<?xml version='1.0'?> <!--*-nxml-*-->
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
-
-<!--
- This file is part of systemd.
-
- Copyright 2012 Lennart Poettering
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
-
- systemd is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
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- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
--->
-
-<refentry id="sd_id128_get_machine">
-
- <refentryinfo>
- <title>sd_id128_get_machine</title>
- <productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
- </refentryinfo>
-
- <refmeta>
- <refentrytitle>sd_id128_get_machine</refentrytitle>
- <manvolnum>3</manvolnum>
- </refmeta>
-
- <refnamediv>
- <refname>sd_id128_get_machine</refname>
- <refname>sd_id128_get_boot</refname>
- <refpurpose>Retrieve 128-bit IDs</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcsynopsisinfo>#include <systemd/sd-id128.h></funcsynopsisinfo>
-
- <funcprototype>
- <funcdef>int <function>sd_id128_get_machine</function></funcdef>
- <paramdef>sd_id128_t* <parameter>ret</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef>int <function>sd_id128_get_boot</function></funcdef>
- <paramdef>sd_id128_t* <parameter>ret</parameter></paramdef>
- </funcprototype>
-
- </funcsynopsis>
- </refsynopsisdiv>
-
- <refsect1>
- <title>Description</title>
-
- <para><function>sd_id128_get_machine()</function>
- returns the machine ID of the executing host. This
- reads and parses the
- <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
- file. This function caches the machine ID internally
- to make retrieving the machine ID a cheap
- operation.</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 at boot and is unique for every running kernel
- instance. See
- <citerefentry><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.</para>
-
- <para>Note that
- <function>sd_id128_get_boot()</function> always returns
- a UUID v4 compatible
- ID. <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>
-
- <para>For more information about the
- <literal>sd_id128_t</literal> type see
- <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
- </refsect1>
-
- <refsect1>
- <title>Return Value</title>
-
- <para>The two calls return 0 on success (in which
- case <parameter>ret</parameter> is filled in), or a
- negative errno-style error code.</para>
- </refsect1>
-
- <refsect1>
- <title>Notes</title>
-
- <para>The <function>sd_id128_get_machine()</function>
- and <function>sd_id128_get_boot()</function>
- interfaces are available as a shared library, which can
- be compiled and linked to with the
- <literal>libsystemd-id128</literal> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
- file.</para>
- </refsect1>
-
- <refsect1>
- <title>See Also</title>
-
- <para>
- <citerefentry><refentrytitle>systemd</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>random</refentrytitle><manvolnum>4</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_id128_randomize</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- </para>
- </refsect1>
+<!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+ -->
+
+<refentry id="sd_id128_get_machine" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>sd_id128_get_machine</title>
+ <productname>systemd</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_id128_get_machine</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_id128_get_machine</refname>
+ <refname>sd_id128_get_machine_app_specific</refname>
+ <refname>sd_id128_get_boot</refname>
+ <refname>sd_id128_get_boot_app_specific</refname>
+ <refname>sd_id128_get_invocation</refname>
+ <refpurpose>Retrieve 128-bit IDs</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <systemd/sd-id128.h></funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_id128_get_machine</function></funcdef>
+ <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>
+ <paramdef>sd_id128_t *<parameter>ret</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_id128_get_boot</function></funcdef>
+ <paramdef>sd_id128_t *<parameter>ret</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_id128_get_boot_app_specific</function></funcdef>
+ <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_invocation</function></funcdef>
+ <paramdef>sd_id128_t *<parameter>ret</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_id128_get_machine()</function> returns the machine ID of the executing host. This reads and
+ parses the <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ 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
+ <function>sd_id128_get_machine_app_specific()</function> is provided, see below.</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>
+
+ <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
+ at boot and is unique for every running kernel instance. See <citerefentry
+ 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>
+
+ <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>
+
+ <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>$INVOCATION_ID</varname> environment
+ variable that the service manager sets when activating a service, see
+ <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details. The
+ ID is cached internally. In future a different mechanism to determine the invocation ID may be added.</para>
+
+ <para>Note that <function>sd_id128_get_machine_app_specific()</function>, <function>sd_id128_get_boot()</function>,
+ <function>sd_id128_get_boot_app_specific()</function>, and <function>sd_id128_get_invocation()</function> always
+ return UUID v4 compatible IDs. <function>sd_id128_get_machine()</function> will also return a UUID v4-compatible
+ ID on new installations but might not on older. It is possible to convert the machine ID into a UUID v4-compatible
+ one. For more information, see
+ <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+
+ <para>For more information about the <literal>sd_id128_t</literal>
+ type see
+ <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>Those calls return 0 on success (in which case <parameter>ret</parameter> is filled in),
+ or a negative errno-style error code. In particular,
+ <function>sd_id128_get_machine()</function>,
+ <function>sd_id128_get_machine_app_specific()</function>, and
+ <function>sd_id128_get_boot_app_specific()</function> return <constant>-ENOENT</constant> if
+ <filename>/etc/machine-id</filename> is missing, and <constant>-ENOMEDIUM</constant> if
+ <filename>/etc/machine-id</filename> is empty or all zeros.</para>
+ </refsect1>
+
+ <xi:include href="libsystemd-pkgconfig.xml" />
+
+ <refsect1>
+ <title>Examples</title>
+
+ <example>
+ <title>Application-specific machine ID</title>
+
+ <para>First, generate the application ID:</para>
+ <programlisting>$ systemd-id128 -p new
+As string:
+c273277323db454ea63bb96e79b53e97
+
+As UUID:
+c2732773-23db-454e-a63b-b96e79b53e97
+
+As man:sd-id128(3) macro:
+#define MESSAGE_XYZ SD_ID128_MAKE(c2,73,27,73,23,db,45,4e,a6,3b,b9,6e,79,b5,3e,97)
+...
+</programlisting>
+
+ <para>Then use the new identifier in an example application:</para>
+
+ <programlisting><xi:include href="id128-app-specific.c" parse="text" /></programlisting>
+ </example>
+ </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>
+ </refsect1>
</refentry>
projects / thirdparty / systemd.git / blobdiff