implementation of session_ticket resumption in tls1.2

Author: tomato42

scripts/tls.py

@@ -324,19 +324,19 @@ def handleArgs(argv, argString, flagsList=[]):
 def printGoodConnection(connection, seconds):
     print("  Handshake time: %.3f seconds" % seconds)
     print("  Version: %s" % connection.getVersionName())
-    print("  Cipher: %s %s" % (connection.getCipherName(), 
+    print("  Cipher: %s %s" % (connection.getCipherName(),
         connection.getCipherImplementation()))
     print("  Ciphersuite: {0}".\
             format(CipherSuite.ietfNames[connection.session.cipherSuite]))
     if connection.session.srpUsername:
         print("  Client SRP username: %s" % connection.session.srpUsername)
     if connection.session.clientCertChain:
-        print("  Client X.509 SHA1 fingerprint: %s" % 
+        print("  Client X.509 SHA1 fingerprint: %s" %
             connection.session.clientCertChain.getFingerprint())
     else:
         print("  No client certificate provided by peer")
     if connection.session.serverCertChain:
-        print("  Server X.509 SHA1 fingerprint: %s" % 
+        print("  Server X.509 SHA1 fingerprint: %s" %
             connection.session.serverCertChain.getFingerprint())
     if connection.version >= (3, 3) and connection.serverSigAlg is not None:
         scheme = SignatureScheme.toRepr(connection.serverSigAlg)
@@ -352,20 +352,21 @@ def printGoodConnection(connection, seconds):
         print("  DH group size: {0} bits".format(connection.dhGroupSize))
     if connection.session.serverName:
         print("  SNI: %s" % connection.session.serverName)
-    if connection.session.tackExt:   
+    if connection.session.tackExt:
         if connection.session.tackInHelloExt:
             emptyStr = "\n  (via TLS Extension)"
         else:
-            emptyStr = "\n  (via TACK Certificate)" 
+            emptyStr = "\n  (via TACK Certificate)"
         print("  TACK: %s" % emptyStr)
         print(str(connection.session.tackExt))
     if connection.session.appProto:
         print("  Application Layer Protocol negotiated: {0}".format(
             connection.session.appProto.decode('utf-8')))
-    print("  Next-Protocol Negotiated: %s" % connection.next_proto) 
+    print("  Next-Protocol Negotiated: %s" % connection.next_proto)
     print("  Encrypt-then-MAC: {0}".format(connection.encryptThenMAC))
     print("  Extended Master Secret: {0}".format(
                                                connection.extendedMasterSecret))
+    print("  Session Resumed: {0}".format(connection.resumed))
 
 def printExporter(connection, expLabel, expLength):
     if expLabel is None:
@@ -464,12 +465,9 @@ def clientCmd(argv):
     # unreasumable, override it
     session.resumable = True
 
-    print("Received {0} ticket[s]".format(len(connection.tickets)))
+    print("Received {0} ticket[s]".format(len(connection.tickets) + len(connection.tls_1_0_tickets)))
     assert connection.tickets is session.tickets
 
-    if not session.tickets:
-        return
-
     if not resumption:
         return
 
@@ -480,11 +478,10 @@ def clientCmd(argv):
     sock.connect(address)
     sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
     connection = TLSConnection(sock)
-
     try:
         start = time_stamp()
         connection.handshakeClientCert(serverName=address[0], alpn=alpn,
-            session=session)
+            session=session, settings=settings)
         stop = time_stamp()
         print("Handshake success")
     except TLSLocalAlert as a:

tests/tlstest.py

@@ -1493,22 +1493,26 @@ def connect():
     testConnClient(connection)
     assert(isinstance(connection.session.serverCertChain, X509CertChain))
     assert(connection.session.serverName == address[0])
+    assert(connection.version == (3, 3))
     assert(not connection.resumed)
     assert(connection.encryptThenMAC)
+    assert(connection.session.tls_1_0_tickets)
     connection.close()
     session = connection.session
 
     # resume
     synchro.recv(1)
     connection = connect()
     settings = HandshakeSettings()
+    settings.macNames.remove("aead")
     settings.maxVersion = (3, 3)
     connection.handshakeClientCert(serverName=address[0], session=session,
                                    settings=settings)
     testConnClient(connection)
     assert(isinstance(connection.session.serverCertChain, X509CertChain))
     assert(connection.session.serverName == address[0])
     assert(connection.resumed)
+    assert(connection.session.encryptThenMAC)
     assert(connection.encryptThenMAC)
     connection.close()
 
@@ -1548,6 +1552,53 @@ def connect():
 
     test_no += 1
 
+    print("Test {0} - session_ticket resumption in TLSv1.2".format(test_no))
+    synchro.recv(1)
+    connection = connect()
+    settings = HandshakeSettings()
+    connection.handshakeClientCert(serverName=address[0], settings=settings)
+    testConnClient(connection)
+    assert isinstance(connection.session.serverCertChain, X509CertChain)
+    assert connection.session.serverName == address[0]
+    assert not connection.resumed
+    session = connection.session
+    connection.close()
+
+    # resume
+    synchro.recv(1)
+    settings = HandshakeSettings()
+    connection = connect()
+    connection.handshakeClientCert(serverName=address[0], settings=settings, session=session)
+    testConnClient(connection)
+    assert connection.resumed
+    connection.close()
+
+    test_no += 1
+
+    print("Test {0} - session_ticket resumption in TLSv1.2 "
+          "with expired ticket".format(test_no))
+    synchro.recv(1)
+    connection = connect()
+    settings = HandshakeSettings()
+    connection.handshakeClientCert(serverName=address[0], settings=settings)
+    testConnClient(connection)
+    assert isinstance(connection.session.serverCertChain, X509CertChain)
+    assert connection.session.serverName == address[0]
+    assert not connection.resumed
+    session = connection.session
+    connection.close()
+
+    # resume
+    synchro.recv(1)
+    settings = HandshakeSettings()
+    connection = connect()
+    connection.handshakeClientCert(serverName=address[0], settings=settings, session=session)
+    testConnClient(connection)
+    assert not connection.resumed
+    connection.close()
+
+    test_no += 1
+
     print("Test {0} - resumption in TLSv1.3".format(test_no))
     synchro.recv(1)
     connection = connect()
@@ -3069,6 +3120,7 @@ def server_bind(self):
     connection.handshakeServer(certChain=x509Chain, privateKey=x509Key,
                                settings=settings)
     testConnServer(connection)
+    assert(not connection.encryptThenMAC)
     connection.close()
 
     test_no += 1
@@ -3078,24 +3130,28 @@ def server_bind(self):
     connection = connect()
     connection.handshakeServer(certChain=x509Chain, privateKey=x509Key)
     testConnServer(connection)
+    assert(not connection.encryptThenMAC)
     connection.close()
 
     test_no += 1
 
     print("Test {0} - resumption with EtM".format(test_no))
     synchro.send(b'R')
     sessionCache = SessionCache()
+    settings = HandshakeSettings()
+    settings.ticketKeys = [getRandomBytes(32)]
     connection = connect()
     connection.handshakeServer(certChain=x509Chain, privateKey=x509Key,
-                               sessionCache=sessionCache)
+                               sessionCache=sessionCache, settings=settings)
     testConnServer(connection)
+    assert(connection.encryptThenMAC)
     connection.close()
 
     # resume
     synchro.send(b'R')
     connection = connect()
     connection.handshakeServer(certChain=x509Chain, privateKey=x509Key,
-                               sessionCache=sessionCache)
+                               sessionCache=sessionCache, settings=settings)
     testConnServer(connection)
     connection.close()
 
@@ -3125,6 +3181,52 @@ def server_bind(self):
 
     test_no += 1
 
+    print("Test {0} - session_ticket resumption in TLSv1.2".format(test_no))
+    synchro.send(b'R')
+    connection = connect()
+    settings = HandshakeSettings()
+    settings.maxVersion = (3, 3)
+    settings.ticketKeys = [getRandomBytes(32)]
+    connection.handshakeServer(certChain=x509Chain, privateKey=x509Key,
+                               settings=settings)
+    testConnServer(connection)
+    connection.close()
+
+    # resume
+    synchro.send(b'R')
+    connection = connect()
+    connection.handshakeServer(certChain=x509Chain, privateKey=x509Key,
+                               settings=settings)
+    testConnServer(connection)
+    connection.close()
+
+    test_no += 1
+
+    print("Test {0} - session_ticket resumption in TLSv1.2 "
+          "with expired ticket".format(test_no))
+    synchro.send(b'R')
+    connection = connect()
+    settings = HandshakeSettings()
+    settings.ticketLifetime = 1
+    settings.maxVersion = (3, 3)
+    settings.ticketKeys = [getRandomBytes(32)]
+    connection.handshakeServer(certChain=x509Chain, privateKey=x509Key,
+                               settings=settings)
+    testConnServer(connection)
+    connection.close()
+
+    time.sleep(2)
+
+    # resume
+    synchro.send(b'R')
+    connection = connect()
+    connection.handshakeServer(certChain=x509Chain, privateKey=x509Key,
+                               settings=settings)
+    testConnServer(connection)
+    connection.close()
+
+    test_no += 1
+
     print("Test {0} - resumption in TLSv1.3".format(test_no))
     synchro.send(b'R')
     connection = connect()
@@ -3155,6 +3257,7 @@ def server_bind(self):
     connection.handshakeServer(certChain=x509Chain, privateKey=x509Key,
                                reqCert=True, settings=settings)
     testConnServer(connection)
+    assert connection.session.clientCertChain
     connection.close()
 
     # resume

tlslite/constants.py

@@ -169,6 +169,7 @@ class ExtensionType(TLSEnum):
     encrypt_then_mac = 22  # RFC 7366
     extended_master_secret = 23  # RFC 7627
     record_size_limit = 28  # RFC 8449
+    session_ticket = 35 # RFC 5077
     extended_random = 40  # draft-rescorla-tls-extended-random-02
     pre_shared_key = 41  # TLS 1.3
     early_data = 42  # TLS 1.3

tlslite/extensions.py

@@ -2111,6 +2111,53 @@ def __init__(self):
             2, 'record_size_limit', ExtensionType.record_size_limit)
 
 
+class SessionTicketExtension(TLSExtension):
+    """
+    Client and server session ticket extension from RFC 5077
+    """
+    def __init__(self):
+        """Create instance of the object."""
+        super(SessionTicketExtension, self).__init__(extType=ExtensionType.
+                                                     session_ticket)
+        self.ticket = None
+
+    def create(self, ticket):
+
+        self.ticket = ticket
+        return self
+
+    @property
+    def extData(self):
+        """Serialise the payload of the extension."""
+        if not self.ticket:
+            return bytearray(0)
+
+        w = Writer()
+        w.bytes += self.ticket
+        return w.bytes
+
+    def parse(self, parser):
+        """
+        Parse the extension from on the wire format.
+
+        :param Parser parser: data to be parsed
+
+        :rtype: SessionTicketExtension
+        """
+        if not parser.getRemainingLength():
+            self.ticket = bytearray(0)
+            return self
+        self.ticket = parser.getFixBytes(parser.getRemainingLength())
+
+        return self
+
+    def __repr__(self):
+        """Return human readable representation of the extension."""
+        return "{0}({1}={2!r})".format(self.__class__.__name__,
+                                       "ticket",
+                                       self.ticket)
+
+
 TLSExtension._universalExtensions = \
     {
         ExtensionType.server_name: SNIExtension,
@@ -2132,7 +2179,8 @@ def __init__(self):
         ExtensionType.pre_shared_key: PreSharedKeyExtension,
         ExtensionType.psk_key_exchange_modes: PskKeyExchangeModesExtension,
         ExtensionType.cookie: CookieExtension,
-        ExtensionType.record_size_limit: RecordSizeLimitExtension}
+        ExtensionType.record_size_limit: RecordSizeLimitExtension,
+        ExtensionType.session_ticket: SessionTicketExtension}
 
 TLSExtension._serverExtensions = \
     {

tlslite/handshakesettings.py

@@ -321,6 +321,11 @@ class HandshakeSettings(object):
     :ivar ticketLifetime: maximum allowed lifetime of ticket encryption key,
         in seconds. 1 day by default
 
+    :vartype ticket_count: int
+    :ivar ticket_count: number of tickets the server will send to the client
+        after establishing the connection in TLS 1.3. If a positive integer,
+        it enabled support for ticket based resumption in TLS 1.2 and earlier.
+
     :vartype psk_modes: list(str)
     :ivar psk_modes: acceptable modes for the PSK key exchange in TLS 1.3