsp;</dt>
	    <dd><b>tls::digest</b> <em>type ?-bin|-hex? ?-key hmac_key? [-file filename | -chan channel | ?-data? data]</em></dd>
	    <dd><b>tls::digests</b></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>
	</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::ciphers"><b>tls::ciphers</b> <i>?protocol? ?verbose? ?supported?</i></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> <i>type ?-bin|-hex? ?-key hmac_key? [-file filename | -chan channel | ?-data? data]</i></a><br>
<a href="#tls::digests"><b>tls::digests</b></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>
</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>

<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>Optional function to set the default options used by
	<strong>tls::socket</strong>. 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>&nbsp;</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 with one additional option:
<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><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>

<blockquote>
    <dl>
	<dt><strong>-alpn</strong> <em>list</em></dt>
	<dd>List of protocols to offer during Application-Layer
	    Protocol Negotiation (ALPN). For example: <em>h2</em> and
	    <em>http/1.1</em>, but not <em>h3</em> or <em>quic</em>.</dd>
	<dt><strong>-cadir</strong> <em>dir</em></dt>
	<dd>Set the CA certificates path. The default directory is platform
	    specific and can be set at compile time. This can be overridden
	    via the <b>SSL_CERT_DIR</b> environment variable.</dd>
	<dt><strong>-cafile </strong><em>filename</em></dt>
	<dd>Set the certificate authority (CA) certificates file. The default
	    is the cert.pem file in the OpsnSSL directory. This can also be
	    overridden via the <b>SSL_CERT_FILE</b> environment variable.</dd>
	<dt><strong>-certfile</strong> <em>filename</em></dt>
	<dd>Specify the filename with the certificate to use.</dd>
	<dt><strong>-cert</strong> <em>filename</em></dt>
	<dd>Specify the contents of a certificate to use, as a DER
	    encoded binary value (X.509 DER).</dd>
	<dt><strong>-cipher</strong> <em>string</em></dt>
	<dd>List of ciphers to use. String is a colon (":") separated list
	    of ciphers or cipher suites. Cipher suites can be combined
	    using the <b>+</b> character. Prefixes can be used to permanently
	    remove ("!"), delete ("-"), or move a cypher to the end of
	    the list ("+"). Keywords <b>@STRENGTH</b> (sort by algorithm
	    key length), <b>@SECLEVEL=</b><i>n</i> (set security level to
	    n), and <b>DEFAULT</b> (use default cipher list, at start only)
	    can also be specified. See OpenSSL documentation for the full
	    list of valid values. (TLS 1.2 and earlier only)</dd>
	<dt><strong>-ciphersuites</strong> <em>string</em></dt>
	<dd>List of cipher suites to use. String is a colon (":")
	    separated list of cipher suite names. (TLS 1.3 only)</dd>
	<dt><strong>-command</strong> <em>callback</em></dt>
	<dd>Callback to invoke at several points during the handshake.
	    This is used to pass errors and tracing information, and
	    it can allow Tcl scripts to perform their own certificate
	    validation in place of the default validation provided by
	    OpenSSL. See <a href="#CALLBACK OPTIONS">CALLBACK OPTIONS</a>
	    for further discussion.</dd>
	<dt><strong>-dhparams </strong><em>filename</em></dt>
	<dd>Specify the Diffie-Hellman parameters file.</dd>
	<dt><strong>-keyfile</strong> <em>filename</em></dt>
	<dd>Specify the private key file. (default is
	    value of -certfile)</dd>
	<dt><strong>-key</strong> <em>filename</em></dt>
	<dd>Specify the private key to use as a DER encoded value (PKCS#1 DER)</dd>
	<dt><strong>-model</strong> <em>channel</em></dt>
	<dd>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>-password</strong> <em>callback</em></dt>
	<dd>Callback to invoke when OpenSSL needs to obtain a password,
	    typically to unlock the private key of a certificate. The
	    callback should return a string which represents the password
	    to be used. See <a href="#CALLBACK OPTIONS">CALLBACK OPTIONS</a>
	    for further discussion.</dd>
	<dt><strong>-post_handshake</strong> <em>bool</em></dt>
	<dd>Allow post-handshake ticket updates.</dd>
	<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>-securitylevel</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>
	<dd>Handshake as server if true, else handshake as
	    client. (default is <em>false</em>)</dd>
	<dt><strong>-servername</strong> <em>host</em></dt>
	<dd>Specify server hostname. Only available if the OpenSSL library
	    the package is linked against supports the TLS hostname extension
	    for 'Server Name Indication' (SNI). Use to name the logical host
	    we are talking to and expecting a certificate for.</dd>
	<dt><strong>-session_id</strong> <em>string</em></dt>
	<dd>Session id to resume session.</dd>
	<dt><strong>-ssl2</strong> <em>bool</em></dt>
	<dd>Enable use of SSL v2. (default is <em>false</em>)</dd>
	<dt><strong>-ssl3 </strong><em>bool</em></dt>
	<dd>Enable use of SSL v3. (default is <em>false</em>)</dd>
	<dt>-<strong>tls1</strong> <em>bool</em></dt>
	<dd>Enable use of TLS v1. (default is <em>true</em>)</dd>
	<dt>-<strong>tls1.1</strong> <em>bool</em></dt>
	<dd>Enable use of TLS v1.1 (default is <em>true</em>)</dd>
	<dt>-<strong>tls1.2</strong> <em>bool</em></dt>
	<dd>Enable use of TLS v1.2 (default is <em>true</em>)</dd>
	<dt>-<strong>tls1.3</strong> <em>bool</em></dt>
	<dd>Enable use of TLS v1.3 (default is <em>true</em>)</dd>
	<dt><strong>-validatecommand</strong> <em>callback</em></dt>
	<dd>Callback to invoke to verify or validate protocol config
	    parameters during the protocol negotiation phase. See
	    <a href="#CALLBACK OPTIONS">CALLBACK OPTIONS</a>
	    for further discussion.</dd>
    </dl>
</blockquote>

    <dt><a name="tls::unimport"><b>tls::unimport </b><i>channel</i></a></dt>
    <dd>Provided for symmetry to <strong>tls::import</strong>, this
      unstacks the SSL-enabling of a regular Tcl channel.  An error
      is thrown if TLS is not the top stacked channel type.</dd>
    <dt>&nbsp;</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>?-local? 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 result is an empty list then the
	SSL handshake has not yet completed. If <em>-local</em> 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>cipher</strong> <em>cipher</em></dt>
	<dd>The current cipher in use between the client and
	    server channels.</dd>
	<dt><strong>peername</strong> <em>name</em></dt>
	<dd>The peername from the certificate.</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>sbits</strong> <em>n</em></dt>
	<dd>The number of bits used for the session key.</dd>
	<dt><strong>signatureHashAlgorithm</strong> <em>algorithm</em></dt>
	<dd>The signature hash algorithm.</dd>
	<dt><strong>signatureType</strong> <em>type</em></dt>
	<dd>The signature type value.</dd>
	<dt><strong>verifyDepth</strong> <em>n</em></dt>
	<dd>Maximum depth for the certificate chain verification.
	    Default is -1, to check all.</dd>
	<dt><strong>verifyMode</strong> <em>list</em></dt>
	<dd>List of certificate verification modes.</dd>
	<dt><strong>verifyResult</strong> <em>result</em></dt>
	<dd>Certificate verification result.</dd>
	<dt><strong>ca_names</strong> <em>list</em></dt>
	<dd>List of the Certificate Authorities used to create the certificate.</dd>
    </dl>
</blockquote>
<blockquote>
	<b>Certificate Status</b>
    <dl>
	<dt><strong>all</strong> <em>string</em></dt>
	<dd>Dump of all certificate info.</dd>

	<dt><strong>version</strong> <em>value</em></dt>
	<dd>The certificate version.</dd>
	<dt><strong>serialNumber</strong> <em>n</em></dt>
	<dd>The serial number of the certificate as hex string.</dd>
	<dt><strong>signature</strong> <em>algorithm</em></dt>
	<dd>Cipher algorithm used for certificate signature.</dd>
	<dt><strong>issuer</strong> <em>dn</em></dt>
	<dd>The distinguished name (DN) of the certificate issuer.</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 expiration date for the certificate.</dd>
	<dt><strong>subject</strong> <em>dn</em></dt>
	<dd>The distinguished name (DN) of the certificate subject.
	    Fields include: Common Name (CN), Organization (O), Locality
	    or City (L), State or Province (S), and Country Name (C).</dd>
	<dt><strong>issuerUniqueID</strong> <em>string</em></dt>
	<dd>The issuer unique id.</dd>
	<dt><strong>subjectUniqueID</strong> <em>string</em></dt>
	<dd>The subject unique id.</dd>

	<dt><strong>num_extensions</strong> <em>n</em></dt>
	<dd>Number of certificate extensions.</dd>
	<dt><strong>extensions</strong> <em>list</em></dt>
	<dd>List of certificate extension names.</dd>
	<dt><strong>authorityKeyIdentifier</strong> <em>string</em></dt>
	<dd>(AKI) Key identifier of the Issuing CA certificate that signed
	    the SSL certificate as hex string. This value matches the SKI
	    value of the Intermediate CA certificate.</dd>
	<dt><strong>subjectKeyIdentifier</strong> <em>string</em></dt>
	<dd>(SKI) Hash of the public key inside the certificate as hex
	   string. Used to identify certificates that contain a particular
	   public key.</dd>
	<dt><strong>subjectAltName</strong> <em>list</em></dt>
	<dd>List of all of the alternative domain names, sub domains,
	    and IP addresses that are secured by the certificate.</dd>
	<dt><strong>ocsp</strong> <em>list</em></dt>
	<dd>List of all Online Certificate Status Protocol (OCSP) URLs.</dd>

	<dt><strong>certificate</strong> <em>cert</em></dt>
	<dd>The PEM encoded certificate.</dd>

	<dt><strong>signatureAlgorithm</strong> <em>algorithm</em></dt>
	<dd>Cipher algorithm used for certificate signature.</dd>
	<dt><strong>signatureValue</strong> <em>string</em></dt>
	<dd>Certificate signature as hex string.</dd>
	<dt><strong>signatureDigest</strong> <em>version</em></dt>
	<dd>Certificate signing digest.</dd>
	<dt><strong>publicKeyAlgorithm</strong> <em>algorithm</em></dt>
	<dd>Certificate signature public key algorithm.</dd>
	<dt><strong>publicKey</strong> <em>string</em></dt>
	<dd>Certificate signature public key as hex string.</dd>
	<dt><strong>bits</strong> <em>n</em></dt>
	<dd>Number of bits used for certificate signature key</dd>
	<dt><strong>self_signed</strong> <em>boolean</em></dt>
	<dd>Is certificate signature self signed.</dd>

	<dt><strong>sha1_hash</strong> <em>hash</em></dt>
	<dd>The SHA1 hash of the certificate as hex string.</dd>
	<dt><strong>sha256_hash</strong> <em>hash</em></dt>
	<dd>The SHA256 hash of the certificate as hex string.</dd>
    </dl>
</blockquote>

    <dt><a name="tls::connection"><strong>tls::connection</strong>
    <em>channel</em></a></dt>
    <dd>Returns the current connection status of an SSL channel. The
	result is a list of key-value pairs describing the
	connected peer.</dd>
<blockquote>
	<b>SSL Status</b>
    <dl>
	<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</strong> <em>boolean</em></dt>
	<dd>Whether protocol renegotiation is supported or not.</dd>
	<dt><strong>securitylevel</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>
    </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>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>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>
    </dl>
</blockquote>
<blockquote>
	<b>Session Info</b>
    <dl>
	<dt><strong>alpn</strong> <em>protocol</em></dt>
	<dd>The protocol selected after Application-Layer Protocol
	    Negotiation (ALPN).</dd>
	<dt><strong>resumable</strong> <em>boolean</em></dt>
	<dd>Can the session be resumed or not.</dd>
	<dt><strong>start_time</strong> <em>seconds</em></dt>
	<dd>Time since session started in seconds since epoch.</dd>
	<dt><strong>timeout</strong> <em>seconds</em></dt>
	<dd>Max duration of session in seconds before time-out.</dd>
	<dt><strong>lifetime</strong> <em>seconds</em></dt>
	<dd>Session ticket lifetime hint in seconds.</dd>
	<dt><strong>session_id</strong> <em>binary_string</em></dt>
	<dd>Unique session id for use in resuming the session.</dd>
	<dt><strong>session_ticket</strong> <em>binary_string</em></dt>
	<dd>Unique session ticket for use in resuming the session.</dd>
	<dt><strong>ticket_app_data</strong> <em>binary_string</em></dt>
	<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::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 where <em>protocol</em> must be one of <b>ssl2, ssl3,
	tls1, tls1.1, tls1.2,</b> or <b>tls1.3</b>. 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::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> <em>type ?-bin|-hex?
	?-key hmac_key? [-file filename | -chan channel | ?-data? data]</em></a></dt>
    <dd>Calculate the message digest for <em>data</em> or file <em>filename</em>
	using <em>type</em> hash algorithm. Returns value as a hex string
	(default) or as a binary value with <em>-bin</em> option. Using
	<em>-chan</em> option, a stacked channel is created and data read
	from the channel is used to calculate a message digest with the result
	returned with the last read operation before EOF. Use <em>-key</em> to
	specify the key and return a Hashed Message Authentication Code (HMAC).
	Type can be any OpenSSL supported hash algorithm including: <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.</dd>

    <dt><a name="tls::digests"><strong>tls::digests</strong></a></dt>
    <dd>Returns a list of the hash algorithms for <b>tls::digest</b> command.</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>
</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
<strong>-command</strong>, <strong>-password</strong>, and
<strong>-validate_command</strong> options passed to either of
<strong>tls::socket</strong> or <strong>tls::import</strong>.
If the callback generates an error, the <b>bgerror</b> command with be
invoked with the error information.
</p>

<blockquote>
<dl>

    <dt><strong>-command</strong> <em>callback</em></dt>
    <dd>
	Invokes the specified <em>callback</em> script at several points
	during the OpenSSL handshake and use. See below for the possible
	arguments passed to the callback script. Values returned from the
	callback are ignored.

	<br>
	<br>

	<dl>

	<dt>
	  <strong>error</strong> <em>channel message</em>
	</dt>
	<dd>
	  The <em>message</em> argument contains an error message generated
	  by the OpenSSL function <code>ERR_reason_error_string()</code>.
	</dd>

	<br>

	<dt>
	  <strong>info</strong> <em>channel 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.
	  <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>
	</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. 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.
	</dd>
	<br>

	<dt>
	  <strong>session</strong> <em>channel 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.
	</dd>
	<br>
	</dl>
    </dd>

    <br>

    <dt><strong>-password</strong> <em>callback</em></dt>
    <dd>
	Invokes the specified <em>callback</em> script when OpenSSL needs to
	obtain a password. See below for the possible arguments passed to
	the callback script. See below for valid return values.

	<br>
	<br>

	<dl>

	<dt>
	  <strong>password</strong> <em>rwflag size</em>
	</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.
	</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.
	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>
	</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.
	</dd>

	<br>

	<dt>
	  <strong>hello</strong> <em>channel servername</em>
	</dt>
	<dd>
	  For servers, this form of callback is invoked during client hello
	  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.
	</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>
	</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
	  <code>0</code> as the peer certificate 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.
	  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
	  by <code>X509_STORE_CTX_get_error()</code>.</li>
	  </ul>
	</dd>
	<br>
	</dl>
    </dd>
</dl>
</blockquote>

<p>
Reference implementations of these callbacks are provided in the
distribution as <strong>tls::callback</strong>, <strong>tls::password</strong>,
and <strong>tls::validate_command</strong> respectively.  Note that these are
<em>sample</em> implementations only.  In a more realistic deployment
you would specify your own callback scripts on each TLS channel using the
<strong>-command</strong>, <strong>-password</strong>, and <strong>-validate_command</strong> options.
</p>

<p>
The default behavior when the <strong>-command</strong> and <strong>-validate_command</strong>
options are not specified is for TLS to process the associated library callbacks
internally. The default behavior when the <strong>-password</strong> option is not
specified is for TLS to process the associated library callbacks by attempting
to call <strong>tls::password</strong>.
The difference between these two behaviors is a consequence of maintaining
compatibility with earlier implementations.
</p>

<p>
The <strong>tls::debug</strong> variable provides some additional
control over these reference callbacks.  Its value is zero by default.
Higher values produce more diagnostic output, and will also force the
verify method in <strong>tls::callback</strong> to accept the
certificate, even when it is invalid.
</p>

<p>
<em>
The use of the reference callbacks <strong>tls::callback</strong>,
<strong>tls::password</strong>, and <strong>tls::validate_command</strong>
is not recommended.  They may be removed from future releases.
</em>
</p>

<p>
<em>
The use of the variable <strong>tls::debug</strong> is not recommended.
It may be removed from future releases.
</em>
</p>

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

TLS key logging can be enabled by setting the environment variable
<b>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.

<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>

<pre><code>
package require http
package require tls

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

set tok [http::geturl https://www.tcl.tk/]
</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. New versions may obsolete older
protocol versions, add or remove ciphers, change default values, etc. Use the
<strong>tls::ciphers</strong> and <strong>tls::protocols</strong> commands to
obtain the supported versions.</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 &copy; 1999 Matt Newman.
Copyright &copy; 2004 Starfish Systems.
</pre>
</body>
</html>