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120 lines
5.8 KiB
XML
120 lines
5.8 KiB
XML
<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="systemd-cryptsetup" conditional='HAVE_LIBCRYPTSETUP'>
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<refentryinfo>
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<title>systemd-cryptsetup</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-cryptsetup</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-cryptsetup</refname>
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<refname>systemd-cryptsetup@.service</refname>
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<!-- <refname>system-systemd\x2dcryptsetup.slice</refname> — this causes meson to go haywire because it
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thinks this is a (windows) path. Let's just not create the alias for this name, and only include it
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in the synopsis. -->
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<refpurpose>Full disk decryption logic</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>systemd-cryptsetup</command>
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<arg choice="opt" rep="repeat">OPTIONS</arg>
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<arg choice="plain">attach</arg>
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<arg choice="plain">VOLUME</arg>
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<arg choice="plain">SOURCE-DEVICE</arg>
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<arg choice="opt">KEY-FILE</arg>
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<arg choice="opt">CONFIG</arg>
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</cmdsynopsis>
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<cmdsynopsis>
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<command>systemd-cryptsetup</command>
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<arg choice="opt" rep="repeat">OPTIONS</arg>
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<arg choice="plain">detach</arg>
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<arg choice="plain">VOLUME</arg>
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</cmdsynopsis>
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<para><filename>systemd-cryptsetup@.service</filename></para>
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<para><filename>system-systemd\x2dcryptsetup.slice</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><filename>systemd-cryptsetup</filename> is used to set up (with <command>attach</command>) and tear
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down (with <command>detach</command>) access to an encrypted block device. It is primarily used via
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<filename>systemd-cryptsetup@.service</filename> during early boot, but may also be be called manually.
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The positional arguments <parameter>VOLUME</parameter>, <parameter>SOURCEDEVICE</parameter>,
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<parameter>KEY-FILE</parameter>, and <parameter>CRYPTTAB-OPTIONS</parameter> have the same meaning as the
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fields in <citerefentry><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
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</para>
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<para><filename>systemd-cryptsetup@.service</filename> is a service responsible for providing access to
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encrypted block devices. It is instantiated for each device that requires decryption.</para>
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<para><filename>systemd-cryptsetup@.service</filename> instances are part of the
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<filename>system-systemd\x2dcryptsetup.slice</filename> slice, which is destroyed only very late in the
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shutdown procedure. This allows the encrypted devices to remain up until filesystems have been unmounted.
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</para>
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<para><filename>systemd-cryptsetup@.service</filename> will ask
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for hard disk passwords via the <ulink
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url="https://systemd.io/PASSWORD_AGENTS/">password agent logic</ulink>, in
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order to query the user for the password using the right mechanism at boot
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and during runtime.</para>
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<para>At early boot and when the system manager configuration is reloaded, <filename>/etc/crypttab</filename> is
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translated into <filename>systemd-cryptsetup@.service</filename> units by
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<citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
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<para>In order to unlock a volume a password or binary key is required.
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<filename>systemd-cryptsetup@.service</filename> tries to acquire a suitable password or binary key via
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the following mechanisms, tried in order:</para>
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<orderedlist>
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<listitem><para>If a key file is explicitly configured (via the third column in
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<filename>/etc/crypttab</filename>), a key read from it is used. If a PKCS#11 token, FIDO2 token or
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TPM2 device is configured (using the <varname>pkcs11-uri=</varname>, <varname>fido2-device=</varname>,
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<varname>tpm2-device=</varname> options) the key is decrypted before use.</para></listitem>
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<listitem><para>If no key file is configured explicitly this way, a key file is automatically loaded
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from <filename>/etc/cryptsetup-keys.d/<replaceable>volume</replaceable>.key</filename> and
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<filename>/run/cryptsetup-keys.d/<replaceable>volume</replaceable>.key</filename>, if present. Here
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too, if a PKCS#11/FIDO2/TPM2 token/device is configured, any key found this way is decrypted before
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use.</para></listitem>
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<listitem><para>If the <varname>try-empty-password</varname> option is specified then unlocking the
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volume with an empty password is attempted.</para></listitem>
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<listitem><para>The kernel keyring is then checked for a suitable cached password from previous
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attempts.</para></listitem>
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<listitem><para>Finally, the user is queried for a password, possibly multiple times, unless
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the <varname>headless</varname> option is set.</para></listitem>
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</orderedlist>
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<para>If no suitable key may be acquired via any of the mechanisms describes above, volume activation fails.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-cryptenroll</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<ulink url="https://systemd.io/TPM2_PCR_MEASUREMENTS">TPM2 PCR Measurements Made by systemd</ulink>
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</para>
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</refsect1>
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</refentry>
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