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514094f9 | 1 | <?xml version='1.0'?> |
3a54a157 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
b5a8703f | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
db9ecf05 | 4 | <!-- SPDX-License-Identifier: LGPL-2.1-or-later --> |
b5a8703f | 5 | |
1ec57f33 | 6 | <refentry id="dnssec-trust-anchors.d" conditional='ENABLE_RESOLVE' |
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7 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
8 | <refentryinfo> | |
9 | <title>dnssec-trust-anchors.d</title> | |
10 | <productname>systemd</productname> | |
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11 | </refentryinfo> |
12 | ||
13 | <refmeta> | |
14 | <refentrytitle>dnssec-trust-anchors.d</refentrytitle> | |
15 | <manvolnum>5</manvolnum> | |
16 | </refmeta> | |
17 | ||
18 | <refnamediv> | |
19 | <refname>dnssec-trust-anchors.d</refname> | |
20 | <refname>systemd.positive</refname> | |
21 | <refname>systemd.negative</refname> | |
22 | <refpurpose>DNSSEC trust anchor configuration files</refpurpose> | |
23 | </refnamediv> | |
24 | ||
25 | <refsynopsisdiv> | |
26 | <para><filename>/etc/dnssec-trust-anchors.d/*.positive</filename></para> | |
27 | <para><filename>/run/dnssec-trust-anchors.d/*.positive</filename></para> | |
28 | <para><filename>/usr/lib/dnssec-trust-anchors.d/*.positive</filename></para> | |
29 | <para><filename>/etc/dnssec-trust-anchors.d/*.negative</filename></para> | |
30 | <para><filename>/run/dnssec-trust-anchors.d/*.negative</filename></para> | |
31 | <para><filename>/usr/lib/dnssec-trust-anchors.d/*.negative</filename></para> | |
32 | </refsynopsisdiv> | |
33 | ||
34 | <refsect1> | |
35 | <title>Description</title> | |
36 | ||
37 | <para>The DNSSEC trust anchor configuration files define positive | |
38 | and negative trust anchors | |
39 | <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
40 | bases DNSSEC integrity proofs on.</para> | |
41 | </refsect1> | |
42 | ||
43 | <refsect1> | |
44 | <title>Positive Trust Anchors</title> | |
45 | ||
46 | <para>Positive trust anchor configuration files contain DNSKEY and | |
47 | DS resource record definitions to use as base for DNSSEC integrity | |
48 | proofs. See <ulink | |
49 | url="https://tools.ietf.org/html/rfc4035#section-4.4">RFC 4035, | |
50 | Section 4.4</ulink> for more information about DNSSEC trust | |
51 | anchors.</para> | |
52 | ||
53 | <para>Positive trust anchors are read from files with the suffix | |
54 | <filename>.positive</filename> located in | |
55 | <filename>/etc/dnssec-trust-anchors.d/</filename>, | |
56 | <filename>/run/dnssec-trust-anchors.d/</filename> and | |
57 | <filename>/usr/lib/dnssec-trust-anchors.d/</filename>. These | |
58 | directories are searched in the specified order, and a trust | |
59 | anchor file of the same name in an earlier path overrides a trust | |
60 | anchor files in a later path. To disable a trust anchor file | |
61 | shipped in <filename>/usr/lib/dnssec-trust-anchors.d/</filename> | |
62 | it is sufficient to provide an identically-named file in | |
63 | <filename>/etc/dnssec-trust-anchors.d/</filename> or | |
64 | <filename>/run/dnssec-trust-anchors.d/</filename> that is either | |
65 | empty or a symlink to <filename>/dev/null</filename> ("masked").</para> | |
66 | ||
67 | <para>Positive trust anchor files are simple text files resembling | |
68 | DNS zone files, as documented in <ulink | |
69 | url="https://tools.ietf.org/html/rfc1035#section-5">RFC 1035, Section | |
70 | 5</ulink>. One DS or DNSKEY resource record may be listed per | |
71 | line. Empty lines and lines starting with a semicolon | |
72 | (<literal>;</literal>) are ignored and considered comments. A DS | |
73 | resource record is specified like in the following example:</para> | |
74 | ||
75 | <programlisting>. IN DS 19036 8 2 49aac11d7b6f6446702e54a1607371607a1a41855200fd2ce1cdde32f24e8fb5</programlisting> | |
76 | ||
77 | <para>The first word specifies the domain, use | |
78 | <literal>.</literal> for the root domain. The domain may be | |
79 | specified with or without trailing dot, which is considered | |
80 | equivalent. The second word must be <literal>IN</literal> the | |
81 | third word <literal>DS</literal>. The following words specify the | |
82 | key tag, signature algorithm, digest algorithm, followed by the | |
83 | hex-encoded key fingerprint. See <ulink | |
84 | url="https://tools.ietf.org/html/rfc4034#section-5">RFC 4034, | |
85 | Section 5</ulink> for details about the precise syntax and meaning | |
86 | of these fields.</para> | |
87 | ||
88 | <para>Alternatively, DNSKEY resource records may be used to define | |
89 | trust anchors, like in the following example:</para> | |
90 | ||
91 | <programlisting>. IN DNSKEY 257 3 8 AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjFFVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoXbfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaDX6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpzW5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relSQageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulqQxA+Uk1ihz0=</programlisting> | |
92 | ||
93 | <para>The first word specifies the domain again, the second word | |
94 | must be <literal>IN</literal>, followed by | |
95 | <literal>DNSKEY</literal>. The subsequent words encode the DNSKEY | |
96 | flags, protocol and algorithm fields, followed by the key data | |
b8e1d4d1 | 97 | encoded in Base64. See <ulink |
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98 | url="https://tools.ietf.org/html/rfc4034#section-2">RFC 4034, |
99 | Section 2</ulink> for details about the precise syntax and meaning | |
100 | of these fields.</para> | |
101 | ||
102 | <para>If multiple DS or DNSKEY records are defined for the same | |
103 | domain (possibly even in different trust anchor files), all keys | |
104 | are used and are considered equivalent as base for DNSSEC | |
105 | proofs.</para> | |
106 | ||
107 | <para>Note that <filename>systemd-resolved</filename> will | |
108 | automatically use a built-in trust anchor key for the Internet | |
109 | root domain if no positive trust anchors are defined for the root | |
110 | domain. In most cases it is hence unnecessary to define an | |
111 | explicit key with trust anchor files. The built-in key is disabled | |
112 | as soon as at least one trust anchor key for the root domain is | |
113 | defined in trust anchor files.</para> | |
114 | ||
115 | <para>It is generally recommended to encode trust anchors in DS | |
116 | resource records, rather than DNSKEY resource records.</para> | |
117 | ||
118 | <para>If a trust anchor specified via a DS record is found revoked | |
119 | it is automatically removed from the trust anchor database for the | |
120 | runtime. See <ulink url="https://tools.ietf.org/html/rfc5011">RFC | |
121 | 5011</ulink> for details about revoked trust anchors. Note that | |
122 | <filename>systemd-resolved</filename> will not update its trust | |
123 | anchor database from DNS servers automatically. Instead, it is | |
124 | recommended to update the resolver software or update the new | |
125 | trust anchor via adding in new trust anchor files.</para> | |
126 | ||
127 | <para>The current DNSSEC trust anchor for the Internet's root | |
b8e1d4d1 | 128 | domain is available at the <ulink |
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129 | url="https://data.iana.org/root-anchors/root-anchors.xml">IANA |
130 | Trust Anchor and Keys</ulink> page.</para> | |
131 | </refsect1> | |
132 | ||
133 | <refsect1> | |
134 | <title>Negative Trust Anchors</title> | |
135 | ||
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136 | <para>Negative trust anchors define domains where DNSSEC validation shall be turned |
137 | off. Negative trust anchor files are found at the same location as positive trust anchor files, | |
138 | and follow the same overriding rules. They are text files with the | |
139 | <filename>.negative</filename> suffix. Empty lines and lines whose first character is | |
140 | <literal>;</literal> are ignored. Each line specifies one domain name which is the root of a DNS | |
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141 | subtree where validation shall be disabled. For example:</para> |
142 | ||
143 | <programlisting># Reverse IPv4 mappings | |
144 | 10.in-addr.arpa | |
145 | 16.172.in-addr.arpa | |
146 | 168.192.in-addr.arpa | |
147 | ... | |
148 | # Some custom domains | |
149 | prod | |
150 | stag | |
151 | </programlisting> | |
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152 | |
153 | <para>Negative trust anchors are useful to support private DNS | |
154 | subtrees that are not referenced from the Internet DNS hierarchy, | |
155 | and not signed.</para> | |
156 | ||
157 | <para><ulink url="https://tools.ietf.org/html/rfc7646">RFC | |
158 | 7646</ulink> for details on negative trust anchors.</para> | |
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159 | |
160 | <para>If no negative trust anchor files are configured a built-in | |
161 | set of well-known private DNS zone domains is used as negative | |
162 | trust anchors.</para> | |
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163 | |
164 | <para>It is also possibly to define per-interface negative trust | |
165 | anchors using the <varname>DNSSECNegativeTrustAnchors=</varname> | |
166 | setting in | |
167 | <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
168 | files.</para> | |
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169 | </refsect1> |
170 | ||
171 | <refsect1> | |
172 | <title>See Also</title> | |
173 | <para> | |
174 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
175 | <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
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176 | <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
177 | <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
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178 | </para> |
179 | </refsect1> | |
180 | ||
181 | </refentry> |