man: document homed key management

Fixes: #15235
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Lennart Poettering 2020-05-05 19:33:27 +02:00
parent 6bae4b905c
commit 6d68a0b3dd
1 changed files with 49 additions and 0 deletions

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@ -47,6 +47,55 @@
<citerefentry><refentrytitle>userdbctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
</refsect1>
<refsect1>
<title>Key Management</title>
<para>User records are cryptographically signed with a public/private key pair (the signature is part of
the JSON record itself). For a user to be permitted to log in locally the public key matching the
signature of their user record must be installed. For a user record to be modified locally the private
key matching the signature must be installed locally, too. The keys are stored in the
<filename>/var/lib/systemd/home/</filename> directory:</para>
<variablelist>
<varlistentry>
<term><filename>/var/lib/systemd/home/local.private</filename></term>
<listitem><para>The private key of the public/private key pair used for local records. Currently,
only a single such key may be installed.</para></listitem>
</varlistentry>
<varlistentry>
<term><filename>/var/lib/systemd/home/local.public</filename></term>
<listitem><para>The public key of the public/private key pair used for local records. Currently,
only a single such key may be installed.</para></listitem>
</varlistentry>
<varlistentry>
<term><filename>/var/lib/systemd/home/*.public</filename></term>
<listitem><para>Additional public keys. Any users whose user records are signed with any of these keys
are permitted to log in locally. An arbitrary number of keys may be installed this
way.</para></listitem>
</varlistentry>
</variablelist>
<para>All key files listed above are in PEM format.</para>
<para>In order to migrate a home directory from a host <literal>foobar</literal> to another host
<literal>quux</literal> it is hence sufficient to copy
<filename>/var/lib/systemd/home/local.public</filename> from the host <literal>foobar</literal> to
<literal>quux</literal>, maybe calling the file on the destination
<filename>/var/lib/systemd/home/foobar.public</filename>, reflecting the origin of the key. If the user
record should be modifiable on <literal>quux</literal> the pair
<filename>/var/lib/systemd/home/local.public</filename> and
<filename>/var/lib/systemd/home/local.private</filename> need to be copied from <literal>foobar</literal>
to <literal>quux</literal>, and placed under the identical paths there, as currently only a single
private key is supported per host. Note of course that the latter means that user records
generated/signed before the key pair is copied in, lose their validity.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>