bunny: fix zone detection (go-acme#2012)

Author: ldez

providers/dns/bunny/bunny.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/go-acme/lego/v4/challenge/dns01"
 	"github.com/go-acme/lego/v4/platform/config/env"
+	"github.com/miekg/dns"
 	"github.com/nrdcg/bunny-go"
 )
 
@@ -190,7 +191,28 @@ func getZone(fqdn string) (string, error) {
 		return "", err
 	}
 
-	return dns01.UnFqdn(authZone), nil
+	zone, _, err := splitDomain(dns01.UnFqdn(authZone))
+	if err != nil {
+		return "", err
+	}
+
+	return zone, nil
+}
+
+func splitDomain(full string) (string, string, error) {
+	split := dns.Split(full)
+	if len(split) < 2 {
+		return "", "", fmt.Errorf("unsupported domain: %s", full)
+	}
+
+	if len(split) == 2 {
+		return full, "", nil
+	}
+
+	domain := full[split[len(split)-2]:]
+	subDomain := full[:split[len(split)-2]-1]
+
+	return domain, subDomain, nil
 }
 
 func pointer[T string | int | int32 | int64](v T) *T { return &v }

providers/dns/bunny/bunny_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/go-acme/lego/v4/platform/tester"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -123,3 +124,83 @@ func TestLiveCleanUp(t *testing.T) {
 	err = provider.CleanUp(envTest.GetDomain(), "", "123d==")
 	require.NoError(t, err)
 }
+
+func Test_splitDomain(t *testing.T) {
+	type expected struct {
+		root       string
+		sub        string
+		requireErr require.ErrorAssertionFunc
+	}
+
+	testCases := []struct {
+		desc     string
+		domain   string
+		expected expected
+	}{
+		{
+			desc:   "empty",
+			domain: "",
+			expected: expected{
+				requireErr: require.Error,
+			},
+		},
+		{
+			desc:   "2 levels",
+			domain: "example.com",
+			expected: expected{
+				root:       "example.com",
+				sub:        "",
+				requireErr: require.NoError,
+			},
+		},
+		{
+			desc:   "3 levels",
+			domain: "_acme-challenge.example.com",
+			expected: expected{
+				root:       "example.com",
+				sub:        "_acme-challenge",
+				requireErr: require.NoError,
+			},
+		},
+		{
+			desc:   "4 levels",
+			domain: "_acme-challenge.sub.example.com",
+			expected: expected{
+				root:       "example.com",
+				sub:        "_acme-challenge.sub",
+				requireErr: require.NoError,
+			},
+		},
+		{
+			desc:   "5 levels",
+			domain: "_acme-challenge.my.sub.example.com",
+			expected: expected{
+				root:       "example.com",
+				sub:        "_acme-challenge.my.sub",
+				requireErr: require.NoError,
+			},
+		},
+		{
+			desc:   "6 levels",
+			domain: "_acme-challenge.my.sub.sub.example.com",
+			expected: expected{
+				root:       "example.com",
+				sub:        "_acme-challenge.my.sub.sub",
+				requireErr: require.NoError,
+			},
+		},
+	}
+
+	for _, test := range testCases {
+		test := test
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			root, sub, err := splitDomain(test.domain)
+			test.expected.requireErr(t, err)
+
+			assert.Equal(t, test.expected.root, root)
+			assert.Equal(t, test.expected.sub, sub)
+		})
+	}
+}