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diff --git a/man/dnssec-trust-anchors.d.xml b/man/dnssec-trust-anchors.d.xml new file mode 100644 index 0000000..39b9515 --- /dev/null +++ b/man/dnssec-trust-anchors.d.xml @@ -0,0 +1,172 @@ +<?xml version='1.0'?> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> +<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> + +<refentry id="dnssec-trust-anchors.d" conditional='ENABLE_RESOLVE' + xmlns:xi="http://www.w3.org/2001/XInclude"> + <refentryinfo> + <title>dnssec-trust-anchors.d</title> + <productname>systemd</productname> + </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 <constant class='dns'>DNSKEY</constant> and + <constant class='dns'>DS</constant> 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 <constant + class='dns'>DS</constant> or <constant class='dns'>DNSKEY</constant> resource record may be listed per + line. Empty lines and lines starting with <literal>#</literal> or <literal>;</literal> are ignored, which + may be used for commenting. A <constant class='dns'>DS</constant> 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, <constant class='dns'>DNSKEY</constant> 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 <constant class='dns'>DNSKEY</constant> + flags, protocol and algorithm fields, followed by the key data encoded in Base64. 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 <constant class='dns'>DS</constant> or <constant class='dns'>DNSKEY</constant> 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 <constant class='dns'>DS</constant> resource + records, rather than <constant class='dns'>DNSKEY</constant> resource records.</para> + + <para>If a trust anchor specified via a <constant class='dns'>DS</constant> 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 at 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 which is the root of a DNS + subtree where validation shall be disabled. For example:</para> + + <programlisting># Reverse IPv4 mappings +10.in-addr.arpa +16.172.in-addr.arpa +168.192.in-addr.arpa +... +# Some custom domains +prod +stag +</programlisting> + + <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> + + <para>If no negative trust anchor files are configured a built-in + set of well-known private DNS zone domains is used as negative + trust anchors.</para> + + <para>It is also possibly to define per-interface negative trust + anchors using the <varname>DNSSECNegativeTrustAnchors=</varname> + setting in + <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> + files.</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>, + <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |