[Bug 1771340] Re: sshd failed on config reload

[Andreas Hasenack]

marking as fix released in the devel task, since the fix is in cosmic.

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

** Changed in: openssh (Ubuntu)
     Assignee: Karl (kstenerud) => (unassigned)

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https://bugs.launchpad.net/bugs/1771340

Title:
  sshd failed on config reload

Status in openssh package in Ubuntu:
  Fix Released
Status in openssh source package in Xenial:
  In Progress

Bug description:
  [Impact]

  sshd doesn't check the configuration when reloading.

  If a user generates an invalid configuration file, sshd will shut down
  and not come back up when the user issues a reload.

  [Test Case]

  $ lxc launch ubuntu:xenial tester
  $ lxc exec tester bash

  # echo "blah blah" >>/etc/ssh/sshd_config
  # systemctl reload sshd
  Job for ssh.service failed because the control process exited with error code. See "systemctl status ssh.service" and "journalctl -xe" for details.
  # systemctl status ssh.service
  ● ssh.service - OpenBSD Secure Shell server
     Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Tue 2018-08-21 18:15:41 UTC; 19s ago

  * The service should have checked the config file, failed to reload,
  but remained active in its current configuration. In this case ssh has
  shut down.

  [Regression Potential]

  This code will only trigger on an invalid configuration file (in which
  case sshd would not load anyway), so there should be no regressions.

  [Other Info]

  autopkgtest [13:45:46]: test regress: -----------------------]
  autopkgtest [13:45:47]: test regress:  - - - - - - - - - - results - - - - - - - - - -
  regress              PASS
  autopkgtest [13:45:47]: @@@@@@@@@@@@@@@@@@@@ summary
  regress              PASS

  [Original Description]

  After adding some lines to /etc/ssh/sshd_config I tried to reload the
  configuration with the command:

  ```
  sudo systemctl reload sshd
  ```

  No error message was returned. So I assumed that the sshd was running
  with the current config. But `sudo systemctl status sshd` told me that
  the service failed due to a wrong option in /etc/ssh/sshd_config.
  Please see the following output:

  ~~~
  :~$ sudo vim /etc/ssh/sshd_config
  :~$ sudo systemctl reload sshd
  :~$ sudo systemctl status sshd
  ● ssh.service - OpenBSD Secure Shell server
     Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Di 2018-05-15 10:00:04 CEST; 8s ago
    Process: 12089 ExecReload=/bin/kill -HUP $MAINPID (code=exited, status=0/SUCCESS)
    Process: 7536 ExecStart=/usr/sbin/sshd -D $SSHD_OPTS (code=exited, status=255)
   Main PID: 7536 (code=exited, status=255)
  ~~~

  I would expect that a warning or error message is returned when the
  service fails while reloading it's configuration.

  A fix for this behaviour would be appreciated.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: openssh-server 1:7.2p2-4ubuntu2.4
  ProcVersionSignature: Ubuntu 3.13.0-112.159-generic 3.13.11-ckt39
  Uname: Linux 3.13.0-112-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.17
  Architecture: amd64
  Date: Tue May 15 10:18:25 2018
  InstallationDate: Installed on 2013-01-10 (1950 days ago)
  InstallationMedia: Ubuntu-Server 12.04.1 LTS "Precise Pangolin" - Release amd64 (20120817.3)
  SourcePackage: openssh
  UpgradeStatus: Upgraded to xenial on 2017-03-12 (428 days ago)
  mtime.conffile..etc.pam.d.sshd: 2017-03-13T19:59:01.965420

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