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16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync<a name="man.isc-hmac-fixup"></a><div class="titlepage"></div>
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync<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>
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync Versions of BIND 9 up to and including BIND 9.6 had a bug causing
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync HMAC-SHA* TSIG keys which were longer than the digest length of the
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync longer than 256 bits, etc) to be used incorrectly, generating a
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync message authentication code that was incompatible with other DNS
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync implementations.
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync This bug has been fixed in BIND 9.7. However, the fix may
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync cause incompatibility between older and newer versions of
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync BIND, when using long keys. <span><strong class="command">isc-hmac-fixup</strong></span>
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync modifies those keys to restore compatibility.
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync specify the key's algorithm and secret on the command line. If the
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync secret is longer than the digest length of the algorithm (64 bytes
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync new secret will be generated consisting of a hash digest of the old
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync secret. (If the secret did not require conversion, then it will be
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync printed without modification.)
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync<a name="id2666637"></a><h2>SECURITY CONSIDERATIONS</h2>
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync are shortened, but as this is how the HMAC protocol works in
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync operation anyway, it does not affect security. RFC 2104 notes,
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync "Keys longer than [the digest length] are acceptable but the
16a8d09569a2ebd598cef72fa605be6fb4563607vboxsync extra length would not significantly increase the function
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