man.isc-hmac-fixup.html revision 09d72af3e9961c210d7baa6179165b6cd81e8dd0
40f53fa8d9c6a4fc38c0014495e7a42b08f52481David Lawrence - Copyright (C) 2004-2015 Internet Systems Consortium, Inc. ("ISC")
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews - Copyright (C) 2000-2003 Internet Software Consortium.
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d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews - purpose with or without fee is hereby granted, provided that the above
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d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews<a name="man.isc-hmac-fixup"></a><div class="titlepage"></div>
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews<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>
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews Versions of BIND 9 up to and including BIND 9.6 had a bug causing
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews HMAC-SHA* TSIG keys which were longer than the digest length of the
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews longer than 256 bits, etc) to be used incorrectly, generating a
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews message authentication code that was incompatible with other DNS
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews implementations.
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews This bug has been fixed in BIND 9.7. However, the fix may
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews cause incompatibility between older and newer versions of
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews BIND, when using long keys. <span><strong class="command">isc-hmac-fixup</strong></span>
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews modifies those keys to restore compatibility.
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews specify the key's algorithm and secret on the command line. If the
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews secret is longer than the digest length of the algorithm (64 bytes
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews new secret will be generated consisting of a hash digest of the old
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews secret. (If the secret did not require conversion, then it will be
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews printed without modification.)
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews<a name="id2626347"></a><h2>SECURITY CONSIDERATIONS</h2>
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews are shortened, but as this is how the HMAC protocol works in
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews operation anyway, it does not affect security. RFC 2104 notes,
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews "Keys longer than [the digest length] are acceptable but the
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews extra length would not significantly increase the function
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews <em class="citetitle">BIND 9 Administrator Reference Manual</em>,
d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews<p><span class="corpauthor">Internet Systems Consortium</span>
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d7c632387465363c23e4ef6a780bc4eaa47ad31dMark Andrews<p style="text-align: center;">BIND 9.11.0pre-alpha</p>