diff options
Diffstat (limited to 'manual/html_node/On-Record-Padding.html')
| -rw-r--r-- | manual/html_node/On-Record-Padding.html | 209 |
1 files changed, 0 insertions, 209 deletions
diff --git a/manual/html_node/On-Record-Padding.html b/manual/html_node/On-Record-Padding.html deleted file mode 100644 index 6cbf8077fc..0000000000 --- a/manual/html_node/On-Record-Padding.html +++ /dev/null @@ -1,209 +0,0 @@ -<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> -<html> -<!-- This manual is last updated 4 March 2015 for version -3.5.4 of GnuTLS. - -Copyright (C) 2001-2015 Free Software Foundation, Inc.\\ -Copyright (C) 2001-2015 Nikos Mavrogiannopoulos - -Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.3 or -any later version published by the Free Software Foundation; with no -Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A -copy of the license is included in the section entitled "GNU Free -Documentation License". --> -<!-- Created by GNU Texinfo 6.1, http://www.gnu.org/software/texinfo/ --> -<head> -<title>GnuTLS 3.5.4: On Record Padding</title> - -<meta name="description" content="GnuTLS 3.5.4: On Record Padding"> -<meta name="keywords" content="GnuTLS 3.5.4: On Record Padding"> -<meta name="resource-type" content="document"> -<meta name="distribution" content="global"> -<meta name="Generator" content="makeinfo"> -<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> -<link href="index.html#Top" rel="start" title="Top"> -<link href="Function-and-Data-Index.html#Function-and-Data-Index" rel="index" title="Function and Data Index"> -<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> -<link href="The-TLS-record-protocol.html#The-TLS-record-protocol" rel="up" title="The TLS record protocol"> -<link href="The-TLS-Alert-Protocol.html#The-TLS-Alert-Protocol" rel="next" title="The TLS Alert Protocol"> -<link href="Weaknesses-and-countermeasures.html#Weaknesses-and-countermeasures" rel="prev" title="Weaknesses and countermeasures"> -<style type="text/css"> -<!-- -a.summary-letter {text-decoration: none} -blockquote.indentedblock {margin-right: 0em} -blockquote.smallindentedblock {margin-right: 0em; font-size: smaller} -blockquote.smallquotation {font-size: smaller} -div.display {margin-left: 3.2em} -div.example {margin-left: 3.2em} -div.lisp {margin-left: 3.2em} -div.smalldisplay {margin-left: 3.2em} -div.smallexample {margin-left: 3.2em} -div.smalllisp {margin-left: 3.2em} -kbd {font-style: oblique} -pre.display {font-family: inherit} -pre.format {font-family: inherit} -pre.menu-comment {font-family: serif} -pre.menu-preformatted {font-family: serif} -pre.smalldisplay {font-family: inherit; font-size: smaller} -pre.smallexample {font-size: smaller} -pre.smallformat {font-family: inherit; font-size: smaller} -pre.smalllisp {font-size: smaller} -span.nolinebreak {white-space: nowrap} -span.roman {font-family: initial; font-weight: normal} -span.sansserif {font-family: sans-serif; font-weight: normal} -ul.no-bullet {list-style: none} -body { - margin: 2%; - padding: 0 5%; - background: #ffffff; -} -h1,h2,h3,h4,h5 { - font-weight: bold; - padding: 5px 5px 5px 5px; - background-color: #c2e0ff; - color: #336699; -} -h1 { - padding: 2em 2em 2em 5%; - color: white; - background: #336699; - text-align: center; - letter-spacing: 3px; -} -h2 { text-decoration: underline; } -pre { - margin: 0 5%; - padding: 0.5em; -} -pre.example,pre.verbatim { - padding-bottom: 1em; - - border: solid #c2e0ff; - background: #f0faff; - border-width: 1px 1px 1px 5px; - margin: 1em auto; - width: 90%; -} - -div.node { - margin: 0 -5% 0 -2%; - padding: 0.5em 0.5em; - margin-top: 0.5em; - margin-bottom: 0.5em; - font-weight: bold; -} -dd, li { - padding-top: 0.1em; - padding-bottom: 0.1em; -} -div.float { - - margin-bottom: 0.5em; - text-align: center; -} - -table { - text-align: left; - margin-left:auto; - margin-right:auto; - border-spacing: 7px; - width: 50%; -} - -th { - padding: 0; - color: #336699; - background-color: #c2e0ff; - border: solid #000000; - border-width: 0px; - margin: 1em auto; - text-align: center; - margin-left:auto; - margin-right:auto; -} - -td { - padding: 0; - border: solid #000000; - background-color: #f0faff; - border-width: 0px; - margin: 1em auto; - text-align: left; - margin-left:auto; - margin-right:auto; - padding-left: 1em; -} - -dl { - text-align: left; - margin-left:auto; - margin-right:auto; - width: 50%; - - padding-left: 1em; - border: solid #c2e0ff; - background: #f0faff; - border-width: 5px 1px 1px 1px; - margin: 1em auto; -} - ---> -</style> - - -</head> - -<body lang="en"> -<a name="On-Record-Padding"></a> -<div class="header"> -<p> -Previous: <a href="Weaknesses-and-countermeasures.html#Weaknesses-and-countermeasures" accesskey="p" rel="prev">Weaknesses and countermeasures</a>, Up: <a href="The-TLS-record-protocol.html#The-TLS-record-protocol" accesskey="u" rel="up">The TLS record protocol</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Function-and-Data-Index.html#Function-and-Data-Index" title="Index" rel="index">Index</a>]</p> -</div> -<hr> -<a name="On-record-padding"></a> -<h4 class="subsection">3.3.4 On record padding</h4> -<a name="index-record-padding"></a> -<a name="index-bad_005frecord_005fmac"></a> - -<p>The TLS protocol allows for extra padding of records in CBC ciphers, to prevent -statistical analysis based on the length of exchanged messages (see [<em>RFC5246</em>] section 6.2.3.2). -GnuTLS appears to be one of few implementations that take advantage of this feature: -the user can provide some plaintext data with a range of lengths she wishes to hide, -and GnuTLS adds extra padding to make sure the attacker cannot tell the real plaintext -length is in a range smaller than the user-provided one. -Use <a href="Core-TLS-API.html#gnutls_005frecord_005fsend_005frange">gnutls_record_send_range</a> to send length-hidden messages and -<a href="Core-TLS-API.html#gnutls_005frecord_005fcan_005fuse_005flength_005fhiding">gnutls_record_can_use_length_hiding</a> to check whether the current -session supports length hiding. Using the standard <a href="Core-TLS-API.html#gnutls_005frecord_005fsend">gnutls_record_send</a> -will only add minimal padding. -</p> -<p>The TLS implementation in the Symbian operating system, frequently -used by Nokia and Sony-Ericsson mobile phones, cannot handle -non-minimal record padding. What happens when one of these clients -handshake with a GnuTLS server is that the client will fail to compute -the correct MAC for the record. The client sends a TLS alert -(<code>bad_record_mac</code>) and disconnects. Typically this will result -in error messages such as ’A TLS fatal alert has been received’, ’Bad -record MAC’, or both, on the GnuTLS server side. -</p> -<p>If compatibility with such devices is a concern, not sending length-hidden messages -solves the problem by using minimal padding. -</p> -<p>If you implement an application that has a configuration file, we -recommend that you make it possible for users or administrators to -specify a GnuTLS protocol priority string, which is used by your -application via <a href="Core-TLS-API.html#gnutls_005fpriority_005fset">gnutls_priority_set</a>. To allow the best -flexibility, make it possible to have a different priority string for -different incoming IP addresses. -</p> - -<hr> -<div class="header"> -<p> -Previous: <a href="Weaknesses-and-countermeasures.html#Weaknesses-and-countermeasures" accesskey="p" rel="prev">Weaknesses and countermeasures</a>, Up: <a href="The-TLS-record-protocol.html#The-TLS-record-protocol" accesskey="u" rel="up">The TLS record protocol</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Function-and-Data-Index.html#Function-and-Data-Index" title="Index" rel="index">Index</a>]</p> -</div> - - - -</body> -</html> |