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6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync<a name="man.isc-hmac-fixup"></a><div class="titlepage"></div>
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync<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>
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync Versions of BIND 9 up to and including BIND 9.6 had a bug causing
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync HMAC-SHA* TSIG keys which were longer than the digest length of the
4d1226da58f42754f7b947e5ab65fb391de20946vboxsync hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync longer than 256 bits, etc) to be used incorrectly, generating a
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync message authentication code that was incompatible with other DNS
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync implementations.
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync This bug has been fixed in BIND 9.7. However, the fix may
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync cause incompatibility between older and newer versions of
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync BIND, when using long keys. <span><strong class="command">isc-hmac-fixup</strong></span>
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync modifies those keys to restore compatibility.
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync specify the key's algorithm and secret on the command line. If the
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync secret is longer than the digest length of the algorithm (64 bytes
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync new secret will be generated consisting of a hash digest of the old
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync secret. (If the secret did not require conversion, then it will be
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync printed without modification.)
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync<a name="id2670054"></a><h2>SECURITY CONSIDERATIONS</h2>
4d1226da58f42754f7b947e5ab65fb391de20946vboxsync Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync are shortened, but as this is how the HMAC protocol works in
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync operation anyway, it does not affect security. RFC 2104 notes,
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync "Keys longer than [the digest length] are acceptable but the
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync extra length would not significantly increase the function
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync <em class="citetitle">BIND 9 Administrator Reference Manual</em>,
6ebc06c9cd87d26f64680c2b58e6805b6b504728vboxsync<p><span class="corpauthor">Internet Systems Consortium</span>