On 6 Nov a visitor deleted the whole MSYS2 installation, the locked
/etc/passwd included, and the site was down for a week: the cleanup job
repaired the runtime with pacman, which was gone too, and never tried to
start the server again because a port-22 query without results counted as
a failed query.
The installer now builds a pristine installation from the official base
archive (hash pinned) and the site's packages in the administrators'
folder. Everything the SYSTEM server trusts comes from there and is kept
in place and locked by the cleanup job: opt/kik, the runtime, passwd,
group, nsswitch.conf, fstab, fstab.d and etc/ssh. The user gets modify
rather than full control, so locked files can no longer be deleted, and
the folders leading to them cannot be renamed. When pacman is gone the
job copies the missing files back from the pristine installation.
Nothing that runs as SYSTEM or Administrator runs a file the user can
write any more: the job ran /usr/bin/pacman.exe as SYSTEM, the installer
ran ldd and pacman from the installation, the Administrator's shell was
a cmdshell.exe in /usr/local/bin, and the Administrator's sessions
searched /usr/bin for programs. The Administrator's shell is PowerShell
now, and deploy.sh speaks it.
server/scripts/rdp.sh opens a headless remote desktop session for when
SSH is down. The shell finds the CLANG64 programs and runs helix through
winpty.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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 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 personal key of the deployer goes into the authorized_keys of the
root user together with the key of the website, and the deployment makes
sure it is in the authorized_keys of the Administrator.
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>
