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feat(install): security baseline: fail2ban, unattended-upgrades, sshd hardening

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Always applied in the Linux block, no prompt, idempotent:
- install_fail2ban: fail2ban + nftables, etc/fail2ban/jail.d/local.conf.
  sshd jail reads the journal (backend systemd, works with or without
  auth.log) and bans the offender on every port, so the SSH port is
  irrelevant: the previous server's jail banned 22 while sshd listened
  on 337. 5 failures / 10 min / 1 h. Loopback + RFC1918 never banned.
- install_unattended_upgrades: package + 20auto-upgrades (the file
  dpkg-reconfigure writes, without the prompt).
- harden_sshd: sshd_config.d/20-hardening.conf (PermitRootLogin no,
  MaxAuthTries 3, LoginGraceTime 20), sshd -t gated: a rejected file is
  removed and the install continues with a warning. Auth methods, port
  and user lists untouched.
Docs: README table + step 13 + packages, CLAUDE.md layout.
This commit is contained in:
bastien
2026-09-22 17:47:34 +02:00
parent 0d2e96819a
commit 55ede6f08c
7 changed files with 94 additions and 2 deletions
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README.md
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@@ -21,6 +21,9 @@ curl -fsSL https://git.bchanot.fr/bchanot/config/raw/branch/master/remote-instal
| `etc/tmpfiles.d/tmp.conf` | Cleanup rules for a disk-backed `/tmp` (wiped at boot, 10-day purge). Deployed by the `/tmp` on disk offer. |
| `etc/systemd/ssh.service.d/override.conf` | `ssh.service` drop-in: sshd exempt from the OOM killer + memory reclaim protection. Deployed by the SSH memory guard offer. |
| `etc/default/earlyoom` | earlyoom arguments: spare sshd/systemd, kill node/java first. Deployed by the SSH memory guard offer. |
| `etc/fail2ban/jail.d/local.conf` | fail2ban sshd jail: journal backend, all-ports ban, 5 tries / 10 min / 1 h, private LAN never banned. Deployed on every Linux install. |
| `etc/apt/apt.conf.d/20auto-upgrades` | Enables unattended security upgrades (what `dpkg-reconfigure` writes). Deployed on every Linux install. |
| `etc/ssh/sshd_config.d/20-hardening.conf` | sshd limits that cannot lock you out: `PermitRootLogin no`, `MaxAuthTries 3`, `LoginGraceTime 20`. Deployed on every Linux install after `sshd -t`. |
| `vim/vimrc` | Vim config: pathogen, molokai, syntastic (C with `-Wall -Werror -Wextra`), NERDTree, 42-style canonical class generators (`:ClassH`, `:ClassC`). |
| `vim/autoload/` | `pathogen.vim` plugin loader (committed). |
| `vim/colors/` | `molokai.vim` colorscheme (committed). |
@@ -66,8 +69,9 @@ What it does:
10. On Linux, installs **code-server** (VS Code in the browser) via its vendor script — skipped if already present — and enables the `code-server@$USER` systemd service.
11. On Linux, sets up **RDP remote login** via `gnome-remote-desktop` (Wayland-native): installs the daemon + `openssl`, generates a self-signed TLS cert once, and prompts interactively for shared "gate" credentials (skipped when no terminal is attached, or already set). Disables `xrdp` if present; opens UFW port `3389` only when UFW is already active.
12. On Linux, installs the **`cloudpex`** NAS mount helper to `/usr/local/bin` via `cloudpex/install.sh`, which prompts for the NAS host, share name, SMB user, mount point and SMB version and writes them to `/etc/cloudpex.conf` (root, `0600`; an existing config is shown and kept unless you say `n`; skipped when no terminal is attached). Nothing is mounted, no password stored, see [`cloudpex/README.md`](cloudpex/README.md).
13. On Linux, at the very end, **offers** (`[y/N]`, skipped when no terminal is attached) to move **`/tmp` to disk**: Ubuntu mounts `/tmp` as a RAM-backed tmpfs capped at 50% of RAM, which agent runs fill, halving the RAM and breaking every shell with "No space left on device". Accepting masks `tmp.mount` and installs `etc/tmpfiles.d/tmp.conf` (wipe at boot, 10-day purge). Effective at the next reboot.
14. On Linux, at the very end, **offers** to keep **SSH reachable under memory pressure**: installs the `ssh.service` drop-in (`OOMScoreAdjust=-1000`, `MemoryMin=256M`) and `earlyoom` with `etc/default/earlyoom` (kills the largest process, `node`/`java` first and never `sshd`, once free RAM and swap both drop under 10%). Restarting `ssh` keeps open sessions. Note: `MemoryMin` protects the sshd daemon only; login sessions live in `user.slice`, so no setting can reserve RAM for a future shell. earlyoom acting in time is the real protection.
13. On Linux, installs the **security baseline**, always, no prompt: **fail2ban** (+ `nftables`) with `etc/fail2ban/jail.d/local.conf` (sshd jail reading the journal, bans the offending IP on every port so the SSH port does not matter, 5 failures in 10 min → 1 h ban, loopback and private LAN ranges never banned); **unattended-upgrades** enabled through `etc/apt/apt.conf.d/20auto-upgrades`; and the **sshd drop-in** `etc/ssh/sshd_config.d/20-hardening.conf` (`PermitRootLogin no`, `MaxAuthTries 3`, `LoginGraceTime 20`), checked with `sshd -t` and removed again if sshd rejects it, then `reload ssh`. Authentication methods, port and user lists are left as they are.
14. On Linux, at the very end, **offers** (`[y/N]`, skipped when no terminal is attached) to move **`/tmp` to disk**: Ubuntu mounts `/tmp` as a RAM-backed tmpfs capped at 50% of RAM, which agent runs fill, halving the RAM and breaking every shell with "No space left on device". Accepting masks `tmp.mount` and installs `etc/tmpfiles.d/tmp.conf` (wipe at boot, 10-day purge). Effective at the next reboot.
15. On Linux, at the very end, **offers** to keep **SSH reachable under memory pressure**: installs the `ssh.service` drop-in (`OOMScoreAdjust=-1000`, `MemoryMin=256M`) and `earlyoom` with `etc/default/earlyoom` (kills the largest process, `node`/`java` first and never `sshd`, once free RAM and swap both drop under 10%). Restarting `ssh` keeps open sessions. Note: `MemoryMin` protects the sshd daemon only; login sessions live in `user.slice`, so no setting can reserve RAM for a future shell. earlyoom acting in time is the real protection.
### Packages installed (apt)
@@ -79,6 +83,7 @@ What it does:
- **Docker**: `docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin` (via Docker's repo)
- **Remote access**: `gnome-remote-desktop openssl` (apt) + `code-server` (via its vendor install script, not apt) — RDP remote login + browser VS Code
- **pipx**: `PyMuPDF` (`pymupdf`), `Markdown` (`markdown_py`)
- **Security baseline (Linux, always)**: `fail2ban nftables unattended-upgrades`
- **Optional (end-of-install offer, Linux)**: `earlyoom`
The script is re-runnable: each run re-backs up to `~/Oldconfig` (overwriting the previous backup), re-clones plugins, skips Docker if already installed, and re-deploys the `bin/` scripts.