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** Branch linked: lp:ubuntu/saucy-proposed/apparmor

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https://bugs.launchpad.net/bugs/1208988

Title:
  AppArmor no longer mediates access to path-based AF_UNIX socket files

Status in AppArmor Linux application security framework:
  Triaged
Status in “apparmor” package in Ubuntu:
  Fix Committed
Status in “apparmor-easyprof-ubuntu” package in Ubuntu:
  Fix Released
Status in “firefox” package in Ubuntu:
  Triaged
Status in “linux” package in Ubuntu:
  Fix Committed
Status in “linux-grouper” package in Ubuntu:
  Fix Committed
Status in “linux-maguro” package in Ubuntu:
  Fix Committed
Status in “linux-mako” package in Ubuntu:
  Fix Committed
Status in “linux-manta” package in Ubuntu:
  Fix Committed
Status in “apparmor” source package in Saucy:
  Fix Committed
Status in “apparmor-easyprof-ubuntu” source package in Saucy:
  Fix Released
Status in “firefox” source package in Saucy:
  Triaged

Bug description:
  [Impact]

   * AppArmor removed unix domain socket mediation as part of the 2.4
  (karmic) rewrite to the security_path hooks so that it could be
  upstreamed into the main kernel. The result being apparmor no longer
  mediates access to AF_UNIX socket files. Or more specifically it does
  not mediation connections between sockets, creation of a socket within
  the filesystem is mediated

   * Confined applications can currently read from and write to any AF_UNIX
     socket files

   * Existing AppArmor profiles that contain file rules granting write access to
     AF_UNIX socket files are effectively being ignored

   * The move from the vfs hooks patches (old, out-of-tree) AppArmor and the security_path hooks
     apparmor incorporated into mainline in 2.6.36 were the cause of this regression.

     apparmor 2.4 (version in karmic) also removed other features are part of the rewrite to
     security_path hooks/upstreaming effort.

   * For Ubuntu, Karmic 9.10  and all newer, releases are affected.
     8.04 LTS used the vfs patches and was not affected.

  * Mediation of unix domain filesystem based sockets is needed for
  13.10 click apps confinement

  [Test Case]

   * Confining dbus-send and sending a message to the system bus is an easy
     manual testing method. Load a profile for dbus-send:

  $ cat << EOF | sudo apparmor_parser -r
  #include <tunables/global>

  /usr/bin/dbus-send {
    #include <abstractions/base>
    /usr/bin/dbus-send r,
  #  /var/run/dbus/system_bus_socket rw,
  }
  EOF

   * Note that the system_bus_socket rule is commented out. Now, run dbus-send
     under strace and see if the connect() fails. Here's the unexpected output,
     taken from an Ubuntu Saucy system:

  $ strace -e connect -- \
   dbus-send --system --dest=org.freedesktop.DBus \
   /org/freedesktop/DBus org.freedesktop.DBus.ListNames
  connect(3, {sa_family=AF_LOCAL, sun_path="/var/run/dbus/system_bus_socket"}, 33) = 0
  +++ exited with 0 +++

   * Here's the expected output, taken from an 8.04 LTS system:

  $ strace -e connect -- \
   dbus-send --system --dest=org.freedesktop.DBus \
   /org/freedesktop/DBus org.freedesktop.DBus.ListNames
  connect(3, {sa_family=AF_FILE, path="/var/run/dbus/system_bus_socket"}, 33) = -1 EACCES (Permission denied)
  Failed to open connection to system message bus: Failed to connect to socket /var/run/dbus/system_bus_socket: Permission denied

   * Or, you can apply the AppArmor regression test suite patch attached to this
     bug and run the automated tests:

  $ cd tests/regression/apparmor
  $ make unix_fd_{server,client} unix_socket_file{,_client} >/dev/null
  $ sudo bash unix_fd_server.sh
  $ sudo bash unix_socket_file.sh

  [Regression Potential]

   * Profiles developed with affected kernels aren't likely to have the necessary
     rules because the proper LSM hook was not implemented in those kernels, so
     the policy writer didn't need to grant access to AF_UNIX socket files

   * The profiles shipped with AppArmor can, and will, be updated to grant access
     to AF_UNIX socket files, but local policy modifications cannot be addressed
     by upstream/distros. Once updated kernels begin enforcing mediation of
     AF_UNIX socket files, rules in local profiles may no longer be sufficient,
     resulting in new AppArmor denials for AF_UNIX socket files.

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