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Diffstat (limited to 'man/sd_id128_get_machine.xml')
| -rw-r--r-- | man/sd_id128_get_machine.xml | 65 |
1 files changed, 53 insertions, 12 deletions
diff --git a/man/sd_id128_get_machine.xml b/man/sd_id128_get_machine.xml index 9a86c24aed..3938c6d836 100644 --- a/man/sd_id128_get_machine.xml +++ b/man/sd_id128_get_machine.xml @@ -44,6 +44,7 @@ <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> @@ -59,6 +60,12 @@ </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> @@ -74,11 +81,22 @@ <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_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 @@ -95,10 +113,10 @@ <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_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> + 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> @@ -117,13 +135,36 @@ <refsect1> <title>Notes</title> - <para>The <function>sd_id128_get_machine()</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 + <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> |