Add apparmor element support to bus config parsing

The <apparmor> element can contain a single mode attribute that has one
of three values:

 "enabled"
 "disabled"
 "required"

"enabled" means that kernel support is autodetected and, if available,
AppArmor mediation occurs in dbus-daemon. If kernel support is not
detected, mediation is disabled. "disabled" means that mediation does
not occur. "required" means that kernel support must be detected for
dbus-daemon to start.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=75113
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Reviewed-by: Simon McVittie <simon.mcvittie@collabora.co.uk>

8 files changed, 154 insertions, 1 deletions

diff --git a/bus/Makefile.am b/bus/Makefile.am
index e0eead3c..9d3cb006 100644
--- a/bus/Makefile.am
+++ b/bus/Makefile.am
@@ -4,6 +4,7 @@ dbus_daemon_execdir = $(DBUS_DAEMONDIR)
 DBUS_BUS_LIBS = \
 	$(XML_LIBS) \
 	$(SELINUX_LIBS) \
+	$(APPARMOR_LIBS) \
 	$(THREAD_LIBS) \
 	$(ADT_LIBS) \
 	$(NETWORK_libs) \
@@ -70,6 +71,8 @@ BUS_SOURCES=					\
 	activation.c				\
 	activation.h				\
 	activation-exit-codes.h			\
+	apparmor.c				\
+	apparmor.h				\
 	bus.c					\
 	bus.h					\
 	config-parser.c				\
diff --git a/bus/apparmor.c b/bus/apparmor.c
new file mode 100644
index 00000000..b53d051d
--- /dev/null
+++ b/bus/apparmor.c
@@ -0,0 +1,79 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ * apparmor.c  AppArmor security checks for D-Bus
+ *
+ * Based on selinux.c
+ *
+ * Copyright © 2014-2015 Canonical, Ltd.
+ *
+ * Licensed under the Academic Free License version 2.1
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
+ *
+ */
+
+#include <config.h>
+#include "apparmor.h"
+
+#ifdef HAVE_APPARMOR
+
+#include <dbus/dbus-internals.h>
+#include <string.h>
+
+typedef enum {
+  APPARMOR_DISABLED,
+  APPARMOR_ENABLED,
+  APPARMOR_REQUIRED
+} AppArmorConfigMode;
+
+/* Store the value of the AppArmor mediation mode in the bus configuration */
+static AppArmorConfigMode apparmor_config_mode = APPARMOR_ENABLED;
+
+#endif /* HAVE_APPARMOR */
+
+dbus_bool_t
+bus_apparmor_set_mode_from_config (const char *mode, DBusError *error)
+{
+#ifdef HAVE_APPARMOR
+  if (mode != NULL)
+  {
+    if (strcmp (mode, "disabled") == 0)
+      apparmor_config_mode = APPARMOR_DISABLED;
+    else if (strcmp (mode, "enabled") == 0)
+      apparmor_config_mode = APPARMOR_ENABLED;
+    else if (strcmp (mode, "required") == 0)
+      apparmor_config_mode = APPARMOR_REQUIRED;
+    else
+      {
+        dbus_set_error (error, DBUS_ERROR_FAILED,
+                        "Mode attribute on <apparmor> must have value "
+                        "\"required\", \"enabled\" or \"disabled\", "
+                        "not \"%s\"", mode);
+        return FALSE;
+      }
+  }
+
+  return TRUE;
+#else
+  if (mode == NULL || strcmp (mode, "disabled") == 0 ||
+                      strcmp (mode, "enabled") == 0)
+    return TRUE;
+
+  dbus_set_error (error, DBUS_ERROR_FAILED,
+                  "Mode attribute on <apparmor> must have value \"enabled\" or "
+                  "\"disabled\" but cannot be \"%s\" when D-Bus is built "
+                  "without AppArmor support", mode);
+  return FALSE;
+#endif
+}
diff --git a/bus/apparmor.h b/bus/apparmor.h
new file mode 100644
index 00000000..0d6f2746
--- /dev/null
+++ b/bus/apparmor.h
@@ -0,0 +1,34 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ * apparmor.c  AppArmor security checks for D-Bus
+ *
+ * Authors: John Johansen <john.johansen@canonical.com>
+ *          Tyler Hicks <tyhicks@canonical.com>
+ * Based on: selinux.h by Matthew Rickard
+ *
+ * Licensed under the Academic Free License version 2.1
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
+ *
+ */
+
+#ifndef BUS_APPARMOR_H
+#define BUS_APPARMOR_H
+
+#include <dbus/dbus.h>
+
+dbus_bool_t bus_apparmor_set_mode_from_config (const char *mode,
+                                               DBusError *error);
+
+#endif /* BUS_APPARMOR_H */
diff --git a/bus/config-parser-common.c b/bus/config-parser-common.c
index c522ff49..5db6b289 100644
--- a/bus/config-parser-common.c
+++ b/bus/config-parser-common.c
@@ -127,6 +127,10 @@ bus_config_parser_element_name_to_type (const char *name)
     {
       return ELEMENT_ALLOW_ANONYMOUS;
     }
+  else if (strcmp (name, "apparmor") == 0)
+    {
+      return ELEMENT_APPARMOR;
+    }
   return ELEMENT_NONE;
 }
 
@@ -181,6 +185,8 @@ bus_config_parser_element_type_to_name (ElementType type)
       return "keep_umask";
     case ELEMENT_ALLOW_ANONYMOUS:
       return "allow_anonymous";
+    case ELEMENT_APPARMOR:
+      return "apparmor";
     }
 
   _dbus_assert_not_reached ("bad element type");
diff --git a/bus/config-parser-common.h b/bus/config-parser-common.h
index 186bf4cf..382a0141 100644
--- a/bus/config-parser-common.h
+++ b/bus/config-parser-common.h
@@ -49,7 +49,8 @@ typedef enum
   ELEMENT_STANDARD_SYSTEM_SERVICEDIRS,
   ELEMENT_KEEP_UMASK,
   ELEMENT_SYSLOG,
-  ELEMENT_ALLOW_ANONYMOUS
+  ELEMENT_ALLOW_ANONYMOUS,
+  ELEMENT_APPARMOR
 } ElementType;
 
 ElementType bus_config_parser_element_name_to_type (const char *element_name);
diff --git a/bus/config-parser.c b/bus/config-parser.c
index ee2d4e7d..58048a50 100644
--- a/bus/config-parser.c
+++ b/bus/config-parser.c
@@ -28,6 +28,7 @@
 #include "utils.h"
 #include "policy.h"
 #include "selinux.h"
+#include "apparmor.h"
 #include <dbus/dbus-list.h>
 #include <dbus/dbus-internals.h>
 #include <dbus/dbus-misc.h>
@@ -1136,6 +1137,27 @@ start_busconfig_child (BusConfigParser   *parser,
 
       return TRUE;
     }
+  else if (element_type == ELEMENT_APPARMOR)
+    {
+      Element *e;
+      const char *mode;
+
+      if ((e = push_element (parser, ELEMENT_APPARMOR)) == NULL)
+        {
+          BUS_SET_OOM (error);
+          return FALSE;
+        }
+
+      if (!locate_attributes (parser, "apparmor",
+                              attribute_names,
+                              attribute_values,
+                              error,
+                              "mode", &mode,
+                              NULL))
+        return FALSE;
+
+      return bus_apparmor_set_mode_from_config (mode, error);
+    }
   else
     {
       dbus_set_error (error, DBUS_ERROR_FAILED,
@@ -2074,6 +2096,7 @@ bus_config_parser_end_element (BusConfigParser   *parser,
     case ELEMENT_STANDARD_SESSION_SERVICEDIRS:
     case ELEMENT_STANDARD_SYSTEM_SERVICEDIRS:
     case ELEMENT_ALLOW_ANONYMOUS:
+    case ELEMENT_APPARMOR:
       break;
     }
 
@@ -2373,6 +2396,7 @@ bus_config_parser_content (BusConfigParser   *parser,
     case ELEMENT_ALLOW_ANONYMOUS:
     case ELEMENT_SELINUX:
     case ELEMENT_ASSOCIATE:
+    case ELEMENT_APPARMOR:
       if (all_whitespace (content))
         return TRUE;
       else
diff --git a/bus/session.conf.in b/bus/session.conf.in
index cfe9544f..d2e3f2d0 100644
--- a/bus/session.conf.in
+++ b/bus/session.conf.in
@@ -25,6 +25,9 @@
     <allow own="*"/>
   </policy>
 
+  <!-- Enable AppArmor mediation when it is available -->
+  <apparmor mode="enabled"/>
+
   <!-- Config files are placed here that among other things, 
        further restrict the above policy for specific services. -->
   <includedir>session.d</includedir>
diff --git a/bus/system.conf.in b/bus/system.conf.in
index ac78c734..fc472bd7 100644
--- a/bus/system.conf.in
+++ b/bus/system.conf.in
@@ -97,6 +97,9 @@
            send_interface="org.freedesktop.DBus.Debug.Stats"/>
   </policy>
 
+  <!-- Enable AppArmor mediation when it is available -->
+  <apparmor mode="enabled"/>
+
   <!-- Config files are placed here that among other things, punch 
        holes in the above policy for specific services. -->
   <includedir>system.d</includedir>