crypto/tls: use correct alerts

BoGo: Resume-Server-PSKBinderFirstExtension
BoGo: Resume-Server-ExtraPSKBinder
BoGo: Resume-Server-ExtraIdentityNoBinder
BoGo: Renegotiate-Server-Forbidden
BoGo: NoNullCompression
BoGo: TrailingMessageData-*

13.go

@@ -56,11 +56,16 @@ CurvePreferenceLoop:
 	hash := hashForSuite(hs.suite)
 	hashSize := hash.Size()
 
-	earlySecret, isPSK := hs.checkPSK()
+	earlySecret, pskAlert := hs.checkPSK()
-	if !isPSK {
+	switch {
+	case pskAlert != alertSuccess:
+		c.sendAlert(pskAlert)
+		return errors.New("tls: invalid client PSK")
+	case earlySecret == nil:
 		earlySecret = hkdfExtract(hash, nil, nil)
+	case earlySecret != nil:
+		c.didResume = true
 	}
-	c.didResume = isPSK
 
 	hs.finishedHash13 = hash.New()
 	hs.finishedHash13.Write(hs.clientHello.marshal())
@@ -94,7 +99,7 @@ CurvePreferenceLoop:
 		return err
 	}
 
-	if !isPSK {
+	if !c.didResume {
 		if err := hs.sendCertificate13(); err != nil {
 			return err
 		}
@@ -151,7 +156,7 @@ func (hs *serverHandshakeState) readClientFinished13() error {
 	expectedVerifyData := hmacOfSum(hash, hs.finishedHash13, hs.clientFinishedKey)
 	if len(expectedVerifyData) != len(clientFinished.verifyData) ||
 		subtle.ConstantTimeCompare(expectedVerifyData, clientFinished.verifyData) != 1 {
-		c.sendAlert(alertHandshakeFailure)
+		c.sendAlert(alertDecryptError)
 		return errors.New("tls: client's Finished message is incorrect")
 	}
 	hs.finishedHash13.Write(clientFinished.marshal())
@@ -403,9 +408,9 @@ func (hs *serverHandshakeState) prepareCipher(handshakeCtx, secret []byte, label
 // https://tools.ietf.org/html/draft-ietf-tls-tls13-18#section-4.2.8.2.
 const ticketAgeSkewAllowance = 10 * time.Second
 
-func (hs *serverHandshakeState) checkPSK() (earlySecret []byte, ok bool) {
+func (hs *serverHandshakeState) checkPSK() (earlySecret []byte, alert alert) {
 	if hs.c.config.SessionTicketsDisabled {
-		return nil, false
+		return nil, alertSuccess
 	}
 
 	foundDHE := false
@@ -416,7 +421,7 @@ func (hs *serverHandshakeState) checkPSK() (earlySecret []byte, ok bool) {
 		}
 	}
 	if !foundDHE {
-		return nil, false
+		return nil, alertSuccess
 	}
 
 	hash := hashForSuite(hs.suite)
@@ -428,7 +433,7 @@ func (hs *serverHandshakeState) checkPSK() (earlySecret []byte, ok bool) {
 			continue
 		}
 		s := &sessionState13{}
-		if ok := s.unmarshal(serializedTicket); !ok {
+		if s.unmarshal(serializedTicket) != alertSuccess {
 			continue
 		}
 		if s.vers != hs.c.vers {
@@ -465,13 +470,15 @@ func (hs *serverHandshakeState) checkPSK() (earlySecret []byte, ok bool) {
 		chHash.Write(hs.clientHello.rawTruncated)
 		expectedBinder := hmacOfSum(hash, chHash, binderFinishedKey)
 
-		if subtle.ConstantTimeCompare(expectedBinder, hs.clientHello.psks[i].binder) == 1 {
+		if subtle.ConstantTimeCompare(expectedBinder, hs.clientHello.psks[i].binder) != 1 {
+			return nil, alertDecryptError
+		}
+
 		if i == 0 && hs.clientHello.earlyData {
 			// This is a ticket intended to be used for 0-RTT
 			if s.maxEarlyDataLen == 0 {
-					// But we had not tagged it as such. We could close the connection
+				// But we had not tagged it as such.
-					// here, but instead we just ignore the ticket and the 0-RTT data.
+				return nil, alertIllegalParameter
-					continue
 			}
 			if hs.c.config.Accept0RTTData {
 				hs.c.ticketMaxEarlyData = int64(s.maxEarlyDataLen)
@@ -480,11 +487,10 @@ func (hs *serverHandshakeState) checkPSK() (earlySecret []byte, ok bool) {
 		}
 		hs.hello13.psk = true
 		hs.hello13.pskIdentity = uint16(i)
-			return earlySecret, true
+		return earlySecret, alertSuccess
-		}
 	}
 
-	return nil, false
+	return nil, alertSuccess
 }
 
 func (hs *serverHandshakeState) sendSessionTicket13() error {

alert.go

@@ -40,6 +40,7 @@ const (
 	alertUserCanceled           alert = 90
 	alertNoRenegotiation        alert = 100
 	alertNoApplicationProtocol  alert = 120
+	alertSuccess                alert = 255 // dummy value returned by unmarshal functions
 )
 
 var alertText = map[alert]string{

common.go

@@ -939,7 +939,7 @@ type Certificate struct {
 
 type handshakeMessage interface {
 	marshal() []byte
-	unmarshal([]byte) bool
+	unmarshal([]byte) alert
 }
 
 // lruSessionCache is a ClientSessionCache implementation that uses an LRU

conn.go

@@ -1126,8 +1126,8 @@ func (c *Conn) readHandshake() (interface{}, error) {
 	// so pass in a fresh copy that won't be overwritten.
 	data = append([]byte(nil), data...)
 
-	if !m.unmarshal(data) {
+	if unmarshalAlert := m.unmarshal(data); unmarshalAlert != alertSuccess {
-		return nil, c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
+		return nil, c.in.setErrorLocked(c.sendAlert(unmarshalAlert))
 	}
 	return m, nil
 }

handshake_client.go

@@ -602,7 +602,7 @@ func (hs *clientHandshakeState) readFinished(out []byte) error {
 	verify := hs.finishedHash.serverSum(hs.masterSecret)
 	if len(verify) != len(serverFinished.verifyData) ||
 		subtle.ConstantTimeCompare(verify, serverFinished.verifyData) != 1 {
-		c.sendAlert(alertHandshakeFailure)
+		c.sendAlert(alertDecryptError)
 		return errors.New("tls: server's Finished message was incorrect")
 	}
 	hs.finishedHash.Write(serverFinished.marshal())

handshake_client_test.go

@@ -1024,7 +1024,7 @@ func TestHostnameInSNI(t *testing.T) {
 		s.Close()
 
 		var m clientHelloMsg
-		if !m.unmarshal(record) {
+		if m.unmarshal(record) != alertSuccess {
 			t.Errorf("unmarshaling ClientHello for %q failed", tt.in)
 			continue
 		}

handshake_messages_test.go

@@ -35,7 +35,7 @@ var tests = []interface{}{
 
 type testMessage interface {
 	marshal() []byte
-	unmarshal([]byte) bool
+	unmarshal([]byte) alert
 	equal(interface{}) bool
 }
 
@@ -59,7 +59,7 @@ func TestMarshalUnmarshal(t *testing.T) {
 			m1 := v.Interface().(testMessage)
 			marshaled := m1.marshal()
 			m2 := iface.(testMessage)
-			if !m2.unmarshal(marshaled) {
+			if m2.unmarshal(marshaled) != alertSuccess {
 				t.Errorf("#%d.%d failed to unmarshal %#v %x", i, j, m1, marshaled)
 				break
 			}
@@ -77,7 +77,7 @@ func TestMarshalUnmarshal(t *testing.T) {
 				// data is optional and the length of the
 				// Finished varies across versions.
 				for j := 0; j < len(marshaled); j++ {
-					if m2.unmarshal(marshaled[0:j]) {
+					if m2.unmarshal(marshaled[0:j]) == alertSuccess {
 						t.Errorf("#%d unmarshaled a prefix of length %d of %#v", i, j, m1)
 						break
 					}
@@ -364,7 +364,7 @@ func TestRejectEmptySCTList(t *testing.T) {
 	serverHelloBytes := serverHello.marshal()
 
 	var serverHelloCopy serverHelloMsg
-	if !serverHelloCopy.unmarshal(serverHelloBytes) {
+	if serverHelloCopy.unmarshal(serverHelloBytes) != alertSuccess {
 		t.Fatal("Failed to unmarshal initial message")
 	}
 
@@ -389,7 +389,7 @@ func TestRejectEmptySCTList(t *testing.T) {
 	serverHelloEmptySCT[42] = byte((len(serverHelloEmptySCT) - 44) >> 8)
 	serverHelloEmptySCT[43] = byte((len(serverHelloEmptySCT) - 44))
 
-	if serverHelloCopy.unmarshal(serverHelloEmptySCT) {
+	if serverHelloCopy.unmarshal(serverHelloEmptySCT) == alertSuccess {
 		t.Fatal("Unmarshaled ServerHello with empty SCT list")
 	}
 }
@@ -407,7 +407,7 @@ func TestRejectEmptySCT(t *testing.T) {
 	serverHelloBytes := serverHello.marshal()
 
 	var serverHelloCopy serverHelloMsg
-	if serverHelloCopy.unmarshal(serverHelloBytes) {
+	if serverHelloCopy.unmarshal(serverHelloBytes) == alertSuccess {
 		t.Fatal("Unmarshaled ServerHello with zero-length SCT")
 	}
 }

handshake_server.go

@@ -222,7 +222,7 @@ Curves:
 	}
 
 	if !foundCompression {
-		c.sendAlert(alertHandshakeFailure)
+		c.sendAlert(alertIllegalParameter)
 		return false, errors.New("tls: client does not support uncompressed connections")
 	}
 	if len(hs.clientHello.compressionMethods) != 1 && c.vers >= VersionTLS13 {
@@ -370,7 +370,7 @@ func (hs *serverHandshakeState) checkForResumption() bool {
 	sessionTicket := append([]uint8{}, hs.clientHello.sessionTicket...)
 	serializedState, usedOldKey := c.decryptTicket(sessionTicket)
 	hs.sessionState = &sessionState{usedOldKey: usedOldKey}
-	if ok := hs.sessionState.unmarshal(serializedState); !ok {
+	if hs.sessionState.unmarshal(serializedState) != alertSuccess {
 		return false
 	}
 
@@ -570,7 +570,11 @@ func (hs *serverHandshakeState) doFullHandshake() error {
 
 	preMasterSecret, err := keyAgreement.processClientKeyExchange(c.config, hs.cert, ckx, c.vers)
 	if err != nil {
-		c.sendAlert(alertHandshakeFailure)
+		if err == errClientKeyExchange {
+			c.sendAlert(alertDecodeError)
+		} else {
+			c.sendAlert(alertInternalError)
+		}
 		return err
 	}
 	hs.masterSecret = masterFromPreMasterSecret(c.vers, hs.suite, preMasterSecret, hs.clientHello.random, hs.hello.random)
@@ -721,7 +725,7 @@ func (hs *serverHandshakeState) readFinished(out []byte) error {
 	verify := hs.finishedHash.clientSum(hs.masterSecret)
 	if len(verify) != len(clientFinished.verifyData) ||
 		subtle.ConstantTimeCompare(verify, clientFinished.verifyData) != 1 {
-		c.sendAlert(alertHandshakeFailure)
+		c.sendAlert(alertDecryptError)
 		return errors.New("tls: client's Finished message is incorrect")
 	}
 

handshake_server_test.go

@@ -246,7 +246,7 @@ func TestRenegotiationExtension(t *testing.T) {
 	var serverHello serverHelloMsg
 	// unmarshal expects to be given the handshake header, but
 	// serverHelloLen doesn't include it.
-	if !serverHello.unmarshal(buf[5 : 9+serverHelloLen]) {
+	if serverHello.unmarshal(buf[5:9+serverHelloLen]) != alertSuccess {
 		t.Fatalf("Failed to parse ServerHello")
 	}
 

ticket.go

@@ -86,9 +86,9 @@ func (s *sessionState) marshal() []byte {
 	return ret
 }
 
-func (s *sessionState) unmarshal(data []byte) bool {
+func (s *sessionState) unmarshal(data []byte) alert {
 	if len(data) < 8 {
-		return false
+		return alertDecodeError
 	}
 
 	s.vers = uint16(data[0])<<8 | uint16(data[1])
@@ -96,14 +96,14 @@ func (s *sessionState) unmarshal(data []byte) bool {
 	masterSecretLen := int(data[4])<<8 | int(data[5])
 	data = data[6:]
 	if len(data) < masterSecretLen {
-		return false
+		return alertDecodeError
 	}
 
 	s.masterSecret = data[:masterSecretLen]
 	data = data[masterSecretLen:]
 
 	if len(data) < 2 {
-		return false
+		return alertDecodeError
 	}
 
 	numCerts := int(data[0])<<8 | int(data[1])
@@ -112,21 +112,24 @@ func (s *sessionState) unmarshal(data []byte) bool {
 	s.certificates = make([][]byte, numCerts)
 	for i := range s.certificates {
 		if len(data) < 4 {
-			return false
+			return alertDecodeError
 		}
 		certLen := int(data[0])<<24 | int(data[1])<<16 | int(data[2])<<8 | int(data[3])
 		data = data[4:]
 		if certLen < 0 {
-			return false
+			return alertDecodeError
 		}
 		if len(data) < certLen {
-			return false
+			return alertDecodeError
 		}
 		s.certificates[i] = data[:certLen]
 		data = data[certLen:]
 	}
 
-	return len(data) == 0
+	if len(data) != 0 {
+		return alertDecodeError
+	}
+	return alertSuccess
 }
 
 type sessionState13 struct {
@@ -195,9 +198,9 @@ func (s *sessionState13) marshal() []byte {
 	return x
 }
 
-func (s *sessionState13) unmarshal(data []byte) bool {
+func (s *sessionState13) unmarshal(data []byte) alert {
 	if len(data) < 24 {
-		return false
+		return alertDecodeError
 	}
 
 	s.vers = uint16(data[0])<<8 | uint16(data[1])
@@ -209,25 +212,25 @@ func (s *sessionState13) unmarshal(data []byte) bool {
 
 	l := int(data[20])<<8 | int(data[21])
 	if len(data) < 22+l+2 {
-		return false
+		return alertDecodeError
 	}
 	s.resumptionSecret = data[22 : 22+l]
 	z := data[22+l:]
 
 	l = int(z[0])<<8 | int(z[1])
 	if len(z) < 2+l+2 {
-		return false
+		return alertDecodeError
 	}
 	s.alpnProtocol = string(z[2 : 2+l])
 	z = z[2+l:]
 
 	l = int(z[0])<<8 | int(z[1])
 	if len(z) != 2+l {
-		return false
+		return alertDecodeError
 	}
 	s.SNI = string(z[2 : 2+l])
 
-	return true
+	return alertSuccess
 }
 
 func (c *Conn) encryptTicket(serialized []byte) ([]byte, error) {