[Bug 1052038] Re: ecryptfs_fnek_sig missing when login at the same time on cron session close

[Tyler Hicks]

Unsubscribing ubuntu-sponsors and ubuntu-sru for the time being. Serge
Hallyn has reported a regression in raring and the daily build PPA and,
at first glance, is likely to have been caused by the fixes for this
bug.

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https://bugs.launchpad.net/bugs/1052038

Title:
  ecryptfs_fnek_sig missing when login at the same time on cron session
  close

Status in eCryptfs:
  In Progress
Status in “ecryptfs-utils” package in Ubuntu:
  Fix Released
Status in “ecryptfs-utils” source package in Oneiric:
  Triaged
Status in “ecryptfs-utils” source package in Precise:
  Triaged
Status in “ecryptfs-utils” source package in Quantal:
  Triaged

Bug description:
  when login at the same time on cron session close, ecryptfs directory
  will not be decrypted properly.

  [IMPACT]
   * folder/file names created by users at the session are unencrypted
   * in desktop session, xdg-user-dirs-gtk-update or other programs creates
     "Desktop", "Download", etc. with unencrypted folder names
     even if encrypted folders with the same name exist.
     On the next login, unencrypted one will be shown with empty content,
     so users feel all data was lost, in spite of actual data is in encrypted one.
   * Reproduced on Oneiric through Quantal

  Bug #623708 has quite similar symptom.

  [Test Case]
   1. Install ecryptfs-utils and expect
      $ sudo apt-get install ecryptfs-utils expect
   2. Create user 'foo', with encrypted home, and password 'ubuntu'
      $ sudo adduser --encrypt-home foo
   3. Download the lp1052038-test expect script from the bug attachments
   4. In terminal 1, run lp1052038-test in a loop that watches for the eCryptfs encrypted
      filename prefix
      $ false ; while [[ $? -ne 0 ]]; do \
  sudo lp1052038-test | grep ECRYPTFS_FNEK_ENCRYPTED ; done
   5. In terminal 2, run a loop that su's from root to user foo. This is the loop that
      will trigger the race condition and cause the loop in terminal 1 to end due to
      encrypted filenames being detected.
      $ while ((1)); do sudo su - foo -c 'sleep 0.1s' ; done

   The expected result is that the loops in terminal 1 and terminal 2 will run forever.
   The buggy result is that the loop in terminal 1 will end with
   ECRYPTFS_FNEK_ENCRYPTED.<remaining encrypted filename> being printed. This typically
   happens within 15 seconds, from my experience.

  [Regression Potential]
   The regression potential is that a user cannot properly access his/her encrypted home
   directory. This would be a serious regression and I've done extensive testing on
   Oneiric, Precise, and Quantal to be sure that this will not happen. I've also tested
   the lesser used encrypted ~/Private use case, as well as the use case where filenames
   are not encrypted but the file contents are encrypted.

  [Other Info]

   Bug reporter's original reproducer instructions:
   1. setup a home directory encrypted with ecryptfs
   2. set cron job of a user,
      for example, just sleeping for 1 minutes
      /etc/cron.d/ecryptfs-test
      "*/2 *    * * *    user1    sleep 1m"

   3. login at the same time on cron session closed
       for example, login near 00 second in odd minute.
      ==========
      Sep 17 23:32:56 ecryptfs-test login[6019]: pam_ecryptfs: Passphrase file wrapped
      Sep 17 23:33:01 ecryptfs-test CRON[6003]: pam_unix(cron:session): session closed for user user1
      Sep 17 23:33:02 ecryptfs-test login[6012]: pam_unix(login:session): session opened for user user1 by user1(uid=0)
      ==========

  Expected results:
   home directory mounted properly

   * mount -l
     /home/user1/.Private on /home/user1 type ecryptfs (ecryptfs_check_dev_ruid,ecryptfs_cipher=aes,ecryptfs_key_bytes=16,ecryptfs_unlink_sigs,ecryptfs_sig=ab224e5125be6655,ecryptfs_fnek_sig=9cb9226b29f1b007)

   * keyctl show
      Session Keyring
             -3 --alswrv   1000    -1  keyring: _uid_ses.1000
      311854780 --alswrv   1000    -1   \_ keyring: _uid.1000
      110408274 --alswrv   1000     0       \_ user: 9cb9226b29f1b007
      923006627 --alswrv   1000     0       \_ user: ab224e5125be6655

  Actual results:
   home directory mounted without folder/file names are decrypted

   * mount -l
     /home/user1/.Private on /home/user1 type ecryptfs (ecryptfs_check_dev_ruid,ecryptfs_cipher=aes,ecryptfs_key_bytes=16,ecryptfs_unlink_sigs,ecryptfs_sig=ab224e5125be6655)

   * keyctl show
      Session Keyring
             -3 --alswrv   1000    -1  keyring: _uid_ses.1000
      311854780 --alswrv   1000    -1   \_ keyring: _uid.1000
       71413043 --alswrv   1000     0       \_ user: ab224e5125be6655

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: ecryptfs-utils 96-0ubuntu3
  ProcVersionSignature: Ubuntu 3.2.0-30.48-generic 3.2.27
  Uname: Linux 3.2.0-30-generic x86_64
  ApportVersion: 2.0.1-0ubuntu13
  Architecture: amd64
  Date: Tue Sep 18 00:21:00 2012
  InstallationMedia: Ubuntu 12.04.1 LTS "Precise Pangolin" - Release amd64 (20120823.1)
  ProcEnviron:
   TERM=screen-bce
   LANG=ja_JP.UTF-8
   SHELL=/bin/bash
  SourcePackage: ecryptfs-utils
  UpgradeStatus: No upgrade log present (probably fresh install)

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