isc-hmac-fixup.html revision 5347c0fcb04eaea19d9f39795646239f487c6207
11e9368a226272085c337e9e74b79808c16fbdbaTinderbox User - Copyright (C) 2010, 2013-2016 Internet Systems Consortium, Inc. ("ISC")
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - This Source Code Form is subject to the terms of the Mozilla Public
4a14ce5ba00ab7bc55c99ffdcf59c7a4ab902721Automatic Updater - License, v. 2.0. If a copy of the MPL was not distributed with this
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - file, You can obtain one at http://mozilla.org/MPL/2.0/.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<a name="man.isc-hmac-fixup"></a><div class="titlepage"></div>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<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>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Versions of BIND 9 up to and including BIND 9.6 had a bug causing
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein HMAC-SHA* TSIG keys which were longer than the digest length of the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
71c66a876ecca77923638d3f94cc0783152b2f03Mark Andrews longer than 256 bits, etc) to be used incorrectly, generating a
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein message authentication code that was incompatible with other DNS
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein implementations.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein This bug has been fixed in BIND 9.7. However, the fix may
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein cause incompatibility between older and newer versions of
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein BIND, when using long keys. <span class="command"><strong>isc-hmac-fixup</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein modifies those keys to restore compatibility.
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User To modify a key, run <span class="command"><strong>isc-hmac-fixup</strong></span> and
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User specify the key's algorithm and secret on the command line. If the
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User secret is longer than the digest length of the algorithm (64 bytes
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein new secret will be generated consisting of a hash digest of the old
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User secret. (If the secret did not require conversion, then it will be
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt printed without modification.)
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<a name="id-1.8"></a><h2>SECURITY CONSIDERATIONS</h2>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Secrets that have been converted by <span class="command"><strong>isc-hmac-fixup</strong></span>
af40ebed6257e4ac1996144530b3de317cf4da11Tinderbox User are shortened, but as this is how the HMAC protocol works in
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt operation anyway, it does not affect security. RFC 2104 notes,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein "Keys longer than [the digest length] are acceptable but the
af40ebed6257e4ac1996144530b3de317cf4da11Tinderbox User extra length would not significantly increase the function
af40ebed6257e4ac1996144530b3de317cf4da11Tinderbox User <em class="citetitle">BIND 9 Administrator Reference Manual</em>,