[Bug 1296415] Re: [security] please use apparmor to restrict access to ofono to approved services

[Jamie Strandboge]

** Description changed:

  NOTE: After further review from the security team, unfortunately what is
  presented as a solution in this bug is not sufficient to block
  unconfined processes from connecting to ofono for essentially two
  reasons:
  
   a) anything that is unconfined can change into another profile, so an unconfined process can simply change into the profile of one of the allowed services, and
   b) this doesn't protect against scenarios where the user is able to alter the behavior of the allowed services running in the user session (eg, indicator-network and ubuntu-system-settings)
  
  'a' is solvable by making sure that the user's session starts under a
  new AppArmor "user-session" profile that prevents changing profile in to
  one of the allowed services (of course, the user session services
  continue to run under their own profiles). We'd have to investigate the
- best method for profile attachment in this case as well.
+ best method for profile attachment in this case as well. An alternative
+ might be to store the profile attachment in the inode of the binary when
+ AppArmor adds this.
  
  'b' is perhaps solvable by more strictly confining these allowed user
  session services (eg, 'audit deny ptrace tracedby peer=user-session,
  audit deny owner /** m, preventing QML loading, future AppArmor
  environment filtering, etc') along with, importantly, hardening these
  services to the point that they can't be controlled via environment,
  configuration, library loading, etc, etc. An alternative solution would
  be to run these services as another user in such a way that the user
  cannot alter their behavior beyond what is exposed in the UI.
  
  Preventing unconfined from doing things is a difficult prospect and
  while I think with the recent improvements with AppArmor over the last
  two cycles finally makes the notion plausible, significant work remains
  to solve 'a' and 'b'. This is cannot be achieved for RTM (note, this
  only affected limiting unconfined and has no effect on application
  isolation, which is in full effect and does not suffer from this at
  all).
  
  Description:
  It would be useful to limit the services that can connect to ofonod over DBus. We can implement this be creating an otherwise permissive AppArmor profile for ofonod that will limit any DBus calls to ofonod to a list of peer profiles (specifically excluding 'unconfined'). The list of peer profiles is:
   - indicator-network
   - network-manager (and dispatcher.d/03mmsproxy)
   - nuntium
   - telepathy-ofono
   - ofono-scripts
   - powerd
   - ubuntu-download-manager
   - system-settings
   - urfkill
  
  Each of the above needs to have a profile created for it, adjusting the
  boot scripts as necessary to ensure that the profile is loaded before
  the service starts. The peer profile implementation will be wide open as
  the purpose of the profile is (currently) to simply ensure the process
  of the service has the correct AppArmor labeling (though this opens the
  possibility to confine these services down the road if desired).
  
  Merge requests have been requested for everything except urfkill, which
  has a debdiff attached to this bug. As mentioned, the AppArmor profiles
  for everything except ofonod is wide open so the risk of regression is
  very low for these. In fact, if it is helpful, everything except ofono
  could be uploaded to the archive independently and at any time.
  
  For ofono, as mentioned, the AppArmor profile is also lenient except for
  the policy for its DBus interface. It is critical that ofono is updated
  at the same time or after all the other packages in this bug, otherwise
  any packages that aren't updated will fail to connect to ofono.
  
  I've been running this configuration on my phone for weeks with no
  denials (excepting 03mmsproxy which I adjusted for yesterday). I've
  tested the packaging on x86 emulator to make sure that the profiles are
  installed and loaded properly on boot.
  
  Test Plan (additional to any existing appropriate test plans)
   1. Install all services on a device
   2. reboot (important to restart the session and any services that aren't
      restarted automatically, like nuntium. reboot is easiest). Note the time
      of the reboot on the device
   3. in addition to any applicable test plans, after full boot:
      adb shell grep DEN /var/log/syslog # there should be no denials for
                                         # ofono after the system boots (there
                                         # likely will be denials during
                                         # upgrade)
      adb shell tail -f /var/log/syslog | grep DEN # run this during all tests
   4. make a call
   5. send a text
   6. send an mms (if possible)
   7. connect to wifi
   8. connect to 3G
   9. download an app
   10. toggle wifi in system-settings
   11. verify ofono-scripts (eg, /usr/share/ofono/scripts/list-modems and
       /usr/share/ofono/scripts/online-modem
   12. double check `adb shell grep DEN /var/log/syslog` for no ofono denials
       during the testing
  
  = Original text =
  We should try to find ways to restrict certain properties and interfaces to well known callers, for example Modem 'Online' should be settable by urfkill only. We don't want to allow other processes to set these properties. This would also help to identify if some unintended process is trying to set such properties by accident.

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https://bugs.launchpad.net/bugs/1296415

Title:
  [security] please use apparmor to restrict access to ofono to approved
  services

Status in “indicator-network” package in Ubuntu:
  In Progress
Status in “isc-dhcp” package in Ubuntu:
  Fix Released
Status in “network-manager” package in Ubuntu:
  In Progress
Status in “nuntium” package in Ubuntu:
  In Progress
Status in “ofono” package in Ubuntu:
  In Progress
Status in “powerd” package in Ubuntu:
  In Progress
Status in “ubuntu-download-manager” package in Ubuntu:
  In Progress
Status in “ubuntu-system-settings” package in Ubuntu:
  In Progress
Status in “urfkill” package in Ubuntu:
  In Progress
Status in “indicator-network” source package in Utopic:
  In Progress
Status in “isc-dhcp” source package in Utopic:
  Fix Released
Status in “network-manager” source package in Utopic:
  In Progress
Status in “nuntium” source package in Utopic:
  In Progress
Status in “ofono” source package in Utopic:
  In Progress
Status in “powerd” source package in Utopic:
  In Progress
Status in “ubuntu-download-manager” source package in Utopic:
  In Progress
Status in “ubuntu-system-settings” source package in Utopic:
  In Progress
Status in “urfkill” source package in Utopic:
  In Progress

Bug description:
  NOTE: After further review from the security team, unfortunately what
  is presented as a solution in this bug is not sufficient to block
  unconfined processes from connecting to ofono for essentially two
  reasons:

   a) anything that is unconfined can change into another profile, so an unconfined process can simply change into the profile of one of the allowed services, and
   b) this doesn't protect against scenarios where the user is able to alter the behavior of the allowed services running in the user session (eg, indicator-network and ubuntu-system-settings)

  'a' is solvable by making sure that the user's session starts under a
  new AppArmor "user-session" profile that prevents changing profile in
  to one of the allowed services (of course, the user session services
  continue to run under their own profiles). We'd have to investigate
  the best method for profile attachment in this case as well. An
  alternative might be to store the profile attachment in the inode of
  the binary when AppArmor adds this.

  'b' is perhaps solvable by more strictly confining these allowed user
  session services (eg, 'audit deny ptrace tracedby peer=user-session,
  audit deny owner /** m, preventing QML loading, future AppArmor
  environment filtering, etc') along with, importantly, hardening these
  services to the point that they can't be controlled via environment,
  configuration, library loading, etc, etc. An alternative solution
  would be to run these services as another user in such a way that the
  user cannot alter their behavior beyond what is exposed in the UI.

  Preventing unconfined from doing things is a difficult prospect and
  while I think with the recent improvements with AppArmor over the last
  two cycles finally makes the notion plausible, significant work
  remains to solve 'a' and 'b'. This is cannot be achieved for RTM
  (note, this only affected limiting unconfined and has no effect on
  application isolation, which is in full effect and does not suffer
  from this at all).

  Description:
  It would be useful to limit the services that can connect to ofonod over DBus. We can implement this be creating an otherwise permissive AppArmor profile for ofonod that will limit any DBus calls to ofonod to a list of peer profiles (specifically excluding 'unconfined'). The list of peer profiles is:
   - indicator-network
   - network-manager (and dispatcher.d/03mmsproxy)
   - nuntium
   - telepathy-ofono
   - ofono-scripts
   - powerd
   - ubuntu-download-manager
   - system-settings
   - urfkill

  Each of the above needs to have a profile created for it, adjusting
  the boot scripts as necessary to ensure that the profile is loaded
  before the service starts. The peer profile implementation will be
  wide open as the purpose of the profile is (currently) to simply
  ensure the process of the service has the correct AppArmor labeling
  (though this opens the possibility to confine these services down the
  road if desired).

  Merge requests have been requested for everything except urfkill,
  which has a debdiff attached to this bug. As mentioned, the AppArmor
  profiles for everything except ofonod is wide open so the risk of
  regression is very low for these. In fact, if it is helpful,
  everything except ofono could be uploaded to the archive independently
  and at any time.

  For ofono, as mentioned, the AppArmor profile is also lenient except
  for the policy for its DBus interface. It is critical that ofono is
  updated at the same time or after all the other packages in this bug,
  otherwise any packages that aren't updated will fail to connect to
  ofono.

  I've been running this configuration on my phone for weeks with no
  denials (excepting 03mmsproxy which I adjusted for yesterday). I've
  tested the packaging on x86 emulator to make sure that the profiles
  are installed and loaded properly on boot.

  Test Plan (additional to any existing appropriate test plans)
   1. Install all services on a device
   2. reboot (important to restart the session and any services that aren't
      restarted automatically, like nuntium. reboot is easiest). Note the time
      of the reboot on the device
   3. in addition to any applicable test plans, after full boot:
      adb shell grep DEN /var/log/syslog # there should be no denials for
                                         # ofono after the system boots (there
                                         # likely will be denials during
                                         # upgrade)
      adb shell tail -f /var/log/syslog | grep DEN # run this during all tests
   4. make a call
   5. send a text
   6. send an mms (if possible)
   7. connect to wifi
   8. connect to 3G
   9. download an app
   10. toggle wifi in system-settings
   11. verify ofono-scripts (eg, /usr/share/ofono/scripts/list-modems and
       /usr/share/ofono/scripts/online-modem
   12. double check `adb shell grep DEN /var/log/syslog` for no ofono denials
       during the testing

  = Original text =
  We should try to find ways to restrict certain properties and interfaces to well known callers, for example Modem 'Online' should be settable by urfkill only. We don't want to allow other processes to set these properties. This would also help to identify if some unintended process is trying to set such properties by accident.

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