man.isc-hmac-fixup.html revision 37664e68e465379878e803fdde2a0beb9a8c0555
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7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox 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>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User Versions of BIND 9 up to and including BIND 9.6 had a bug causing
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User HMAC-SHA* TSIG keys which were longer than the digest length of the
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User longer than 256 bits, etc) to be used incorrectly, generating a
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User message authentication code that was incompatible with other DNS
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User implementations.
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User This bug has been fixed in BIND 9.7. However, the fix may
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User cause incompatibility between older and newer versions of
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User BIND, when using long keys. <span><strong class="command">isc-hmac-fixup</strong></span>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User modifies those keys to restore compatibility.
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User specify the key's algorithm and secret on the command line. If the
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User secret is longer than the digest length of the algorithm (64 bytes
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
a1ff871f78b7d907d6fc3a382beea2a640fe8423Tinderbox User new secret will be generated consisting of a hash digest of the old
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt secret. (If the secret did not require conversion, then it will be
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User printed without modification.)
adabefa84c3dcf048566cc23fd457c577f208eeaTinderbox User<a name="id2619105"></a><h2>SECURITY CONSIDERATIONS</h2>
adabefa84c3dcf048566cc23fd457c577f208eeaTinderbox User Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
adabefa84c3dcf048566cc23fd457c577f208eeaTinderbox User are shortened, but as this is how the HMAC protocol works in
801d3c8888d6026eb1fd31c23e51e4f54dbc317eTinderbox User operation anyway, it does not affect security. RFC 2104 notes,
801d3c8888d6026eb1fd31c23e51e4f54dbc317eTinderbox User "Keys longer than [the digest length] are acceptable but the
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User extra length would not significantly increase the function
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