<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>
<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>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. 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. 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 is empty
+ or all zeros.</para>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
return 0;
}
-_public_ int sd_id128_get_machine_app_specific(sd_id128_t app_id, sd_id128_t *ret) {
+static int get_app_specific(sd_id128_t base, sd_id128_t app_id, sd_id128_t *ret) {
_cleanup_(khash_unrefp) khash *h = NULL;
- sd_id128_t m, result;
+ sd_id128_t result;
const void *p;
int r;
- assert_return(ret, -EINVAL);
-
- r = sd_id128_get_machine(&m);
- if (r < 0)
- return r;
+ assert(ret);
- r = khash_new_with_key(&h, "hmac(sha256)", &m, sizeof(m));
+ r = khash_new_with_key(&h, "hmac(sha256)", &base, sizeof(base));
if (r < 0)
return r;
*ret = make_v4_uuid(result);
return 0;
}
+
+_public_ int sd_id128_get_machine_app_specific(sd_id128_t app_id, sd_id128_t *ret) {
+ sd_id128_t id;
+ int r;
+
+ assert_return(ret, -EINVAL);
+
+ r = sd_id128_get_machine(&id);
+ if (r < 0)
+ return r;
+
+ return get_app_specific(id, app_id, ret);
+}
+
+_public_ int sd_id128_get_boot_app_specific(sd_id128_t app_id, sd_id128_t *ret) {
+ sd_id128_t id;
+ int r;
+
+ assert_return(ret, -EINVAL);
+
+ r = sd_id128_get_boot(&id);
+ if (r < 0)
+ return r;
+
+ return get_app_specific(id, app_id, ret);
+}