Build Housecarl 0.1.0: the nftables firewall manager

Zones, address sets (IPv4 and IPv6 mixed, dynamic sets with timeouts) and
services, ordered rules in the early, input, forward and output chains,
port forwards with hairpin NAT and IPv6 pinholes, source NAT, redirects,
and switchable built-ins (loopback, conntrack, ICMPv6, antispoofing, MSS
clamping, DHCPv6 client, flowtable). Every change is validated, checked
with nft -c and applied in one transaction to Housecarl's own table,
inet housecarl; changes made over the network roll back unless
confirmed, and the confirmed ruleset is loaded at boot by
housecarl-ruleset.service. An empty configuration applies nothing.

Also: hit counters and the drop log (nflog), 'hc import' of an existing
nftables ruleset and 'hc takeover', the hc CLI, the REST API and the web
UI, users, scoped tokens (sets:write:NAME), the audit log, the web UI's
certificate through Jarl, Debian packages, docs, unit tests with real
nft 1.1.3, and an e2e test with real traffic (71 checks).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/permissions.md

@@ -0,0 +1,86 @@
+# Users, permissions and tokens
+
+## Users
+
+**Administrators** may do everything, including managing users. Everyone
+else gets **grants**, `resource:access`:
+
+| Resource | read | write |
+|---|---|---|
+| `config` | settings, zones, sets, services, rules, NAT, the ruleset, history, interfaces, probation (the web UI shows the forms locked) | change them, undo, import, confirm and roll back |
+| `sets` | dynamic sets' entries | add and remove entries |
+| `log` | hit counters and the log | – |
+| `audit` | the audit log | – |
+| `*` | all of the above | |
+
+A `sets` grant can name the sets it covers: `sets:write:guests` may
+change the entries of the set `guests` and no other;
+`sets:read:guests,blocked` may read two. That is the grant for another
+program, such as Steward's captive portal, which should be able to let a
+client in and nothing more. A dynamic set's entries need a `sets` grant
+even for those with `config:write`.
+
+Only administrators may delete other tables (`hc takeover`), and manage
+users and the certificate (`hc cert`, Server → Certificate).
+
+**Roles** are ready-made sets of grants:
+
+| Role | Grants |
+|---|---|
+| `viewer` | `config:read sets:read log:read` |
+| `operator` | `config:write sets:write log:read audit:read` |
+| `log` | `log:read`, e.g. for a monitoring script |
+
+```sh
+hc user add sam --role operator
+hc user add portal --no-password --grant sets:write:guests     # tokens only
+hc user update sam --grant config:read --grant log:read
+```
+
+The last administrator can't be removed, demoted or disabled.
+
+## API tokens
+
+A token has its user's permissions, or fewer. A token made with `--role`
+or `--grant` can do only that, even if its user can do more:
+
+```sh
+hc token create portal --user portal --grant sets:write:guests --expires 365d
+```
+
+The secret is shown once; only its hash is stored. A restricted token can
+only create tokens with a subset of its own grants. The web UI only offers
+roles within what your account may do; a token with more would get no
+more than its user anyway.
+
+**Rotating** gives a token a new secret, keeping its ID, name and
+permissions, so only the programs that use it need updating:
+
+```sh
+hc token rotate 7 --grace 1h           # the old secret works for another hour
+hc token rotate --current --save       # this CLI's own token
+```
+
+A token that expires gets its lifetime again, from now (`--expires 90d`
+or `never` to change it). Without `--grace` the old secret stops at once:
+use that when it may have leaked. Using an old secret during its grace
+period is logged, naming the token and the address, so you can find the
+programs still to update. A restricted token may rotate itself and tokens
+no wider than itself. `hc token list` shows when each token was last
+used, and from where. `hc token revoke ID` stops one at once.
+
+## The local socket
+
+On the firewall, `/run/housecarl/housecarl.sock` lets root and the
+`housecarl` user act as administrator without a token, and their changes
+aren't on probation. The audit log shows them by their system user name.
+Both can already change the machine's firewall, so this adds convenience,
+not power. Anyone else on the socket needs a token, and their changes are
+on probation like any other.
+
+## The audit log
+
+Logins (and failed ones), users, tokens, every configuration change (with
+its history entry), confirmations and rollbacks, imports, takeovers and
+dynamic set entries are recorded with who, from where and how: `session`,
+`token` or `socket`.