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+ This file is part of elogind.
Copyright 2012 Lennart Poettering
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<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 an 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 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>
+ <refentryinfo>
+ <title>sd_id128_get_machine</title>
+ <productname>elogind</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_machine_app_specific</refname>
+ <refname>sd_id128_get_boot</refname>
+ <refname>sd_id128_get_invocation</refname>
+ <refpurpose>Retrieve 128-bit IDs</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <elogind/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_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. 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>
+
+ <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>
+ 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>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>, <function>sd_id128_get_machine_app_specific()</function>
+ <function>sd_id128_get_boot()</function> and <function>sd_id128_get_invocation()</function> interfaces are
+ available as a shared library, which can be compiled and linked to with the
+ <literal>libsystemd</literal> <citerefentry
+ project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Examples</title>
+
+ <example>
+ <title>Application-specific machine ID</title>
+
+ <para>Here's a simple example for an application specific machine ID:</para>
+
+ <programlisting>#include <systemd/sd-id128.h>
+#include <stdio.h>
+
+#define OUR_APPLICATION_ID SD_ID128_MAKE(c2,73,27,73,23,db,45,4e,a6,3b,b9,6e,79,b5,3e,97)
+
+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>
+ </example>
+ </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>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>
~ianmdlvl / elogind.git / blobdiff