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3b4098640dd85040270f39b9a5ee5e22de99d3d6Mark Andrews - Copyright (C) 2010 Internet Systems Consortium, Inc. ("ISC")
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5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews - purpose with or without fee is hereby granted, provided that the above
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5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews<a name="man.isc-hmac-fixup"></a><div class="titlepage"></div>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark 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>
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
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews cause incompatibility between older and newer versions of
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews BIND, when using long keys. <span><strong class="command">isc-hmac-fixup</strong></span>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews modifies those keys to restore compatibility.
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews 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
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews 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
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews secret. (If the secret did not require conversion, then it will be
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews printed without modification.)
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews<a name="id2648353"></a><h2>SECURITY CONSIDERATIONS</h2>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews are shortened, but as this is how the HMAC protocol works in
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews operation anyway, it does not affect security. RFC 2104 notes,
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews "Keys longer than [the digest length] are acceptable but the
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews extra length would not significantly increase the function
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews <em class="citetitle">BIND 9 Administrator Reference Manual</em>,
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews<p><span class="corpauthor">Internet Systems Consortium</span>
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