authz: add QAuthZListFile object type for a file access control list

Add a QAuthZListFile object type that implements the QAuthZ interface. This
built-in implementation is a proxy around the QAuthZList object type,
initializing it from an external file, and optionally, automatically
reloading it whenever it changes.

To create an instance of this object via the QMP monitor, the syntax
used would be:

      {
        "execute": "object-add",
        "arguments": {
          "qom-type": "authz-list-file",
          "id": "authz0",
          "props": {
            "filename": "/etc/qemu/vnc.acl",
	    "refresh": true
          }
        }
      }

If "refresh" is "yes", inotify is used to monitor the file,
automatically reloading changes. If an error occurs during reloading,
all authorizations will fail until the file is next successfully
loaded.

The /etc/qemu/vnc.acl file would contain a JSON representation of a
QAuthZList object

    {
      "rules": [
         { "match": "fred", "policy": "allow", "format": "exact" },
         { "match": "bob", "policy": "allow", "format": "exact" },
         { "match": "danb", "policy": "deny", "format": "glob" },
         { "match": "dan*", "policy": "allow", "format": "exact" },
      ],
      "policy": "deny"
    }

This sets up an authorization rule that allows 'fred', 'bob' and anyone
whose name starts with 'dan', except for 'danb'. Everyone unmatched is
denied.

The object can be loaded on the comand line using

   -object authz-list-file,id=authz0,filename=/etc/qemu/vnc.acl,refresh=yes

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

1 files changed, 111 insertions, 0 deletions

diff --git a/include/authz/listfile.h b/include/authz/listfile.h
new file mode 100644
index 0000000000..bcc8d80743
--- /dev/null
+++ b/include/authz/listfile.h
@@ -0,0 +1,111 @@
+/*
+ * QEMU list file authorization driver
+ *
+ * Copyright (c) 2018 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef QAUTHZ_LIST_FILE_H__
+#define QAUTHZ_LIST_FILE_H__
+
+#include "authz/list.h"
+#include "qapi/qapi-types-authz.h"
+#include "qemu/filemonitor.h"
+
+#define TYPE_QAUTHZ_LIST_FILE "authz-list-file"
+
+#define QAUTHZ_LIST_FILE_CLASS(klass)                        \
+    OBJECT_CLASS_CHECK(QAuthZListFileClass, (klass),        \
+                       TYPE_QAUTHZ_LIST_FILE)
+#define QAUTHZ_LIST_FILE_GET_CLASS(obj)              \
+    OBJECT_GET_CLASS(QAuthZListFileClass, (obj),    \
+                      TYPE_QAUTHZ_LIST_FILE)
+#define QAUTHZ_LIST_FILE(obj) \
+    INTERFACE_CHECK(QAuthZListFile, (obj),          \
+                    TYPE_QAUTHZ_LIST_FILE)
+
+typedef struct QAuthZListFile QAuthZListFile;
+typedef struct QAuthZListFileClass QAuthZListFileClass;
+
+
+/**
+ * QAuthZListFile:
+ *
+ * This authorization driver provides a file mechanism
+ * for granting access by matching user names against a
+ * file of globs. Each match rule has an associated policy
+ * and a catch all policy applies if no rule matches
+ *
+ * To create an instance of this class via QMP:
+ *
+ *  {
+ *    "execute": "object-add",
+ *    "arguments": {
+ *      "qom-type": "authz-list-file",
+ *      "id": "authz0",
+ *      "props": {
+ *        "filename": "/etc/qemu/myvm-vnc.acl",
+ *        "refresh": true
+ *      }
+ *    }
+ *  }
+ *
+ * If 'refresh' is 'yes', inotify is used to monitor for changes
+ * to the file and auto-reload the rules.
+ *
+ * The myvm-vnc.acl file should contain the parameters for
+ * the QAuthZList object in JSON format:
+ *
+ *      {
+ *        "rules": [
+ *           { "match": "fred", "policy": "allow", "format": "exact" },
+ *           { "match": "bob", "policy": "allow", "format": "exact" },
+ *           { "match": "danb", "policy": "deny", "format": "exact" },
+ *           { "match": "dan*", "policy": "allow", "format": "glob" }
+ *        ],
+ *        "policy": "deny"
+ *      }
+ *
+ * The object can be created on the command line using
+ *
+ *   -object authz-list-file,id=authz0,\
+ *           filename=/etc/qemu/myvm-vnc.acl,refresh=yes
+ *
+ */
+struct QAuthZListFile {
+    QAuthZ parent_obj;
+
+    QAuthZ *list;
+    char *filename;
+    bool refresh;
+    QFileMonitor *file_monitor;
+    int file_watch;
+};
+
+
+struct QAuthZListFileClass {
+    QAuthZClass parent_class;
+};
+
+
+QAuthZListFile *qauthz_list_file_new(const char *id,
+                                     const char *filename,
+                                     bool refresh,
+                                     Error **errp);
+
+
+#endif /* QAUTHZ_LIST_FILE_H__ */
+