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<?xml version="1.0" ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>SSL_CTX_set_record_padding_callback</title> <meta http-equiv="content-type" content="text/html; charset=utf-8" /> <link rev="made" href="mailto:root@hsxx.drive.ne.jp" /> </head> <body style="background-color: white"> <!-- INDEX BEGIN --> <div name="index"> <p><a name="__index__"></a></p> <ul> <li><a href="#name">NAME</a></li> <li><a href="#synopsis">SYNOPSIS</a></li> <li><a href="#description">DESCRIPTION</a></li> <li><a href="#return_values">RETURN VALUES</a></li> <li><a href="#notes">NOTES</a></li> <li><a href="#see_also">SEE ALSO</a></li> <li><a href="#history">HISTORY</a></li> <li><a href="#copyright">COPYRIGHT</a></li> </ul> <hr name="index" /> </div> <!-- INDEX END --> <p> </p> <hr /> <h1><a name="name">NAME</a></h1> <p>SSL_CTX_set_record_padding_callback, SSL_set_record_padding_callback, SSL_CTX_set_record_padding_callback_arg, SSL_set_record_padding_callback_arg, SSL_CTX_get_record_padding_callback_arg, SSL_get_record_padding_callback_arg, SSL_CTX_set_block_padding, SSL_set_block_padding - install callback to specify TLS 1.3 record padding</p> <p> </p> <hr /> <h1><a name="synopsis">SYNOPSIS</a></h1> <pre> #include <openssl/ssl.h></pre> <pre> void SSL_CTX_set_record_padding_callback(SSL_CTX *ctx, size_t (*cb)(SSL *s, int type, size_t len, void *arg)); void SSL_set_record_padding_callback(SSL *ssl, size_t (*cb)(SSL *s, int type, size_t len, void *arg));</pre> <pre> void SSL_CTX_set_record_padding_callback_arg(SSL_CTX *ctx, void *arg); void *SSL_CTX_get_record_padding_callback_arg(const SSL_CTX *ctx);</pre> <pre> void SSL_set_record_padding_callback_arg(SSL *ssl, void *arg); void *SSL_get_record_padding_callback_arg(const SSL *ssl);</pre> <pre> int SSL_CTX_set_block_padding(SSL_CTX *ctx, size_t block_size); int SSL_set_block_padding(SSL *ssl, size_t block_size);</pre> <p> </p> <hr /> <h1><a name="description">DESCRIPTION</a></h1> <p><code>SSL_CTX_set_record_padding_callback()</code> or <code>SSL_set_record_padding_callback()</code> can be used to assign a callback function <em>cb</em> to specify the padding for TLS 1.3 records. The value set in <strong>ctx</strong> is copied to a new SSL by <code>SSL_new()</code>.</p> <p><code>SSL_CTX_set_record_padding_callback_arg()</code> and <code>SSL_set_record_padding_callback_arg()</code> assign a value <strong>arg</strong> that is passed to the callback when it is invoked. The value set in <strong>ctx</strong> is copied to a new SSL by <code>SSL_new()</code>.</p> <p><code>SSL_CTX_get_record_padding_callback_arg()</code> and <code>SSL_get_record_padding_callback_arg()</code> retrieve the <strong>arg</strong> value that is passed to the callback.</p> <p><code>SSL_CTX_set_block_padding()</code> and <code>SSL_set_block_padding()</code> pads the record to a multiple of the <strong>block_size</strong>. A <strong>block_size</strong> of 0 or 1 disables block padding. The limit of <strong>block_size</strong> is SSL3_RT_MAX_PLAIN_LENGTH.</p> <p>The callback is invoked for every record before encryption. The <strong>type</strong> parameter is the TLS record type that is being processed; may be one of SSL3_RT_APPLICATION_DATA, SSL3_RT_HANDSHAKE, or SSL3_RT_ALERT. The <strong>len</strong> parameter is the current plaintext length of the record before encryption. The <strong>arg</strong> parameter is the value set via <code>SSL_CTX_set_record_padding_callback_arg()</code> or <code>SSL_set_record_padding_callback_arg()</code>.</p> <p> </p> <hr /> <h1><a name="return_values">RETURN VALUES</a></h1> <p>The <code>SSL_CTX_get_record_padding_callback_arg()</code> and <code>SSL_get_record_padding_callback_arg()</code> functions return the <strong>arg</strong> value assigned in the corresponding set functions.</p> <p>The <code>SSL_CTX_set_block_padding()</code> and <code>SSL_set_block_padding()</code> functions return 1 on success or 0 if <strong>block_size</strong> is too large.</p> <p>The <strong>cb</strong> returns the number of padding bytes to add to the record. A return of 0 indicates no padding will be added. A return value that causes the record to exceed the maximum record size (SSL3_RT_MAX_PLAIN_LENGTH) will pad out to the maximum record size.</p> <p> </p> <hr /> <h1><a name="notes">NOTES</a></h1> <p>The default behavior is to add no padding to the record.</p> <p>A user-supplied padding callback function will override the behavior set by <code>SSL_set_block_padding()</code> or <code>SSL_CTX_set_block_padding()</code>. Setting the user-supplied callback to NULL will restore the configured block padding behavior.</p> <p>These functions only apply to TLS 1.3 records being written.</p> <p>Padding bytes are not added in constant-time.</p> <p> </p> <hr /> <h1><a name="see_also">SEE ALSO</a></h1> <p><em>ssl(7)</em>, <em>SSL_new(3)</em></p> <p> </p> <hr /> <h1><a name="history">HISTORY</a></h1> <p>The record padding API was added for TLS 1.3 support in OpenSSL 1.1.1.</p> <p> </p> <hr /> <h1><a name="copyright">COPYRIGHT</a></h1> <p>Copyright 2017-2019 The OpenSSL Project Authors. All Rights Reserved.</p> <p>Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.</p> </body> </html>