fix: detect and warn on inconsistent SSL host/certificate configuration

internal/adc/translator/apisixtls.go

@@ -50,6 +50,14 @@ func (t *Translator) TranslateApisixTls(tctx *provider.TranslateContext, tls *ap
 		return nil, err
 	}
 
+	// APISIX serves the cert regardless of SAN, so this is advisory: warn when a
+	// declared host isn't covered by the cert SANs (clients may reject it).
+	if uncovered, sans := uncoveredSNIHosts(cert, tls.Spec.Hosts); len(uncovered) > 0 {
+		t.Log.Info("ApisixTls certificate does not cover all declared SNI hosts",
+			"namespace", tls.Namespace, "name", tls.Name,
+			"uncoveredHosts", uncovered, "certificateSANs", sans)
+	}
+
 	// Convert hosts to strings
 	snis := make([]string, len(tls.Spec.Hosts))
 	for i, host := range tls.Spec.Hosts {
@@ -97,3 +105,28 @@ func (t *Translator) TranslateApisixTls(tctx *provider.TranslateContext, tls *ap
 	result.SSL = append(result.SSL, ssl)
 	return result, nil
 }
+
+// uncoveredSNIHosts returns the declared hosts not covered by any DNS SAN in the
+// certificate (wildcard-aware), plus the cert SANs for logging. Returns nothing
+// when the cert declares no DNS SANs or can't be parsed, since coverage can't be
+// judged there.
+func uncoveredSNIHosts(cert []byte, hosts []apiv2.HostType) (uncovered []string, sans []string) {
+	sans, err := sslutils.ExtractHostsFromCertificate(cert)
+	if err != nil || len(sans) == 0 {
+		return nil, nil
+	}
+	for _, h := range hosts {
+		host := string(h)
+		covered := false
+		for _, san := range sans {
+			if sslutils.HostCoveredBy(host, san) {
+				covered = true
+				break
+			}
+		}
+		if !covered {
+			uncovered = append(uncovered, host)
+		}
+	}
+	return uncovered, sans
+}

internal/adc/translator/apisixtls_test.go

@@ -0,0 +1,94 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package translator
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"math/big"
+	"slices"
+	"testing"
+	"time"
+
+	apiv2 "github.com/apache/apisix-ingress-controller/api/v2"
+)
+
+func genCertWithSANs(t *testing.T, sans []string) []byte {
+	t.Helper()
+	priv, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		t.Fatalf("failed to generate key: %v", err)
+	}
+	serial, err := rand.Int(rand.Reader, big.NewInt(1<<62))
+	if err != nil {
+		t.Fatalf("failed to generate serial: %v", err)
+	}
+	cn := "test"
+	if len(sans) > 0 {
+		cn = sans[0]
+	}
+	template := &x509.Certificate{
+		SerialNumber:          serial,
+		Subject:               pkix.Name{CommonName: cn},
+		DNSNames:              sans,
+		NotBefore:             time.Now().Add(-time.Hour),
+		NotAfter:              time.Now().Add(24 * time.Hour),
+		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		BasicConstraintsValid: true,
+	}
+	der, err := x509.CreateCertificate(rand.Reader, template, template, &priv.PublicKey, priv)
+	if err != nil {
+		t.Fatalf("failed to create cert: %v", err)
+	}
+	return pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: der})
+}
+
+func hostTypes(hosts ...string) []apiv2.HostType {
+	out := make([]apiv2.HostType, 0, len(hosts))
+	for _, h := range hosts {
+		out = append(out, apiv2.HostType(h))
+	}
+	return out
+}
+
+func TestUncoveredSNIHosts(t *testing.T) {
+	cases := []struct {
+		name          string
+		sans          []string
+		hosts         []string
+		wantUncovered []string
+	}{
+		{"exact match", []string{"shop.example.com"}, []string{"shop.example.com"}, nil},
+		{"wildcard covers subdomain", []string{"*.example.com"}, []string{"shop.example.com"}, nil},
+		{"declared host not in SANs", []string{"internal.corp.local"}, []string{"shop.example.com"}, []string{"shop.example.com"}},
+		{"one of many uncovered", []string{"a.example.com"}, []string{"a.example.com", "b.example.com"}, []string{"b.example.com"}},
+		{"no DNS SANs is lenient", nil, []string{"shop.example.com"}, nil},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			uncovered, _ := uncoveredSNIHosts(genCertWithSANs(t, c.sans), hostTypes(c.hosts...))
+			if !slices.Equal(uncovered, c.wantUncovered) {
+				t.Fatalf("uncoveredSNIHosts() = %v, want %v", uncovered, c.wantUncovered)
+			}
+		})
+	}
+}

internal/ssl/util.go

@@ -180,6 +180,77 @@ func NormalizeHosts(hosts []string) []string {
 	return normalized
 }
 
+// HostsOverlap reports whether two SNI host patterns can both match a common
+// concrete hostname. It understands single-label wildcards ("*.example.com"
+// matches "app.example.com" but not "a.b.example.com"). Two distinct wildcards
+// never share a concrete host.
+func HostsOverlap(a, b string) bool {
+	a = strings.ToLower(strings.TrimSpace(a))
+	b = strings.ToLower(strings.TrimSpace(b))
+	if a == "" || b == "" {
+		return false
+	}
+	if a == b {
+		return true
+	}
+	aWild := strings.HasPrefix(a, "*.")
+	bWild := strings.HasPrefix(b, "*.")
+	switch {
+	case aWild && bWild:
+		return false
+	case aWild:
+		return wildcardCovers(a, b)
+	case bWild:
+		return wildcardCovers(b, a)
+	default:
+		return false
+	}
+}
+
+// wildcardCovers reports whether wildcard "*.suffix" matches the exact host,
+// i.e. host is exactly "<single-label>.suffix".
+func wildcardCovers(wildcard, host string) bool {
+	suffix := wildcard[1:] // ".example.com"
+	if !strings.HasSuffix(host, suffix) {
+		return false
+	}
+	label := host[:len(host)-len(suffix)]
+	return label != "" && !strings.Contains(label, ".")
+}
+
+// HostCoveredBy reports whether a certificate SAN covers an SNI host. Coverage
+// is directional: an exact SAN covers only the identical host; a wildcard SAN
+// "*.suffix" covers single-label subdomains "<label>.suffix". A wildcard host is
+// covered only by an identical wildcard SAN (an exact SAN can't serve it).
+func HostCoveredBy(host, san string) bool {
+	host = strings.ToLower(strings.TrimSpace(host))
+	san = strings.ToLower(strings.TrimSpace(san))
+	if host == "" || san == "" {
+		return false
+	}
+	if host == san {
+		return true
+	}
+	if strings.HasPrefix(san, "*.") {
+		return wildcardCovers(san, host)
+	}
+	return false
+}
+
+// ParentWildcard returns the single-label covering wildcard for an exact host,
+// e.g. "app.example.com" -> "*.example.com". Returns "" if host is empty, is
+// itself a wildcard, or has no parent label.
+func ParentWildcard(host string) string {
+	if host == "" || strings.HasPrefix(host, "*.") {
+		return ""
+	}
+	i := strings.IndexByte(host, '.')
+	if i < 0 || i == len(host)-1 {
+		return ""
+	}
+	return "*." + host[i+1:]
+}
+
 // CertificateHash returns the SHA-256 hash of the leaf certificate contained in the PEM data.
 // The hash is calculated from the DER-encoded bytes so that formatting differences (whitespace,
 // line endings, certificate ordering) do not affect the result.

internal/ssl/util_test.go

@@ -0,0 +1,81 @@
+// Licensed to the Apache Software Foundation (ASF) under one or more
+// contributor license agreements.  See the NOTICE file distributed with
+// this work for additional information regarding copyright ownership.
+// The ASF licenses this file to You under the Apache License, Version 2.0
+// (the "License"); you may not use this file except in compliance with
+// the License.  You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ssl
+
+import "testing"
+
+func TestHostsOverlap(t *testing.T) {
+	cases := []struct {
+		a, b string
+		want bool
+	}{
+		{"example.com", "example.com", true},        // identical exact
+		{"*.example.com", "*.example.com", true},    // identical wildcard
+		{"app.example.com", "*.example.com", true},  // exact covered by wildcard
+		{"*.example.com", "app.example.com", true},  // wildcard covers exact (inverse)
+		{"App.Example.com", "*.EXAMPLE.com", true},  // case-insensitive
+		{"a.b.example.com", "*.example.com", false}, // multi-label not covered
+		{"example.com", "*.example.com", false},     // apex not covered by its wildcard
+		{"app.example.com", "app.other.com", false}, // different exacts
+		{"*.example.com", "*.other.com", false},     // distinct wildcards never overlap
+		{"*.a.example.com", "*.example.com", false}, // wildcards at different depths
+		{"", "example.com", false},                  // empty
+	}
+	for _, c := range cases {
+		if got := HostsOverlap(c.a, c.b); got != c.want {
+			t.Errorf("HostsOverlap(%q, %q) = %v, want %v", c.a, c.b, got, c.want)
+		}
+	}
+}
+
+func TestHostCoveredBy(t *testing.T) {
+	cases := []struct {
+		host, san string
+		want      bool
+	}{
+		{"app.example.com", "app.example.com", true},       // exact SAN covers exact host
+		{"app.example.com", "*.example.com", true},         // wildcard SAN covers subdomain
+		{"App.Example.com", "*.EXAMPLE.com", true},         // case-insensitive
+		{"*.example.com", "*.example.com", true},           // wildcard host needs identical wildcard SAN
+		{"*.example.com", "app.example.com", false},        // exact SAN can't cover a wildcard host
+		{"a.b.example.com", "*.example.com", false},        // wildcard SAN is single-label only
+		{"shop.example.com", "internal.corp.local", false}, // unrelated SAN
+		{"example.com", "*.example.com", false},            // apex not covered by its wildcard
+		{"app.example.com", "", false},                     // empty SAN
+	}
+	for _, c := range cases {
+		if got := HostCoveredBy(c.host, c.san); got != c.want {
+			t.Errorf("HostCoveredBy(%q, %q) = %v, want %v", c.host, c.san, got, c.want)
+		}
+	}
+}
+
+func TestParentWildcard(t *testing.T) {
+	cases := []struct {
+		host, want string
+	}{
+		{"app.example.com", "*.example.com"},
+		{"example.com", "*.com"},
+		{"*.example.com", ""}, // already a wildcard
+		{"localhost", ""},     // no parent label
+		{"", ""},
+	}
+	for _, c := range cases {
+		if got := ParentWildcard(c.host); got != c.want {
+			t.Errorf("ParentWildcard(%q) = %q, want %q", c.host, got, c.want)
+		}
+	}
+}

internal/webhook/v1/apisixtls_webhook.go

@@ -74,16 +74,17 @@ func (v *ApisixTlsCustomValidator) ValidateCreate(ctx context.Context, obj runti
 	}
 
 	detector := sslvalidator.NewConflictDetector(v.Client)
-	conflicts := detector.DetectConflicts(ctx, tls)
-	if len(conflicts) > 0 {
-		return nil, fmt.Errorf("%s", sslvalidator.FormatConflicts(conflicts))
-	}
-
 	warnings := v.collectWarnings(ctx, tls)
+	// Overlapping SSL config is advisory: APISIX serves overlapping objects and
+	// resolves by SNI, so warn instead of denying.
+	skipADCValidation := v.initErr != nil || len(warnings) > 0
+	if conflicts := detector.DetectConflicts(ctx, tls); len(conflicts) > 0 {
+		warnings = append(warnings, sslvalidator.FormatConflicts(conflicts))
+	}
 	// Skip ADC validation when secrets are missing: the translator cannot
 	// load cert/key material, so validation would always fail. The missing-
 	// secret warnings are sufficient to inform the user.
-	if v.initErr != nil || len(warnings) > 0 {
+	if skipADCValidation {
 		return warnings, nil
 	}
 

internal/webhook/v1/gateway_webhook.go

@@ -88,14 +88,15 @@ func (v *GatewayCustomValidator) ValidateCreate(ctx context.Context, obj runtime
 	}
 
 	detector := sslvalidator.NewConflictDetector(v.Client)
-	conflicts := detector.DetectConflicts(ctx, gateway)
-	if len(conflicts) > 0 {
-		return nil, fmt.Errorf("%s", sslvalidator.FormatConflicts(conflicts))
-	}
-
 	warnings := v.warnIfMissingGatewayProxyForGateway(ctx, gateway)
 	warnings = append(warnings, v.collectReferenceWarnings(ctx, gateway)...)
 
+	// Overlapping SSL config is advisory: APISIX serves overlapping objects and
+	// resolves by SNI, so warn instead of denying.
+	if conflicts := detector.DetectConflicts(ctx, gateway); len(conflicts) > 0 {
+		warnings = append(warnings, sslvalidator.FormatConflicts(conflicts))
+	}
+
 	return warnings, nil
 }
 
@@ -117,14 +118,15 @@ func (v *GatewayCustomValidator) ValidateUpdate(ctx context.Context, oldObj, new
 	}
 
 	detector := sslvalidator.NewConflictDetector(v.Client)
-	conflicts := detector.DetectConflicts(ctx, gateway)
-	if len(conflicts) > 0 {
-		return nil, fmt.Errorf("%s", sslvalidator.FormatConflicts(conflicts))
-	}
-
 	warnings := v.warnIfMissingGatewayProxyForGateway(ctx, gateway)
 	warnings = append(warnings, v.collectReferenceWarnings(ctx, gateway)...)
 
+	// Overlapping SSL config is advisory: APISIX serves overlapping objects and
+	// resolves by SNI, so warn instead of denying.
+	if conflicts := detector.DetectConflicts(ctx, gateway); len(conflicts) > 0 {
+		warnings = append(warnings, sslvalidator.FormatConflicts(conflicts))
+	}
+
 	return warnings, nil
 }