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diff --git a/man/sd_id128_get_machine.xml b/man/sd_id128_get_machine.xml new file mode 100644 index 0000000..35a3045 --- /dev/null +++ b/man/sd_id128_get_machine.xml @@ -0,0 +1,212 @@ +<?xml version='1.0'?> <!--*-nxml-*--> +<!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-or-later --> + +<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 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. 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_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> + + <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 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 + <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.</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" /> + + <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> |