[Bug 318752] Re: D-Bus Policy needs checking

Bug Watch Updater 318752 at bugs.launchpad.net
Wed Aug 10 19:03:31 UTC 2011

** Changed in: sugar (Debian)
       Status: Unknown => Fix Released

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  D-Bus Policy needs checking

Status in Sugar Learning Platform:
Status in “sugar” package in Ubuntu:
  Fix Released
Status in “sugar” package in Debian:
  Fix Released

Bug description:
  sugar builds one or more binary packages that contain D-Bus system
  bus services.  The following were detected:

    universe/x11/sugar  etc/dbus-1/system.d/NetworkManagerInfo.conf

  The D-Bus policy needs checking!

  It was discovered that the default policy of the D-Bus system bus was
  not as was expected, due to a quirk of the language.  In fact, whereas
  the default policy was supposed to have been that messages would not be
  allowed by default, the default was in fact that messages _were_

  CVE-2008-4311 was issued, and a new release of D-Bus was updated to
  correct the default policy to be deny-by-default.


  It was quickly discovered that the policy files shipped by most services
  no longer worked, and that many were (inadvertently, perhaps) relying on
  the misconfiguration of the daemon.

  A new version of D-Bus has been uploaded to jaunty co correct this.

  Please read the following carefully to assist with updating the

  The default policy of the D-Bus system bus is:

   - Name ownership is DENIED by default.

   - Method calls are DENIED by default.

   - Replies to method calls, including errors, are PERMITTED by

   - Signals are PERMITTED by default.

  Therefore each service MUST, in its policy configuration:

   - Permit an appropriate user to own the name it wishes to claim:

          <policy user="example">
              <allow own="com.ubuntu.Example" />

   - Allow method calls to be made on objects it exports, for particular
     users.  This may be done in a number of different ways.

     You may simply allow all method calls to your claimed name:

          <policy context="default">
              <allow send_destination="com.ubuntu.example" />

     You may allow method calls to particular interfaces you export,
     especially useful if you have privileged and non-privileged

          <policy context="default">
              <allow send_destination="com.ubuntu.example"
                     send_interface="com.ubuntu.Example" />

          <policy user="root">
              <allow send_destination="com.ubuntu.example"
                     send_interface="com.ubuntu.Example.System" />

      *IMPORTANT* you MUST include send_destination on ALL allow or deny
      tags.  Omitting it is a SERIOUS bug!

                  <!-- !! SERIOUS BUG !! -->
                  <allow send_interface="x.y.z" />

          This allows any service to receive method calls of the given
          interface, not just your own service!

          It also implicitly allows any service to receive method calls
          with no interface specified, in case they match this interface!

          Using the above means you are potentially allowing exploiting of
          a different service.  DO NOT DO IT!

                  <!-- !! SERIOUS BUG !! -->
                  <deny send_interface="x.y.z" />

          This denies all services from receiving method calls of the
          given interface, not just your own service!  It also implicitly
          denies all services from receiving method calls with no
          interface specified.  DO NOT DO IT!

   - You must allow standard interfaces as well, such as Introspection and

          <policy context="default">
              <allow send_destination="com.ubuntu.example"
                     send_interface="org.freedesktop.DBus.Introspectable" />
              <allow send_destination="com.ubuntu.example"
                     send_interface="org.freedesktop.DBus.Properties" />

   - You should not normally allow receipt of any messages sent from your
     interface, this is also the default.

     (ie. remove any lines of the form <allow receive_*>)

   - You do not normally need to deny any messages, this is the default.

     (ie. remove any lines of the form <deny...>)

  You should fully test the service with the new D-Bus after updating the
  policy, you'll need to restart the bus daemon for that (it's probably
  easier to reboot).

  If messages are being denied, it will be logged in /var/log/auth.log as

  Dec 19 14:17:53 space-ghost dbus: Rejected send message, 1 matched
  rules; type="method_return", sender=":1.26" (uid=0 pid=2966
  comm="/usr/libexec/nm-dispatcher.action ") interface="(unset)"
  member="(unset)" error name="(unset)" requested
  _reply=0 destination=":1.18" (uid=0 pid=2806 comm="NetworkManager

  Be aware that a denied message may still happen if you have other
  invalid policy installed (such as those which don't qualify allow/deny
  rules with the destination!).  Take the opportunity to fix all you see.

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