[Bug 1902236] Re: Duplicated root and nobody returned by getent on Focal

[Łukasz Zemczak]

Hello Simon, or anyone else affected,

Accepted systemd into focal-proposed. The package will build now and be
available at
https://launchpad.net/ubuntu/+source/systemd/245.4-4ubuntu3.5 in a few
hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
focal to verification-done-focal. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-focal. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: systemd (Ubuntu Focal)
       Status: In Progress => Fix Committed

** Tags added: verification-needed verification-needed-focal

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https://bugs.launchpad.net/bugs/1902236

Title:
  Duplicated root and nobody returned by getent on Focal

Status in systemd:
  Fix Released
Status in systemd package in Ubuntu:
  Fix Released
Status in systemd source package in Focal:
  Fix Committed

Bug description:
  [impact]

  getent password or getent group returns duplicate, false/synthesized,
  entries for root and nobody

  [test case]

  root at lp1902236-f:~# getent passwd | grep root
  root:x:0:0:root:/root:/bin/bash
  root:x:0:0:root:/root:/bin/sh
  root at lp1902236-f:~# getent group | grep root
  root:x:0:
  root:x:0:

  root at lp1902236-f:~# getent passwd | grep nobody
  nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
  nobody:x:65534:65534:nobody:/:/usr/sbin/nologin
  root at lp1902236-f:~# getent group | grep nogroup
  nogroup:x:65534:
  nogroup:x:65534:

  [regression potential]

  any regression would likely result in incorrect results to calls to
  getent or other programs using libnss-systemd

  [scope]

  this is needed only for f

  this was fixed upstream by commit
  9494da41c271bb9519d3484b6016526a72cc6be5 which was included first in
  v246, so this is fixed in g and later already.

  b and earlier doesn't show the duplication.

  [original description]

  * Summary

  systemd's NSS integration causes getent passwd/group to return
  duplicated entries for root/root and nobody/nogroup. The root account
  also gets a different shell (/bin/sh instead of /bin/bash).

  * Steps to reproduce:

  1) create a container
  $ lxc launch images:ubuntu/focal test-nobody
  2) check the root and nobody accounts
  $ lxc exec test-nobody -- getent passwd | grep -E '^(root|nobody):'
  3) check the root and nogroup groups
  $ lxc exec test-nobody -- getent group | grep -E '^(root|nogroup):'

  2 and 3 should report a single entry for each account/group but they
  return dups like this:

  root:x:0:0:root:/root:/bin/bash
  nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
  root:x:0:0:root:/root:/bin/sh
  nobody:x:65534:65534:nobody:/:/usr/sbin/nologin

  * Description

  The problem seems to come from the NSS integration:

  $ lxc exec test-nobody -- grep -wF systemd /etc/nsswitch.conf
  passwd:         files systemd
  group:          files systemd

  as the /etc/passwd and /etc/group file contain no dups:

  $ lxc exec test-nobody -- grep ^nobody: /etc/passwd
  nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
  $ lxc exec test-nobody -- grep ^nogroup: /etc/group
  nogroup:x:65534:

  Removing systemd from /etc/nsswitch.conf indeed removes the dup.

  An alternative way of seeing what systemd adds on top of the flat
  files:

  $ lxc exec test-nobody -- bash -c 'diff -u /etc/passwd <(getent passwd)'
  --- /etc/passwd	2020-10-30 13:07:52.219261001 +0000
  +++ /dev/fd/63	2020-10-30 13:29:38.396928732 +0000
  @@ -24,3 +24,5 @@
   _apt:x:105:65534::/nonexistent:/usr/sbin/nologin
   ubuntu:x:1000:1000::/home/ubuntu:/bin/bash
   systemd-coredump:x:999:999:systemd Core Dumper:/:/usr/sbin/nologin
  +root:x:0:0:root:/root:/bin/sh
  +nobody:x:65534:65534:nobody:/:/usr/sbin/nologin

  $ lxc exec test-nobody -- bash -c 'diff -u /etc/group <(getent group)'
  --- /etc/group	2020-10-30 13:07:52.211261089 +0000
  +++ /dev/fd/63	2020-10-30 13:29:45.892846747 +0000
  @@ -50,3 +50,5 @@
   ubuntu:x:1000:
   ssh:x:111:
   systemd-coredump:x:999:
  +root:x:0:
  +nogroup:x:65534:

  * Additional information

  This bug seems to occur on Focal alone as Bionic and Groovy are not
  affected.

  $ lsb_release -rd
  Description:	Ubuntu 20.04.1 LTS
  Release:	20.04

  $ apt-cache policy base-passwd systemd
  base-passwd:
    Installed: 3.5.47
    Candidate: 3.5.47
    Version table:
   *** 3.5.47 500
          500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages
          100 /var/lib/dpkg/status
  systemd:
    Installed: 245.4-4ubuntu3.2
    Candidate: 245.4-4ubuntu3.2
    Version table:
   *** 245.4-4ubuntu3.2 500
          500 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
          100 /var/lib/dpkg/status
       245.4-4ubuntu3 500
          500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages

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