profiles: add accessability abstraction

[Steve Beattie]

In https://code.launchpad.net/~sdeziel/apparmor/wireshark-refresh/+merge/291820 it was pointed out that a more generic accessibility abstraction would be useful, as a number of applications have duplicated rules for dealing with accessibility on the dbus session bus, specifically stuff like:

  dbus (send)
      bus=session
      peer=(name=org.a11y.Bus),
  dbus (receive)
      bus=session
      interface=org.a11y.atspi**,

[Jamie Strandboge (jdstrand)]

We already have dbus-accessibility-strict and dbus-accessibility. Snappy uses this instead of dbus-accessibility:

# accessibility (a11y)
#include <abstractions/dbus-session-strict>
dbus (send)
    bus=session
    path=/org/a11y/bus
    interface=org.a11y.Bus
    member=GetAddress
    peer=(label=unconfined),

#include <abstractions/dbus-accessibility-strict>

# Allow the accessibility services in the user session to send us any events
dbus (receive)
    bus=accessibility
    peer=(label=unconfined),

# Allow querying for capabilities and registering
dbus (send)
    bus=accessibility
    path="/org/a11y/atspi/accessible/root"
    interface="org.a11y.atspi.Socket"
    member="Embed"
    peer=(name=org.a11y.atspi.Registry, label=unconfined),
dbus (send)
    bus=accessibility
    path="/org/a11y/atspi/registry"
    interface="org.a11y.atspi.Registry"
    member="GetRegisteredEvents"
    peer=(name=org.a11y.atspi.Registry, label=unconfined),
dbus (send)
    bus=accessibility
    path="/org/a11y/atspi/registry/deviceeventcontroller"
    interface="org.a11y.atspi.DeviceEventController"
    member="Get{DeviceEvent,Keystroke}Listeners"
    peer=(name=org.a11y.atspi.Registry, label=unconfined),
dbus (send)
    bus=accessibility
    path="/org/a11y/atspi/registry/deviceeventcontroller"
    interface="org.a11y.atspi.DeviceEventController"
    member="NotifyListenersSync"
    peer=(name=org.a11y.atspi.Registry, label=unconfined),

# org.a11y.atspi is not designed for application isolation and these rules
# can be used to send change events for other processes.
dbus (send)
    bus=accessibility
    path="/org/a11y/atspi/accessible/root"
    interface="org.a11y.atspi.Event.Object"
    member="ChildrenChanged"
    peer=(name=org.freedesktop.DBus, label=unconfined),
dbus (send)
    bus=accessibility
    path="/org/a11y/atspi/accessible/root"
    interface="org.a11y.atspi.Accessible"
    member="Get*"
    peer=(label=unconfined),
dbus (send)
    bus=accessibility
    path="/org/a11y/atspi/accessible/[0-9]*"
    interface="org.a11y.atspi.Event.Object"
    member="{ChildrenChanged,PropertyChange,StateChanged,TextCaretMoved}"
    peer=(name=org.freedesktop.DBus, label=unconfined),
dbus (send)
    bus=accessibility
    path="/org/a11y/atspi/accessible/[0-9]*"
    interface="org.freedesktop.DBus.Properties"
    member="Get{,All}"
    peer=(label=unconfined),

dbus (send)
    bus=accessibility
    path="/org/a11y/atspi/cache"
    interface="org.a11y.atspi.Cache"
    member="{Add,Remove}Accessible"
    peer=(name=org.freedesktop.DBus, label=unconfined),

Note that almost all of the above is covered by this rule in the dbus-accessibility abstraction:

  dbus bus=accessibility,

I *think* all we should do in apparmor is add this to dbus-accessibility:

dbus (send)
    bus=session
    path=/org/a11y/bus
    interface=org.a11y.Bus
    member=GetAddress
    peer=(label=unconfined),

If this isn't sufficient, I'd be interested in seeing the denials.