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fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox 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>
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User<a name="id-1.14.30.7"></a><h2>DESCRIPTION</h2>
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt Versions of BIND 9 up to and including BIND 9.6 had a bug causing
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt HMAC-SHA* TSIG keys which were longer than the digest length of the
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt longer than 256 bits, etc) to be used incorrectly, generating a
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt message authentication code that was incompatible with other DNS
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt implementations.
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt This bug has been fixed in BIND 9.7. However, the fix may
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt cause incompatibility between older and newer versions of
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt BIND, when using long keys. <span class="command"><strong>isc-hmac-fixup</strong></span>
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt modifies those keys to restore compatibility.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt To modify a key, run <span class="command"><strong>isc-hmac-fixup</strong></span> and
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt specify the key's algorithm and secret on the command line. If the
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt secret is longer than the digest length of the algorithm (64 bytes
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt new secret will be generated consisting of a hash digest of the old
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt secret. (If the secret did not require conversion, then it will be
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt printed without modification.)
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User<a name="id-1.14.30.8"></a><h2>SECURITY CONSIDERATIONS</h2>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt Secrets that have been converted by <span class="command"><strong>isc-hmac-fixup</strong></span>
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt are shortened, but as this is how the HMAC protocol works in
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt operation anyway, it does not affect security. RFC 2104 notes,
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt "Keys longer than [the digest length] are acceptable but the
0f66aced2640d964aeb6db41210711ba0640d7f2Evan Hunt extra length would not significantly increase the function
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