jensandClaude Sonnet 5
92d871f2da
Records the host's service inventory, setup runbook, mail account list, sync plan, package diff vs. clean install, and hardening TODOs, including today's SSH hardening (key-only, no root login) and the fail2ban sshd findtime fix for a low-and-slow brute-force evasion pattern. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01RdTyvEJkfNLDVAWt8WQ6X9
77 lines
4.5 KiB
Markdown
77 lines
4.5 KiB
Markdown
# alpha.jayfield.org — TODO
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Outstanding hardening items (see `README.md` for the full service overview).
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Nothing here is urgent; all are low-risk, no-downtime changes.
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- [x] **Lock down the dyndns TSIG key file permissions** — done 2026-07-19
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`/etc/bind/dyndns.jayfield.org.key` was `644` (world-readable), holding
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the shared secret that authenticates dynamic DNS updates for
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`dyndns.jayfield.org` with no IP-based `allow-update` backing it up.
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Fixed: `chmod 640` + `chown root:bind` (owner was already correct),
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matching `rndc.key`'s permissions.
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- [x] **Suppress BIND version disclosure** — done 2026-07-19
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No `version` statement in `named.conf.options`, so
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`dig CH TXT version.bind @ns1.jayfield.org` leaked the exact BIND
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version (`9.18.39`) — a minor fingerprinting aid for attackers.
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Fixed: added `version "unknown";` inside the `options {}` block,
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validated with `named-checkconf`, and applied via `rndc reload`.
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Verified `dig CH TXT version.bind` now returns `"unknown"`.
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- [x] **Add response rate limiting (RRL)** — done 2026-07-19
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No `rate-limit {}` block was configured. Since `allow-query { any; }`
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is required for a public authoritative zone, RRL is the standard
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mitigation against the server being used for spoofed-source DNS
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reflection/amplification against third parties.
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Fixed: added `rate-limit { responses-per-second 10; window 5; }` to
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`named.conf.options`, validated with `named-checkconf`, and applied
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via `rndc reload`. Started with conservative defaults (10/s, 5s
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window) — revisit if legitimate high-volume resolvers get throttled.
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- [x] **Add HSTS headers to all vhosts** — done 2026-07-19
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No vhost sent a `Strict-Transport-Security` header, leaving a window
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for on-path SSL-stripping on a user's very first plaintext request to
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any domain.
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Fixed: added `Header always set Strict-Transport-Security
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"max-age=63072000; includeSubDomains"` to all 6 domain `:443` blocks
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(`dyndns`, `jayfield.org`, `www`, `mail`, `web`, `cloud`) — skipped
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`default-ssl.conf` since it's the self-signed catch-all with no real
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trusted hostname for a browser to pin. Validated with
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`apache2ctl configtest`, applied via `systemctl reload apache2`,
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verified live with `curl -sI` against all 6 domains.
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- [x] **`jayfield.org` had no `:80` vhost of its own** — done 2026-07-19
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Bare `http://jayfield.org` fell through to the `dyndns` default vhost
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and redirected to the wrong domain.
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Fixed: added a `:80` block to `jayfield.org.conf` redirecting to
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`https://jayfield.org/`, matching the `dyndns`/`mail` pattern.
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Verified: `curl -sI http://jayfield.org/` → `302` with
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`Location: https://jayfield.org/`.
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- [x] **SSH: disable root login + password auth** — done 2026-07-19
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`PermitRootLogin yes` and `PasswordAuthentication yes` were both still
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enabled (the "known deviation" flagged in `SETUP.md` §1) — every
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credential-stuffing bot on the internet got a real login prompt to
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grind against.
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Fixed: `PermitRootLogin no`, `PasswordAuthentication no`,
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`PubkeyAuthentication yes` in `/etc/ssh/sshd_config` (backed up as
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`sshd_config.bak.20260719225249`). The `Match Group sftp` block's own
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`PasswordAuthentication yes` was left as-is — separate, already-chrooted,
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no-shell/no-forwarding accounts, not part of this risk. Validated with
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`sshd -t`, applied via `systemctl reload sshd`, verified live with
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`sshd -T` and a fresh key-only connection before considering it done.
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- [x] **fail2ban: `sshd` jail was evadable via low-and-slow attempts** — done 2026-07-19
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Default `findtime=30m`/`maxretry=3` never triggered for `47.76.192.176`,
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which had been hitting `root`/`jayfield` logins roughly every 33 minutes
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for most of a day — just outside the 30-minute window, so failures kept
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aging out before reaching 3 strikes. Confirmed via `fail2ban.log`
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(`Found`/`Ban` counts) that no other jail showed the same per-IP timing
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pattern; a separate, *distributed* single-shot scan on `apache-noscript`
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was noted but left open (see `README.md`).
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Fixed: `/etc/fail2ban/jail.d/sshd-findtime.local` overrides `sshd` to
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`findtime=1d`, `maxretry=4`, `bantime=1d`, kept in its own drop-in
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rather than editing the Debian-packaged jail file. Applied via
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`fail2ban-client reload sshd`; `47.76.192.176` was banned on its very
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next attempt after the change.
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