sd-id128: add sd_id128_get_boot_app_specific()

master
Zbigniew Jędrzejewski-Szmek 4 years ago
parent ff7dad484c
commit 65d410c7ca
  1. 4
      TODO
  2. 1
      man/rules/meson.build
  3. 58
      man/sd_id128_get_machine.xml
  4. 2
      src/libsystemd/libsystemd.sym
  5. 38
      src/libsystemd/sd-id128/sd-id128.c
  6. 1
      src/systemd/sd-id128.h

@ -181,10 +181,6 @@ Features:
* add bpf-based implementation of devices cgroup controller logic for compat
with cgroupsv2 as supported by newest kernel
* introduce sd_id128_get_boot_app_specific() which is like
sd_id128_get_machine_app_specific(). After all on long-running systems both
IDs have similar properties.
* sd-bus: add vtable flag, that may be used to request client creds implicitly
and asynchronously before dispatching the operation

@ -438,6 +438,7 @@ manpages = [
['sd_id128_get_machine',
'3',
['sd_id128_get_boot',
'sd_id128_get_boot_app_specific',
'sd_id128_get_invocation',
'sd_id128_get_machine_app_specific'],
''],

@ -22,6 +22,7 @@
<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>
@ -46,6 +47,12 @@
<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>
@ -69,19 +76,25 @@
<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
@ -89,10 +102,11 @@
<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>
@ -104,10 +118,12 @@
<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" />

@ -648,4 +648,6 @@ global:
sd_hwdb_enumerate;
sd_hwdb_unrefp;
sd_id128_get_boot_app_specific;
} LIBSYSTEMD_239;

@ -284,19 +284,15 @@ _public_ int sd_id128_randomize(sd_id128_t *ret) {
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;
@ -314,3 +310,29 @@ _public_ int sd_id128_get_machine_app_specific(sd_id128_t app_id, sd_id128_t *re
*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);
}

@ -42,6 +42,7 @@ int sd_id128_randomize(sd_id128_t *ret);
int sd_id128_get_machine(sd_id128_t *ret);
int sd_id128_get_machine_app_specific(sd_id128_t app_id, sd_id128_t *ret);
int sd_id128_get_boot_app_specific(sd_id128_t app_id, sd_id128_t *ret);
int sd_id128_get_boot(sd_id128_t *ret);
int sd_id128_get_invocation(sd_id128_t *ret);

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