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514094f9 | 1 | <?xml version='1.0'?> |
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2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | ||
5 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
1ec57f33 | 9 | <refentry id="dnssec-trust-anchors.d" conditional='ENABLE_RESOLVE' |
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10 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
11 | <refentryinfo> | |
12 | <title>dnssec-trust-anchors.d</title> | |
13 | <productname>systemd</productname> | |
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14 | </refentryinfo> |
15 | ||
16 | <refmeta> | |
17 | <refentrytitle>dnssec-trust-anchors.d</refentrytitle> | |
18 | <manvolnum>5</manvolnum> | |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
22 | <refname>dnssec-trust-anchors.d</refname> | |
23 | <refname>systemd.positive</refname> | |
24 | <refname>systemd.negative</refname> | |
25 | <refpurpose>DNSSEC trust anchor configuration files</refpurpose> | |
26 | </refnamediv> | |
27 | ||
28 | <refsynopsisdiv> | |
29 | <para><filename>/etc/dnssec-trust-anchors.d/*.positive</filename></para> | |
30 | <para><filename>/run/dnssec-trust-anchors.d/*.positive</filename></para> | |
31 | <para><filename>/usr/lib/dnssec-trust-anchors.d/*.positive</filename></para> | |
32 | <para><filename>/etc/dnssec-trust-anchors.d/*.negative</filename></para> | |
33 | <para><filename>/run/dnssec-trust-anchors.d/*.negative</filename></para> | |
34 | <para><filename>/usr/lib/dnssec-trust-anchors.d/*.negative</filename></para> | |
35 | </refsynopsisdiv> | |
36 | ||
37 | <refsect1> | |
38 | <title>Description</title> | |
39 | ||
40 | <para>The DNSSEC trust anchor configuration files define positive | |
41 | and negative trust anchors | |
42 | <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
43 | bases DNSSEC integrity proofs on.</para> | |
44 | </refsect1> | |
45 | ||
46 | <refsect1> | |
47 | <title>Positive Trust Anchors</title> | |
48 | ||
49 | <para>Positive trust anchor configuration files contain DNSKEY and | |
50 | DS resource record definitions to use as base for DNSSEC integrity | |
51 | proofs. See <ulink | |
52 | url="https://tools.ietf.org/html/rfc4035#section-4.4">RFC 4035, | |
53 | Section 4.4</ulink> for more information about DNSSEC trust | |
54 | anchors.</para> | |
55 | ||
56 | <para>Positive trust anchors are read from files with the suffix | |
57 | <filename>.positive</filename> located in | |
58 | <filename>/etc/dnssec-trust-anchors.d/</filename>, | |
59 | <filename>/run/dnssec-trust-anchors.d/</filename> and | |
60 | <filename>/usr/lib/dnssec-trust-anchors.d/</filename>. These | |
61 | directories are searched in the specified order, and a trust | |
62 | anchor file of the same name in an earlier path overrides a trust | |
63 | anchor files in a later path. To disable a trust anchor file | |
64 | shipped in <filename>/usr/lib/dnssec-trust-anchors.d/</filename> | |
65 | it is sufficient to provide an identically-named file in | |
66 | <filename>/etc/dnssec-trust-anchors.d/</filename> or | |
67 | <filename>/run/dnssec-trust-anchors.d/</filename> that is either | |
68 | empty or a symlink to <filename>/dev/null</filename> ("masked").</para> | |
69 | ||
70 | <para>Positive trust anchor files are simple text files resembling | |
71 | DNS zone files, as documented in <ulink | |
72 | url="https://tools.ietf.org/html/rfc1035#section-5">RFC 1035, Section | |
73 | 5</ulink>. One DS or DNSKEY resource record may be listed per | |
74 | line. Empty lines and lines starting with a semicolon | |
75 | (<literal>;</literal>) are ignored and considered comments. A DS | |
76 | resource record is specified like in the following example:</para> | |
77 | ||
78 | <programlisting>. IN DS 19036 8 2 49aac11d7b6f6446702e54a1607371607a1a41855200fd2ce1cdde32f24e8fb5</programlisting> | |
79 | ||
80 | <para>The first word specifies the domain, use | |
81 | <literal>.</literal> for the root domain. The domain may be | |
82 | specified with or without trailing dot, which is considered | |
83 | equivalent. The second word must be <literal>IN</literal> the | |
84 | third word <literal>DS</literal>. The following words specify the | |
85 | key tag, signature algorithm, digest algorithm, followed by the | |
86 | hex-encoded key fingerprint. See <ulink | |
87 | url="https://tools.ietf.org/html/rfc4034#section-5">RFC 4034, | |
88 | Section 5</ulink> for details about the precise syntax and meaning | |
89 | of these fields.</para> | |
90 | ||
91 | <para>Alternatively, DNSKEY resource records may be used to define | |
92 | trust anchors, like in the following example:</para> | |
93 | ||
94 | <programlisting>. IN DNSKEY 257 3 8 AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjFFVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoXbfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaDX6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpzW5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relSQageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulqQxA+Uk1ihz0=</programlisting> | |
95 | ||
96 | <para>The first word specifies the domain again, the second word | |
97 | must be <literal>IN</literal>, followed by | |
98 | <literal>DNSKEY</literal>. The subsequent words encode the DNSKEY | |
99 | flags, protocol and algorithm fields, followed by the key data | |
b8e1d4d1 | 100 | encoded in Base64. See <ulink |
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101 | url="https://tools.ietf.org/html/rfc4034#section-2">RFC 4034, |
102 | Section 2</ulink> for details about the precise syntax and meaning | |
103 | of these fields.</para> | |
104 | ||
105 | <para>If multiple DS or DNSKEY records are defined for the same | |
106 | domain (possibly even in different trust anchor files), all keys | |
107 | are used and are considered equivalent as base for DNSSEC | |
108 | proofs.</para> | |
109 | ||
110 | <para>Note that <filename>systemd-resolved</filename> will | |
111 | automatically use a built-in trust anchor key for the Internet | |
112 | root domain if no positive trust anchors are defined for the root | |
113 | domain. In most cases it is hence unnecessary to define an | |
114 | explicit key with trust anchor files. The built-in key is disabled | |
115 | as soon as at least one trust anchor key for the root domain is | |
116 | defined in trust anchor files.</para> | |
117 | ||
118 | <para>It is generally recommended to encode trust anchors in DS | |
119 | resource records, rather than DNSKEY resource records.</para> | |
120 | ||
121 | <para>If a trust anchor specified via a DS record is found revoked | |
122 | it is automatically removed from the trust anchor database for the | |
123 | runtime. See <ulink url="https://tools.ietf.org/html/rfc5011">RFC | |
124 | 5011</ulink> for details about revoked trust anchors. Note that | |
125 | <filename>systemd-resolved</filename> will not update its trust | |
126 | anchor database from DNS servers automatically. Instead, it is | |
127 | recommended to update the resolver software or update the new | |
128 | trust anchor via adding in new trust anchor files.</para> | |
129 | ||
130 | <para>The current DNSSEC trust anchor for the Internet's root | |
b8e1d4d1 | 131 | domain is available at the <ulink |
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132 | url="https://data.iana.org/root-anchors/root-anchors.xml">IANA |
133 | Trust Anchor and Keys</ulink> page.</para> | |
134 | </refsect1> | |
135 | ||
136 | <refsect1> | |
137 | <title>Negative Trust Anchors</title> | |
138 | ||
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139 | <para>Negative trust anchors define domains where DNSSEC validation shall be turned |
140 | off. Negative trust anchor files are found at the same location as positive trust anchor files, | |
141 | and follow the same overriding rules. They are text files with the | |
142 | <filename>.negative</filename> suffix. Empty lines and lines whose first character is | |
143 | <literal>;</literal> are ignored. Each line specifies one domain name which is the root of a DNS | |
144 | subtree where validation shall be disabled.</para> | |
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145 | |
146 | <para>Negative trust anchors are useful to support private DNS | |
147 | subtrees that are not referenced from the Internet DNS hierarchy, | |
148 | and not signed.</para> | |
149 | ||
150 | <para><ulink url="https://tools.ietf.org/html/rfc7646">RFC | |
151 | 7646</ulink> for details on negative trust anchors.</para> | |
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152 | |
153 | <para>If no negative trust anchor files are configured a built-in | |
154 | set of well-known private DNS zone domains is used as negative | |
155 | trust anchors.</para> | |
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156 | |
157 | <para>It is also possibly to define per-interface negative trust | |
158 | anchors using the <varname>DNSSECNegativeTrustAnchors=</varname> | |
159 | setting in | |
160 | <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
161 | files.</para> | |
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162 | </refsect1> |
163 | ||
164 | <refsect1> | |
165 | <title>See Also</title> | |
166 | <para> | |
167 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
168 | <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
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169 | <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
170 | <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
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171 | </para> |
172 | </refsect1> | |
173 | ||
174 | </refentry> |