【转载】D-Bus系列之获取发送者UID及PID的方法

转载自：https://qytz-notes.readthedocs.io/tech/dbus/dbus-get-uid.html

D-Bus系列之获取发送者UID及PID的方法

获取PID及UID的原理

org.freedesktop.DBus提供了一系列的消息，其中就有根据服务名获取进程PID及UID的接口
"org.freedesktop.DBus", --服务
"/org/freedesktop/DBus", --对象
"org.freedesktop.DBus", --接口
"GetConnectionUnixProcessID", --方法
 UINT32 GetConnectionUnixProcessID (in STRING bus_name);
"GetConnectionUnixUser", --方法
UINT32 GetConnectionUnixUser (in STRING bus_name);

QT DBUS获取的方法及示例

QT DBUS提供了相关调用的封装:

const QDBusMessage & QDBusContext::message () const Returns the message that generated this call.
QString QDBusMessage::service () const Returns the name of the service or the bus address of the remote method call.
QDBusReply QDBusConnectionInterface::servicePid ( const QString & serviceName ) const Returns the Unix Process ID (PID) for the process currently holding the bus service serviceName.

例如：

bool SomeMethod( const QString &name )
{
     qDebug() << "PID is: " << connection().interface()->servicePid( message().service() );
}

D-Bus glib绑定及GDBus

D-Bus Glib 的绑定提供了获取发送者名字的方法：

const char *dbus_message_get_sender(DBusMessage *message);

但是没有提供获取进程PID及UID的方法，需自己编写代码调用GetConnectionUnixProcessID 和GetConnectionUnixUser方法。好像GDbus也没有提供，只找到了g_dbus_message_get_sender()方法。

/* proxy for getting PID info */
g_dbus_proxy_new_for_bus(G_BUS_TYPE_SYSTEM,
    G_DBUS_PROXY_FLAGS_DO_NOT_LOAD_PROPERTIES,
    NULL,
    "org.freedesktop.DBus",
    "/org/freedesktop/DBus",
    "org.freedesktop.DBus",
    NULL,
    (GAsyncReadyCallback)dbus_proxy_connect_cb,
    NULL);
void
dbus_proxy_connect_cb(GObject *source_object,
               GAsyncResult *res,
               gpointer user_data)
{
    GError *error = NULL;

    dbus_proxy = g_dbus_proxy_new_finish (res, &error);
    if (error) {
        g_warning("dbus_proxy_connect_cb failed: %s", error->message);
        g_error_free(error);
        dbus_proxy = NULL;
    }
    else {
        g_debug("dbus_proxy_connect_cb succeeded");
    }
}
gboolean
handle_request_sys_state (PowerdSource *obj, GDBusMethodInvocation     *invocation, int state)
{
    // get the name of the dbus object that called us
    owner = g_dbus_method_invocation_get_sender(invocation);
    if (dbus_proxy) {
        result = g_dbus_proxy_call_sync(dbus_proxy,
                "GetConnectionUnixProcessID",
                g_variant_new("(s)", owner),
                G_DBUS_CALL_FLAGS_NONE,
                -1,
                NULL,
                &error);
        if (error) {
            g_error("Unable to get PID for %s: %s", owner, error->message);
            g_error_free(error);
            error = NULL;
        }
        else {
            g_variant_get(result, "(u)", &owner_pid);
            g_info("request is from pid %d\n", owner_pid);
        }
    }
    ...
}