crypto/tls: finish the session ticket state checks

13.go

@@ -434,11 +434,14 @@ func (hs *serverHandshakeState) checkPSK() (earlySecret []byte, ok bool) {
 
 		// This enforces the stricter 0-RTT requirements on all ticket uses.
 		// The benefit of using PSK+ECDHE without 0-RTT are small enough that
-		// we can give them up in the edge case of changed suite or ALPN.
+		// we can give them up in the edge case of changed suite or ALPN or SNI.
 		if s.suite != hs.suite.id {
 			continue
 		}
-		if s.alpnProtocol != hs.hello13Enc.alpnProtocol {
+		if s.alpnProtocol != hs.c.clientProtocol {
+			continue
+		}
+		if s.SNI != hs.c.serverName {
 			continue
 		}
 
@@ -451,11 +454,20 @@ func (hs *serverHandshakeState) checkPSK() (earlySecret []byte, ok bool) {
 		expectedBinder := hmacOfSum(hash, chHash, binderFinishedKey)
 
 		if subtle.ConstantTimeCompare(expectedBinder, hs.clientHello.psks[i].binder) == 1 {
+			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
+					// here, but instead we just ignore the ticket and the 0-RTT data.
+					continue
+				}
+				if hs.c.config.Accept0RTTData {
+					hs.c.ticketMaxEarlyData = int64(s.maxEarlyDataLen)
+					hs.hello13Enc.earlyData = true
+				}
+			}
 			hs.hello13.psk = true
 			hs.hello13.pskIdentity = uint16(i)
-			if i == 0 && hs.clientHello.earlyData && hs.c.config.Accept0RTTData {
-				hs.hello13Enc.earlyData = true
-			}
 			return earlySecret, true
 		}
 	}
@@ -496,6 +508,9 @@ func (hs *serverHandshakeState) sendSessionTicket13() error {
 			uint32(ageAddBuf[2])<<8 | uint32(ageAddBuf[3]),
 		createdAt:        uint64(time.Now().Unix()),
 		resumptionSecret: resumptionSecret,
+		alpnProtocol:     c.clientProtocol,
+		SNI:              c.serverName,
+		maxEarlyDataLen:  c.config.Max0RTTDataSize,
 	}
 
 	ticket, err := c.encryptTicket(sessionState.marshal())

conn.go

@@ -83,6 +83,10 @@ type Conn struct {
 	clientProtocol         string
 	clientProtocolFallback bool
 
+	// ticketMaxEarlyData is the maximum bytes of 0-RTT application data
+	// that the client is allowed to send on the ticket it used.
+	ticketMaxEarlyData int64
+
 	// input/output
 	in, out   halfConn     // in.Mutex < out.Mutex
 	rawInput  *block       // raw input, right off the wire
@@ -106,6 +110,8 @@ type Conn struct {
 
 	// earlyDataBytes is the number of bytes of early data received so
 	// far. Tracked to enforce max_early_data_size.
+	// We don't keep track of rejected 0-RTT data since there's no need
+	// to ever buffer it. in.Mutex.
 	earlyDataBytes int64
 
 	tmp [16]byte
@@ -778,6 +784,12 @@ func (c *Conn) readRecord(want recordType) error {
 			c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
 			break
 		}
+		if c.phase == readingEarlyData {
+			c.earlyDataBytes += int64(len(b.data) - b.off)
+			if c.earlyDataBytes > c.ticketMaxEarlyData {
+				return c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
+			}
+		}
 		c.input = b
 		b = nil
 

handshake_messages_test.go

@@ -338,9 +338,11 @@ func (*sessionState13) Generate(rand *rand.Rand, size int) reflect.Value {
 	s.vers = uint16(rand.Intn(10000))
 	s.suite = uint16(rand.Intn(10000))
 	s.ageAdd = uint32(rand.Intn(0xffffffff))
+	s.maxEarlyDataLen = uint32(rand.Intn(0xffffffff))
 	s.createdAt = uint64(rand.Int63n(0xfffffffffffffff))
 	s.resumptionSecret = randomBytes(rand.Intn(100), rand)
 	s.alpnProtocol = randomString(rand.Intn(100), rand)
+	s.SNI = randomString(rand.Intn(100), rand)
 	return reflect.ValueOf(s)
 }
 

ticket.go

@@ -134,10 +134,10 @@ type sessionState13 struct {
 	suite            uint16
 	ageAdd           uint32
 	createdAt        uint64
+	maxEarlyDataLen  uint32
 	resumptionSecret []byte
 	alpnProtocol     string
-	// TODO(filippo): add and check SNI
+	SNI              string
-	// TODO(filippo): add and check maxEarlyDataLength
 }
 
 func (s *sessionState13) equal(i interface{}) bool {
@@ -148,13 +148,16 @@ func (s *sessionState13) equal(i interface{}) bool {
 
 	return s.vers == s1.vers &&
 		s.suite == s1.suite &&
-		s.alpnProtocol == s1.alpnProtocol &&
 		s.ageAdd == s1.ageAdd &&
-		bytes.Equal(s.resumptionSecret, s1.resumptionSecret)
+		s.createdAt == s1.createdAt &&
+		s.maxEarlyDataLen == s1.maxEarlyDataLen &&
+		bytes.Equal(s.resumptionSecret, s1.resumptionSecret) &&
+		s.alpnProtocol == s1.alpnProtocol &&
+		s.SNI == s1.SNI
 }
 
 func (s *sessionState13) marshal() []byte {
-	length := 2 + 2 + 4 + 8 + 2 + len(s.resumptionSecret) + 2 + len(s.alpnProtocol)
+	length := 2 + 2 + 4 + 8 + 4 + 2 + len(s.resumptionSecret) + 2 + len(s.alpnProtocol) + 2 + len(s.SNI)
 
 	x := make([]byte, length)
 	x[0] = byte(s.vers >> 8)
@@ -173,19 +176,27 @@ func (s *sessionState13) marshal() []byte {
 	x[13] = byte(s.createdAt >> 16)
 	x[14] = byte(s.createdAt >> 8)
 	x[15] = byte(s.createdAt)
-	x[16] = byte(len(s.resumptionSecret) >> 8)
+	x[16] = byte(s.maxEarlyDataLen >> 24)
-	x[17] = byte(len(s.resumptionSecret))
+	x[17] = byte(s.maxEarlyDataLen >> 16)
-	copy(x[18:], s.resumptionSecret)
+	x[18] = byte(s.maxEarlyDataLen >> 8)
-	z := x[18+len(s.resumptionSecret):]
+	x[19] = byte(s.maxEarlyDataLen)
+	x[20] = byte(len(s.resumptionSecret) >> 8)
+	x[21] = byte(len(s.resumptionSecret))
+	copy(x[22:], s.resumptionSecret)
+	z := x[22+len(s.resumptionSecret):]
 	z[0] = byte(len(s.alpnProtocol) >> 8)
 	z[1] = byte(len(s.alpnProtocol))
 	copy(z[2:], s.alpnProtocol)
+	z = z[2+len(s.alpnProtocol):]
+	z[0] = byte(len(s.SNI) >> 8)
+	z[1] = byte(len(s.SNI))
+	copy(z[2:], s.SNI)
 
 	return x
 }
 
 func (s *sessionState13) unmarshal(data []byte) bool {
-	if len(data) < 18 {
+	if len(data) < 24 {
 		return false
 	}
 
@@ -194,15 +205,29 @@ func (s *sessionState13) unmarshal(data []byte) bool {
 	s.ageAdd = uint32(data[4])<<24 | uint32(data[5])<<16 | uint32(data[6])<<8 | uint32(data[7])
 	s.createdAt = uint64(data[8])<<56 | uint64(data[9])<<48 | uint64(data[10])<<40 | uint64(data[11])<<32 |
 		uint64(data[12])<<24 | uint64(data[13])<<16 | uint64(data[14])<<8 | uint64(data[15])
-	l := int(data[16])<<8 | int(data[17])
+	s.maxEarlyDataLen = uint32(data[16])<<24 | uint32(data[17])<<16 | uint32(data[18])<<8 | uint32(data[19])
-	if len(data) < 18+l+2 {
+
+	l := int(data[20])<<8 | int(data[21])
+	if len(data) < 22+l+2 {
 		return false
 	}
-	s.resumptionSecret = data[18 : 18+l]
+	s.resumptionSecret = data[22 : 22+l]
-	z := data[18+l:]
+	z := data[22+l:]
+
 	l = int(z[0])<<8 | int(z[1])
-	s.alpnProtocol = string(z[2:])
+	if len(z) < 2+l+2 {
-	return l == len(s.alpnProtocol)
+		return false
+	}
+	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
+	}
+	s.SNI = string(z[2 : 2+l])
+
+	return true
 }
 
 func (c *Conn) encryptTicket(serialized []byte) ([]byte, error) {