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feat: log in and sudo over SSH with a CanoKey touch

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The CanoKey resident SSH key (`ryan@canokey-moe`, the backup once a new primary key is enrolled) is now authorized for ryan and root on every host, and sudo on server and agent hosts accepts its touch through the forwarded agent (`pam_rssh`). Without the key or a forwarded agent, sudo asks for the password and login falls back to the file keys. Only `canokeySshKeys` can satisfy sudo.

Risks to weigh:

- Colmena deploys need one touch per host connection, since the agent offers the CanoKey key first.
- Desktops now forward the agent to every `hostsAddr` alias, as they already did for `192.168.*`; while a session is open, root there can request signatures, each needing a touch.

### Verification

- `just test` exits 0; CI passed on the first commit.
- Evaluated: sudo PAM stack `rssh` → `unix` → `deny` on shoryu, kana, akane and k3s-test-1-master-1, ai-niri keeps `pam_u2f`; shoryu root and ryan list `ryan@canokey-moe`.
- Not yet verified on a running host.

### Manual step after merge

Deploy the servers, then `just niri`; close old multiplexed connections (`ssh -O exit <host>`) and try `sudo true` over SSH.

AI assistance: DeepSeek Harness (claude-opus-5-5).

Assisted-by: DeepSeek Harness (claude-opus-5-5)
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ryan4yin | 二花 authored and GitHub committed 2026-11-06 03:26:59 -06:00
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docs/SECURITY.md
+16 -16
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@@ -33,19 +33,19 @@ small, reversible controls and narrow exceptions; benchmark before adopting expe
## Architecture and trust boundaries
| Boundary | Current design | Limitation |
| --------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| Administration | Key-based SSH; root key login retained for Colmena/MicroVM deployment; only keys declared in Nix are honoured, and no password or keyboard-interactive login; remote-builder host keys only reach `nix-daemon` | Deployment credentials are root-equivalent file keys, usable by any same-user process through the desktop SSH agent; one stolen key reaches every host |
| Host network | Shared nftables firewall trusts the home LAN, tailnet interface and local Podman bridge; IPv6 link-local is accepted | These are broad trust zones, not service-level least privilege; router exposure and tailnet ACLs require separate verification |
| Monitoring | node/smartctl exporters bind the host LAN IPv4 (9100/9633); firewall rules restrict exporter ports 9100, 9835 and 9633 to the monitoring host over IPv4. RAPL counters are exposed only on x86 server hosts, to `node-exporter` through the `rapl` group. | nvidia_gpu_exporter (9835) still binds wildcard; the IPv6 denial for those three ports is in the shared firewall; current running hosts require separate verification. The node_exporter account can measure package energy for local side channels; interactive users, desktops, and guests keep the kernel-default root-only permission. |
| VM hosts | shoryu, shushou and youko run guests behind `br0`; ruby/kana are libvirt guests | A bridge is not network isolation; host compromise affects its guests |
| k3s | Three control-plane and three worker MicroVMs; Cilium, API VIP and NFS CSI | Cluster-admin, privileged/host-mounted pods and writable NFS data are powerful trust boundaries |
| MicroVM storage | Host store shared read-only through virtiofs; guest `/etc`, `/var` and `/home` persisted in separate images | Read-only store does not isolate the host-side virtiofs implementation or protect writable guest state |
| Desktop apps | Selected apps use nixpak/bubblewrap; Podman is rootless | Rules and shared directories vary per app; user namespaces are needed for these sandboxes |
| Security keys | idols-ai/shoukei use a CanoKey for touch-based sudo (pam_u2f, password fallback), one resident `ed25519-sk` SSH key for GitHub and all hosts, FIDO2 LUKS unlock on shoukei and on-card OpenPGP subkeys; key management happens only in the phone app ([setup](./security-keys.md)) | Touch-only sudo can be triggered by any same-user process; per-host file SSH keys and passphrases stay valid as fallback, so their weaknesses remain until retired |
| Secrets | agenix declarations here, encrypted data in the private nix-secrets repository | Recipients and plaintext file permissions must be reviewed; root on a recipient can read its decrypted secrets |
| Supply chain | Locked flake inputs; explicit binary-cache trust keys on NixOS; normal user is not a Nix trusted-user | A trusted cache or imported Nix module can supply code executed as root; a lock file is not a security audit |
| Recovery | NixOS generations, btrbk/restic, hourly read-only snapshots of the REST store, and documented backup procedures | A rollback does not undo compromised data or secrets; backup configuration alone does not prove restore works; the offsite immutable copy is still planned |
| Boundary | Current design | Limitation |
| --------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| Administration | Key-based SSH; root key login retained for Colmena/MicroVM deployment; only keys declared in Nix are honoured, and no password or keyboard-interactive login; remote-builder host keys only reach `nix-daemon` | Deployment credentials are root-equivalent file keys, usable by any same-user process through the desktop SSH agent; one stolen key reaches every host |
| Host network | Shared nftables firewall trusts the home LAN, tailnet interface and local Podman bridge; IPv6 link-local is accepted | These are broad trust zones, not service-level least privilege; router exposure and tailnet ACLs require separate verification |
| Monitoring | node/smartctl exporters bind the host LAN IPv4 (9100/9633); firewall rules restrict exporter ports 9100, 9835 and 9633 to the monitoring host over IPv4. RAPL counters are exposed only on x86 server hosts, to `node-exporter` through the `rapl` group. | nvidia_gpu_exporter (9835) still binds wildcard; the IPv6 denial for those three ports is in the shared firewall; current running hosts require separate verification. The node_exporter account can measure package energy for local side channels; interactive users, desktops, and guests keep the kernel-default root-only permission. |
| VM hosts | shoryu, shushou and youko run guests behind `br0`; ruby/kana are libvirt guests | A bridge is not network isolation; host compromise affects its guests |
| k3s | Three control-plane and three worker MicroVMs; Cilium, API VIP and NFS CSI | Cluster-admin, privileged/host-mounted pods and writable NFS data are powerful trust boundaries |
| MicroVM storage | Host store shared read-only through virtiofs; guest `/etc`, `/var` and `/home` persisted in separate images | Read-only store does not isolate the host-side virtiofs implementation or protect writable guest state |
| Desktop apps | Selected apps use nixpak/bubblewrap; Podman is rootless | Rules and shared directories vary per app; user namespaces are needed for these sandboxes |
| Security keys | idols-ai/shoukei use a CanoKey for touch-based sudo (pam_u2f, password fallback; servers via pam_rssh and the forwarded agent), one resident `ed25519-sk` SSH key for GitHub and all hosts, FIDO2 LUKS unlock on shoukei and on-card OpenPGP subkeys; key management happens only in the phone app ([setup](./security-keys.md)) | Touch-only sudo can be triggered by any same-user process, and on a server by root through the forwarded agent; per-host file SSH keys and passphrases stay valid as fallback, so their weaknesses remain until retired |
| Secrets | agenix declarations here, encrypted data in the private nix-secrets repository | Recipients and plaintext file permissions must be reviewed; root on a recipient can read its decrypted secrets |
| Supply chain | Locked flake inputs; explicit binary-cache trust keys on NixOS; normal user is not a Nix trusted-user | A trusted cache or imported Nix module can supply code executed as root; a lock file is not a security audit |
| Recovery | NixOS generations, btrbk/restic, hourly read-only snapshots of the REST store, and documented backup procedures | A rollback does not undo compromised data or secrets; backup configuration alone does not prove restore works; the offsite immutable copy is still planned |
Sources: [host layout](../hosts/README.md), [k3s deployment](../hosts/k8s/README.md),
[firewall](../modules/nixos/base/networking/firewall.nix), [SSH](../modules/nixos/base/ssh.nix),
@@ -322,9 +322,9 @@ isolation. Source review and socket metadata—not reads of private credentials
- The current desktop session's SSH-agent socket is owned by and writable to the current UID.
Same-user subprocesses can potentially use its signing interface; read-only mounts do not prevent
socket use. Private-key bytes were not inspected and no signing operation was requested.
- `ssh -G` reports forwarding for explicit `192.168.*` destinations, but not the sampled `shoryu`
alias or GitHub destination. Do not treat forwarding as enabled for every LAN alias, or remove it
without checking deployment/build workflows.
- Agent forwarding is on for `192.168.*` destinations and the `hostsAddr` aliases (servers use it
for pam_rssh sudo), not for GitHub or other hosts. Do not remove it without checking
deployment/build workflows.
- All nine desktop wrappers use shared nixpak policies: cleared environment, filtered session D-Bus
and selected mounts. The [permission inventory](../hardening/README.md#app-permissions) lists each
app's file, network, credential and media grants.
docs/security-keys.md
+38 -24
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@@ -4,7 +4,7 @@ How the CanoKey (or a YubiKey) is set up and used on the desktops: initial setup
key, and recovery. Commands here are the single source; the Nix files only point to this page.
Scope: **idols-ai** and **shoukei** (`modules.desktop.canokey.enable`). frieren only shares the
GnuPG `scdaemon` setting; servers never use a key.
GnuPG `scdaemon` setting. Servers never see a key; they only ask the forwarded agent for sudo.
## Principle
@@ -18,13 +18,14 @@ Management and use happen on different devices.
is unreachable from them ([hardening](../hardening/README.md)). Unsandboxed software is trusted;
if it is malicious, the PC is compromised regardless.
| Use | Config | Daily use | Fallback without the key |
| ------------ | ------------------------------------------------------------------------------------------------------------------ | ---------------------------------------- | ----------------------------------------- |
| Browsers | [nixpak FIDO2 passthrough](../hardening/nixpaks/default.nix) | FIDO2 PIN and/or touch, as the site asks | site recovery codes, other registered key |
| sudo | [canokey.nix](../modules/nixos/desktop/canokey.nix), registrations in [vars](../vars/default.nix) `canokeyU2fKeys` | touch | password |
| SSH | [ssh.nix](../home/base/tui/ssh.nix), public keys in [vars](../vars/default.nix) `mainSshAuthorizedKeys` | touch per connection | per-host file keys |
| shoukei LUKS | [hardware-configuration.nix](../hosts/12kingdoms-shoukei/hardware-configuration.nix) `crypttabExtraOpts` | FIDO2 PIN + touch | passphrase (prompted after 10 s) |
| pass / GPG | [gpg](../home/base/tui/gpg/default.nix) `scdaemonSettings.disable-ccid` | OpenPGP PIN once per plug-in, then touch | off-card subkey backup |
| Use | Config | Daily use | Fallback without the key |
| ------------ | ---------------------------------------------------------------------------------------------------------------------- | ---------------------------------------- | ----------------------------------------- |
| Browsers | [nixpak FIDO2 passthrough](../hardening/nixpaks/default.nix) | FIDO2 PIN and/or touch, as the site asks | site recovery codes, other registered key |
| sudo | [canokey.nix](../modules/nixos/desktop/canokey.nix), registrations in [vars](../vars/default.nix) `canokeyU2fKeys` | touch | password |
| sudo via SSH | [ssh-agent-sudo.nix](../modules/nixos/server/ssh-agent-sudo.nix), keys in [vars](../vars/default.nix) `canokeySshKeys` | touch | password |
| SSH | [ssh.nix](../home/base/tui/ssh.nix), public keys in [vars](../vars/default.nix) `mainSshAuthorizedKeys` | touch per connection | per-host file keys |
| shoukei LUKS | [hardware-configuration.nix](../hosts/12kingdoms-shoukei/hardware-configuration.nix) `crypttabExtraOpts` | FIDO2 PIN + touch | passphrase (prompted after 10 s) |
| pass / GPG | [gpg](../home/base/tui/gpg/default.nix) `scdaemonSettings.disable-ccid` | OpenPGP PIN once per plug-in, then touch | off-card subkey backup |
Login (greetd) stays password-based: the password also unlocks GNOME Keyring.
@@ -97,6 +98,7 @@ smartcard-backed OpenPGP operations; the sound comes from Noctalia's notificatio
| -------------------------------------- | -------- | ----------------------------------------------------- |
| sudo (pam-u2f) | yes | CTAPHID keepalive / U2F `0x6985` from the FIDO hidraw |
| ssh/scp/rsync/git over ssh (FIDO2 key) | yes | same |
| sudo on a server (pam_rssh) | yes | same; the forwarded agent signs on the local key |
| WebAuthn in browsers | yes | same; browsers read the same hidraw interface |
| pass / GPG decrypt and sign | yes | gpg-agent proxy; heuristic, see below |
| PIV / OATH | no | the detector has no source for those applets |
@@ -141,12 +143,24 @@ empty, sudo is unchanged.
Every host shares the origin `pam://ryan4yin`, so one registration covers idols-ai and shoukei.
### sudo via SSH
Servers and agent hosts (`modules/nixos/server/ssh-agent-sudo.nix`) run pam_rssh: sudo there sends a
challenge back through the forwarded agent, and the CanoKey signs it after a touch. Nothing to
enroll beyond the SSH key below. Only the `canokeySshKeys` count, so a file key in the agent cannot
satisfy sudo. Agent forwarding is on for `192.168.*` and the `hostsAddr` aliases
([ssh.nix](../home/base/tui/ssh.nix)); without a forwarded agent, or with the key unplugged, sudo
asks for the password.
While a session is open, root on that server can also use the forwarded agent. Each signature still
needs a touch, so an unexpected blink is the signal to refuse it.
### SSH
One SSH key, used for GitHub and every host, lives on the key as a resident credential:
```bash
ssh-keygen -t ed25519-sk -O resident -O application=ssh:ryan4yin -C ryan@canokey
ssh-keygen -t ed25519-sk -O resident -O application=ssh:ryan4yin -C ryan@canokey-<name>
```
This writes `~/.ssh/id_ed25519_sk` on the machine that runs it. On each other desktop, export the
@@ -174,10 +188,10 @@ How it works, and what the prompts mean:
connection: `AddKeysToAgent yes` keeps the unlocked handle in the agent, which still asks the key
for each signature.
Add the public key to `mainSshAuthorizedKeys` in [vars/default.nix](../vars/default.nix) and to
GitHub. GitHub tries `id_ed25519_sk` before the per-host key; other hosts try it as a default
identity. Keys already loaded in `ssh-agent` are offered first, so the per-host keys can still win
until they are retired.
Add the public key to `canokeySshKeys` in [vars/default.nix](../vars/default.nix), which is part of
`mainSshAuthorizedKeys`, and to GitHub. GitHub tries `id_ed25519_sk` before the per-host key; other
hosts try it as a default identity. Keys already loaded in `ssh-agent` are offered first, so the
per-host keys can still win until they are retired.
### shoukei LUKS
@@ -227,27 +241,27 @@ it is. On a YubiKey, manage settings with Yubico Authenticator or `ykman`; OpenP
| Device | Section 1 again |
| Browsers | Register it on every site as an additional security key |
| sudo | `pamu2fcfg --nouser --origin=pam://ryan4yin` with only the backup plugged in; append to `canokeyU2fKeys` |
| SSH | Create a resident key on it with the same command; add its public key to `mainSshAuthorizedKeys` and GitHub. Use it with `ssh-add -K` (loads resident keys into the agent) instead of exporting a file |
| SSH | Create a resident key on it with the same command; add its public key to `canokeySshKeys` and GitHub. Use it with `ssh-add -K` (loads resident keys into the agent) instead of exporting a file |
| shoukei LUKS | Run the same `systemd-cryptenroll --fido2-device=auto` with only the backup plugged in; it takes the next slot |
| OpenPGP | Import the subkeys from the backup into a fresh, temporary `GNUPGHOME`, `keytocard` them onto the backup key, then delete that `GNUPGHOME`. The stubs remember the card serial; after swapping cards run `gpg-connect-agent "scd serialno" "learn --force" /bye` |
## 4. Lost key or reset
| Situation | Action | Lost |
| ------------------------------------ | ------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------- |
| Key lost | Remove its `canokeyU2fKeys` entry and SSH public key; `systemd-cryptenroll --wipe-slot=<n>`; remove it on each site | nothing, if a backup key or the passwords remain |
| FIDO2 PIN forgotten or locked | Phone app: reset the WebAuthn application (needs the Admin PIN) | all passkeys, the SSH resident key, LUKS and sudo enrollments; redo section 2 |
| OpenPGP PIN locked | `gpg --card-edit` → `admin` → `passwd`, unblock with the OpenPGP Admin PIN or Reset Code | nothing |
| All OpenPGP PINs and Reset Code lost | Phone app: reset the OpenPGP application | on-card subkeys; re-import from the backup |
| Admin PIN forgotten | Exhaust the Admin PIN, then in the app tap Reset and touch the key while the LED blinks, repeating until it stops | all user data; serial and attestation keys stay |
| Situation | Action | Lost |
| ------------------------------------ | -------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------- |
| Key lost | Remove its `canokeyU2fKeys` entry and SSH public keys; `systemd-cryptenroll --wipe-slot=<n>`; remove it on each site | nothing, if a backup key or the passwords remain |
| FIDO2 PIN forgotten or locked | Phone app: reset the WebAuthn application (needs the Admin PIN) | all passkeys, the SSH resident key, LUKS and sudo enrollments; redo section 2 |
| OpenPGP PIN locked | `gpg --card-edit` → `admin` → `passwd`, unblock with the OpenPGP Admin PIN or Reset Code | nothing |
| All OpenPGP PINs and Reset Code lost | Phone app: reset the OpenPGP application | on-card subkeys; re-import from the backup |
| Admin PIN forgotten | Exhaust the Admin PIN, then in the app tap Reset and touch the key while the LED blinks, repeating until it stops | all user data; serial and attestation keys stay |
After any reset, rerun sections 1 and 2 for the affected applications.
## Enrollment status
| Key | Firmware | sudo | SSH | shoukei LUKS | OpenPGP | Browsers |
| ------------------------ | -------- | ----------------- | ---------------------------------------------------------- | ----------------------------- | ----------- | -------------------------------- |
| CanoKey Canary (primary) | 3.0.3 | works on idols-ai | key created; public key not yet in `mainSshAuthorizedKeys` | enrolled; unlock not verified | on the card | WebAuthn works in Firefox/Chrome |
| Key | Firmware | sudo | SSH | shoukei LUKS | OpenPGP | Browsers |
| -------------------------------------- | -------- | ----------------- | ------------------------------------------------------- | ----------------------------- | ----------- | -------------------------------- |
| CanoKey Canary (backup, `canokey-moe`) | 3.0.3 | works on idols-ai | public key in `canokeySshKeys`; host login not verified | enrolled; unlock not verified | on the card | WebAuthn works in Firefox/Chrome |
shoukei's first boots with the FIDO2 slot asked for the PIN, then fell back to the passphrase: USB
only came up after switch-root, because on linux-asahi 7.2 its dwc3/PHY depend on the Thunderbolt
home/base/tui/ssh.nix
+9 -1
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@@ -65,7 +65,15 @@ in
}
// lanHost;
}
// lib.genAttrs (builtins.attrNames myvars.networking.hostsAddr) (_: lanHost);
# Aliases forward the agent like their addresses do; servers ask it for sudo
# (modules/nixos/server/ssh-agent-sudo.nix).
// lib.genAttrs (builtins.attrNames myvars.networking.hostsAddr) (
_:
{
ForwardAgent = true;
}
// lanHost
);
};
# Keep ~/.ssh/config a real, user-owned file rather than a /nix/store symlink.
modules/nixos/server/server-aarch64.nix
+1
View File
@@ -15,6 +15,7 @@
../base/packages.nix
../base/ssh.nix
../base/user-group.nix
./ssh-agent-sudo.nix
# This server imports base files individually instead of the whole
# modules/nixos/base group, so pull the shared firewall in explicitly.
modules/nixos/server/server.nix
+1
View File
@@ -3,6 +3,7 @@
imports = [
../base
../nushell-login.nix
./ssh-agent-sudo.nix
../../base
];
modules/nixos/server/ssh-agent-sudo.nix
+20
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@@ -0,0 +1,20 @@
{
lib,
pkgs,
myvars,
...
}:
{
# sudo over SSH accepts a CanoKey touch through the forwarded agent; without
# it, sudo asks for the password as before. Only the hardware-backed keys are
# trusted, so a file key loaded in the agent cannot sign for sudo silently.
# Setup and limits: docs/security-keys.md.
security.pam.rssh = {
enable = true;
settings = {
auth_key_file = "${pkgs.writeText "sudo-ssh-agent-keys" (lib.concatLines myvars.canokeySshKeys)}";
cue = true;
};
};
security.pam.services.sudo.rssh = true;
}
vars/default.nix
+13 -2
View File
@@ -1,5 +1,15 @@
{ lib }:
let
# CanoKey resident SSH keys: they log in like the main keys, and they are the
# only keys pam_rssh accepts for sudo on servers through the forwarded agent
# (modules/nixos/server/ssh-agent-sudo.nix).
canokeySshKeys = [
# CanoKey Canary (backup)
"sk-ssh-ed25519@openssh.com AAAAGnNrLXNzaC1lZDI1NTE5QG9wZW5zc2guY29tAAAAIKgfNy/wJgTw6auO4RmRHR9kh1Mt5TYNkomMDFLJ4Kw6AAAADHNzaDpyeWFuNHlpbg== ryan@canokey-moe"
];
in
{
inherit canokeySshKeys;
username = "ryan";
userfullname = "Ryan Yin";
useremail = "xiaoyin_c@qq.com";
@@ -28,11 +38,12 @@
"ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIIKlN+Q/GxvwxDX/OAjJHaNFEznEN4Tw4E4TwqQu/eD6 ryan@idols-ai"
"ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIJwoI5MAogEa726jwwHL5EgM1X/i2A5d2pgV7i7t8fzB ryan@shoukei"
"ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDc1PNTXzzvd93E+e9LXvnEzqgUI5gMTEF/IitvzgmL+ ryan@frieren"
];
]
++ canokeySshKeys;
# CanoKey U2F registrations for sudo (modules/nixos/desktop/canokey.nix).
# Key handles and public keys only, so they are safe to commit.
canokeyU2fKeys = [
# CanoKey Canary (primary)
# CanoKey Canary (backup)
"DwXDxVU+NDTUZs/d2EjpsPAh4mrg7dqdg/mAozkw/mUAAdEYDZIbm8kTBUGA49wXW0ZvSpF9VNYh2w84Xz9nAIAW////+Q==,6hqEjWBJ+ueBKBJaNijNkUsmlgEHMgv0KdpprqdJjHKoU/FKpeqo12SWlvdgiIVWvqTaGfe4fNu/ckcGY5mlsA==,es256,+presence"
];
secondaryAuthorizedKeys = [