jakman85andClaude Opus 5
5c43fbac65
The tunnel never came up on its first reconcile with a real key. One line of my
own manifest was the whole cause. Measured on prod 2026-10-06:
[#] ip link add dev wg0 type wireguard <- fine
[#] wg addconf wg0 /dev/fd/63 <- fine
[#] ip -4 address add 10.90.0.1/24 dev wg0 <- fine
[#] ip link set mtu 1420 up dev wg0 <- fine
[#] sysctl -q -w net.ipv4.ip_forward=1
sysctl: permission denied on key "net.ipv4.ip_forward"
[#] ip link delete dev wg0
**** Tunnel failed, will stop all others! ****
Not a missing capability: with hostNetwork the runtime mounts /proc/sys
READ-ONLY (confirmed in the pod's /proc/mounts), because those sysctls are the
HOST's globals. CAP_NET_ADMIN cannot lift a read-only mount, so the write can
never succeed here -- and wg-quick treats a failed PostUp as fatal, so it
deleted the interface it had just built.
The line was never needed. node_baseline already sets ip_forward=1, and reading
it from the pod returns 1. My header comment said exactly that ("so no pod
sysctl is needed") and then emitted the sysctl anyway, justified as "re-asserted
so this component does not silently depend on another role's sysctl file". That
defensive re-assertion is the entire outage. In a hostNetwork pod: VERIFY host
state, never write it.
Replaced with a read in the init container -- `grep -qx 1
/proc/sys/net/ipv4/ip_forward` -- failing closed with a message naming the
node_baseline role. Still fail-closed on purpose: a tunnel that comes up unable
to forward satisfies every probe here and silently drops all client traffic.
Also documents, in the manifest and the runbook, that the image's `chown:
Operation not permitted` run and its "we will not provide support for it"
warning are expected and harmless -- capabilities are dropped to NET_ADMIN so
its s6 init has no CAP_CHOWN, /config is a writable tmpfs, everything runs as
root, and wg-quick proceeds (it did; the failure was 30 lines later).
Three other unknowns closed by the same reconcile, now recorded in the README:
the kernel module reaches the pod (ip link add type wireguard works, no
CAP_SYS_MODULE needed); allowPrivilegeEscalation:false does NOT break the s6
init; and the image's iptables is nf_tables (xtables-nft-multi) matching Debian
13, which closes the worst documented fear -- rules landing in a table the
kernel never consults.
No sensitive paths; merges on a green gate with no override.
Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
289 lines
15 KiB
Markdown
289 lines
15 KiB
Markdown
# vpn-remote-access — standing up the WireGuard remote-access VPN, and proving it
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**Status: the in-cluster half is shipped; the VPN is INERT until three manual steps are done.**
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All three are off-repo by necessity — a kernel module, a private key, and a router port-forward.
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**Alert:** pod-down is covered generically (`KubePodNotReady` / `KubeDeploymentReplicasMismatch`).
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There is **no peer-level alerting** — see "Why there is no connection alert". This is an **operator
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procedure**, not an incident page.
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**Files:** `platform/vpn-ingress/` (namespace, peer register, DaemonSet, baseline policy),
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`clusters/base/vpn-ingress.yaml` (its Flux tier), `clusters/base/cluster-vars.yaml`
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(`WG_CLIENT_CIDR`), `infra/ansible/roles/node_baseline/defaults/main.yml` (the `wireguard` module),
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`infra/vpn-ingress/new-peer.sh` (device enrolment).
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**Design rationale:** `platform/vpn-ingress/README.md` — read "Why `hostNetwork` is required"
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before changing anything about how this is wired.
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**Not to be confused with** `vpn-down` / `vpn-egress-stale`, which are about `platform/vpn-egress`
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(pods *out* through PIA). This page is remote clients *in*.
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## What this gives you
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A device — Android, Linux, Windows, macOS, iOS — dials in over **udp/51820** from anywhere and
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behaves like a machine on the LAN: full reach to `192.168.2.0/24`, the Gateway's web UIs, PiHole
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DNS, and internet egress out the house WAN.
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Authorisation is one thing only: the device's **public key is in
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`platform/vpn-ingress/peers.yaml`**. An unlisted key gets no reply at all.
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> **An enrolled device is as privileged as a machine sitting in the house** — including the three
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> k3s nodes (`192.168.2.10/.11/.12`: apiserver 6443, kubelet 10250, SSH 22). That is what "reach
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> the entire local network" means. Revoke a lost device promptly: delete its stanza, PR, merge.
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## Step 1 — load the `wireguard` module on every node (once)
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The DaemonSet creates its `wg0` link in the host netns with `CAP_NET_ADMIN` only; it is
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deliberately **not** granted `CAP_SYS_MODULE`, so it cannot autoload the module. Without it
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`wg-quick` fails outright and the pod CrashLoops.
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```bash
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# operator action (Ansible is not an agent action). Ansible lives ONLY in the pinned toolbox,
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# and ansible.cfg is only picked up from infra/ansible, so cd there inside the container.
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./infra/devcontainer/dev.sh run bash -c \
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'cd /work/infra/ansible && ansible-playbook playbooks/node-baseline.yml -e k3s_hosts=k3s_prod --tags system'
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```
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Three details in that command are load-bearing, not style:
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- **`-e k3s_hosts=k3s_prod`.** `node-baseline.yml` targets `k3s_servers` by default, which is the
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**dev** group — and dev was decommissioned, so an unqualified run does nothing useful. This is
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the targeting pattern `infra/ansible/README.md` "Targeting prod" documents for every playbook.
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- **`--tags system`, and never an untagged run.** The two kernel-module tasks carry the `system`
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tag. An untagged run would also execute the `disks` tasks, which assert on block-device variables
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prod has deliberately left as placeholders (`infra/PROD-PROVISIONING.md` §2) — the playbook's own
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header warns about this. `--tags system` is broader than the modules alone (it also re-asserts
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sysctls, iscsid, qemu-guest-agent and the swap masking) but every one of those is idempotent and
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already in its desired state on a live node.
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- **It is a playbook, not a wrapper script.** There is no `site.sh` in this repo; `playbooks/site.yml`
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is the full bring-up chain and is the wrong tool here.
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Verify on each node — the module is in-tree since kernel 5.6, so nothing is installed, only loaded:
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```bash
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# expected: a `wireguard` line, and the modules-load.d file naming it for the next boot
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lsmod | grep '^wireguard'
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grep -w wireguard /etc/modules-load.d/k3s-cilium-longhorn.conf
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```
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## Step 2 — fill in the server key (once)
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The key is **SOPS-encrypted in this tree** (R-SEC-01, spec docs/07), not created by hand:
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`platform/vpn-ingress/wg-server-key.sops.yaml`. It is already committed — encrypted, with a
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`REPLACE-ME` placeholder — and it is already listed in the component's `resources:` with a
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`decryption:` patch in both overlays. **Nothing needs wiring. You are only replacing one value.**
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Why in git rather than `kubectl create secret`: an out-of-band Secret puts the one credential every
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enrolled device depends on outside the GitOps tree, where a cluster rebuild silently loses it — and
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losing it means re-enrolling every device, because each client profile pins this key's public half.
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Everything below runs **inside the dev container** — `wg`, `sops` and `qrencode` are all baked into
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the image (CLAUDE.md §5: the toolchain lives only in the pinned container; don't install it on the
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host). One shell, one toolchain.
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**1. Generate the key straight into the encrypted file.** One pipeline: `wg genkey` makes it,
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`sops set` writes it into the already-encrypted document in place. The plaintext never lands on
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disk and never reaches a terminal.
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```bash
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./infra/devcontainer/dev.sh run bash -c '
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cd /work
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umask 077
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sops set platform/vpn-ingress/wg-server-key.sops.yaml \
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"[\"stringData\"][\"privatekey\"]" "\"$(wg genkey)\""
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'
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```
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**2. Record it in your PASSWORD MANAGER.** Derive both halves from the file you just wrote:
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```bash
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# the PUBLIC half — safe to display, and what every client profile carries
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./infra/devcontainer/dev.sh run bash -c 'cd /work && sops -d --extract "[\"stringData\"][\"privatekey\"]" \
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platform/vpn-ingress/wg-server-key.sops.yaml | wg pubkey'
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# the PRIVATE half — paste into the password manager, then clear your scrollback
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./infra/devcontainer/dev.sh run bash -c 'cd /work && sops -d --extract "[\"stringData\"][\"privatekey\"]" \
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platform/vpn-ingress/wg-server-key.sops.yaml'
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```
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The second command is the one place this key is deliberately shown. The encrypted file is in git and
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Velero captures this namespace to R2, so the password-manager copy is belt-and-braces — but it is
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the only copy that survives losing the cluster *and* the backups, and the key cannot be regenerated
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without invalidating every client profile.
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**3. Confirm the value is a real key**, without printing it — if `wg pubkey` prints a key, the
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value is valid; if it errors, it is still wrong:
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```bash
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./infra/devcontainer/dev.sh run bash -c 'cd /work && sops -d --extract "[\"stringData\"][\"privatekey\"]" \
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platform/vpn-ingress/wg-server-key.sops.yaml | wg pubkey >/dev/null && echo "valid WireGuard key"'
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```
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That is the same check the pod's init container runs, so a pass here predicts a pass there.
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**4. PR it, and merge.** Flux rolls the DaemonSet and the pods leave CrashLoop.
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If you would rather use an editor than `sops set`:
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`./infra/devcontainer/dev.sh run sops platform/vpn-ingress/wg-server-key.sops.yaml` (replace
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`REPLACE-ME`, save, exit — it re-encrypts on write).
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### What the pod tells you if this went wrong
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The init container validates the value with `wg pubkey` before writing `wg0.conf`, and names the
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specific failure in its log — so you never get a server that silently cannot complete a handshake:
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| pod log says | meaning |
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|---|---|
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| `still the committed REPLACE-ME PLACEHOLDER` | step 3 not done (the expected fresh-install state) |
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| `It is EMPTY` | the value was blanked |
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| `still SOPS CIPHERTEXT (starts with ENC[)` | the Secret reached the cluster undecrypted — this environment's overlay is missing its `vpn-ingress` decryption patch. **This is the dangerous one:** the Secret applies cleanly and every Flux condition stays green |
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| `wg pubkey rejected it` with none of the above | a mangled value, or a *public* key pasted by mistake |
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| `net.ipv4.ip_forward is 0 on this node` | the node_baseline role has not run here (step 1). The pod **cannot** set this itself — under `hostNetwork` the runtime mounts `/proc/sys` read-only, because it is the host's global setting |
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### What a healthy start looks like
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Measured on prod 2026-10-06. The init container logs one line, naming the shape and never the key:
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```
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wg0.conf assembled: 0 peer(s), server 10.90.0.1/24, udp/51820.
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```
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then the `wireguard` container brings the tunnel up:
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```
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**** Found WG conf /config/wg_confs/wg0.conf, adding to list ****
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**** Activating tunnel /config/wg_confs/wg0.conf ****
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[#] ip link add dev wg0 type wireguard
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[#] wg addconf wg0 /dev/fd/63
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[#] ip -4 address add 10.90.0.1/24 dev wg0
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[#] ip link set mtu 1420 up dev wg0
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```
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**Ignore the `chown: ... Operation not permitted` run before that**, and the image's own
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"Permissions could not be set ... we will not provide support for it". Capabilities are dropped to
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`NET_ADMIN` only, so its s6 init has no `CAP_CHOWN`; `/config` is a writable tmpfs, everything runs
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as root, and `wg-quick` proceeds. It is wrong about the cause and it does not matter.
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**A pod stuck `0/1 Running` with `Startup probe failed: Unable to access interface: No such device`
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means `wg-quick` tore the tunnel down** — read the `wireguard` container log for the `[#]` line it
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died on. That is the shape of a real failure; the probe is doing its job of refusing to call a
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server without a `wg0` "ready".
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## Step 3 — forward udp/51820 on the router (once)
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On the SOHO router at `192.168.2.1`, forward **WAN udp/51820** to **one node address**, e.g.
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`192.168.2.10:51820`. This is hand-made and off-repo; it is the half CI can never check.
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Pick any node — all three run an identical listener. Note which one you chose here:
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```
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# WAN udp/51820 -> 192.168.2.__ (k3s-prod-_) set <date>
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```
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**Node loss = failover is this one line.** Re-point the forward at another node address; every
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device keeps working with the same profile, because all three nodes answer the same keys.
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Do **not** also expose this on tcp, and do not change the port hoping for obscurity — WireGuard is
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already silent to unauthenticated probes (README, "Why this is safe to expose").
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## Step 4 — confirm the listener is healthy
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```bash
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./infra/devcontainer/dev.sh run bash -c \
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'kubectl --context k3s-prod -n vpn-ingress get ds wireguard -o wide'
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# expected: DESIRED 3 CURRENT 3 READY 3
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./infra/devcontainer/dev.sh run bash -c \
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'kubectl --context k3s-prod -n vpn-ingress exec ds/wireguard -- wg show'
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# expected: `interface: wg0`, `listening port: 51820`, and (before step 5) NO peers.
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```
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A zero-peer interface that is Ready is the **correct** state before any device is enrolled: it
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listens, and refuses every handshake because no key is trusted.
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The readiness/liveness probe is `wg show wg0`, and that is load-bearing rather than cosmetic: a
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port probe cannot distinguish "wg0 never came up" from "working", because WireGuard is silent to
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unauthenticated traffic either way. If the pod is Ready, the interface exists.
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## Step 5 — enrol a device
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```bash
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# in the dev container, like everything else
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./infra/devcontainer/dev.sh run bash -c './infra/vpn-ingress/new-peer.sh pixel-8 2' # full tunnel
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./infra/devcontainer/dev.sh run bash -c './infra/vpn-ingress/new-peer.sh thinkpad 3 --split' # LAN only
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```
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It derives the server's public key from `wg-server-key.sops.yaml` itself, so there is no local key
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copy to keep in step with anything. Profiles land in `.cache/wg-peers/` — gitignored, and persistent
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because the repo is the container's only read-write mount.
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It generates the device's keypair, writes a `0600` client profile, prints a QR code, and prints the
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`[Peer]` stanza to add. It refuses to write a profile anywhere git does not ignore.
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Then:
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1. Paste the stanza into `platform/vpn-ingress/peers.yaml` under `data.peers.conf`, keeping the
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`# <name> — <owner>, enrolled <date>` comment. `wg show` can only ever print the key, so that
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comment is the only record of which stanza belongs to which device.
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2. PR → merge. Flux rolls the DaemonSet (~1 min).
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3. Get the profile onto the device (QR scan for phones; "Import tunnel from file" on
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Windows/macOS; `/etc/wireguard/<name>.conf` + `wg-quick@<name>` on Linux).
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4. **Delete the profile from your machine**: `shred -u <path>`. It is the only copy of that
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device's private key — the server never sees it and it cannot be re-derived.
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Until the PR is merged the device handshakes and gets silence, exactly like an unknown key.
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## Step 6 — verify it end to end (from OFF the LAN)
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**This is the only honest test, and it cannot be run from inside the house.** Put the phone on
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cellular, with Wi-Fi off, and check all four — each proves a different hop:
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| # | Check | Proves |
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|---|---|---|
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| 1 | tunnel shows a recent handshake in the WireGuard app | the WAN forward + the server key + the peer stanza |
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| 2 | `ping 192.168.2.1` (the router) | decrypt → FORWARD → LAN, and the SNAT return path |
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| 3 | open `https://plex.home.keithjackson.dev` | PiHole DNS over the tunnel **and** the Gateway accepting a `host`-identity source — the specific thing a pod-networked VPN would have 403'd |
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| 4 | visit an IP-echo site; it should show `136.51.115.252` | full-tunnel WAN egress out the house, not the carrier |
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Then confirm server-side:
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```bash
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./infra/devcontainer/dev.sh run bash -c \
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'kubectl --context k3s-prod -n vpn-ingress exec ds/wireguard -- wg show'
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# a `latest handshake` under ~3 min, and non-zero transfer, on the expected peer.
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```
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**If check 3 fails while 2 passes**, the tunnel is fine and the problem is DNS or the Gateway, not
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WireGuard. Check the client's `DNS = 192.168.2.23` and that PiHole is up.
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**If 1 and 2 pass but large transfers hang**, it is MTU. The profile ships `MTU = 1420` (1500 − 60
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bytes of WireGuard encapsulation); drop the client to `1280` and re-test.
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**If nothing handshakes at all**, you cannot tell a wrong forward from a wrong key from outside —
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by design. Work inwards: `wg show` on the node holding the forward will show *zero* received bytes
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if the router is not delivering the packets, and a `handshake` with no completed session if it is.
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## Revoking a device
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Delete its `[Peer]` stanza from `peers.yaml`, PR, merge. Nothing else — the key stops working on the
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next reconcile. **Never re-use that address octet**: an old profile would silently start working
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again as a different device.
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## Why there is no connection alert
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A WireGuard exporter would publish `wireguard_latest_handshake_seconds` per peer and make
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"something connected at 03:00" alertable. It needs a second `NET_ADMIN` container inside the pod
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that terminates the internet-facing tunnel, and that was not worth shipping unverified. **It is the
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top follow-up for this component.** Until then:
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* pod-down is covered generically by kube-prometheus-stack's `KubePodNotReady` /
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`KubeDeploymentReplicasMismatch`;
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* "who is connected" is an on-demand question — `wg show`, above;
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* **never** `wg showconf` — it prints the server's private key.
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## Known limitations
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* **No IPv6 in the tunnel.** A full-tunnel client with native IPv6 still reaches IPv6 sites outside
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the tunnel. Functionally harmless; a privacy leak if hiding the client's network was the point.
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* **Client IPs are not preserved** on the LAN side: everything arrives SNATed as the node's
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address. A static route for `10.90.0.0/24` → the forwarded node, added on the router, would
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preserve them — at the cost of another hand-maintained off-repo route.
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* **Rollouts briefly drop the forwarded node.** `maxUnavailable: 1`, so one node at a time; clients
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re-handshake automatically (retry every 5s, rekey every 2 min).
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