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33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User<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>
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User Versions of BIND 9 up to and including BIND 9.6 had a bug causing
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User HMAC-SHA* TSIG keys which were longer than the digest length of the
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User longer than 256 bits, etc) to be used incorrectly, generating a
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User message authentication code that was incompatible with other DNS
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User implementations.
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User This bug has been fixed in BIND 9.7. However, the fix may
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User cause incompatibility between older and newer versions of
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User BIND, when using long keys. <span><strong class="command">isc-hmac-fixup</strong></span>
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User modifies those keys to restore compatibility.
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User specify the key's algorithm and secret on the command line. If the
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User secret is longer than the digest length of the algorithm (64 bytes
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User new secret will be generated consisting of a hash digest of the old
a1ff871f78b7d907d6fc3a382beea2a640fe8423Tinderbox User secret. (If the secret did not require conversion, then it will be
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User printed without modification.)
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User<a name="id2655787"></a><h2>SECURITY CONSIDERATIONS</h2>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User are shortened, but as this is how the HMAC protocol works in
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User operation anyway, it does not affect security. RFC 2104 notes,
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User "Keys longer than [the digest length] are acceptable but the
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User extra length would not significantly increase the function
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User <em class="citetitle">BIND 9 Administrator Reference Manual</em>,
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User<p><span class="corpauthor">Internet Systems Consortium</span>
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