From 86308c9780e4284f512130f277371347b94d9e81 Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Thu, 26 Jan 2023 19:14:08 +0100
Subject: [PATCH] Fix ACME DNS challenge for top-level domains in a zone

e.g. "*.emersion.fr" when the zone is "emersion.fr".

Fixes: 662136ea745b ("Add support for ACME DNS hooks")
---
 dns.go | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/dns.go b/dns.go
index 077f7c7..b1156e8 100644
--- a/dns.go
+++ b/dns.go
@@ -62,10 +62,20 @@ func (provider *commandDNSProvider) DeleteRecords(ctx context.Context, zone stri
 }
 
 func domainFromACMEChallengeRecord(zone string, rec *libdns.Record) (string, error) {
-	if rec.Type != "TXT" || !strings.HasPrefix(rec.Name, "_acme-challenge.") {
+	relZone := strings.TrimSuffix(zone, ".")
+
+	var domain string
+	if rec.Name == "_acme-challenge" {
+		// Root domain
+		domain = relZone
+	} else if strings.HasPrefix(rec.Name, "_acme-challenge.") {
+		// Subdomain
+		relName := strings.TrimPrefix(rec.Name, "_acme-challenge.")
+		domain = relName + "." + relZone
+	}
+	if rec.Type != "TXT" || domain == "" {
 		return "", fmt.Errorf("DNS record doesn't look like an ACME challenge: %v %v", rec.Type, rec.Name)
 	}
-	relName := strings.TrimPrefix(rec.Name, "_acme-challenge.")
-	relZone := strings.TrimSuffix(zone, ".")
-	return relName + "." + relZone, nil
+
+	return domain, nil
 }