The root user now owns the whole MSYS2 installation and can run pacman. The
login path the journey depends on - the sshd, the login shell zsh and cat - is
kept as a protected copy in C:\msys2\opt\kik that only SYSTEM and the
administrators may write, and the sshd runs as SYSTEM from there (the new
KiK sshd task; the msys2-sshd service is disabled). Replacing the user's own
/usr/bin/sshd therefore cannot touch the running server.
opt/kik is two levels below C:\msys2, so its runtime resolves the same
installation root and the login shell and the user's tools share one cygwin
runtime. A separate second installation does not work: two runtimes in one
process tree corrupt each other's file descriptors and pacman cannot lock its
database.
/etc/passwd and /etc/ssh are read-only to the user, /opt/kik is first on PATH
so cat README survives even if the user deletes their own /usr/bin/cat, and
the restore task rebuilds the protected copy and re-applies the permissions
every 30 minutes.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The user could empty the authorized_keys and break the login of the
website, change the shell configuration to break the prompt, and write
startup files that zsh reads on every login. The shell configuration and
the key are now read-only for the user, and the shell reads its
configuration from ~/.zsh, so the files in the home directory are
ignored.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
The user could delete the whole home directory, which takes the website
down with it: sshd cannot log in without it. The home directory and the
files that have to stay in it now belong to the administrators, so the
user may change them but not remove them. Their own files stay theirs.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
MSYS2 only copies /etc/skel into a home directory that does not exist yet
when the user logs in. The cleanup always creates the home first, so the
default files never arrived.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
The keys of the people who deploy are in the repository now: in home/ for
the root user and in admin/ for the Administrator. The resources mirror
both home directories, and the deploy script no longer reads any private
key.
Co-Authored-By: Claude Code <noreply@anthropic.com>
The key that the website logs in with was written into the authorized_keys
of the Administrator, which would have given everyone who has the website
administrator rights on the box. It only gets access as the root user.
The deploy script logs in as Administrator with the personal key of the
deployer instead, from the agent or from -i.
Co-Authored-By: Claude Code <noreply@anthropic.com>
The key that the website logs in with lives in the home directory of the
user, so a deleted home directory took it away and the site could not
connect any more. The key is now one of the copies the cleanup restores,
and it is merged into the authorized_keys of the user, so that keys they
added stay.
The installer writes the same key for the Administrator, and the deploy
script checks that it is the key the website uses.
Co-Authored-By: Claude Code <noreply@anthropic.com>
The cleanup job now restores the whole home directory instead of only
the four text files: the directory itself, the shell configuration that
gives the prompt, and the files. Anything that is not a regular file is
replaced, so the files stay text files.
The README in server/ describes the security model: the box is a
disposable VPS that may be compromised, the root user may do whatever
they want, and only the prompt, the home directory and the four files
are kept working.
Co-Authored-By: Claude Code <noreply@anthropic.com>
The README and Code of Conduct files move to server/resources, the
scripts that build and deploy them to server/scripts. The new
install_restore_task.ps1 installs a scheduled task as SYSTEM that puts
the files back every 30 minutes, so the shell server's root user can
neither stop it nor change the copies it restores from.
Co-Authored-By: Claude Code <noreply@anthropic.com>
