Pull request 2459: AG-45496-fix-tls-warning

Squashed commit of the following:

commit 9b634e388c
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Wed Aug 27 20:20:43 2025 +0300

    home: add tests

commit ab84e3be17
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Wed Aug 27 13:42:25 2025 +0300

    all: fix tls warning

CHANGELOG.md

@@ -17,6 +17,11 @@ See also the [v0.107.66 GitHub milestone][ms-v0.107.66].
 
 NOTE: Add new changes BELOW THIS COMMENT.
 -->
+
+### Fixed
+
+- Missing warning on the *Encryption Settings* page when using a certificate without an IP address.
+
 <!--
 NOTE: Add new changes ABOVE THIS COMMENT.
 -->

internal/home/tls.go

@@ -907,11 +907,13 @@ func (m *tlsManager) validateCertificate(
 	certChain []byte,
 	serverName string,
 ) (ok bool, err error) {
+	// parseErr is a non-critical parse warning.
+	var parseErr error
 	var certs []*x509.Certificate
-	certs, status.ValidCert, err = m.parseCertChain(ctx, certChain)
+	certs, status.ValidCert, parseErr = m.parseCertChain(ctx, certChain)
 	if !status.ValidCert {
 		// Don't wrap the error, since it's informative enough as is.
-		return false, err
+		return false, parseErr
 	}
 
 	mainCert := certs[0]
@@ -930,7 +932,8 @@ func (m *tlsManager) validateCertificate(
 
 	status.ValidChain = true
 
-	return true, nil
+	// Propagate the non-critical parse warning.
+	return true, parseErr
 }
 
 // Key types.

internal/home/tls_internal_test.go

@@ -106,6 +106,29 @@ func TestValidateCertificates(t *testing.T) {
 		assert.Equal(t, notAfter, status.NotAfter)
 		assert.True(t, status.ValidPair)
 	})
+
+	t.Run("no_ip_in_cert", func(t *testing.T) {
+		caCert, chainPEM, leafKeyPEM := newCertWithoutIP(t)
+
+		m.rootCerts = x509.NewCertPool()
+		m.rootCerts.AddCert(caCert)
+
+		status := &tlsConfigStatus{}
+		var ok bool
+		ok, err = m.validateCertificate(ctx, status, chainPEM, "")
+		assert.True(t, ok)
+		assert.ErrorIs(t, err, errNoIPInCert)
+		assert.True(t, status.ValidCert)
+		assert.True(t, status.ValidChain)
+
+		status = &tlsConfigStatus{}
+		err = m.validateCertificates(ctx, status, chainPEM, leafKeyPEM, "")
+		assert.ErrorIs(t, err, errNoIPInCert)
+		assert.True(t, status.ValidCert)
+		assert.True(t, status.ValidChain)
+		assert.True(t, status.ValidKey)
+		assert.True(t, status.ValidPair)
+	})
 }
 
 // storeGlobals is a test helper function that saves global variables and
@@ -145,6 +168,68 @@ func storeGlobals(tb testing.TB) {
 	})
 }
 
+// newCertWithoutIP generates a CA certificate, a leaf certificate without an IP
+// address, and the PEM-encoded leaf private key.
+func newCertWithoutIP(tb testing.TB) (
+	caCert *x509.Certificate,
+	chainPEM []byte,
+	leafKeyPEM []byte,
+) {
+	tb.Helper()
+
+	caKey, err := rsa.GenerateKey(rand.Reader, 2048)
+	require.NoError(tb, err)
+
+	now := time.Now()
+	caTmpl := &x509.Certificate{
+		SerialNumber:          big.NewInt(1),
+		NotBefore:             now.Add(-time.Hour),
+		NotAfter:              now.Add(time.Hour),
+		IsCA:                  true,
+		BasicConstraintsValid: true,
+		KeyUsage:              x509.KeyUsageCertSign | x509.KeyUsageCRLSign,
+	}
+
+	caDER, err := x509.CreateCertificate(rand.Reader, caTmpl, caTmpl, &caKey.PublicKey, caKey)
+	require.NoError(tb, err)
+
+	caCert, err = x509.ParseCertificate(caDER)
+	require.NoError(tb, err)
+
+	leafKey, err := rsa.GenerateKey(rand.Reader, 2048)
+	require.NoError(tb, err)
+
+	leafTmpl := &x509.Certificate{
+		SerialNumber: big.NewInt(2),
+		NotBefore:    now.Add(-time.Hour),
+		NotAfter:     now.Add(time.Hour),
+		KeyUsage:     x509.KeyUsageDigitalSignature,
+	}
+
+	leafDER, err := x509.CreateCertificate(
+		rand.Reader,
+		leafTmpl,
+		caTmpl,
+		&leafKey.PublicKey,
+		caKey,
+	)
+	require.NoError(tb, err)
+
+	buf := bytes.Buffer{}
+	err = pem.Encode(&buf, &pem.Block{Type: "CERTIFICATE", Bytes: leafDER})
+	require.NoError(tb, err)
+
+	err = pem.Encode(&buf, &pem.Block{Type: "CERTIFICATE", Bytes: caDER})
+	require.NoError(tb, err)
+
+	leafKeyPEM = pem.EncodeToMemory(&pem.Block{
+		Type:  "RSA PRIVATE KEY",
+		Bytes: x509.MarshalPKCS1PrivateKey(leafKey),
+	})
+
+	return caCert, buf.Bytes(), leafKeyPEM
+}
+
 // newCertAndKey is a helper function that generates certificate and key.
 func newCertAndKey(tb testing.TB, n int64) (certDER []byte, key *rsa.PrivateKey) {
 	tb.Helper()