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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - Copyright (C) 2004-2015 Internet Systems Consortium, Inc. ("ISC")
75c0816e8295e180f4bc7f10db3d0d880383bc1cMark Andrews - Copyright (C) 2000-2003 Internet Software Consortium.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - Permission to use, copy, modify, and/or distribute this software for any
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - purpose with or without fee is hereby granted, provided that the above
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<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>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews Versions of BIND 9 up to and including BIND 9.6 had a bug causing
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews HMAC-SHA* TSIG keys which were longer than the digest length of the
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews longer than 256 bits, etc) to be used incorrectly, generating a
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews message authentication code that was incompatible with other DNS
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews implementations.
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews 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><strong class="command">isc-hmac-fixup</strong></span>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews modifies those keys to restore compatibility.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews specify the key's algorithm and secret on the command line. If the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein secret is longer than the digest length of the algorithm (64 bytes
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews new secret will be generated consisting of a hash digest of the old
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein secret. (If the secret did not require conversion, then it will be
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein printed without modification.)
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<a name="id2626552"></a><h2>SECURITY CONSIDERATIONS</h2>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein are shortened, but as this is how the HMAC protocol works in
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews operation anyway, it does not affect security. RFC 2104 notes,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein "Keys longer than [the digest length] are acceptable but the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein extra length would not significantly increase the function
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="citetitle">BIND 9 Administrator Reference Manual</em>,
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews<p><span class="corpauthor">Internet Systems Consortium</span>
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