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Diffstat (limited to 'man/resolved.conf.xml')
| -rw-r--r-- | man/resolved.conf.xml | 71 |
1 files changed, 53 insertions, 18 deletions
diff --git a/man/resolved.conf.xml b/man/resolved.conf.xml index 8473bbe5c9..5da2d5488e 100644 --- a/man/resolved.conf.xml +++ b/man/resolved.conf.xml @@ -125,22 +125,38 @@ </varlistentry> <varlistentry> + <term><varname>MulticastDNS=</varname></term> + <listitem><para>Takes a boolean argument or + <literal>resolve</literal>. Controls Multicast DNS support + (<ulink url="https://tools.ietf.org/html/rfc6762">RFC + 6762</ulink>) on the local host. If true, enables full + Multicast DNS responder and resolver support. If false, + disables both. If set to <literal>resolve</literal>, only + resolution support is enabled, but responding is + disabled. Note that + <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> + also maintains per-interface Multicast DNS settings. Multicast + DNS will be enabled on an interface only if the per-interface + and the 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> + <literal>allow-downgrade</literal>. If true all DNS lookups are + DNSSEC-validated locally (excluding LLMNR and Multicast + DNS). 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>allow-downgrade</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 @@ -160,8 +176,8 @@ 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> + <literal>allow-downgrade</literal> the resolver will + automatically turn off 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 @@ -173,11 +189,30 @@ 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 + true on systems where it is known 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> + <literal>allow-downgrade</literal>.</para> + + <para>In addition to this global DNSSEC setting + <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> + also maintains per-interface DNSSEC settings. For system DNS + servers (see above), only the global DNSSEC setting is in + effect. For per-interface DNS servers the per-interface + setting is in effect, unless it is unset in which case the + global setting is used instead.</para> + + <para>Site-private DNS zones generally conflict with DNSSEC + operation, unless a negative (if the private zone is not + signed) or positive (if the private zone is signed) trust + anchor is configured for them. If + <literal>allow-downgrade</literal> mode is selected, it is + attempted to detect site-private DNS zones using top-level + domains (TLDs) that are not known by the DNS root server. This + logic does not work in all private zone setups.</para> + + <para>Defaults to off.</para> </listitem> </varlistentry> |