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d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync<a name="man.isc-hmac-fixup"></a><div class="titlepage"></div>
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync<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>
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync Versions of BIND 9 up to and including BIND 9.6 had a bug causing
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync HMAC-SHA* TSIG keys which were longer than the digest length of the
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync longer than 256 bits, etc) to be used incorrectly, generating a
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync message authentication code that was incompatible with other DNS
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync implementations.
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync This bug has been fixed in BIND 9.7. However, the fix may
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync cause incompatibility between older and newer versions of
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync BIND, when using long keys. <span class="command"><strong>isc-hmac-fixup</strong></span>
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync modifies those keys to restore compatibility.
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync To modify a key, run <span class="command"><strong>isc-hmac-fixup</strong></span> and
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync specify the key's algorithm and secret on the command line. If the
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync secret is longer than the digest length of the algorithm (64 bytes
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync new secret will be generated consisting of a hash digest of the old
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync secret. (If the secret did not require conversion, then it will be
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync printed without modification.)
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync<a name="id-1.14.30.8"></a><h2>SECURITY CONSIDERATIONS</h2>
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync Secrets that have been converted by <span class="command"><strong>isc-hmac-fixup</strong></span>
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync are shortened, but as this is how the HMAC protocol works in
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync operation anyway, it does not affect security. RFC 2104 notes,
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync "Keys longer than [the digest length] are acceptable but the
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync extra length would not significantly increase the function
d1c5a03c19683c719b94496bb998fde2f2e5e622vboxsync <em class="citetitle">BIND 9 Administrator Reference Manual</em>,