<?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+ -->
<refentry id="sd_id128_get_machine" xmlns:xi="http://www.w3.org/2001/XInclude">
<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>
<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>
<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>
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_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. The application-specific ID should be generated via
- a tool like <command>journalctl --new-id128</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.</para>
+ 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
<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>
- 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
+ <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>
<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>
- and <function>sd_id128_get_machine_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>,
+ <function>sd_id128_get_machine_app_specific()</function>, and
+ <function>sd_id128_get_boot_app_specific()</function> when <filename>/etc/machine-id</filename> is
+ missing.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ENOMEDIUM</constant></term>
+
+ <listitem><para>Returned by <function>sd_id128_get_machine()</function>,
+ <function>sd_id128_get_machine_app_specific()</function>, and
+ <function>sd_id128_get_boot_app_specific()</function> when <filename>/etc/machine-id</filename> is
+ empty or all zeros.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ENXIO</constant></term>
+
+ <listitem><para>Returned by <function>sd_id128_get_invocation()</function> if no invocation ID is
+ set.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EIO</constant></term>
+
+ <listitem><para>Returned by any of the functions described here when the configured value has
+ invalid format.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EPERM</constant></term>
+
+ <listitem><para>Requested information could not be retrieved because of insufficient permissions.
+ </para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect2>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<example>
<title>Application-specific machine ID</title>
- <para>Here's a simple example for an application specific machine ID:</para>
+ <para>First, generate the application ID:</para>
+ <programlisting>$ systemd-id128 -p new
+As string:
+c273277323db454ea63bb96e79b53e97
+
+As UUID:
+c2732773-23db-454e-a63b-b96e79b53e97
- <programlisting>#include <systemd/sd-id128.h>
-#include <stdio.h>
+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>
-#define OUR_APPLICATION_ID SD_ID128_MAKE(c2,73,27,73,23,db,45,4e,a6,3b,b9,6e,79,b5,3e,97)
+ <para>Then use the new identifier in an example application:</para>
-int main(int argc, char *argv[]) {
- sd_id128_t id;
- sd_id128_get_machine_app_specific(OUR_APPLICATION_ID, &id);
- printf("Our application ID: " SD_ID128_FORMAT_STR "\n", SD_ID128_FORMAT_VAL(id));
- return 0;
-}</programlisting>
+ <programlisting><xi:include href="id128-app-specific.c" parse="text" /></programlisting>
</example>
</refsect1>
<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>,
projects / thirdparty / systemd.git / blobdiff