[Bug 1831765] [NEW] Privilege Separation Directory default

[Luke A. Perkins]

Public bug reported:

Ubuntu: 18.04.2 LTS
OpenSSH: 7.6p1

I am having a problem starting multiple sshd processes. The default location of the sshd privilege separation directory is hard-coded to /run/sshd (see man page). The original OpenSSH 7.6p1 located this file are /var/empty. Somehow the default location in the pathnames.h for _PATH_PRIVSEP_CHROOT_DIR has been changed from /var/empty to /run/sshd. I have asked OpenSSH to provision the ability to change this directory location from either the command-line or the sshd_config file; Theo de Raadt, et. al. pretty much said "NO!" using some rather provocative language.
Here is the problem with using /run/sshd:
1) Every time there is a boot, the /run directory is cleaned out.
2) The /etc/init.d/ssh script is required to check and mkdir the /run/sshd directory.
3) If you have multiple service scripts, like lan_ssh and wan_ssh, the 2 scripts conflict in the generation and creation of the /run/sshd directory.
4) The only work-around I have found is to have a rc.local script mkdir the /run/sshd directory and remove the mkdir /run/sshd from the /etc/init.d/ scripts.
If we revert back to the /var/empty directory approach and remove the "mkdir /run/sshd" operation from the /etc/init.d/ script(s), this problem goes away since the system does not recreate /var during every boot.
This would require 1 of 2 changes to the existing release of sshd, specifically:
1) Change the default location of the privilege separation directory from /run/sshd back to the original /var/empty. This would require the install script to create this directory if it does not already exist.
2) Modify the sshd.c file to provision the ability to change the default location of the privilege separation directory.

** Affects: openssh (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1831765

Title:
  Privilege Separation Directory default

Status in openssh package in Ubuntu:
  New

Bug description:
  Ubuntu: 18.04.2 LTS
  OpenSSH: 7.6p1

  I am having a problem starting multiple sshd processes. The default location of the sshd privilege separation directory is hard-coded to /run/sshd (see man page). The original OpenSSH 7.6p1 located this file are /var/empty. Somehow the default location in the pathnames.h for _PATH_PRIVSEP_CHROOT_DIR has been changed from /var/empty to /run/sshd. I have asked OpenSSH to provision the ability to change this directory location from either the command-line or the sshd_config file; Theo de Raadt, et. al. pretty much said "NO!" using some rather provocative language.
  Here is the problem with using /run/sshd:
  1) Every time there is a boot, the /run directory is cleaned out.
  2) The /etc/init.d/ssh script is required to check and mkdir the /run/sshd directory.
  3) If you have multiple service scripts, like lan_ssh and wan_ssh, the 2 scripts conflict in the generation and creation of the /run/sshd directory.
  4) The only work-around I have found is to have a rc.local script mkdir the /run/sshd directory and remove the mkdir /run/sshd from the /etc/init.d/ scripts.
  If we revert back to the /var/empty directory approach and remove the "mkdir /run/sshd" operation from the /etc/init.d/ script(s), this problem goes away since the system does not recreate /var during every boot.
  This would require 1 of 2 changes to the existing release of sshd, specifically:
  1) Change the default location of the privilege separation directory from /run/sshd back to the original /var/empty. This would require the install script to create this directory if it does not already exist.
  2) Modify the sshd.c file to provision the ability to change the default location of the privilege separation directory.

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