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[Marc Deslauriers <marc.deslauriers@xxxxxxxxxxxxx>]

** Changed in: apport (Ubuntu Trusty)
       Status: Triaged => Fix Released

** Changed in: apport (Ubuntu Utopic)
       Status: Triaged => Fix Released

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https://bugs.launchpad.net/bugs/1438758

Title:
  User to root privilege escalation (ab)using the crash forwarding
  feature of apport

Status in Apport crash detection/reporting:
  Fix Released
Status in apport package in Ubuntu:
  In Progress
Status in apport source package in Trusty:
  Fix Released
Status in apport source package in Utopic:
  Fix Released
Status in apport source package in Vivid:
  In Progress
Status in apport package in Debian:
  New

Bug description:
  Back in Ubuntu 14.04, I introduced an apport feature that will have it
  forward any crash to another apport running in the task's namespace
  (in the case where the pid of the task in its namespace isn't equal to
  that in the host namespace).

  This feature simply checks for the presence of
  /usr/share/apport/apport in the task's root directory. If it exists,
  it will chroot and exec the script.

  The problem is that as apport is a coredump handler triggered by the
  kernel, it'll always run as real root, regardless of the crashed
  task's owner and namespace.

  This therefore allows an unprivileged user to craft a specific
  filesystem structure, pivot_root to it, then crash a process inside
  it, causing apport outside of the namespace to execute a script as
  real root. By bind-mounting /proc from the host into that namespace,
  the unprivileged user can then access any file on the host as real
  root, causing the privilege escalation.

  An exploit is attached to this bug. It's been confirmed to be runnable
  as a nobody user on a regular Ubuntu system and to successfully read
  any file on the host.

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