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319f8f820db4356edaff70c2e019376e1ec71487vboxsync<tr><th colspan="3" align="center"><span class="application">isc-hmac-fixup</span></th></tr>
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319f8f820db4356edaff70c2e019376e1ec71487vboxsync<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
319f8f820db4356edaff70c2e019376e1ec71487vboxsync<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>
319f8f820db4356edaff70c2e019376e1ec71487vboxsync Versions of BIND 9 up to and including BIND 9.6 had a bug causing
319f8f820db4356edaff70c2e019376e1ec71487vboxsync HMAC-SHA* TSIG keys which were longer than the digest length of the
319f8f820db4356edaff70c2e019376e1ec71487vboxsync hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
319f8f820db4356edaff70c2e019376e1ec71487vboxsync longer than 256 bits, etc) to be used incorrectly, generating a
319f8f820db4356edaff70c2e019376e1ec71487vboxsync message authentication code that was incompatible with other DNS
319f8f820db4356edaff70c2e019376e1ec71487vboxsync implementations.
319f8f820db4356edaff70c2e019376e1ec71487vboxsync This bug has been fixed in BIND 9.7. However, the fix may
319f8f820db4356edaff70c2e019376e1ec71487vboxsync cause incompatibility between older and newer versions of
319f8f820db4356edaff70c2e019376e1ec71487vboxsync BIND, when using long keys. <span><strong class="command">isc-hmac-fixup</strong></span>
319f8f820db4356edaff70c2e019376e1ec71487vboxsync modifies those keys to restore compatibility.
319f8f820db4356edaff70c2e019376e1ec71487vboxsync To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and
319f8f820db4356edaff70c2e019376e1ec71487vboxsync specify the key's algorithm and secret on the command line. If the
319f8f820db4356edaff70c2e019376e1ec71487vboxsync secret is longer than the digest length of the algorithm (64 bytes
319f8f820db4356edaff70c2e019376e1ec71487vboxsync for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
319f8f820db4356edaff70c2e019376e1ec71487vboxsync new secret will be generated consisting of a hash digest of the old
319f8f820db4356edaff70c2e019376e1ec71487vboxsync secret. (If the secret did not require conversion, then it will be
319f8f820db4356edaff70c2e019376e1ec71487vboxsync printed without modification.)
319f8f820db4356edaff70c2e019376e1ec71487vboxsync<a name="id2666741"></a><h2>SECURITY CONSIDERATIONS</h2>
319f8f820db4356edaff70c2e019376e1ec71487vboxsync Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
319f8f820db4356edaff70c2e019376e1ec71487vboxsync are shortened, but as this is how the HMAC protocol works in
319f8f820db4356edaff70c2e019376e1ec71487vboxsync operation anyway, it does not affect security. RFC 2104 notes,
319f8f820db4356edaff70c2e019376e1ec71487vboxsync "Keys longer than [the digest length] are acceptable but the
319f8f820db4356edaff70c2e019376e1ec71487vboxsync extra length would not significantly increase the function
319f8f820db4356edaff70c2e019376e1ec71487vboxsync <em class="citetitle">BIND 9 Administrator Reference Manual</em>,
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