sd-bus: properly handle creds that are known but undefined for a process

[thirdparty/systemd.git] / man / sd_bus_creds_get_pid.xml

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<refentry id="sd_bus_creds_get_pid" conditional="ENABLE_KDBUS">

  <refentryinfo>
    <title>sd_bus_creds_get_pid</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>A monkey with a typewriter</contrib>
        <firstname>Zbigniew</firstname>
        <surname>Jędrzejewski-Szmek</surname>
        <email>zbyszek@in.waw.pl</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_creds_get_pid</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_creds_get_pid</refname>
    <refname>sd_bus_creds_get_tid</refname>
    <refname>sd_bus_creds_get_uid</refname>
    <refname>sd_bus_creds_get_gid</refname>
    <refname>sd_bus_creds_get_comm</refname>
    <refname>sd_bus_creds_get_tid_comm</refname>
    <refname>sd_bus_creds_get_exe</refname>
    <refname>sd_bus_creds_get_cmdline</refname>
    <refname>sd_bus_creds_get_cgroup</refname>
    <refname>sd_bus_creds_get_unit</refname>
    <refname>sd_bus_creds_get_user_unit</refname>
    <refname>sd_bus_creds_get_slice</refname>
    <refname>sd_bus_creds_get_session</refname>
    <refname>sd_bus_creds_get_owner_uid</refname>
    <refname>sd_bus_creds_has_effective_cap</refname>
    <refname>sd_bus_creds_has_permitted_cap</refname>
    <refname>sd_bus_creds_has_inheritable_cap</refname>
    <refname>sd_bus_creds_has_bounding_cap</refname>
    <refname>sd_bus_creds_get_selinux_context</refname>
    <refname>sd_bus_creds_get_audit_session_id</refname>
    <refname>sd_bus_creds_get_audit_login_uid</refname>
    <refname>sd_bus_creds_get_unique_name</refname>
    <refname>sd_bus_creds_get_well_known_names</refname>
    <refname>sd_bus_creds_get_connection_name</refname>

    <refpurpose>Retrieve fields from a credentials object</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_pid</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>pid_t *<parameter>pid</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_tid</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>pid_t *<parameter>tid</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_pid</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>uid_t *<parameter>uid</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_gid</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>gid_t *<parameter>gid</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_comm</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>const char **<parameter>comm</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_tid_comm</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>const char **<parameter>comm</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_exe</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>const char **<parameter>exe</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_cmdline</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>char ***<parameter>cmdline</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_cgroup</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>const char **<parameter>cgroup</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_unit</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>const char **<parameter>unit</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_user_unit</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>const char **<parameter>unit</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_slice</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>const char **<parameter>slice</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_session</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>const char **<parameter>slice</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_owner_uid</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>uid_t *<parameter>uid</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_has_effective_cap</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>int <parameter>capability</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_has_permitted_cap</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>int <parameter>capability</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_has_inheritable_cap</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>int <parameter>capability</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_has_bounding_cap</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>int <parameter>capability</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_selinux_context</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>const char **<parameter>context</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_audit_session_id</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>uint32_t *<parameter>sessionid</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_audit_login_uid</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>uid_t *<parameter>loginuid</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_unique_name</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>const char **<parameter>name</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_well_known_names</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>char ***<parameter>name</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_creds_get_connection_name</function></funcdef>
        <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
        <paramdef>const char **<parameter>name</parameter></paramdef>
      </funcprototype>

    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>These functions return information from an
    <parameter>sd_bus_creds</parameter> object. It may be created with
    <citerefentry><refentrytitle>sd_bus_creds_new_from_pid</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    in which case it will describe the specified process, or it may be
    created by
    <citerefentry><refentrytitle>sd_bus_get_owner_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    in which case it will describe the process at the other endpoint
    of a connection.
    </para>

    <para><function>sd_bus_creds_get_pid()</function> will retrieve the
    PID (process identifier).</para>

    <para><function>sd_bus_creds_get_tid()</function> will retrieve the
    TID (thread identifier).</para>

    <para><function>sd_bus_creds_get_uid()</function> will retrieve the
    numeric UID (user identifier).</para>

    <para><function>sd_bus_creds_get_gid()</function> will retrieve the
    numeric GID (group identifier).</para>

    <para><function>sd_bus_creds_get_comm()</function> will retrieve the
    comm field (truncated name of the executable, as stored in
    <filename>/proc/<replaceable>pid</replaceable>/comm</filename>).
    </para>

    <para><function>sd_bus_creds_get_tid_comm()</function> will retrieve
    the comm field of the thread (as stored in
    <filename>/proc/<replaceable>pid</replaceable>/task/<replaceable>tid</replaceable>/comm</filename>).
    </para>

    <para><function>sd_bus_creds_get_exe()</function> will retrieve the
    path to the program (as stored in the
    <filename>/proc/<replaceable>pid</replaceable>/exe</filename>
    link, but with <literal> (deleted)</literal> suffix removed).
    </para>

    <para><function>sd_bus_creds_get_cmdline()</function> will retrieve
    an array of command line arguments (as stored in
    <filename>/proc/<replaceable>pid</replaceable>/cmdline</filename>).
    </para>

    <para><function>sd_bus_creds_get_cgroup()</function> will retrieve
    the cgroup path. See <ulink
    url="https://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>.
    </para>

    <para><function>sd_bus_creds_get_unit()</function> will retrieve the
    systemd unit name (in the system instance of systemd) that the
    process is part of. See
    <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
    </para>

    <para><function>sd_bus_creds_get_user_unit()</function> will
    retrieve the systemd unit name (in the user instance of systemd)
    that the process is part of. See
    <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
    </para>

    <para><function>sd_bus_creds_get_slice()</function> will retrieve
    the systemd slice (a unit in the system instance of systemd) that
    the process is part of. See
    <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
    </para>

    <para><function>sd_bus_creds_get_session()</function> will retrieve
    the logind session that the process is part of. See
    <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
    </para>

    <para><function>sd_bus_creds_get_owner_uid()</function> will retrieve
    the numeric UID (user identifier) of the user who owns the slice
    that the process is part of. See
    <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    <!-- and
    <citerefentry><refentrytitle>systemd-user-sessions.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> -->.
    </para>

    <para><function>sd_bus_creds_has_effective_cap()</function> will
    check whether the capability specified by
    <parameter>capability</parameter> was set in the effective
    capabilities mask. A positive return value means that is was
    set, zero means that it was not set, and a negative return
    value signifies an error. See
    <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
    and <varname>Capabilities=</varname> and
    <varname>CapabilityBoundingSet=</varname> settings in
    <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
    </para>

    <para><function>sd_bus_creds_has_permitted_cap()</function> is
    similar to <function>sd_bus_creds_has_effective_cap()</function>,
    but will check the permitted capabilities mask.</para>

    <para><function>sd_bus_creds_has_inheritable_cap()</function> is
    similar to <function>sd_bus_creds_has_effective_cap()</function>,
    but will check the inheritable capabilities mask.</para>

    <para><function>sd_bus_creds_has_bounding_cap()</function> is
    similar to <function>sd_bus_creds_has_effective_cap()</function>,
    but will check the bounding capabilities mask.</para>

    <para><function>sd_bus_creds_get_selinux_context()</function> will
    retrieve the SELinux security context (label) of the process.</para>

    <para><function>sd_bus_creds_get_audit_session_id()</function> will
    retrieve the audit session identifier of the process.</para>

    <para><function>sd_bus_creds_get_audit_login_uid()</function> will
    retrieve the audit user login identifier (the identifier of the
    user who is "responsible" for the session).</para>

    <para><function>sd_bus_creds_get_unique_name()</function> will
    retrieve the D-Bus unique name. See <ulink
    url="http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names-bus">The
    D-Bus specification</ulink>.</para>

    <para><function>sd_bus_creds_get_well_known_names()</function> will
    retrieve the set of D-Bus well-known names. See <ulink
    url="http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names-bus">The
    D-Bus specification</ulink>.</para>

    <para><function>sd_bus_creds_get_connection_name()</function> will
    retrieve a descriptive name of the bus connection of the
    peer. This name is useful to discern multiple bus connections by
    the same peer, and may be altered by the peer with the
    <citerefentry><refentrytitle>sd_bus_set_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    call.</para>

    <para>All functions that take a <parameter>const
    char**</parameter> parameter will store the answer there as an
    address of a NUL-terminated string. It will be valid as long as
    <parameter>c</parameter> remains valid, and should not be freed or
    modified by the caller.</para>

    <para>All functions that take a <parameter>char***</parameter>
    parameter will store the answer there as an address of a an array
    of strings. Each invidividual string is NUL-terminated, and the
    array is NULL-terminated as a whole. It will be valid as long as
    <parameter>c</parameter> remains valid, and should not be freed or
    modified by the caller.</para>
  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para>On success, these calls return 0 or a positive integer. On
    failure, these calls return a negative errno-style error code.
    </para>
  </refsect1>

  <refsect1>
    <title>Errors</title>

    <para>Returned errors may indicate the following problems:</para>

    <variablelist>
      <varlistentry>
        <term><constant>-ENODATA</constant></term>

        <listitem><para>Given field is not available in
        <parameter>c</parameter>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-ENOENT</constant></term>

        <listitem><para>Given field is not specified for the sender.
        This will be returned by <function>sd_bus_get_unit()</function>,
        <function>sd_bus_get_user_unit()</function>,
        <function>sd_bus_get_slice()</function>,
        <function>sd_bus_get_session()</function>, and
        <function>sd_bus_get_name_creds_uid()</function> if the sender is not
        part of a systemd system unit, systemd user unit, systemd
        slice, logind session, or a systemd user session.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-ENXIO</constant></term>

        <listitem><para>An error occurred in parsing cgroup paths.
        <filename>libsystemd</filename> might be out of sync with
        the running systemd version.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-EINVAL</constant></term>

        <listitem><para>Specified pointer parameter is <constant>NULL</constant>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-ENOMEM</constant></term>

        <listitem><para>Memory allocation failed.</para></listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Notes</title>

    <para><function>sd_bus_open_user()</function> and other functions
    described here are available as a shared library, which can be
    compiled and linked to with the
    <constant>libsystemd</constant> <citerefentry project='die-net'><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-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>fork</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>execve</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
      <citerefentry project='man-pages'><refentrytitle>credentials</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
      <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry project='man-pages'><refentrytitle>proc</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>