diff options
Diffstat (limited to 'man')
| -rw-r--r-- | man/dnssec-trust-anchors.d.xml | 189 | ||||
| -rw-r--r-- | man/resolved.conf.xml | 58 | ||||
| -rw-r--r-- | man/systemd-resolved.service.xml | 2 |
3 files changed, 249 insertions, 0 deletions
diff --git a/man/dnssec-trust-anchors.d.xml b/man/dnssec-trust-anchors.d.xml new file mode 100644 index 0000000000..9a7cf3c881 --- /dev/null +++ b/man/dnssec-trust-anchors.d.xml @@ -0,0 +1,189 @@ +<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> + +<!-- + This file is part of systemd. + + Copyright 2016 Lennart Poettering + + systemd is free software; you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 2.1 of the License, or + (at your option) any later version. + + systemd is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with systemd; If not, see <http://www.gnu.org/licenses/>. +--> + +<refentry id="dnssec-trust-anchors.d" conditional='ENABLE_RESOLVED' + xmlns:xi="http://www.w3.org/2001/XInclude"> + <refentryinfo> + <title>dnssec-trust-anchors.d</title> + <productname>systemd</productname> + + <authorgroup> + <author> + <contrib>Developer</contrib> + <firstname>Lennart</firstname> + <surname>Poettering</surname> + <email>lennart@poettering.net</email> + </author> + </authorgroup> + </refentryinfo> + + <refmeta> + <refentrytitle>dnssec-trust-anchors.d</refentrytitle> + <manvolnum>5</manvolnum> + </refmeta> + + <refnamediv> + <refname>dnssec-trust-anchors.d</refname> + <refname>systemd.positive</refname> + <refname>systemd.negative</refname> + <refpurpose>DNSSEC trust anchor configuration files</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <para><filename>/etc/dnssec-trust-anchors.d/*.positive</filename></para> + <para><filename>/run/dnssec-trust-anchors.d/*.positive</filename></para> + <para><filename>/usr/lib/dnssec-trust-anchors.d/*.positive</filename></para> + <para><filename>/etc/dnssec-trust-anchors.d/*.negative</filename></para> + <para><filename>/run/dnssec-trust-anchors.d/*.negative</filename></para> + <para><filename>/usr/lib/dnssec-trust-anchors.d/*.negative</filename></para> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para>The DNSSEC trust anchor configuration files define positive + and negative trust anchors + <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> + bases DNSSEC integrity proofs on.</para> + </refsect1> + + <refsect1> + <title>Positive Trust Anchors</title> + + <para>Positive trust anchor configuration files contain DNSKEY and + DS resource record definitions to use as base for DNSSEC integrity + proofs. See <ulink + url="https://tools.ietf.org/html/rfc4035#section-4.4">RFC 4035, + Section 4.4</ulink> for more information about DNSSEC trust + anchors.</para> + + <para>Positive trust anchors are read from files with the suffix + <filename>.positive</filename> located in + <filename>/etc/dnssec-trust-anchors.d/</filename>, + <filename>/run/dnssec-trust-anchors.d/</filename> and + <filename>/usr/lib/dnssec-trust-anchors.d/</filename>. These + directories are searched in the specified order, and a trust + anchor file of the same name in an earlier path overrides a trust + anchor files in a later path. To disable a trust anchor file + shipped in <filename>/usr/lib/dnssec-trust-anchors.d/</filename> + it is sufficient to provide an identically-named file in + <filename>/etc/dnssec-trust-anchors.d/</filename> or + <filename>/run/dnssec-trust-anchors.d/</filename> that is either + empty or a symlink to <filename>/dev/null</filename> ("masked").</para> + + <para>Positive trust anchor files are simple text files resembling + DNS zone files, as documented in <ulink + url="https://tools.ietf.org/html/rfc1035#section-5">RFC 1035, Section + 5</ulink>. One DS or DNSKEY resource record may be listed per + line. Empty lines and lines starting with a semicolon + (<literal>;</literal>) are ignored and considered comments. A DS + resource record is specified like in the following example:</para> + + <programlisting>. IN DS 19036 8 2 49aac11d7b6f6446702e54a1607371607a1a41855200fd2ce1cdde32f24e8fb5</programlisting> + + <para>The first word specifies the domain, use + <literal>.</literal> for the root domain. The domain may be + specified with or without trailing dot, which is considered + equivalent. The second word must be <literal>IN</literal> the + third word <literal>DS</literal>. The following words specify the + key tag, signature algorithm, digest algorithm, followed by the + hex-encoded key fingerprint. See <ulink + url="https://tools.ietf.org/html/rfc4034#section-5">RFC 4034, + Section 5</ulink> for details about the precise syntax and meaning + of these fields.</para> + + <para>Alternatively, DNSKEY resource records may be used to define + trust anchors, like in the following example:</para> + + <programlisting>. IN DNSKEY 257 3 8 AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjFFVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoXbfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaDX6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpzW5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relSQageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulqQxA+Uk1ihz0=</programlisting> + + <para>The first word specifies the domain again, the second word + must be <literal>IN</literal>, followed by + <literal>DNSKEY</literal>. The subsequent words encode the DNSKEY + flags, protocol and algorithm fields, followed by the key data + encoded in Base64. See See <ulink + url="https://tools.ietf.org/html/rfc4034#section-2">RFC 4034, + Section 2</ulink> for details about the precise syntax and meaning + of these fields.</para> + + <para>If multiple DS or DNSKEY records are defined for the same + domain (possibly even in different trust anchor files), all keys + are used and are considered equivalent as base for DNSSEC + proofs.</para> + + <para>Note that <filename>systemd-resolved</filename> will + automatically use a built-in trust anchor key for the Internet + root domain if no positive trust anchors are defined for the root + domain. In most cases it is hence unnecessary to define an + explicit key with trust anchor files. The built-in key is disabled + as soon as at least one trust anchor key for the root domain is + defined in trust anchor files.</para> + + <para>It is generally recommended to encode trust anchors in DS + resource records, rather than DNSKEY resource records.</para> + + <para>If a trust anchor specified via a DS record is found revoked + it is automatically removed from the trust anchor database for the + runtime. See <ulink url="https://tools.ietf.org/html/rfc5011">RFC + 5011</ulink> for details about revoked trust anchors. Note that + <filename>systemd-resolved</filename> will not update its trust + anchor database from DNS servers automatically. Instead, it is + recommended to update the resolver software or update the new + trust anchor via adding in new trust anchor files.</para> + + <para>The current DNSSEC trust anchor for the Internet's root + domain is available a the <ulink + url="https://data.iana.org/root-anchors/root-anchors.xml">IANA + Trust Anchor and Keys</ulink> page.</para> + </refsect1> + + <refsect1> + <title>Negative Trust Anchors</title> + + <para>Negative trust anchors define domains where DNSSEC + validation shall be turned off. Negative trust anchor files are + found at the same location as positive trust anchor files, and + follow the same overriding rules. They are text files with the + <filename>.negative</filename> suffix. Empty lines and lines whose + first character is <literal>;</literal> are ignored. Each line + specifies one domain name where DNSSEC validation shall be + disabled on.</para> + + <para>Negative trust anchors are useful to support private DNS + subtrees that are not referenced from the Internet DNS hierarchy, + and not signed.</para> + + <para><ulink url="https://tools.ietf.org/html/rfc7646">RFC + 7646</ulink> for details on negative trust anchors.</para> + </refsect1> + + <refsect1> + <title>See Also</title> + <para> + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> diff --git a/man/resolved.conf.xml b/man/resolved.conf.xml index 4680b6a4e5..8473bbe5c9 100644 --- a/man/resolved.conf.xml +++ b/man/resolved.conf.xml @@ -124,6 +124,63 @@ global setting is on.</para></listitem> </varlistentry> + <varlistentry> + <term><varname>DNSSEC=</varname></term> + <listitem><para>Takes a boolean argument or + <literal>downgrade-ok</literal>. If true all DNS lookups are + DNSSEC-validated locally. If a response for a lookup request + is detected invalid this is returned as lookup failure to + applications. Note that this mode requires a DNS server that + supports DNSSEC. If the DNS server does not properly support + DNSSEC all validations will fail. If set to + <literal>downgrade-ok</literal> DNSSEC validation is + attempted, but if the server does not support DNSSEC properly, + DNSSEC mode is automatically disabled. Note that this mode + makes DNSSEC validation vulnerable to "downgrade" attacks, + where an attacker might be able to trigger a downgrade to + non-DNSSEC mode by synthesizing a DNS response that suggests + DNSSEC was not supported. If set to false, DNS lookups are not + DNSSEC validated.</para> + + <para>Note that DNSSEC validation requires retrieval of + additional DNS data, and thus results in a small DNS look-up + time penalty.</para> + + <para>DNSSEC requires knowledge of "trust anchors" to prove + data integrity. The trust anchor for the Internet root domain + is built into the resolver, additional trust anchors may be + defined with + <citerefentry><refentrytitle>dnssec-trust-anchors.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>. + Trust anchors may change in regular intervals, and old trust + anchors may be revoked. In such a case DNSSEC validation is + not possible until new trust anchors are configured locally or + the resolver software package is updated with the new root + trust anchor. In effect, when the built-in trust anchor is + revoked and <varname>DNSSEC=</varname> is true, all further + lookups will fail, as it cannot be proved anymore whether + lookups are correctly signed, or validly unsigned. If + <varname>DNSSEC=</varname> is set to + <literal>downgrade-ok</literal> the resolver will + automatically turn of DNSSEC validation in such a case.</para> + + <para>Client programs looking up DNS data will be informed + whether lookups could be verified using DNSSEC, or whether the + returned data could not be verified (either because the data + was found unsigned in the DNS, or the DNS server did not + support DNSSEC or no appropriate trust anchors were known). In + the latter case it is assumed that client programs employ a + secondary scheme to validate the returned DNS data, should + this be required.</para> + + <para>It is recommended to set <varname>DNSSEC=</varname> to + true on systems where it is kown that the DNS server supports + DNSSEC correctly, and where software or trust anchor updates + happen regularly. On other systems it is recommended to set + <varname>DNSSEC=</varname> to + <literal>missing-ok</literal>.</para> + </listitem> + </varlistentry> + </variablelist> </refsect1> @@ -133,6 +190,7 @@ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry><refentrytitle>dnssec-trust-anchors.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>, <citerefentry><refentrytitle>resolv.conf</refentrytitle><manvolnum>4</manvolnum></citerefentry> </para> </refsect1> diff --git a/man/systemd-resolved.service.xml b/man/systemd-resolved.service.xml index 10198812e1..8e1ca1c092 100644 --- a/man/systemd-resolved.service.xml +++ b/man/systemd-resolved.service.xml @@ -144,7 +144,9 @@ <para> <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>dnssec-trust-anchors.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>, <citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> </para> |