[Bug 1861909] Re: Please ship ec2-instance-connect.conf instead of creating it in postinst

[Balint Reczey]

@sil2100 Oh, no, I've missed that! Thanks for catching that!

** Tags removed: verification-done verification-done-bionic
** Tags added: one one-eoan verification-dverification-needed-bionic verification-needed verification-needed-bionic verification-needed-xenial

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https://bugs.launchpad.net/bugs/1861909

Title:
  Please ship ec2-instance-connect.conf instead of creating it in
  postinst

Status in ec2-instance-connect package in Ubuntu:
  Fix Released
Status in ec2-instance-connect source package in Xenial:
  Fix Committed
Status in ec2-instance-connect source package in Bionic:
  Fix Committed
Status in ec2-instance-connect source package in Eoan:
  Fix Committed

Bug description:
  [Impact]

   * The ssh.service drop-in is placed and removed in maintainer scripts
  based on the current ssh configuration checks which are incomplete.
  The drop-in is also not owned by the package.

  [Test Case]

   * Install the fixed package. The drop-in should be listed among the package's files:
  $ dpkg -L ec2-instance-connect 
  ...
  /lib/systemd/system/ssh.service.d/ec2-instance-connect.conf
  ...

  * Upgrade package from previous version. The drop-in should replace
  the old one.

  * Change /etc/ssh/sshd_config to set AuthorizedKeysCommand
    Install the fixed package. A warning should appear and sshd should not be restarted by the package's maintainer scripts.

  [Regression Potential]

  * The change is made to make installation and upgrades more reliable. The test cases check package installs and upgrades where regressions could happen due to implementation mistakes.
  * The unfixed version of the package did not place the drop-in when it detected setting AuthorizedKeysCommand in sshd_conf, while the fixed version installs the drop-in, just does not restart the ssh service. This can block users from logging in via ssh if only the sshd_conf's AuthorizedKeysCommand configuration enabled their login and the ssh service got restarted after installing/upgrading ec2-instance-connect.
  This is a known change in behavior and is mitigated by showing a warning when this potentially problematic configuration is detected. It is also worth noting that in case the drop-in overrides the configuration in sshd_conf it is still possible to log in via EC2 Instance Connect, the login method the package enables.

  [Other Info]

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