<?xml version='1.0'?> <!--*-nxml-*-->
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
-
-<!--
- SPDX-License-Identifier: LGPL-2.1+
--->
+<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="sd_id128_get_machine" xmlns:xi="http://www.w3.org/2001/XInclude">
<refnamediv>
<refname>sd_id128_get_machine</refname>
+ <refname>sd_id128_get_app_specific</refname>
<refname>sd_id128_get_machine_app_specific</refname>
<refname>sd_id128_get_boot</refname>
<refname>sd_id128_get_boot_app_specific</refname>
<paramdef>sd_id128_t *<parameter>ret</parameter></paramdef>
</funcprototype>
+ <funcprototype>
+ <funcdef>int <function>sd_id128_get_app_specific</function></funcdef>
+ <paramdef>sd_id128_t <parameter>base</parameter></paramdef>
+ <paramdef>sd_id128_t <parameter>app_id</parameter></paramdef>
+ <paramdef>sd_id128_t *<parameter>ret</parameter></paramdef>
+ </funcprototype>
+
<funcprototype>
<funcdef>int <function>sd_id128_get_machine_app_specific</function></funcdef>
<paramdef>sd_id128_t <parameter>app_id</parameter></paramdef>
file. This function caches the machine ID internally to make retrieving the machine ID a cheap operation. This ID
may be used wherever a unique identifier for the local system is needed. However, it is recommended to use this ID
as-is only in trusted environments. In untrusted environments it is recommended to derive an application specific
- ID from this machine ID, in an irreversable (cryptographically secure) way. To make this easy
+ ID from this machine ID, in an irreversible (cryptographically secure) way. To make this easy
<function>sd_id128_get_machine_app_specific()</function> is provided, see below.</para>
+ <para><function>sd_id128_get_app_specific()</function> returns a machine ID that is a combination of the
+ <parameter>base</parameter> and <parameter>app_id</parameter> parameters. Internally, this function
+ calculates HMAC-SHA256 of the <parameter>app_id</parameter> parameter keyed by the
+ <parameter>base</parameter> parameter, and truncates this result to fit in
+ <structname>sd_id128_t</structname> and turns it into a valid Variant 1 Version 4 UUID, in accordance
+ with <ulink url="https://tools.ietf.org/html/rfc4122">RFC 4122</ulink>. Neither of the two input
+ parameters can be calculated from the output parameter <parameter>ret</parameter>.</para>
+
<para><function>sd_id128_get_machine_app_specific()</function> is similar to
- <function>sd_id128_get_machine()</function>, but retrieves a machine ID that is specific to the application that is
- identified by the indicated application ID. It is recommended to use this function instead of
- <function>sd_id128_get_machine()</function> when passing an ID to untrusted environments, in order to make sure
- that the original machine ID may not be determined externally. This way, the ID used by the application remains
- stable on a given machine, but cannot be easily correlated with IDs used in other applications on the same
- machine. The application-specific ID should be generated via a tool like <command>systemd-id128 new</command>,
- and may be compiled into the application. This function will return the same application-specific ID for each
- combination of machine ID and application ID. Internally, this function calculates HMAC-SHA256 of the application
- ID, keyed by the machine ID.</para>
+ <function>sd_id128_get_machine()</function>, but retrieves a machine ID that is specific to the
+ application that is identified by the indicated application ID. It is recommended to use this function
+ instead of <function>sd_id128_get_machine()</function> when passing an ID to untrusted environments, in
+ order to make sure that the original machine ID may not be determined externally. This way, the ID used
+ by the application remains stable on a given machine, but cannot be easily correlated with IDs used in
+ other applications on the same machine. The application-specific ID should be generated via a tool like
+ <command>systemd-id128 new</command>, and may be compiled into the application. This function will return
+ the same application-specific ID for each combination of machine ID and application ID. Internally, this
+ function calls <function>sd_id128_get_app_specific()</function> with the result from
+ <function>sd_id128_get_machine()</function> and the <parameter>app_id</parameter> parameter.</para>
<para><function>sd_id128_get_boot()</function> returns the boot ID of the executing kernel. This reads and parses
the <filename>/proc/sys/kernel/random/boot_id</filename> file exposed by the kernel. It is randomly generated early
project='man-pages'><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more
information. This function also internally caches the returned ID to make this call a cheap operation. It is
recommended to use this ID as-is only in trusted environments. In untrusted environments it is recommended to
- derive an application specific ID using <function>sd_id128_get_machine_app_specific()</function>, see below.</para>
+ derive an application specific ID using <function>sd_id128_get_boot_app_specific()</function>, see below.</para>
<para><function>sd_id128_get_boot_app_specific()</function> is analogous to
- <function>sd_id128_get_machine_app_specific()</function> but returns an ID that changes between boots. Some
- machines may be used for a long time without rebooting, hence the boot ID may remain constant for a long time, and
- has properties similar to the machine ID during that time.</para>
+ <function>sd_id128_get_machine_app_specific()</function>, but returns an ID that changes between
+ boots. Some machines may be used for a long time without rebooting, hence the boot ID may remain constant
+ for a long time, and has properties similar to the machine ID during that time.</para>
<para><function>sd_id128_get_invocation()</function> returns the invocation ID of the currently executed
- service. In its current implementation, this reads and parses the <varname>$INVOCATION_ID</varname> environment
- variable that the service manager sets when activating a service, see
- <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details. The
- ID is cached internally. In future a different mechanism to determine the invocation ID may be added.</para>
-
- <para>Note that <function>sd_id128_get_machine_app_specific()</function>, <function>sd_id128_get_boot()</function>,
- <function>sd_id128_get_boot_app_specific()</function>, and <function>sd_id128_get_invocation()</function> always
- return UUID v4 compatible IDs. <function>sd_id128_get_machine()</function> will also return a UUID v4-compatible
- ID on new installations but might not on older. It is possible to convert the machine ID into a UUID v4-compatible
- one. For more information, see
- <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+ service. In its current implementation, this tries to read and parse the following:
+ <itemizedlist>
+ <listitem>
+ <para>The <varname>$INVOCATION_ID</varname> environment variable that the service manager sets when
+ activating a service.</para>
+ </listitem>
+ <listitem>
+ <para>An entry in the kernel keyring that the system service manager sets when activating a service.
+ </para>
+ </listitem>
+ </itemizedlist>
+ See <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for details. The ID is cached internally. In future a different mechanism to determine the invocation ID
+ may be added.</para>
+
+ <para>Note that <function>sd_id128_get_machine_app_specific()</function>,
+ <function>sd_id128_get_boot()</function>, <function>sd_id128_get_boot_app_specific()</function>, and
+ <function>sd_id128_get_invocation()</function> always return UUID Variant 1 Version 4 compatible IDs.
+ <function>sd_id128_get_machine()</function> will also return a UUID Variant 1 Version 4 compatible ID on
+ new installations but might not on older. It is possible to convert the machine ID non-reversibly into a
+ UUID Variant 1 Version 4 compatible one. For more information, see
+ <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>. It is
+ hence guaranteed that these functions will never return the ID consisting of all zero or all one bits
+ (<constant>SD_ID128_NULL</constant>, <constant>SD_ID128_ALLF</constant>) — with the possible exception of
+ <function>sd_id128_get_machine()</function>, as mentioned.</para>
<para>For more information about the <literal>sd_id128_t</literal>
type see
<title>Return Value</title>
<para>Those calls return 0 on success (in which case <parameter>ret</parameter> is filled in),
- or a negative errno-style error code. In particular,
- <function>sd_id128_get_machine()</function>,
- <function>sd_id128_get_machine_app_specific()</function>, and
- <function>sd_id128_get_boot_app_specific()</function> return <constant>-ENOENT</constant> if
- <filename>/etc/machine-id</filename> is missing, and <constant>-ENOMEDIUM</constant> if is empty
- or all zeros.</para>
+ or a negative errno-style error code.</para>
+
+ <refsect2>
+ <title>Errors</title>
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>-ENOENT</constant></term>
+
+ <listitem><para>Returned by <function>sd_id128_get_machine()</function> and
+ <function>sd_id128_get_machine_app_specific()</function> when <filename>/etc/machine-id</filename>
+ is missing.</para>
+
+ <xi:include href="version-info.xml" xpointer="v242"/></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ENOMEDIUM</constant></term>
+
+ <listitem><para>Returned by <function>sd_id128_get_machine()</function> and
+ <function>sd_id128_get_machine_app_specific()</function> when <filename>/etc/machine-id</filename>
+ is empty or all zeros. Also returned by <function>sd_id128_get_invocation()</function> when the
+ invocation ID is all zeros.</para>
+
+ <xi:include href="version-info.xml" xpointer="v242"/></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ENOPKG</constant></term>
+
+ <listitem><para>Returned by <function>sd_id128_get_machine()</function> and
+ <function>sd_id128_get_machine_app_specific()</function> when the content of
+ <filename>/etc/machine-id</filename> is <literal>uninitialized</literal>.</para>
+
+ <xi:include href="version-info.xml" xpointer="v253"/></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ENOSYS</constant></term>
+
+ <listitem><para>Returned by <function>sd_id128_get_boot()</function> and
+ <function>sd_id128_get_boot_app_specific()</function> when <filename>/proc/</filename> is not
+ mounted.</para>
+
+ <xi:include href="version-info.xml" xpointer="v253"/></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ENXIO</constant></term>
+
+ <listitem><para>Returned by <function>sd_id128_get_invocation()</function> if no invocation ID is
+ set. Also returned by <function>sd_id128_get_app_specific()</function>,
+ <function>sd_id128_get_machine_app_specific()</function>, and
+ <function>sd_id128_get_boot_app_specific()</function> when the <parameter>app_id</parameter>
+ parameter is all zeros.</para>
+
+ <xi:include href="version-info.xml" xpointer="v242"/></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EUCLEAN</constant></term>
+
+ <listitem><para>Returned by any of the functions described here when the configured value has
+ invalid format.</para>
+
+ <xi:include href="version-info.xml" xpointer="v253"/></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EPERM</constant></term>
+
+ <listitem><para>Requested information could not be retrieved because of insufficient permissions.
+ </para>
+
+ <xi:include href="version-info.xml" xpointer="v242"/></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect2>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
</example>
</refsect1>
+ <refsect1>
+ <title>History</title>
+ <para><function>sd_id128_get_machine()</function> and
+ <function>sd_id128_get_boot()</function> were added in version 187.</para>
+ <para><function>sd_id128_get_invocation()</function> was added in version 232.</para>
+ <para><function>sd_id128_get_machine_app_specific()</function> was added in version 233.</para>
+ <para><function>sd_id128_get_boot_app_specific()</function> was added in version 240.</para>
+ <para><function>sd_id128_get_app_specific()</function> was added in version 255.</para>
+ </refsect1>
+
<refsect1>
<title>See Also</title>
- <para>
- <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd-id128</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_id128_randomize</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry project='man-pages'><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry>
- </para>
+ <para><simplelist type="inline">
+ <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
+ <member><citerefentry><refentrytitle>systemd-id128</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
+ <member><citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
+ <member><citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
+ <member><citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
+ <member><citerefentry><refentrytitle>sd_id128_randomize</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
+ <member><citerefentry project='man-pages'><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry></member>
+ </simplelist></para>
</refsect1>
</refentry>
projects / thirdparty / systemd.git / blobdiff