modified: README.md

modified:   certbot_dns_netbox/dns_netbox.py

README.md

@@ -1,6 +1,6 @@
 # certbot-dns-netbox
 
-Certbot DNS-01 authenticator plugin that updates the challenge TXT record in
+Certbot DNS-01 authenticator plugin that updates the challenge TXT records in
 [NetBox DNS](https://github.com/sys4/netbox-plugin-dns) (the `netbox-dns`
 NetBox plugin) via the bundled `nbapi.py` API helper.
 
@@ -13,16 +13,27 @@ and the plugin **never creates or deletes records**:
 
 1. looks up the existing TXT records for the FQDN (records can be filtered by
    `fqdn`, `zone` and `view` by name),
-2. writes the challenge token into the existing record. If the record does
-   not exist yet, certbot aborts with an error: create the record once
-   beforehand (in the NetBox UI or your tooling) and rerun,
-3. leaves the record in place after validation so it can be updated again on
-   the next renewal.
+2. writes each challenge token into one of the pre-provisioned records,
+   claiming one record per token,
+3. leaves the records in place after validation so they can be updated again
+   on the next renewal.
 
-Because a single record holds a single token, a certificate request must not
-combine a domain and its wildcard (`-d example.com -d '*.example.com'`): both
-map to the same `_acme-challenge.example.com` record, and the second token
-would overwrite the first. Issue those as separate certificates.
+### Provisioning
+
+The challenge TXT records must be created beforehand in netbox-dns, in the
+view configured via `search_view` (`certbot_dns_netbox/dns_netbox.py`,
+default: `global`). Each challenge token needs its own record:
+
+| Certificate request                                    | TXT records needed |
+| ------------------------------------------------------ | ------------------ |
+| `-d example.com` or `-d '*.example.com'`               | 1                  |
+| `-d example.com -d '*.example.com'` (apex + wildcard)  | 2                  |
+
+All records for a challenge share the same name (e.g. name
+`_acme-challenge.unifi` in zone `ewcs.ch`); netbox-dns allows multiple TXT
+records with different values for the same name. If a certificate request
+needs more records than exist, certbot aborts with an error. Renewals simply
+rewrite the values, so the records never need to be touched again.
 
 Connection settings are taken from the environment, exactly as `nbapi.py`
 expects them:
@@ -94,6 +105,6 @@ certbot certonly --dry-run \
     -d sub.example.com                # end-to-end against the staging ACME API
 ```
 
-Watch the `_acme-challenge` TXT record in the `global` view: its value changes
-to the challenge token during the run and remains in place afterwards. The
-next renewal updates the same record again.
+Watch the `_acme-challenge` TXT records in the `global` view: their values
+change to the challenge tokens during the run and remain in place afterwards.
+The next renewal updates the same records again.

certbot_dns_netbox/dns_netbox.py

@@ -1,10 +1,11 @@
 """NetBox DNS (netbox-plugin-dns) DNS-01 authenticator plugin for Certbot.
 
-The TXT record required for the ACME dns-01 challenge is managed
-exclusively through the netbox-dns record API endpoint, via the bundled
-nbapi.py helper. The zone endpoint is never queried and the plugin never
-creates or deletes records: an existing TXT record (created beforehand in
-NetBox) is updated with the challenge token and left in place afterwards.
+The TXT records for the ACME dns-01 challenge are managed exclusively
+through the netbox-dns record API endpoint, via the bundled nbapi.py
+helper. The zone endpoint is never queried and the plugin never creates
+or deletes records: the challenge TXT records (created beforehand in
+NetBox, one per challenge token) are updated with the challenge tokens
+and left in place afterwards.
 
 Connection settings are taken from the environment, exactly as nbapi.py
 expects them:
@@ -59,8 +60,8 @@ class Authenticator(dns_common.DNSAuthenticator):
 
     def more_info(self) -> str:
         return (
-            "This plugin updates an existing DNS TXT record in netbox-dns "
-            "with the token of the dns-01 challenge."
+            "This plugin updates pre-provisioned DNS TXT records in "
+            "netbox-dns with the tokens of the dns-01 challenges."
         )
 
     def _setup_credentials(self) -> None:
@@ -106,8 +107,8 @@ class _NetboxDnsClient:
 
     Only the record API endpoint is used, so the API token needs no
     permissions on zones. Records are never created or deleted: the
-    challenge TXT record must already exist in NetBox and is updated in
-    place.
+    challenge TXT records must be provisioned beforehand in NetBox, one
+    per challenge token, and are updated in place.
     """
 
     def __init__(self, ttl: Optional[int] = None, insecure: bool = False):
@@ -118,6 +119,10 @@ class _NetboxDnsClient:
 
         self._nbapi = nbapi
         self._ttl = ttl
+        # record ids claimed by this certbot run; each challenge token gets
+        # its own pre-provisioned record so multiple tokens for the same
+        # name (e.g. apex and wildcard) do not overwrite each other.
+        self._claimed: set = set()
         if insecure:
             nbapi.disable_ssl_verify()
 
@@ -141,30 +146,43 @@ class _NetboxDnsClient:
             ) from e
 
     def update_txt_record(self, record_fqdn: str, validation: str) -> None:
-        """Write the challenge token into the existing TXT record."""
+        """Write the challenge token into one of the pre-provisioned records.
+
+        Each challenge token claims its own record so that several tokens
+        for the same name (e.g. apex and wildcard on one certificate) stay
+        live simultaneously.
+        """
         fqdn = self._fqdn(record_fqdn)
         records = self._get_txt_records(fqdn)
 
-        if any(record["value"] == validation for record in records):
-            logger.debug(
-                "TXT record for %s already has the expected value.", record_fqdn
-            )
-            return
+        for record in records:
+            if record["value"] == validation and not record.get("managed"):
+                self._claimed.add(record["id"])
+                logger.debug(
+                    "TXT record for %s already has the expected value.",
+                    record_fqdn,
+                )
+                return
 
-        existing = [record for record in records if not record.get("managed")]
-        if not existing:
+        existing = sorted(
+            (record for record in records if not record.get("managed")),
+            key=lambda record: record["id"],
+        )
+        free = [record for record in existing if record["id"] not in self._claimed]
+        if not free:
             raise errors.PluginError(
-                f"No updatable TXT record found for {record_fqdn} in view "
-                f"{search_view!r}. This plugin only updates existing records: "
-                "create the record once (type TXT) and rerun certbot."
+                f"Not enough TXT records for {record_fqdn} in view "
+                f"{search_view!r}: {len(existing)} record(s) exist, but all of "
+                "them are already in use by this certificate request. Add "
+                "another TXT record with the same name and rerun certbot."
             )
 
-        patch = {"id": existing[0]["id"], "value": validation}
+        target = free[0]
+        patch = {"id": target["id"], "value": validation}
         if self._ttl:
             patch["ttl"] = self._ttl
         self._nbapi.modify_dns_record(patch)
+        self._claimed.add(target["id"])
         logger.info(
-            "Updated TXT record %s (id %s).",
-            existing[0]["fqdn"],
-            existing[0]["id"],
+            "Updated TXT record %s (id %s).", target["fqdn"], target["id"]
         )