gcloud: support GCE_ZONE_ID to bypass zone list (#2081)

Co-authored-by: Fernandez Ludovic <ldez@users.noreply.github.com>

cmd/zz_gen_cmd_dnshelp.go

@@ -1108,6 +1108,7 @@ func displayDNSHelp(w io.Writer, name string) error {
 		ew.writeln(`	- "GCE_POLLING_INTERVAL":	Time between DNS propagation check`)
 		ew.writeln(`	- "GCE_PROPAGATION_TIMEOUT":	Maximum waiting time for DNS propagation`)
 		ew.writeln(`	- "GCE_TTL":	The TTL of the TXT record used for the DNS challenge`)
+		ew.writeln(`	- "GCE_ZONE_ID":	Allows to skip the automatic detection of the zone`)
 
 		ew.writeln()
 		ew.writeln(`More information: https://go-acme.github.io/lego/dns/gcloud`)

docs/content/dns/zz_gen_gcloud.md

@@ -58,6 +58,7 @@ More information [here]({{< ref "dns#configuration-and-credentials" >}}).
 | `GCE_POLLING_INTERVAL` | Time between DNS propagation check |
 | `GCE_PROPAGATION_TIMEOUT` | Maximum waiting time for DNS propagation |
 | `GCE_TTL` | The TTL of the TXT record used for the DNS challenge |
+| `GCE_ZONE_ID` | Allows to skip the automatic detection of the zone |
 
 The environment variable names can be suffixed by `_FILE` to reference a file instead of a value.
 More information [here]({{< ref "dns#configuration-and-credentials" >}}).

providers/dns/gcloud/gcloud.toml

@@ -21,6 +21,7 @@ GCE_PROJECT="gc-project-id" GCE_SERVICE_ACCOUNT_FILE="/path/to/svc/account/file.
     GCE_SERVICE_ACCOUNT = "Account"
   [Configuration.Additional]
     GCE_ALLOW_PRIVATE_ZONE = "Allows requested domain to be in private DNS zone, works only with a private ACME server (by default: false)"
+    GCE_ZONE_ID = "Allows to skip the automatic detection of the zone"
     GCE_POLLING_INTERVAL = "Time between DNS propagation check"
     GCE_PROPAGATION_TIMEOUT = "Maximum waiting time for DNS propagation"
     GCE_TTL = "The TTL of the TXT record used for the DNS challenge"

providers/dns/gcloud/googlecloud.go

@@ -32,6 +32,7 @@ const (
 
 	EnvServiceAccount   = envNamespace + "SERVICE_ACCOUNT"
 	EnvProject          = envNamespace + "PROJECT"
+	EnvZoneID           = envNamespace + "ZONE_ID"
 	EnvAllowPrivateZone = envNamespace + "ALLOW_PRIVATE_ZONE"
 	EnvDebug            = envNamespace + "DEBUG"
 
@@ -44,6 +45,7 @@ const (
 type Config struct {
 	Debug              bool
 	Project            string
+	ZoneID             string
 	AllowPrivateZone   bool
 	PropagationTimeout time.Duration
 	PollingInterval    time.Duration
@@ -55,6 +57,7 @@ type Config struct {
 func NewDefaultConfig() *Config {
 	return &Config{
 		Debug:              env.GetOrDefaultBool(EnvDebug, false),
+		ZoneID:             env.GetOrDefaultString(EnvZoneID, ""),
 		AllowPrivateZone:   env.GetOrDefaultBool(EnvAllowPrivateZone, false),
 		TTL:                env.GetOrDefaultInt(EnvTTL, dns01.DefaultTTL),
 		PropagationTimeout: env.GetOrDefaultSecond(EnvPropagationTimeout, 180*time.Second),
@@ -310,24 +313,16 @@ func (d *DNSProvider) Timeout() (timeout, interval time.Duration) {
 
 // getHostedZone returns the managed-zone.
 func (d *DNSProvider) getHostedZone(domain string) (string, error) {
-	authZone, err := dns01.FindZoneByFqdn(dns01.ToFqdn(domain))
+	authZone, zones, err := d.lookupHostedZoneID(domain)
 	if err != nil {
-		return "", fmt.Errorf("designate: could not find zone for FQDN %q: %w", domain, err)
+		return "", err
 	}
 
-	zones, err := d.client.ManagedZones.
-		List(d.config.Project).
-		DnsName(authZone).
-		Do()
-	if err != nil {
-		return "", fmt.Errorf("API call failed: %w", err)
-	}
-
-	if len(zones.ManagedZones) == 0 {
+	if len(zones) == 0 {
 		return "", fmt.Errorf("no matching domain found for domain %s", authZone)
 	}
 
-	for _, z := range zones.ManagedZones {
+	for _, z := range zones {
 		if z.Visibility == "public" || z.Visibility == "" || (z.Visibility == "private" && d.config.AllowPrivateZone) {
 			return z.Name, nil
 		}
@@ -340,6 +335,45 @@ func (d *DNSProvider) getHostedZone(domain string) (string, error) {
 	return "", fmt.Errorf("no public zone found for domain %s", authZone)
 }
 
+// lookupHostedZoneID finds the managed zone ID in Google.
+//
+// Be careful here.
+// An automated system might run in a GCloud Service Account, with access to edit the zone
+//
+//	(gcloud dns managed-zones get-iam-policy $zone_id) (role roles/dns.admin)
+//
+// but not with project-wide access to list all zones
+//
+//	(gcloud projects get-iam-policy $project_id) (a role with permission dns.managedZones.list)
+//
+// If we force a zone list to succeed, we demand more permissions than needed.
+func (d *DNSProvider) lookupHostedZoneID(domain string) (string, []*dns.ManagedZone, error) {
+	// GCE_ZONE_ID override for service accounts to avoid needing zones-list permission
+	if d.config.ZoneID != "" {
+		zone, err := d.client.ManagedZones.Get(d.config.Project, d.config.ZoneID).Do()
+		if err != nil {
+			return "", nil, fmt.Errorf("API call ManagedZones.Get for explicit zone ID %q in project %q failed: %w", d.config.ZoneID, d.config.Project, err)
+		}
+
+		return zone.DnsName, []*dns.ManagedZone{zone}, nil
+	}
+
+	authZone, err := dns01.FindZoneByFqdn(dns01.ToFqdn(domain))
+	if err != nil {
+		return "", nil, fmt.Errorf("could not find zone for FQDN %q: %w", domain, err)
+	}
+
+	zones, err := d.client.ManagedZones.
+		List(d.config.Project).
+		DnsName(authZone).
+		Do()
+	if err != nil {
+		return "", nil, fmt.Errorf("API call ManagedZones.List failed: %w", err)
+	}
+
+	return authZone, zones.ManagedZones, nil
+}
+
 func (d *DNSProvider) findTxtRecords(zone, fqdn string) ([]*dns.ResourceRecordSet, error) {
 	recs, err := d.client.ResourceRecordSets.List(d.config.Project, zone).Name(fqdn).Type("TXT").Do()
 	if err != nil {