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<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Copyright" content="1999 Matt Newman / 2004 Starfish Systems">
<title>TLS (SSL) TCL Commands</title>
<link rel="stylesheet" href="docs.css" type="text/css" media="all">
</head>
<body class="vsc-initialized">
<h2>Tcl Tls Extension Documentation</h2>
<h2>TCL Tls Extension Documentation</h2>
<dl>
<dd><a href="#NAME">NAME</a>
<dl>
<dd><b>tls</b> - binding to <b>OpenSSL</b> library
for socket and I/O channel communications.</dd>
for encrypted 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>?<b>8.5</b>?</em></dd>
<dd><b>package require tls</b></dd>
<dt> </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> </dt>
<dd><b>tls::protocols</b></dd>
<dd><b>tls::version</b></dd>
</dl>
<dd><b>package require Tcl</b> <em>?<b>8.5-</b>?</em></dd>
<dd><b>package require tls</b> <em>?<b>1.8-</b>?</em></dd>
<dt> </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> </dt>
<dd><b>tls::protocols</b></dd>
<dd><b>tls::version</b></dd>
</dl></dd>
</dd>
for socket and I/O channel communications.</p>
for encrypted socket and I/O channel communications.</p>
<hr>
<h3><a name="SYNOPSIS">SYNOPSIS</a></h3>
<p><b>package require Tcl</b> <em>?<b>8.5</b>?</em><br>
<b>package require tls</b><br>
<p><b>package require Tcl</b> <em>?<b>8.5-</b>?</em><br>
<b>package require tls</b> <em>?<b>1.8-</b>?</em><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>
<hr>
<h3><a name="DESCRIPTION">DESCRIPTION</a></h3>
<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.
binding to <a href="https://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.
the SSL/TLS session.
</p>
<hr>
<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>
which provides compatibility with the native TCL <strong>socket</strong>
command. In such cases <strong>tls::import</strong> should not be
used directly.</p>
directly this routine has no effect. Any of the options
that <strong>tls::socket</strong> accepts can be set
directly, this command has no effect. This command supports all of the
same options as the <strong>tls::socket</strong> command, though you
using this command, though you should limit your options
to only TLS related ones.</dd>
<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>
<dd>This is a helper function that utilizes the underlying commands
(<strong>socket</strong> and <strong>tls::import</strong>) to create
the connection. It behaves the same as the native TCL <strong>socket</strong>
command except the options can also include any of the
applicable <a href="#tls::import"><strong>tls:import</strong></a>
options with one additional option:</dd>
<blockquote>
<dl>
argument (default is <em>false</em>).</dd>
argument (default is <em>false</em>).</dd>
</dl>
</blockquote>
<dd>Add SSL/TLS encryption to a regular Tcl channel. It need
<dd>Add SSL/TLS encryption to a regular TCL channel. It need
not be a socket, but must provide bi-directional flow. Also
set session parameters for SSL handshake.</dd>
<dl>
<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>
certificates are stored. The default 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>
<dd>Specifies the file with the Certificate Authority (CA) certificates
to use. The default is <b>cert.pem</b>, in the OpenSSL 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>Specifies the file with the certificate to use in PEM format.
This also contains the public key.</dd>
<dt><strong>-cert</strong> <em>binary_string</em></dt>
<dd>Specify the contents of a certificate to use, as a DER
encoded binary value (X.509 DER).</dd>
<dd>List of ciphers to use. String is a colon (":") separated list
of ciphers. Ciphers can be combined
using the <b>+</b> character. Prefixes can be used to permanently
remove ("!"), delete ("-"), or move a cypher to the end of
<dd>Specifies the list of ciphers to use for TLS 1.2 and earlier. String is a
colon (":") separated list of ciphers. Ciphers can be combined using the
<b>+</b> character. Prefixes can be used to permanently remove ("!"),
delete ("-"), or move a cipher to the end of the list ("+"). Keywords
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>
<dd>List of cipher suites to use. String is a colon (":")
separated list of cipher suite names. (TLS 1.3 only)</dd>
<dd>Specifies the list of cipher suites to use for TLS 1.3. String is a colon
(":") separated list of cipher suite names.</dd>
<dt><strong>-command</strong> <em>callback</em></dt>
<dd>Callback command to invoke at several points during the handshake.
This is used to pass errors and tracing information, and
<dd>Specifies the callback command to be invoked at several points during the
handshake to pass errors, tracing information, and protocol messages.
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>
<dd>Specify the Diffie-Hellman parameters file.</dd>
<dd>Specifies the Diffie-Hellman (DH) parameters file.</dd>
<dt><strong>-keyfile</strong> <em>filename</em></dt>
<dd>Specify the private key file. (default is
<dd>Specifies the private key file. (default is value of -certfile).</dd>
value of -certfile)</dd>
<dd>Specify the private key to use as a DER encoded value (PKCS#1 DER)</dd>
<dd>Specifies the private key to use as a DER encoded string (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 command to invoke when OpenSSL needs to obtain a password.
Typically used 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>
<dd>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.
See <a href="#CALLBACK OPTIONS">CALLBACK OPTIONS</a> for more info.</dd>
for further discussion.</dd>
<dd>Allow post-handshake ticket updates.</dd>
<dd>Allow post-handshake session 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>
<dd>Request a certificate from peer during the SSL handshake. This is
needed to do certificate validation. (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 and a either a -cadir, -cafile, or platform
<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
and a either a -cadir, -cafile, or platform default must be provided in
default must be provided in order to validate against.
(default is <em>false</em>)</dd>
<dd>Set security level. Must be 0 to 5. The security level affects
the 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>
<dd>Specifies the security level (value from 0 to 5). The security level
affects the 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>Set to act as a server and respond with a server handshake when
a client connects and provides a client handshake.
<dd>Specifies whether to act as a server and respond with a server
handshake when a client connects and provides a client handshake.
(default is <em>false</em>)</dd>
<dt><strong>-servername</strong> <em>host</em></dt>
<dd>Specify server's hostname. Used to set the TLS 'Server Name
Indication' (SNI) extension. Set to the expected servername
in the server's certificate or one of the subjectAltName
<dd>Specify server's hostname. This is used to set the TLS Server Name
Indication (SNI) extension. Set this to the expected servername in the
server's certificate or one of the subjectAltName alternates.</dd>
alternates.</dd>
<dd>Session id to resume session.</dd>
<dd>Specifies the 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 command to invoke to verify or validate protocol config
parameters during the protocol negotiation phase. See
<a href="#CALLBACK OPTIONS">CALLBACK OPTIONS</a>
<dd>Specifies the callback command to invoke to validate protocol
config parameters 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
<a href="#CALLBACK OPTIONS">CALLBACK OPTIONS</a> for more info.</dd>
for further discussion.</dd>
</dl>
</blockquote>
unstacks the encryption of a regular Tcl channel. An error
is thrown if TLS is not the top stacked channel type.</dd>
<em>?</em><b>-local</b><em>? channel</em></a></dt>
<blockquote>
<b>SSL Status</b>
<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 for the channel.</dd>
<dd>The current cipher in use for the session.</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>
|
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<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>
</blockquote>
<dt><a name="tls::protocols"><strong>tls::protocols</strong></a></dt>
<dd>Returns a list of the supported protocols. Valid values are:
<dd>Returns a list of the supported SSL/TLS 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> </dt>
<dt><a name="tls::version"><strong>tls::version</strong></a></dt>
<dd>Returns the OpenSSL version string.</dd>
</dl>
<hr>
<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 will be
invoked with the error information.
</p>
<blockquote>
<br>
<br>
<dl>
<strong>error</strong> <em>channelId message</em>
<strong>error</strong> <em>channelId message</em>
</dt>
<dd>
This form of callback is invoked whenever an error occurs during the
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.
This form of callback is invoked whenever an error occurs during the
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>
<strong>info</strong> <em>channelId 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_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>
This form of callback is invoked by the OpenSSL function
<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>
<strong>message</strong> <em>channelId direction version content_type message</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.
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.
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.
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>
<strong>session</strong> <em>channelId 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> 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.
This form of callback is invoked by the OpenSSL function
<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>
<br>
</dl>
<br>
<dl>
<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>
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>
<br>
</dl>
<br>
<dl>
<br>
<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> 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>
<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
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>
<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>
<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 the integer depth of the
certificate in the certificate chain, where 0 is 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 the boolean validity of the
current certificate where 0 is invalid and 1 is valid.</li>
<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>
</blockquote>
and <strong>tls::validate_command</strong> respectively. Note that these are
<em>sample</em> implementations only. In a more realistic deployment
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.
<strong>-command</strong>, <strong>-password</strong>, and
<strong>-validate_command</strong> options.
</p>
is not recommended. They may be removed from future releases.
is not recommended. They may be removed from future releases.
</em>
</p>
<hr>
<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.
control over these reference callbacks. Its value is zero by default.
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 if the <b>tls::validate_command</b>
callback is used for the <b>-validatecommand</b> option.
</p>
Example #1: Use HTTP package
<p>Example #1: Use HTTP package</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 \
-command ::tls::callback -password ::tls::password -validatecommand ::tls::validate_command]
|