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| -rw-r--r-- | man/resolved.conf.xml | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/man/resolved.conf.xml b/man/resolved.conf.xml index 4680b6a4e5..857a93b653 100644 --- a/man/resolved.conf.xml +++ b/man/resolved.conf.xml @@ -124,6 +124,61 @@ 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. However, 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> |