/contrib/bind9/bin/tools/isc-hmac-fixup.html
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1<!-- 2 - Copyright (C) 2010 Internet Systems Consortium, Inc. ("ISC") 3 - 4 - Permission to use, copy, modify, and/or distribute this software for any 5 - purpose with or without fee is hereby granted, provided that the above 6 - copyright notice and this permission notice appear in all copies. 7 - 8 - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH 9 - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY 10 - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, 11 - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 12 - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE 13 - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 14 - PERFORMANCE OF THIS SOFTWARE. 15--> 16<!-- $Id$ --> 17<html> 18<head> 19<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> 20<title>isc-hmac-fixup</title> 21<meta name="generator" content="DocBook XSL Stylesheets V1.71.1"> 22</head> 23<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en"> 24<a name="man.isc-hmac-fixup"></a><div class="titlepage"></div> 25<div class="refnamediv"> 26<h2>Name</h2> 27<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p> 28</div> 29<div class="refsynopsisdiv"> 30<h2>Synopsis</h2> 31<div class="cmdsynopsis"><p><code class="command">isc-hmac-fixup</code> {<em class="replaceable"><code>algorithm</code></em>} {<em class="replaceable"><code>secret</code></em>}</p></div> 32</div> 33<div class="refsect1" lang="en"> 34<a name="id2543352"></a><h2>DESCRIPTION</h2> 35<p> 36 Versions of BIND 9 up to and including BIND 9.6 had a bug causing 37 HMAC-SHA* TSIG keys which were longer than the digest length of the 38 hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys 39 longer than 256 bits, etc) to be used incorrectly, generating a 40 message authentication code that was incompatible with other DNS 41 implementations. 42 </p> 43<p> 44 This bug has been fixed in BIND 9.7. However, the fix may 45 cause incompatibility between older and newer versions of 46 BIND, when using long keys. <span><strong class="command">isc-hmac-fixup</strong></span> 47 modifies those keys to restore compatibility. 48 </p> 49<p> 50 To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and 51 specify the key's algorithm and secret on the command line. If the 52 secret is longer than the digest length of the algorithm (64 bytes 53 for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a 54 new secret will be generated consisting of a hash digest of the old 55 secret. (If the secret did not require conversion, then it will be 56 printed without modification.) 57 </p> 58</div> 59<div class="refsect1" lang="en"> 60<a name="id2543376"></a><h2>SECURITY CONSIDERATIONS</h2> 61<p> 62 Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span> 63 are shortened, but as this is how the HMAC protocol works in 64 operation anyway, it does not affect security. RFC 2104 notes, 65 "Keys longer than [the digest length] are acceptable but the 66 extra length would not significantly increase the function 67 strength." 68 </p> 69</div> 70<div class="refsect1" lang="en"> 71<a name="id2543389"></a><h2>SEE ALSO</h2> 72<p> 73 <em class="citetitle">BIND 9 Administrator Reference Manual</em>, 74 <em class="citetitle">RFC 2104</em>. 75 </p> 76</div> 77<div class="refsect1" lang="en"> 78<a name="id2543406"></a><h2>AUTHOR</h2> 79<p><span class="corpauthor">Internet Systems Consortium</span> 80 </p> 81</div> 82</div></body> 83</html>