# checker-alias

CNAME / DNAME / ALIAS chain checker for [happyDomain](https://www.happydomain.org/).

Walks the alias chain of a name, validates hop count, TTLs, target
resolvability, apex coexistence (RFC 1912 §2.4, RFC 1034 §3.6.2,
RFC 2181 §10.1), DNAME substitutions, and DNSSEC signing of the CNAME
RRset.

## Usage

### Standalone HTTP server

```bash
# Build and run
make
./checker-alias -listen :8080
```

The server exposes:

- `GET /health` — health check
- `POST /collect` — collect alias observations (happyDomain external checker protocol)

### Docker

```bash
make docker
docker run -p 8080:8080 happydomain/checker-alias
```

### happyDomain plugin

```bash
make plugin
# produces checker-alias.so, loadable by happyDomain as a Go plugin
```

The plugin exposes a `NewCheckerPlugin` symbol returning the checker
definition and observation provider, which happyDomain registers in its
global registries at load time.

### Versioning

The binary, plugin, and Docker image embed a version string overridable
at build time:

```bash
make CHECKER_VERSION=1.2.3
make plugin CHECKER_VERSION=1.2.3
make docker CHECKER_VERSION=1.2.3
```

### happyDomain remote endpoint

Set the `endpoint` admin option for the alias checker to the URL of the
running checker-alias server (e.g., `http://checker-alias:8080`).
happyDomain will delegate observation collection to this endpoint.

## Options

| Id                        | Type | Default | Description                                                                 |
|---------------------------|------|---------|-----------------------------------------------------------------------------|
| `maxChainLength`          | uint | `8`     | Above this number of hops the chain is reported as critical.                |
| `minTargetTTL`            | uint | `60`    | Hops with a TTL below this threshold are flagged as a warning.              |
| `requireResolvableTarget` | bool | `true`  | When enabled, a final target with no A/AAAA is critical (otherwise warning).|
| `allowApexCNAME`          | bool | `false` | When enabled, a CNAME at apex is only a warning (RFC 1912 forbids it).      |
| `recognizeApexFlattening` | bool | `true`  | Recognize provider-side ALIAS/ANAME flattening as informational.            |

Finding codes emitted by the checker include: `alias_no_apex`,
`alias_loop`, `alias_chain_too_long`, `alias_query_failed`,
`alias_rcode`, `alias_low_ttl`, `alias_cname_at_apex`,
`alias_apex_flattening`, `alias_coexisting_rrset`,
`alias_cname_not_signed`, `alias_target_unresolvable`,
`alias_multiple_records`.

## License

Licensed under the **MIT License** (see `LICENSE`).