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506bfe33206b2fece40ef25f695af39dd4130facjkaluza>BIND 9 Administrator Reference Manual</TH
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44ff304057225e944e220e981d434a046d14cf06covener><H1
5d1ba75b8794925e67591c209085a49279791de9covener><A
5d1ba75b8794925e67591c209085a49279791de9covenerNAME="ch04"
5d1ba75b8794925e67591c209085a49279791de9covener>Chapter 4. Advanced Concepts</A
032982212dbcc7c3cce95bf89c503bb56e185ac7kbrand></H1
032982212dbcc7c3cce95bf89c503bb56e185ac7kbrand><DIV
032982212dbcc7c3cce95bf89c503bb56e185ac7kbrandCLASS="TOC"
032982212dbcc7c3cce95bf89c503bb56e185ac7kbrand><DL
caad2986f81ab263f7af41467dd622dc9add17f3ylavic><DT
caad2986f81ab263f7af41467dd622dc9add17f3ylavic><B
caad2986f81ab263f7af41467dd622dc9add17f3ylavic>Table of Contents</B
caad2986f81ab263f7af41467dd622dc9add17f3ylavic></DT
45a10d38e6051fd7bdf9d742aaae633d97ff02abjailletc><DT
f7317ff316c2b141feea31bddb74d5d3fa1584edjorton>4.1. <A
f7317ff316c2b141feea31bddb74d5d3fa1584edjortonHREF="Bv9ARM.ch04.html#dynamic_update"
2165214331e4afafca4048f66f303d0253d7b001covener>Dynamic Update</A
a34684a59b60a4173c25035d0c627ef17e6dc215rpluem></DT
a34684a59b60a4173c25035d0c627ef17e6dc215rpluem><DT
1e2d421a36999d292042a5539971070d54aa6c63ylavic>4.2. <A
1e2d421a36999d292042a5539971070d54aa6c63ylavicHREF="Bv9ARM.ch04.html#incremental_zone_transfers"
1e2d421a36999d292042a5539971070d54aa6c63ylavic>Incremental Zone Transfers (IXFR)</A
fa7ed98b9dc94c5845cf845aea0a44ecacd290c9humbedooh></DT
fa7ed98b9dc94c5845cf845aea0a44ecacd290c9humbedooh><DT
fa7ed98b9dc94c5845cf845aea0a44ecacd290c9humbedooh>4.3. <A
0b67eb8568cd58bb77082703951679b42cf098actrawickHREF="Bv9ARM.ch04.html#AEN673"
0b67eb8568cd58bb77082703951679b42cf098actrawick>Split DNS</A
0b67eb8568cd58bb77082703951679b42cf098actrawick></DT
0b67eb8568cd58bb77082703951679b42cf098actrawick><DT
5ef3c61605a3a021ff71f488983cb0065f8e1a79covener>4.4. <A
fb1985a97912b25ec6564c73e610a31e5fc6e25fcovenerHREF="Bv9ARM.ch04.html#tsig"
09c87c777bed1655621bb20e1c46cb6b1a63279dcovener>TSIG</A
6502b7b32f980cc2093bb3ebce37e5e4dc68fba4ylavic></DT
6502b7b32f980cc2093bb3ebce37e5e4dc68fba4ylavic><DT
3060ce7f798fbda7999cd4ddf89b525d2b294185covener>4.5. <A
c1a63b8fad09c419c1a64f75993feb8a343a6801ylavicHREF="Bv9ARM.ch04.html#AEN833"
c1a63b8fad09c419c1a64f75993feb8a343a6801ylavic>TKEY</A
c1a63b8fad09c419c1a64f75993feb8a343a6801ylavic></DT
e6b4bd1113567627ab6bb6c6a7105e1e01a7d889jailletc><DT
e6b4bd1113567627ab6bb6c6a7105e1e01a7d889jailletc>4.6. <A
e466c40e1801982602ee0200c9e8b61cc148742djailletcHREF="Bv9ARM.ch04.html#AEN848"
e466c40e1801982602ee0200c9e8b61cc148742djailletc>SIG(0)</A
457468b82e59d01eba00dd9d0817309c8f5e414ejim></DT
457468b82e59d01eba00dd9d0817309c8f5e414ejim><DT
457468b82e59d01eba00dd9d0817309c8f5e414ejim>4.7. <A
04983e3bd1754764eec7d6bb772fe3b0bf391771jortonHREF="Bv9ARM.ch04.html#DNSSEC"
04983e3bd1754764eec7d6bb772fe3b0bf391771jorton>DNSSEC</A
15890c9306ba98f6fc243e15a3c4778ddc7d773erpluem></DT
15660979a30d251681463de2e0584853890082accovener><DT
15660979a30d251681463de2e0584853890082accovener>4.8. <A
49dacedb6c387b786b7911082ff35121a45f414bcovenerHREF="Bv9ARM.ch04.html#AEN933"
49dacedb6c387b786b7911082ff35121a45f414bcovener>IPv6 Support in <SPAN
cfd9415521847b2f9394fad04fb701cfb955f503rjungCLASS="acronym"
cfd9415521847b2f9394fad04fb701cfb955f503rjung>BIND</SPAN
cfd9415521847b2f9394fad04fb701cfb955f503rjung> 9</A
28c31fb73c1264bd1d0ff932573677030b024c7dwrowe></DT
28c31fb73c1264bd1d0ff932573677030b024c7dwrowe></DL
28c31fb73c1264bd1d0ff932573677030b024c7dwrowe></DIV
28c31fb73c1264bd1d0ff932573677030b024c7dwrowe><DIV
28c31fb73c1264bd1d0ff932573677030b024c7dwroweCLASS="sect1"
8491e0600f69b0405e156ea8a419653c065c645bcovener><H1
63b9f1f5880391261705f696d7d65507bbe9ace3covenerCLASS="sect1"
63b9f1f5880391261705f696d7d65507bbe9ace3covener><A
63b9f1f5880391261705f696d7d65507bbe9ace3covenerNAME="dynamic_update"
49dacedb6c387b786b7911082ff35121a45f414bcovener>4.1. Dynamic Update</A
49dacedb6c387b786b7911082ff35121a45f414bcovener></H1
49dacedb6c387b786b7911082ff35121a45f414bcovener><P
49dacedb6c387b786b7911082ff35121a45f414bcovener>Dynamic update is the term used for the ability under
3c990331fc6702119e4f5b8ba9eae3021aea5265jim certain specified conditions to add, modify or delete records or
3c990331fc6702119e4f5b8ba9eae3021aea5265jim RRsets in the master zone files. Dynamic update is fully described
3c990331fc6702119e4f5b8ba9eae3021aea5265jim in RFC 2136.</P
3c990331fc6702119e4f5b8ba9eae3021aea5265jim><P
fc42512879dd0504532f52fe5d0d0383dda96a1eniq>Dynamic update is enabled on a zone-by-zone basis, by
fc42512879dd0504532f52fe5d0d0383dda96a1eniq including an <B
fc42512879dd0504532f52fe5d0d0383dda96a1eniqCLASS="command"
0451df5dc50fa5d8b3e07d92ee6a92e36a1181a5niq>allow-update</B
0451df5dc50fa5d8b3e07d92ee6a92e36a1181a5niq> or
0451df5dc50fa5d8b3e07d92ee6a92e36a1181a5niq <B
da0442c0440caef34706e2c2f3af05cb65921cc0jailletcCLASS="command"
983528026996668ea295be95aedb9c7a346af470ylavic>update-policy</B
da0442c0440caef34706e2c2f3af05cb65921cc0jailletc> clause in the
da0442c0440caef34706e2c2f3af05cb65921cc0jailletc <B
06b8f183140c8e02e0974e938a05078b511d1603covenerCLASS="command"
06b8f183140c8e02e0974e938a05078b511d1603covener>zone</B
06b8f183140c8e02e0974e938a05078b511d1603covener> statement.</P
15890c9306ba98f6fc243e15a3c4778ddc7d773erpluem><P
259878293a997ff49f5ddfc53d3739cbdc25444ecovener>Updating of secure zones (zones using DNSSEC) is modelled
259878293a997ff49f5ddfc53d3739cbdc25444ecovener after the <I
259878293a997ff49f5ddfc53d3739cbdc25444ecovenerCLASS="emphasis"
259878293a997ff49f5ddfc53d3739cbdc25444ecovener>simple-secure-update</I
15890c9306ba98f6fc243e15a3c4778ddc7d773erpluem> proposal, a
b54b024c06a19926832d77d40ba35ad8c41e4d3dminfrin work in progress in the DNS Extensions working group of the IETF.
b54b024c06a19926832d77d40ba35ad8c41e4d3dminfrin (See <A
b54b024c06a19926832d77d40ba35ad8c41e4d3dminfrinHREF="http://www.ietf.org/html.charters/dnsext-charter.html"
65967d05f839dbf27cf91d91fa79585eeae19660minfrinTARGET="_top"
65967d05f839dbf27cf91d91fa79585eeae19660minfrin>http://www.ietf.org/html.charters/dnsext-charter.html</A
65967d05f839dbf27cf91d91fa79585eeae19660minfrin>
65967d05f839dbf27cf91d91fa79585eeae19660minfrin for information about the DNS Extensions working group.) SIG and
8152945ae46857b170cb227e79bb799f4fc7710dminfrin NXT records affected by updates are automatically regenerated by
8152945ae46857b170cb227e79bb799f4fc7710dminfrin the server using an online zone key. Update authorization is based
8152945ae46857b170cb227e79bb799f4fc7710dminfrin on transaction signatures and an explicit server policy.</P
8152945ae46857b170cb227e79bb799f4fc7710dminfrin><P
75f5c2db254c0167a0e396254460de09b775d203trawick>The zone files of dynamic zones cannot normally be edited by hand.
75f5c2db254c0167a0e396254460de09b775d203trawick The zone file on disk at any given time may not contain the latest
75f5c2db254c0167a0e396254460de09b775d203trawick changes performed by dynamic update. The zone file is only
4f0358189bfa57b8e75bd6b94db264302a8f336amrumph written to disk only occasionally, and when shutting down the server using
4f0358189bfa57b8e75bd6b94db264302a8f336amrumph <B
4f0358189bfa57b8e75bd6b94db264302a8f336amrumphCLASS="command"
5716f9c6daa92dde5f2f9d11ed63f7c9549c223atrawick>rndc stop</B
5716f9c6daa92dde5f2f9d11ed63f7c9549c223atrawick>. Changes that have occurred since the
5716f9c6daa92dde5f2f9d11ed63f7c9549c223atrawick zone file was last written to disk are stored only in the zone's
5716f9c6daa92dde5f2f9d11ed63f7c9549c223atrawick journal (<TT
54d750a84a175d8e338880514d440773eb986b50covenerCLASS="filename"
54d750a84a175d8e338880514d440773eb986b50covener>.jnl</TT
54d750a84a175d8e338880514d440773eb986b50covener>) file.</P
54d750a84a175d8e338880514d440773eb986b50covener><P
54d750a84a175d8e338880514d440773eb986b50covener>If you have to make changes to a dynamic zone
54d750a84a175d8e338880514d440773eb986b50covener manually, the following procedure will work: Shut down
54d750a84a175d8e338880514d440773eb986b50covener the server using <B
54d750a84a175d8e338880514d440773eb986b50covenerCLASS="command"
7a3aa12f0eda24793ee26d6a179bd53132e9dae8covener>rndc stop</B
54d750a84a175d8e338880514d440773eb986b50covener> (sending a signal
54d750a84a175d8e338880514d440773eb986b50covener or using <B
83b50288fa7d306324bba68832011ea08f5c7832covenerCLASS="command"
4e30ef014533a7e93c92d88306291f5e49c9692ftrawick>rndc halt</B
83b50288fa7d306324bba68832011ea08f5c7832covener> is <I
5f066f496cd9f20a2a701255bc67d44e7cb46daetrawickCLASS="emphasis"
5f066f496cd9f20a2a701255bc67d44e7cb46daetrawick>not</I
5f066f496cd9f20a2a701255bc67d44e7cb46daetrawick>
2e15620d724fb8e3a5be183b917359a2fd6e9468covener sufficient). Wait for the server to exit,
2e15620d724fb8e3a5be183b917359a2fd6e9468covener then <I
2e15620d724fb8e3a5be183b917359a2fd6e9468covenerCLASS="emphasis"
2e15620d724fb8e3a5be183b917359a2fd6e9468covener>remove</I
1b988c41ee505962781d110a3e4c2c90f1ea0aa4covener> the zone's
1b988c41ee505962781d110a3e4c2c90f1ea0aa4covener <TT
1b988c41ee505962781d110a3e4c2c90f1ea0aa4covenerCLASS="filename"
1b988c41ee505962781d110a3e4c2c90f1ea0aa4covener>.jnl</TT
b8efdc95bec9cf089aa1be0bfd07d46aa1137a7acovener> file, edit the zone file,
b8efdc95bec9cf089aa1be0bfd07d46aa1137a7acovener and restart the server. Removing the <TT
b8efdc95bec9cf089aa1be0bfd07d46aa1137a7acovenerCLASS="filename"
f06e7c4b1bce6b6491e5de0b7998d3f5696b293dchrisd>.jnl</TT
f06e7c4b1bce6b6491e5de0b7998d3f5696b293dchrisd>
f06e7c4b1bce6b6491e5de0b7998d3f5696b293dchrisd file is necessary because the manual edits will not be
179565be4043d7e5f9161aa75271fa0a001866d9covener present in the journal, rendering it inconsistent with the
179565be4043d7e5f9161aa75271fa0a001866d9covener contents of the zone file.</P
179565be4043d7e5f9161aa75271fa0a001866d9covener></DIV
111436a32ba1254291e4883292fb116d15fe8f64covener><DIV
fce4949fb0b309a5744afcd503c6ed2d35621ee2covenerCLASS="sect1"
fce4949fb0b309a5744afcd503c6ed2d35621ee2covener><H1
fce4949fb0b309a5744afcd503c6ed2d35621ee2covenerCLASS="sect1"
fce4949fb0b309a5744afcd503c6ed2d35621ee2covener><A
7b7430e701e9a31ce809da7c220bb8dfcf68c86etrawickNAME="incremental_zone_transfers"
7b7430e701e9a31ce809da7c220bb8dfcf68c86etrawick>4.2. Incremental Zone Transfers (IXFR)</A
7b7430e701e9a31ce809da7c220bb8dfcf68c86etrawick></H1
ccc20788c1e5fc973f36df634399c89acb70deaejerenkrantz><P
ccc20788c1e5fc973f36df634399c89acb70deaejerenkrantz>The incremental zone transfer (IXFR) protocol is a way for
ccc20788c1e5fc973f36df634399c89acb70deaejerenkrantz slave servers to transfer only changed data, instead of having to
273e512f20f262e5e2aa8e0e83371d1929fb76adjkaluza transfer the entire zone. The IXFR protocol is documented in RFC
273e512f20f262e5e2aa8e0e83371d1929fb76adjkaluza 1995. See <A
273e512f20f262e5e2aa8e0e83371d1929fb76adjkaluzaHREF="Bv9ARM.ch09.html#proposed_standards"
efe780dcf13b2b95effabf897d694d8f23feac74trawick>Proposed Standards</A
fe83f60b41477b14a37edcfcd1f7f5c5a1ebfe44minfrin></P
fe83f60b41477b14a37edcfcd1f7f5c5a1ebfe44minfrin><P
fe83f60b41477b14a37edcfcd1f7f5c5a1ebfe44minfrin>When acting as a master, <SPAN
993d1261a278d7322bccef219101220b7b4fb8c5jkaluzaCLASS="acronym"
993d1261a278d7322bccef219101220b7b4fb8c5jkaluza>BIND</SPAN
993d1261a278d7322bccef219101220b7b4fb8c5jkaluza> 9 supports IXFR for those zones
ba050a6f942b9fa0e81ed73437588005c569655ccovenerwhere the necessary change history information is available. These
ba050a6f942b9fa0e81ed73437588005c569655ccovenerinclude master zones maintained by dynamic update and slave zones
ba050a6f942b9fa0e81ed73437588005c569655ccovenerwhose data was obtained by IXFR, but not manually maintained master
ba050a6f942b9fa0e81ed73437588005c569655ccovenerzones nor slave zones obtained by performing a full zone transfer
135ddda3a989215d2bedbcf1529bfb269c3eda23niq(AXFR).</P
135ddda3a989215d2bedbcf1529bfb269c3eda23niq><P
135ddda3a989215d2bedbcf1529bfb269c3eda23niq>When acting as a slave, <SPAN
001a44c352f89c9ec332ffd3e0a6927dcd19432chumbedoohCLASS="acronym"
001a44c352f89c9ec332ffd3e0a6927dcd19432chumbedooh>BIND</SPAN
001a44c352f89c9ec332ffd3e0a6927dcd19432chumbedooh> 9 will attempt to use IXFR unless
efe780dcf13b2b95effabf897d694d8f23feac74trawickit is explicitly disabled. For more information about disabling
793214f67dede32edfd9ee96c664ead04d175cbbjfclereIXFR, see the description of the <B
cc5a4a08dc9783fcbc52ce86f11e01c281a43810minfrinCLASS="command"
9b0076ddd1103e5fa9c1f9bafde4b06ce244fbaecovener>request-ixfr</B
9b0076ddd1103e5fa9c1f9bafde4b06ce244fbaecovener> clause
9b0076ddd1103e5fa9c1f9bafde4b06ce244fbaecovenerof the <B
249d09d51808cb7981af99762c3b3736ca126cd5jkaluzaCLASS="command"
249d09d51808cb7981af99762c3b3736ca126cd5jkaluza>server</B
249d09d51808cb7981af99762c3b3736ca126cd5jkaluza> statement.</P
249d09d51808cb7981af99762c3b3736ca126cd5jkaluza></DIV
56589be3d7a3e9343370df240010c6928cc78b39jkaluza><DIV
56589be3d7a3e9343370df240010c6928cc78b39jkaluzaCLASS="sect1"
56589be3d7a3e9343370df240010c6928cc78b39jkaluza><H1
77ca16c5676da23155311e13cee61e7eaba9fa3ejailletcCLASS="sect1"
77ca16c5676da23155311e13cee61e7eaba9fa3ejailletc><A
77ca16c5676da23155311e13cee61e7eaba9fa3ejailletcNAME="AEN673"
77ca16c5676da23155311e13cee61e7eaba9fa3ejailletc>4.3. Split DNS</A
f87299dab99bc04b51a6b8cad51b6795db862c0atrawick></H1
f87299dab99bc04b51a6b8cad51b6795db862c0atrawick><P
f87299dab99bc04b51a6b8cad51b6795db862c0atrawick>Setting up different views, or visibility, of DNS space to
4d12805e6c18253040223ea637acd6b3b3c18f60jortoninternal and external resolvers is usually referred to as a <I
4d12805e6c18253040223ea637acd6b3b3c18f60jortonCLASS="emphasis"
4d12805e6c18253040223ea637acd6b3b3c18f60jorton>Split
85eacfc96a04547ef25aabbc06440039715084c2jortonDNS</I
85eacfc96a04547ef25aabbc06440039715084c2jorton> setup. There are several reasons an organization
e5d909f2b06bd880fb3675cd49363df981caa631trawickwould want to set up its DNS this way.</P
a4df2cd1e1391575a327c2a90ba4315f805a0a78covener><P
a4df2cd1e1391575a327c2a90ba4315f805a0a78covener>One common reason for setting up a DNS system this way is
a4df2cd1e1391575a327c2a90ba4315f805a0a78covenerto hide "internal" DNS information from "external" clients on the
cb666b29f81df1d11d65002250153353568021fccovenerInternet. There is some debate as to whether or not this is actually useful.
cb666b29f81df1d11d65002250153353568021fccovenerInternal DNS information leaks out in many ways (via email headers,
cb666b29f81df1d11d65002250153353568021fccovenerfor example) and most savvy "attackers" can find the information
6a80c3c6f4b8ea7ba5e89402b8b779b09ce020e0covenerthey need using other means.</P
1c2cab00d988fc48cbe59032cf76cc0bab20d6f7covener><P
6a80c3c6f4b8ea7ba5e89402b8b779b09ce020e0covener>Another common reason for setting up a Split DNS system is
75a230a728338d84dcfe81edd375352f34de22d0covenerto allow internal networks that are behind filters or in RFC 1918
75a230a728338d84dcfe81edd375352f34de22d0covenerspace (reserved IP space, as documented in RFC 1918) to resolve DNS
75a230a728338d84dcfe81edd375352f34de22d0coveneron the Internet. Split DNS can also be used to allow mail from outside
1f50dc34ae069adeed20b2986e5ffdefa5c410e0covenerback in to the internal network.</P
1f50dc34ae069adeed20b2986e5ffdefa5c410e0covener><P
1f50dc34ae069adeed20b2986e5ffdefa5c410e0covener>Here is an example of a split DNS setup:</P
63a5ea80bddcc84a462e40f402b4f330e0e05411covener><P
63a5ea80bddcc84a462e40f402b4f330e0e05411covener>Let's say a company named <I
63a5ea80bddcc84a462e40f402b4f330e0e05411covenerCLASS="emphasis"
63a5ea80bddcc84a462e40f402b4f330e0e05411covener>Example, Inc.</I
65a4e663b82f8bce28ac22ab2edfd7502de36998sf> (example.com)
65a4e663b82f8bce28ac22ab2edfd7502de36998sfhas several corporate sites that have an internal network with reserved
65a4e663b82f8bce28ac22ab2edfd7502de36998sfInternet Protocol (IP) space and an external demilitarized zone (DMZ),
65a4e663b82f8bce28ac22ab2edfd7502de36998sfor "outside" section of a network, that is available to the public.</P
c7de1955eb0eaeabf7042902476397692672d549sf><P
74e7f6c55fd67b10cb400b3f6d1dc718a303d944minfrin><I
74e7f6c55fd67b10cb400b3f6d1dc718a303d944minfrinCLASS="emphasis"
74e7f6c55fd67b10cb400b3f6d1dc718a303d944minfrin>Example, Inc.</I
74e7f6c55fd67b10cb400b3f6d1dc718a303d944minfrin> wants its internal clients
a511a29faf2ff7ead3b67680154a624effb31aafminfrinto be able to resolve external hostnames and to exchange mail with
a511a29faf2ff7ead3b67680154a624effb31aafminfrinpeople on the outside. The company also wants its internal resolvers
a511a29faf2ff7ead3b67680154a624effb31aafminfrinto have access to certain internal-only zones that are not available
a511a29faf2ff7ead3b67680154a624effb31aafminfrinat all outside of the internal network.</P
a511a29faf2ff7ead3b67680154a624effb31aafminfrin><P
63921358ef93fcb41bc71d9894221ba3d7fbb87bminfrin>In order to accomplish this, the company will set up two sets
63921358ef93fcb41bc71d9894221ba3d7fbb87bminfrinof nameservers. One set will be on the inside network (in the reserved
63921358ef93fcb41bc71d9894221ba3d7fbb87bminfrinIP space) and the other set will be on bastion hosts, which are "proxy"
deec48c67d4786bc77112ffbf3a4e70b931097edminfrinhosts that can talk to both sides of its network, in the DMZ.</P
6d601599d3d65df0410eae6e573e75b2dbfb1fb4minfrin><P
6d601599d3d65df0410eae6e573e75b2dbfb1fb4minfrin>The internal servers will be configured to forward all queries,
6d601599d3d65df0410eae6e573e75b2dbfb1fb4minfrinexcept queries for <TT
6d601599d3d65df0410eae6e573e75b2dbfb1fb4minfrinCLASS="filename"
684e0cfc200f66287a93bbd1708d1dd8a92a7eefcovener>site1.internal</TT
684e0cfc200f66287a93bbd1708d1dd8a92a7eefcovener>, <TT
5c43d2fb853f84497b5ece2d414ef9484aa87e5fsfCLASS="filename"
05a5a9c3e16f21566e1b61f4bd68025ce1b741ccjoes>site2.internal</TT
05a5a9c3e16f21566e1b61f4bd68025ce1b741ccjoes>, <TT
ef82e8fa164e0a1f8b813f7deb6b7ead96018c94niqCLASS="filename"
26c5829347f6a355c00f1ba0301d575056b69536niq>site1.example.com</TT
ef82e8fa164e0a1f8b813f7deb6b7ead96018c94niq>,
ef82e8fa164e0a1f8b813f7deb6b7ead96018c94niqand <TT
ef82e8fa164e0a1f8b813f7deb6b7ead96018c94niqCLASS="filename"
ef82e8fa164e0a1f8b813f7deb6b7ead96018c94niq>site2.example.com</TT
ef82e8fa164e0a1f8b813f7deb6b7ead96018c94niq>, to the servers in the
ef82e8fa164e0a1f8b813f7deb6b7ead96018c94niqDMZ. These internal servers will have complete sets of information
413ee814748f37be168ff12407fa6dba0ceeabe6trawickfor <TT
c12917da693bae4028a1d5a5e8224bceed8c739dsfCLASS="filename"
c12917da693bae4028a1d5a5e8224bceed8c739dsf>site1.example.com</TT
eafcc0ebf263d0ba69855b6e10958c4c1a2361bdsf>, <TT
eafcc0ebf263d0ba69855b6e10958c4c1a2361bdsfCLASS="filename"
eafcc0ebf263d0ba69855b6e10958c4c1a2361bdsf>site2.example.com</TT
eafcc0ebf263d0ba69855b6e10958c4c1a2361bdsf>,<I
eafcc0ebf263d0ba69855b6e10958c4c1a2361bdsfCLASS="emphasis"
d7ffd2da16d58b1a0de212e4d56f7aebb72bef26sf> </I
d7ffd2da16d58b1a0de212e4d56f7aebb72bef26sf><TT
d7ffd2da16d58b1a0de212e4d56f7aebb72bef26sfCLASS="filename"
4576c1a9ef54cd1e5555ee07d016a7f559f80338sf>site1.internal</TT
4576c1a9ef54cd1e5555ee07d016a7f559f80338sf>,
4576c1a9ef54cd1e5555ee07d016a7f559f80338sfand <TT
9811aed12bbc71783d2e544ccb5fecd193843eadsfCLASS="filename"
9811aed12bbc71783d2e544ccb5fecd193843eadsf>site2.internal</TT
9811aed12bbc71783d2e544ccb5fecd193843eadsf>.</P
88fac54d9d64f85bbdab5d7010816f4377f95bd7rjung><P
88fac54d9d64f85bbdab5d7010816f4377f95bd7rjung>To protect the <TT
bd3f5647b96d378d9c75c954e3f13582af32c643sfCLASS="filename"
bd3f5647b96d378d9c75c954e3f13582af32c643sf>site1.internal</TT
bd3f5647b96d378d9c75c954e3f13582af32c643sf> and <TT
bd3f5647b96d378d9c75c954e3f13582af32c643sfCLASS="filename"
bd3f5647b96d378d9c75c954e3f13582af32c643sf>site2.internal</TT
2a7beea91d46beb41f043a84eaad060047ee04aafabien> domains,
2a7beea91d46beb41f043a84eaad060047ee04aafabienthe internal nameservers must be configured to disallow all queries
2a7beea91d46beb41f043a84eaad060047ee04aafabiento these domains from any external hosts, including the bastion
2a7beea91d46beb41f043a84eaad060047ee04aafabienhosts.</P
584a85dd4047e38d3ed3a29b6662fcc9d100ae4csf><P
584a85dd4047e38d3ed3a29b6662fcc9d100ae4csf>The external servers, which are on the bastion hosts, will
584a85dd4047e38d3ed3a29b6662fcc9d100ae4csfbe configured to serve the "public" version of the <TT
f21e9e3d0bfb7a507ecc5bc963f2159d693503d1sfCLASS="filename"
f21e9e3d0bfb7a507ecc5bc963f2159d693503d1sf>site1</TT
f21e9e3d0bfb7a507ecc5bc963f2159d693503d1sf> and <TT
f6b9c755a0b793e8a3a3aebd327ca20a86478117sfCLASS="filename"
f6b9c755a0b793e8a3a3aebd327ca20a86478117sf>site2.example.com</TT
f6b9c755a0b793e8a3a3aebd327ca20a86478117sf> zones.
132ee6ac1c26d6e8953836316ba50734eefab47bsfThis could include things such as the host records for public servers
132ee6ac1c26d6e8953836316ba50734eefab47bsf(<TT
132ee6ac1c26d6e8953836316ba50734eefab47bsfCLASS="filename"
85eacfc96a04547ef25aabbc06440039715084c2jorton>www.example.com</TT
85eacfc96a04547ef25aabbc06440039715084c2jorton> and <TT
85eacfc96a04547ef25aabbc06440039715084c2jortonCLASS="filename"
536d2e7cd1fdec1255b8c3bdf41fdc714c506a54trawick>ftp.example.com</TT
536d2e7cd1fdec1255b8c3bdf41fdc714c506a54trawick>),
536d2e7cd1fdec1255b8c3bdf41fdc714c506a54trawickand mail exchange (MX) records (<TT
536d2e7cd1fdec1255b8c3bdf41fdc714c506a54trawickCLASS="filename"
79c5787b92ac5f0e1cc82393816c77a006399316trawick>a.mx.example.com</TT
79c5787b92ac5f0e1cc82393816c77a006399316trawick> and <TT
79c5787b92ac5f0e1cc82393816c77a006399316trawickCLASS="filename"
79c5787b92ac5f0e1cc82393816c77a006399316trawick>b.mx.example.com</TT
c967bf3bc89e8aa60dbd30d9da388e448ddc1cc4trawick>).</P
79c5787b92ac5f0e1cc82393816c77a006399316trawick><P
79c5787b92ac5f0e1cc82393816c77a006399316trawick>In addition, the public <TT
79c5787b92ac5f0e1cc82393816c77a006399316trawickCLASS="filename"
79c5787b92ac5f0e1cc82393816c77a006399316trawick>site1</TT
79c5787b92ac5f0e1cc82393816c77a006399316trawick> and <TT
7b395e4e878c28a4784919cfd2e704ddd14a3390jortonCLASS="filename"
7b395e4e878c28a4784919cfd2e704ddd14a3390jorton>site2.example.com</TT
7b395e4e878c28a4784919cfd2e704ddd14a3390jorton> zones
7b395e4e878c28a4784919cfd2e704ddd14a3390jortonshould have special MX records that contain wildcard (`*') records
536e48c08d674acac5d44929318f2ad928edc361jortonpointing to the bastion hosts. This is needed because external mail
536e48c08d674acac5d44929318f2ad928edc361jortonservers do not have any other way of looking up how to deliver mail
e81785da447b469da66f218b3f0244aab507958djortonto those internal hosts. With the wildcard records, the mail will
e81785da447b469da66f218b3f0244aab507958djortonbe delivered to the bastion host, which can then forward it on to
3e4e54d4e3fc0123c63d57aa84ac7ad7a8c73ff8jortoninternal hosts.</P
3e4e54d4e3fc0123c63d57aa84ac7ad7a8c73ff8jorton><P
3e4e54d4e3fc0123c63d57aa84ac7ad7a8c73ff8jorton>Here's an example of a wildcard MX record:</P
53e9b27aba029b18be814df40bcf6f0428771d1efuankg><PRE
53e9b27aba029b18be814df40bcf6f0428771d1efuankgCLASS="programlisting"
53e9b27aba029b18be814df40bcf6f0428771d1efuankg><TT
53e9b27aba029b18be814df40bcf6f0428771d1efuankgCLASS="literal"
53e9b27aba029b18be814df40bcf6f0428771d1efuankg>* IN MX 10 external1.example.com.</TT
6bb524f1895f30265a1431afc460977d391cb36bsf></PRE
6bb524f1895f30265a1431afc460977d391cb36bsf><P
ca61ccd0c306c2c72df153688ba1b49f3eceed80sf>Now that they accept mail on behalf of anything in the internal
6bb524f1895f30265a1431afc460977d391cb36bsfnetwork, the bastion hosts will need to know how to deliver mail
e6dd71992459d05a676b98b7963423dc5dc1e24aminfrinto internal hosts. In order for this to work properly, the resolvers on
e6dd71992459d05a676b98b7963423dc5dc1e24aminfrinthe bastion hosts will need to be configured to point to the internal
e6dd71992459d05a676b98b7963423dc5dc1e24aminfrinnameservers for DNS resolution.</P
e6dd71992459d05a676b98b7963423dc5dc1e24aminfrin><P
23f1535d6a60817d2846bac0aea230ea475d7dccminfrin>Queries for internal hostnames will be answered by the internal
23f1535d6a60817d2846bac0aea230ea475d7dccminfrinservers, and queries for external hostnames will be forwarded back
23f1535d6a60817d2846bac0aea230ea475d7dccminfrinout to the DNS servers on the bastion hosts.</P
23f1535d6a60817d2846bac0aea230ea475d7dccminfrin><P
ec7520b24cd80d34d82bbcaca153cbb23cc04bc0rjung>In order for all this to work properly, internal clients will
ec7520b24cd80d34d82bbcaca153cbb23cc04bc0rjungneed to be configured to query <I
ec7520b24cd80d34d82bbcaca153cbb23cc04bc0rjungCLASS="emphasis"
ec7520b24cd80d34d82bbcaca153cbb23cc04bc0rjung>only</I
ec7520b24cd80d34d82bbcaca153cbb23cc04bc0rjung> the internal
ec7520b24cd80d34d82bbcaca153cbb23cc04bc0rjungnameservers for DNS queries. This could also be enforced via selective
ec7520b24cd80d34d82bbcaca153cbb23cc04bc0rjungfiltering on the network.</P
ec7520b24cd80d34d82bbcaca153cbb23cc04bc0rjung><P
6249dfa569d3b4f1f539665b979a80c6e335d93etrawick>If everything has been set properly, <I
6249dfa569d3b4f1f539665b979a80c6e335d93etrawickCLASS="emphasis"
0827cb14e550f6f65018431c22c2c913631c8f25kbrand>Example, Inc.</I
6249dfa569d3b4f1f539665b979a80c6e335d93etrawick>'s
ae600ca541efc686b34f8b1f21bd3d0741d37674covenerinternal clients will now be able to:</P
6249dfa569d3b4f1f539665b979a80c6e335d93etrawick><P
cfa64348224b66dd1c9979b809406c4d15b1c137fielding></P
74499a117b3b2cd9666715a14f90c0e5d1a4ee8ajim><UL
cfa64348224b66dd1c9979b809406c4d15b1c137fielding><LI
74499a117b3b2cd9666715a14f90c0e5d1a4ee8ajim><P
cfa64348224b66dd1c9979b809406c4d15b1c137fielding>Look up any hostnames in the <TT
74499a117b3b2cd9666715a14f90c0e5d1a4ee8ajimCLASS="literal"
cfa64348224b66dd1c9979b809406c4d15b1c137fielding>site1</TT
74499a117b3b2cd9666715a14f90c0e5d1a4ee8ajim> and
cfa64348224b66dd1c9979b809406c4d15b1c137fielding<TT
CLASS="literal"
>site2.example.com</TT
> zones.</P
></LI
><LI
><P
>Look up any hostnames in the <TT
CLASS="literal"
>site1.internal</TT
> and
<TT
CLASS="literal"
>site2.internal</TT
> domains.</P
></LI
><LI
><P
>Look up any hostnames on the Internet.</P
></LI
><LI
><P
>Exchange mail with internal AND external people.</P
></LI
></UL
><P
>Hosts on the Internet will be able to:</P
><P
></P
><UL
><LI
><P
>Look up any hostnames in the <TT
CLASS="literal"
>site1</TT
> and
<TT
CLASS="literal"
>site2.example.com</TT
> zones.</P
></LI
><LI
><P
>Exchange mail with anyone in the <TT
CLASS="literal"
>site1</TT
> and
<TT
CLASS="literal"
>site2.example.com</TT
> zones.</P
></LI
></UL
><P
>Here is an example configuration for the setup we just
described above. Note that this is only configuration information;
for information on how to configure your zone files, see <A
HREF="Bv9ARM.ch03.html#sample_configuration"
>Section 3.1</A
></P
><P
>Internal DNS server config:</P
><PRE
CLASS="programlisting"
>&#13;
acl internals { 172.16.72.0/24; 192.168.1.0/24; };
acl externals { <TT
CLASS="varname"
>bastion-ips-go-here</TT
>; };
options {
...
...
forward only;
forwarders { // forward to external servers
<TT
CLASS="varname"
>bastion-ips-go-here</TT
>;
};
allow-transfer { none; }; // sample allow-transfer (no one)
allow-query { internals; externals; }; // restrict query access
allow-recursion { internals; }; // restrict recursion
...
...
};
zone "site1.example.com" { // sample slave zone
type master;
file "m/site1.example.com";
forwarders { }; // do normal iterative
// resolution (do not forward)
allow-query { internals; externals; };
allow-transfer { internals; };
};
zone "site2.example.com" {
type slave;
file "s/site2.example.com";
masters { 172.16.72.3; };
forwarders { };
allow-query { internals; externals; };
allow-transfer { internals; };
};
zone "site1.internal" {
type master;
file "m/site1.internal";
forwarders { };
allow-query { internals; };
allow-transfer { internals; }
};
zone "site2.internal" {
type slave;
file "s/site2.internal";
masters { 172.16.72.3; };
forwarders { };
allow-query { internals };
allow-transfer { internals; }
};
</PRE
><P
>External (bastion host) DNS server config:</P
><PRE
CLASS="programlisting"
>&#13;acl internals { 172.16.72.0/24; 192.168.1.0/24; };
acl externals { bastion-ips-go-here; };
options {
...
...
allow-transfer { none; }; // sample allow-transfer (no one)
allow-query { internals; externals; }; // restrict query access
allow-recursion { internals; externals; }; // restrict recursion
...
...
};
zone "site1.example.com" { // sample slave zone
type master;
file "m/site1.foo.com";
allow-query { any; };
allow-transfer { internals; externals; };
};
zone "site2.example.com" {
type slave;
file "s/site2.foo.com";
masters { another_bastion_host_maybe; };
allow-query { any; };
allow-transfer { internals; externals; }
};
</PRE
><P
>In the <TT
CLASS="filename"
>resolv.conf</TT
> (or equivalent) on
the bastion host(s):</P
><PRE
CLASS="programlisting"
>&#13;search ...
nameserver 172.16.72.2
nameserver 172.16.72.3
nameserver 172.16.72.4
</PRE
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="tsig"
>4.4. TSIG</A
></H1
><P
>This is a short guide to setting up Transaction SIGnatures
(TSIG) based transaction security in <SPAN
CLASS="acronym"
>BIND</SPAN
>. It describes changes
to the configuration file as well as what changes are required for
different features, including the process of creating transaction
keys and using transaction signatures with <SPAN
CLASS="acronym"
>BIND</SPAN
>.</P
><P
><SPAN
CLASS="acronym"
>BIND</SPAN
> primarily supports TSIG for server to server communication.
This includes zone transfer, notify, and recursive query messages.
Resolvers based on newer versions of <SPAN
CLASS="acronym"
>BIND</SPAN
> 8 have limited support
for TSIG.</P
><P
>TSIG might be most useful for dynamic update. A primary
server for a dynamic zone should use access control to control
updates, but IP-based access control is insufficient. Key-based
access control is far superior, see <A
HREF="Bv9ARM.ch09.html#proposed_standards"
>Proposed Standards</A
>. The <B
CLASS="command"
>nsupdate</B
>
program supports TSIG via the <TT
CLASS="option"
>-k</TT
> and
<TT
CLASS="option"
>-y</TT
> command line options.</P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN764"
>4.4.1. Generate Shared Keys for Each Pair of Hosts</A
></H2
><P
>A shared secret is generated to be shared between <I
CLASS="emphasis"
>host1</I
> and <I
CLASS="emphasis"
>host2</I
>.
An arbitrary key name is chosen: "host1-host2.". The key name must
be the same on both hosts.</P
><DIV
CLASS="sect3"
><H3
CLASS="sect3"
><A
NAME="AEN769"
>4.4.1.1. Automatic Generation</A
></H3
><P
>The following command will generate a 128 bit (16 byte) HMAC-MD5
key as described above. Longer keys are better, but shorter keys
are easier to read. Note that the maximum key length is 512 bits;
keys longer than that will be digested with MD5 to produce a 128
bit key.</P
><P
><TT
CLASS="userinput"
><B
>dnssec-keygen -a hmac-md5 -b 128 -n HOST host1-host2.</B
></TT
></P
><P
>The key is in the file <TT
CLASS="filename"
>Khost1-host2.+157+00000.private</TT
>.
Nothing directly uses this file, but the base-64 encoded string
following "<TT
CLASS="literal"
>Key:</TT
>"
can be extracted from the file and used as a shared secret:</P
><PRE
CLASS="programlisting"
>Key: La/E5CjG9O+os1jq0a2jdA==</PRE
><P
>The string "<TT
CLASS="literal"
>La/E5CjG9O+os1jq0a2jdA==</TT
>" can
be used as the shared secret.</P
></DIV
><DIV
CLASS="sect3"
><H3
CLASS="sect3"
><A
NAME="AEN780"
>4.4.1.2. Manual Generation</A
></H3
><P
>The shared secret is simply a random sequence of bits, encoded
in base-64. Most ASCII strings are valid base-64 strings (assuming
the length is a multiple of 4 and only valid characters are used),
so the shared secret can be manually generated.</P
><P
>Also, a known string can be run through <B
CLASS="command"
>mmencode</B
> or
a similar program to generate base-64 encoded data.</P
></DIV
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN785"
>4.4.2. Copying the Shared Secret to Both Machines</A
></H2
><P
>This is beyond the scope of DNS. A secure transport mechanism
should be used. This could be secure FTP, ssh, telephone, etc.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN788"
>4.4.3. Informing the Servers of the Key's Existence</A
></H2
><P
>Imagine <I
CLASS="emphasis"
>host1</I
> and <I
CLASS="emphasis"
>host 2</I
> are
both servers. The following is added to each server's <TT
CLASS="filename"
>named.conf</TT
> file:</P
><PRE
CLASS="programlisting"
>&#13;key host1-host2. {
algorithm hmac-md5;
secret "La/E5CjG9O+os1jq0a2jdA==";
};
</PRE
><P
>The algorithm, hmac-md5, is the only one supported by <SPAN
CLASS="acronym"
>BIND</SPAN
>.
The secret is the one generated above. Since this is a secret, it
is recommended that either <TT
CLASS="filename"
>named.conf</TT
> be non-world
readable, or the key directive be added to a non-world readable
file that is included by <TT
CLASS="filename"
>named.conf</TT
>.</P
><P
>At this point, the key is recognized. This means that if the
server receives a message signed by this key, it can verify the
signature. If the signature succeeds, the response is signed by
the same key.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN800"
>4.4.4. Instructing the Server to Use the Key</A
></H2
><P
>Since keys are shared between two hosts only, the server must
be told when keys are to be used. The following is added to the <TT
CLASS="filename"
>named.conf</TT
> file
for <I
CLASS="emphasis"
>host1</I
>, if the IP address of <I
CLASS="emphasis"
>host2</I
> is
10.1.2.3:</P
><PRE
CLASS="programlisting"
>&#13;server 10.1.2.3 {
keys { host1-host2. ;};
};
</PRE
><P
>Multiple keys may be present, but only the first is used.
This directive does not contain any secrets, so it may be in a world-readable
file.</P
><P
>If <I
CLASS="emphasis"
>host1</I
> sends a message that is a request
to that address, the message will be signed with the specified key. <I
CLASS="emphasis"
>host1</I
> will
expect any responses to signed messages to be signed with the same
key.</P
><P
>A similar statement must be present in <I
CLASS="emphasis"
>host2</I
>'s
configuration file (with <I
CLASS="emphasis"
>host1</I
>'s address) for <I
CLASS="emphasis"
>host2</I
> to
sign request messages to <I
CLASS="emphasis"
>host1</I
>.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN816"
>4.4.5. TSIG Key Based Access Control</A
></H2
><P
><SPAN
CLASS="acronym"
>BIND</SPAN
> allows IP addresses and ranges to be specified in ACL
definitions and
<B
CLASS="command"
>allow-{ query | transfer | update }</B
> directives.
This has been extended to allow TSIG keys also. The above key would
be denoted <B
CLASS="command"
>key host1-host2.</B
></P
><P
>An example of an allow-update directive would be:</P
><PRE
CLASS="programlisting"
>&#13;allow-update { key host1-host2. ;};
</PRE
><P
>This allows dynamic updates to succeed only if the request
was signed by a key named
"<B
CLASS="command"
>host1-host2.</B
>".</P
><P
>You may want to read about the more
powerful <B
CLASS="command"
>update-policy</B
> statement in <A
HREF="Bv9ARM.ch06.html#dynamic_update_policies"
>Section 6.2.22.4</A
>.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN829"
>4.4.6. Errors</A
></H2
><P
>The processing of TSIG signed messages can result in
several errors. If a signed message is sent to a non-TSIG aware
server, a FORMERR will be returned, since the server will not
understand the record. This is a result of misconfiguration,
since the server must be explicitly configured to send a TSIG
signed message to a specific server.</P
><P
>If a TSIG aware server receives a message signed by an
unknown key, the response will be unsigned with the TSIG
extended error code set to BADKEY. If a TSIG aware server
receives a message with a signature that does not validate, the
response will be unsigned with the TSIG extended error code set
to BADSIG. If a TSIG aware server receives a message with a time
outside of the allowed range, the response will be signed with
the TSIG extended error code set to BADTIME, and the time values
will be adjusted so that the response can be successfully
verified. In any of these cases, the message's rcode is set to
NOTAUTH.</P
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="AEN833"
>4.5. TKEY</A
></H1
><P
><B
CLASS="command"
>TKEY</B
> is a mechanism for automatically
generating a shared secret between two hosts. There are several
"modes" of <B
CLASS="command"
>TKEY</B
> that specify how the key is
generated or assigned. <SPAN
CLASS="acronym"
>BIND</SPAN
> implements only one of these modes,
the Diffie-Hellman key exchange. Both hosts are required to have
a Diffie-Hellman KEY record (although this record is not required
to be present in a zone). The <B
CLASS="command"
>TKEY</B
> process
must use signed messages, signed either by TSIG or SIG(0). The
result of <B
CLASS="command"
>TKEY</B
> is a shared secret that can be
used to sign messages with TSIG. <B
CLASS="command"
>TKEY</B
> can also
be used to delete shared secrets that it had previously
generated.</P
><P
>The <B
CLASS="command"
>TKEY</B
> process is initiated by a client
or server by sending a signed <B
CLASS="command"
>TKEY</B
> query
(including any appropriate KEYs) to a TKEY-aware server. The
server response, if it indicates success, will contain a
<B
CLASS="command"
>TKEY</B
> record and any appropriate keys. After
this exchange, both participants have enough information to
determine the shared secret; the exact process depends on the
<B
CLASS="command"
>TKEY</B
> mode. When using the Diffie-Hellman
<B
CLASS="command"
>TKEY</B
> mode, Diffie-Hellman keys are exchanged,
and the shared secret is derived by both participants.</P
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="AEN848"
>4.6. SIG(0)</A
></H1
><P
><SPAN
CLASS="acronym"
>BIND</SPAN
> 9 partially supports DNSSEC SIG(0) transaction
signatures as specified in RFC 2535. SIG(0) uses public/private
keys to authenticate messages. Access control is performed in the
same manner as TSIG keys; privileges can be granted or denied
based on the key name.</P
><P
>When a SIG(0) signed message is received, it will only be
verified if the key is known and trusted by the server; the server
will not attempt to locate and/or validate the key.</P
><P
>SIG(0) signing of multiple-message TCP streams is not
supported.</P
><P
><SPAN
CLASS="acronym"
>BIND</SPAN
> 9 does not ship with any tools that generate SIG(0)
signed messages.</P
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="DNSSEC"
>4.7. DNSSEC</A
></H1
><P
>Cryptographic authentication of DNS information is possible
through the DNS Security (<I
CLASS="emphasis"
>DNSSEC</I
>) extensions,
defined in RFC 2535. This section describes the creation and use
of DNSSEC signed zones.</P
><P
>In order to set up a DNSSEC secure zone, there are a series
of steps which must be followed. <SPAN
CLASS="acronym"
>BIND</SPAN
> 9 ships
with several tools
that are used in this process, which are explained in more detail
below. In all cases, the "<TT
CLASS="option"
>-h</TT
>" option prints a
full list of parameters. Note that the DNSSEC tools require the
keyset and signedkey files to be in the working directory, and
that the tools shipped with BIND 9.0.x are not fully compatible
with the current ones.</P
><P
>There must also be communication with the administrators of
the parent and/or child zone to transmit keys and signatures. A
zone's security status must be indicated by the parent zone for a
DNSSEC capable resolver to trust its data.</P
><P
>For other servers to trust data in this zone, they must
either be statically configured with this zone's zone key or the
zone key of another zone above this one in the DNS tree.</P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN865"
>4.7.1. Generating Keys</A
></H2
><P
>The <B
CLASS="command"
>dnssec-keygen</B
> program is used to
generate keys.</P
><P
>A secure zone must contain one or more zone keys. The
zone keys will sign all other records in the zone, as well as
the zone keys of any secure delegated zones. Zone keys must
have the same name as the zone, a name type of
<B
CLASS="command"
>ZONE</B
>, and must be usable for authentication.
It is recommended that zone keys be mandatory to implement a
cryptographic algorithm; currently the only key mandatory to
implement an algorithm is DSA.</P
><P
>The following command will generate a 768 bit DSA key for
the <TT
CLASS="filename"
>child.example</TT
> zone:</P
><P
><TT
CLASS="userinput"
><B
>dnssec-keygen -a DSA -b 768 -n ZONE child.example.</B
></TT
></P
><P
>Two output files will be produced:
<TT
CLASS="filename"
>Kchild.example.+003+12345.key</TT
> and
<TT
CLASS="filename"
>Kchild.example.+003+12345.private</TT
> (where
12345 is an example of a key tag). The key file names contain
the key name (<TT
CLASS="filename"
>child.example.</TT
>), algorithm (3
is DSA, 1 is RSA, etc.), and the key tag (12345 in this case).
The private key (in the <TT
CLASS="filename"
>.private</TT
> file) is
used to generate signatures, and the public key (in the
<TT
CLASS="filename"
>.key</TT
> file) is used for signature
verification.</P
><P
>To generate another key with the same properties (but with
a different key tag), repeat the above command.</P
><P
>The public keys should be inserted into the zone file with
<B
CLASS="command"
>$INCLUDE</B
> statements, including the
<TT
CLASS="filename"
>.key</TT
> files.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN885"
>4.7.2. Creating a Keyset</A
></H2
><P
>The <B
CLASS="command"
>dnssec-makekeyset</B
> program is used
to create a key set from one or more keys.</P
><P
>Once the zone keys have been generated, a key set must be
built for transmission to the administrator of the parent zone,
so that the parent zone can sign the keys with its own zone key
and correctly indicate the security status of this zone. When
building a key set, the list of keys to be included and the TTL
of the set must be specified, and the desired signature validity
period of the parent's signature may also be specified.</P
><P
>The list of keys to be inserted into the key set may also
included non-zone keys present at the top of the zone.
<B
CLASS="command"
>dnssec-makekeyset</B
> may also be used at other
names in the zone.</P
><P
>The following command generates a key set containing the
above key and another key similarly generated, with a TTL of
3600 and a signature validity period of 10 days starting from
now.</P
><P
><TT
CLASS="userinput"
><B
>dnssec-makekeyset -t 3600 -e +864000 Kchild.example.+003+12345 Kchild.example.+003+23456</B
></TT
></P
><P
>One output file is produced:
<TT
CLASS="filename"
>keyset-child.example.</TT
>. This file should be
transmitted to the parent to be signed. It includes the keys,
as well as signatures over the key set generated by the zone
keys themselves, which are used to prove ownership of the
private keys and encode the desired validity period.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN897"
>4.7.3. Signing the Child's Keyset</A
></H2
><P
>The <B
CLASS="command"
>dnssec-signkey</B
> program is used to
sign one child's keyset.</P
><P
>If the <TT
CLASS="filename"
>child.example</TT
> zone has any
delegations which are secure, for example,
<TT
CLASS="filename"
>grand.child.example</TT
>, the
<TT
CLASS="filename"
>child.example</TT
> administrator should receive
keyset files for each secure subzone. These keys must be signed
by this zone's zone keys.</P
><P
>The following command signs the child's key set with the
zone keys:</P
><P
><TT
CLASS="userinput"
><B
>dnssec-signkey keyset-grand.child.example. Kchild.example.+003+12345 Kchild.example.+003+23456</B
></TT
></P
><P
>One output file is produced:
<TT
CLASS="filename"
>signedkey-grand.child.example.</TT
>. This file
should be both transmitted back to the child and retained. It
includes all keys (the child's keys) from the keyset file and
signatures generated by this zone's zone keys.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN910"
>4.7.4. Signing the Zone</A
></H2
><P
>The <B
CLASS="command"
>dnssec-signzone</B
> program is used to
sign a zone.</P
><P
>Any <TT
CLASS="filename"
>signedkey</TT
> files corresponding to
secure subzones should be present, as well as a
<TT
CLASS="filename"
>signedkey</TT
> file for this zone generated by
the parent (if there is one). The zone signer will generate
<TT
CLASS="literal"
>NXT</TT
> and <TT
CLASS="literal"
>SIG</TT
> records for
the zone, as well as incorporate the zone key signature from the
parent and indicate the security status at all delegation
points.</P
><P
>The following command signs the zone, assuming it is in a
file called <TT
CLASS="filename"
>zone.child.example</TT
>. By
default, all zone keys which have an available private key are
used to generate signatures.</P
><P
><TT
CLASS="userinput"
><B
>dnssec-signzone -o child.example zone.child.example</B
></TT
></P
><P
>One output file is produced:
<TT
CLASS="filename"
>zone.child.example.signed</TT
>. This file
should be referenced by <TT
CLASS="filename"
>named.conf</TT
> as the
input file for the zone.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN926"
>4.7.5. Configuring Servers</A
></H2
><P
>Unlike in <SPAN
CLASS="acronym"
>BIND</SPAN
> 8, data is not verified on load in <SPAN
CLASS="acronym"
>BIND</SPAN
> 9,
so zone keys for authoritative zones do not need to be specified
in the configuration file.</P
><P
>The public key for any security root must be present in
the configuration file's <B
CLASS="command"
>trusted-keys</B
>
statement, as described later in this document. </P
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="AEN933"
>4.8. IPv6 Support in <SPAN
CLASS="acronym"
>BIND</SPAN
> 9</A
></H1
><P
><SPAN
CLASS="acronym"
>BIND</SPAN
> 9 fully supports all currently defined forms of IPv6
name to address and address to name lookups. It will also use
IPv6 addresses to make queries when running on an IPv6 capable
system.</P
><P
>For forward lookups, <SPAN
CLASS="acronym"
>BIND</SPAN
> 9 supports both A6 and AAAA
records. The use of AAAA records is deprecated, but it is still
useful for hosts to have both AAAA and A6 records to maintain
backward compatibility with installations where AAAA records are
still used. In fact, the stub resolvers currently shipped with
most operating system support only AAAA lookups, because following
A6 chains is much harder than doing A or AAAA lookups.</P
><P
>For IPv6 reverse lookups, <SPAN
CLASS="acronym"
>BIND</SPAN
> 9 supports the new
"bitstring" format used in the <I
CLASS="emphasis"
>ip6.arpa</I
>
domain, as well as the older, deprecated "nibble" format used in
the <I
CLASS="emphasis"
>ip6.int</I
> domain.</P
><P
><SPAN
CLASS="acronym"
>BIND</SPAN
> 9 includes a new lightweight resolver library and
resolver daemon which new applications may choose to use to avoid
the complexities of A6 chain following and bitstring labels, see <A
HREF="Bv9ARM.ch05.html"
>Chapter 5</A
>.</P
><P
>For an overview of the format and structure of IPv6 addresses,
see <A
HREF="Bv9ARM.ch09.html#ipv6addresses"
>Section A.3.1</A
>.</P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN949"
>4.8.1. Address Lookups Using AAAA Records</A
></H2
><P
>The AAAA record is a parallel to the IPv4 A record. It
specifies the entire address in a single record. For
example,</P
><PRE
CLASS="programlisting"
>&#13;$ORIGIN example.com.
host 3600 IN AAAA 3ffe:8050:201:1860:42::1
</PRE
><P
>While their use is deprecated, they are useful to support
older IPv6 applications. They should not be added where they
are not absolutely necessary.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN954"
>4.8.2. Address Lookups Using A6 Records</A
></H2
><P
>The A6 record is more flexible than the AAAA record, and
is therefore more complicated. The A6 record can be used to
form a chain of A6 records, each specifying part of the IPv6
address. It can also be used to specify the entire record as
well. For example, this record supplies the same data as the
AAAA record in the previous example:</P
><PRE
CLASS="programlisting"
>&#13;$ORIGIN example.com.
host 3600 IN A6 0 3ffe:8050:201:1860:42::1
</PRE
><DIV
CLASS="sect3"
><H3
CLASS="sect3"
><A
NAME="AEN958"
>4.8.2.1. A6 Chains</A
></H3
><P
>A6 records are designed to allow network
renumbering. This works when an A6 record only specifies the
part of the address space the domain owner controls. For
example, a host may be at a company named "company." It has
two ISPs which provide IPv6 address space for it. These two
ISPs fully specify the IPv6 prefix they supply.</P
><P
>In the company's address space:</P
><PRE
CLASS="programlisting"
>&#13;$ORIGIN example.com.
host 3600 IN A6 64 0:0:0:0:42::1 company.example1.net.
host 3600 IN A6 64 0:0:0:0:42::1 company.example2.net.
</PRE
><P
>ISP1 will use:</P
><PRE
CLASS="programlisting"
>&#13;$ORIGIN example1.net.
company 3600 IN A6 0 3ffe:8050:201:1860::
</PRE
><P
>ISP2 will use:</P
><PRE
CLASS="programlisting"
>&#13;$ORIGIN example2.net.
company 3600 IN A6 0 1234:5678:90ab:fffa::
</PRE
><P
>When <TT
CLASS="literal"
>host.example.com</TT
> is looked up,
the resolver (in the resolver daemon or caching name server)
will find two partial A6 records, and will use the additional
name to find the remainder of the data.</P
></DIV
><DIV
CLASS="sect3"
><H3
CLASS="sect3"
><A
NAME="AEN969"
>4.8.2.2. A6 Records for DNS Servers</A
></H3
><P
>When an A6 record specifies the address of a name
server, it should use the full address rather than specifying
a partial address. For example:</P
><PRE
CLASS="programlisting"
>&#13;$ORIGIN example.com.
@ 14400 IN NS ns0
14400 IN NS ns1
ns0 14400 IN A6 0 3ffe:8050:201:1860:42::1
ns1 14400 IN A 192.168.42.1
</PRE
><P
>It is recommended that IPv4-in-IPv6 mapped addresses not
be used. If a host has an IPv4 address, use an A record, not
an A6, with <TT
CLASS="literal"
>::ffff:192.168.42.1</TT
> as the
address.</P
></DIV
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN975"
>4.8.3. Address to Name Lookups Using Nibble Format</A
></H2
><P
>While the use of nibble format to look up names is
deprecated, it is supported for backwards compatiblity with
existing IPv6 applications.</P
><P
>When looking up an address in nibble format, the address
components are simply reversed, just as in IPv4, and
<TT
CLASS="literal"
>ip6.int.</TT
> is appended to the resulting name.
For example, the following would provide reverse name lookup for
a host with address
<TT
CLASS="literal"
>3ffe:8050:201:1860:42::1</TT
>.</P
><PRE
CLASS="programlisting"
>&#13;$ORIGIN 0.6.8.1.1.0.2.0.0.5.0.8.e.f.f.3.ip6.int.
1.0.0.0.0.0.0.0.0.0.0.0.2.4.0.0 14400 IN PTR host.example.com.
</PRE
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN982"
>4.8.4. Address to Name Lookups Using Bitstring Format</A
></H2
><P
>Bitstring labels can start and end on any bit boundary,
rather than on a multiple of 4 bits as in the nibble
format. They also use <I
CLASS="emphasis"
>ip6.arpa</I
> rather than
<I
CLASS="emphasis"
>ip6.int</I
>.</P
><P
>To replicate the previous example using bitstrings:</P
><PRE
CLASS="programlisting"
>&#13;$ORIGIN \[x3ffe805002011860/64].ip6.arpa.
\[x0042000000000001/64] 14400 IN PTR host.example.com.
</PRE
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="AEN989"
>4.8.5. Using DNAME for Delegation of IPv6 Reverse Addresses</A
></H2
><P
>In IPV6, the same host may have many addresses from many
network providers. Since the trailing portion of the address
usually remains constant, <B
CLASS="command"
>DNAME</B
> can help
reduce the number of zone files used for reverse mapping that
need to be maintained.</P
><P
>For example, consider a host which has two providers
(<TT
CLASS="literal"
>example.net</TT
> and
<TT
CLASS="literal"
>example2.net</TT
>) and
therefore two IPv6 addresses. Since the host chooses its own 64
bit host address portion, the provider address is the only part
that changes:</P
><PRE
CLASS="programlisting"
>&#13;$ORIGIN example.com.
host IN A6 64 ::1234:5678:1212:5675 cust1.example.net.
IN A6 64 ::1234:5678:1212:5675 subnet5.example2.net.
$ORIGIN example.net.
cust1 IN A6 48 0:0:0:dddd:: ipv6net.example.net.
ipv6net IN A6 0 aa:bb:cccc::
$ORIGIN example2.net.
subnet5 IN A6 48 0:0:0:1:: ipv6net2.example2.net.
ipv6net2 IN A6 0 6666:5555:4::
</PRE
><P
>This sets up forward lookups. To handle the reverse lookups,
the provider <TT
CLASS="literal"
>example.net</TT
>
would have:</P
><PRE
CLASS="programlisting"
>&#13;$ORIGIN \[x00aa00bbcccc/48].ip6.arpa.
\[xdddd/16] IN DNAME ipv6-rev.example.com.
</PRE
><P
>and <TT
CLASS="literal"
>example2.net</TT
> would have:</P
><PRE
CLASS="programlisting"
>&#13;$ORIGIN \[x666655550004/48].ip6.arpa.
\[x0001/16] IN DNAME ipv6-rev.example.com.
</PRE
><P
><TT
CLASS="literal"
>example.com</TT
>
needs only one zone file to handle both of these reverse
mappings:</P
><PRE
CLASS="programlisting"
>&#13;$ORIGIN ipv6-rev.example.com.
\[x1234567812125675/64] IN PTR host.example.com.
</PRE
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