/contrib/bind9/doc/arm/managed-keys.xml

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 18<!-- $Id: managed-keys.xml,v 1.3 2010/02/03 23:49:07 tbox Exp $ -->
 19
 20<sect1 id="rfc5011.support">
 21  <title>Dynamic Trust Anchor Management</title>
 22  <para>BIND 9.7.0 introduces support for RFC 5011, dynamic trust
 23  anchor management. Using this feature allows 
 24  <command>named</command> to keep track of changes to critical
 25  DNSSEC keys without any need for the operator to make changes to
 26  configuration files.</para>
 27  <sect2>
 28    <title>Validating Resolver</title>
 29    <!-- TODO: command tag is overloaded for configuration and executables -->
 30    <para>To configure a validating resolver to use RFC 5011 to
 31    maintain a trust anchor, configure the trust anchor using a 
 32    <command>managed-keys</command> statement. Information about
 33    this can be found in 
 34    <xref linkend="managed-keys" />.</para>
 35    <!-- TODO: managed-keys examples
 36also in DNSSEC section above here in ARM -->
 37  </sect2>
 38  <sect2>
 39    <title>Authoritative Server</title>
 40    <para>To set up an authoritative zone for RFC 5011 trust anchor
 41    maintenance, generate two (or more) key signing keys (KSKs) for
 42    the zone. Sign the zone with one of them; this is the "active"
 43    KSK. All KSK's which do not sign the zone are "stand-by"
 44    keys.</para>
 45    <para>Any validating resolver which is configured to use the
 46    active KSK as an RFC 5011-managed trust anchor will take note
 47    of the stand-by KSKs in the zone's DNSKEY RRset, and store them
 48    for future reference. The resolver will recheck the zone
 49    periodically, and after 30 days, if the new key is still there,
 50    then the key will be accepted by the resolver as a valid trust
 51    anchor for the zone. Any time after this 30-day acceptance
 52    timer has completed, the active KSK can be revoked, and the
 53    zone can be "rolled over" to the newly accepted key.</para>
 54    <para>The easiest way to place a stand-by key in a zone is to
 55    use the "smart signing" features of 
 56    <command>dnssec-keygen</command> and 
 57    <command>dnssec-signzone</command>. If a key with a publication
 58    date in the past, but an activation date which is unset or in
 59    the future, " 
 60    <command>dnssec-signzone -S</command>" will include the DNSKEY
 61    record in the zone, but will not sign with it:</para>
 62    <screen>
 63$ <userinput>dnssec-keygen -K keys -f KSK -P now -A now+2y example.net</userinput>
 64$ <userinput>dnssec-signzone -S -K keys example.net</userinput>
 65</screen>
 66    <para>To revoke a key, the new command 
 67    <command>dnssec-revoke</command> has been added. This adds the
 68    REVOKED bit to the key flags and re-generates the 
 69    <filename>K*.key</filename> and 
 70    <filename>K*.private</filename> files.</para>
 71    <para>After revoking the active key, the zone must be signed
 72    with both the revoked KSK and the new active KSK. (Smart
 73    signing takes care of this automatically.)</para>
 74    <para>Once a key has been revoked and used to sign the DNSKEY
 75    RRset in which it appears, that key will never again be
 76    accepted as a valid trust anchor by the resolver. However,
 77    validation can proceed using the new active key (which had been
 78    accepted by the resolver when it was a stand-by key).</para>
 79    <para>See RFC 5011 for more details on key rollover
 80    scenarios.</para>
 81    <para>When a key has been revoked, its key ID changes,
 82    increasing by 128, and wrapping around at 65535. So, for
 83    example, the key "<filename>Kexample.com.+005+10000</filename>" becomes
 84    "<filename>Kexample.com.+005+10128</filename>".</para>
 85    <para>If two keys have ID's exactly 128 apart, and one is
 86    revoked, then the two key ID's will collide, causing several
 87    problems. To prevent this, 
 88    <command>dnssec-keygen</command> will not generate a new key if
 89    another key is present which may collide. This checking will
 90    only occur if the new keys are written to the same directory
 91    which holds all other keys in use for that zone.</para>
 92    <para>Older versions of BIND 9 did not have this precaution.
 93    Exercise caution if using key revocation on keys that were
 94    generated by previous releases, or if using keys stored in
 95    multiple directories or on multiple machines.</para>
 96    <para>It is expected that a future release of BIND 9 will
 97    address this problem in a different way, by storing revoked
 98    keys with their original unrevoked key ID's.</para>
 99  </sect2>
100</sect1>