allow reading 0 bytes from socket

since to trigger and finish PHA the client and server needs to read
from socket, allow reading 0 bytes, just to trigger buffer processing

Author: tomato42

tests/tlstest.py

@@ -77,6 +77,7 @@ def testConnClient(conn):
     conn.write(b1)
     conn.write(b10)
     conn.write(b100)
+    conn.write(b1000)
     r1 = conn.read(min=1, max=1)
     assert len(r1) == 1
     assert r1 == b1
@@ -86,7 +87,6 @@ def testConnClient(conn):
     r100 = conn.read(min=100, max=100)
     assert len(r100) == 100
     assert r100 == b100
-    conn.write(b1000)
     r1000 = conn.read(min=1000, max=1000)
     assert len(r1000) == 1000
     assert r1000 == b1000
@@ -715,6 +715,8 @@ def connect():
     settings.maxVersion = (3, 4)
     connection.handshakeClientCert(x509Chain, x509Key, settings=settings)
     synchro.recv(1)
+    b = connection.read(0, 0)
+    assert b == b''
     testConnClient(connection)
     assert(isinstance(connection.session.serverCertChain, X509CertChain))
     connection.close()

tlslite/tlsrecordlayer.py

@@ -328,7 +328,14 @@ def readAsync(self, max=None, min=1):
             allowedTypes = ContentType.application_data
             allowedHsTypes = None
         try:
-            while len(self._readBuffer) < min and not self.closed:
+            try_once = True
+            # perform a read even if we were asked to read 0 bytes, but only
+            # if the buffer is empty; this is used to trigger
+            # processing of NST, KeyUpdate and PHA
+            while (len(self._readBuffer) < min or
+                    (not self._readBuffer and try_once)) \
+                    and not self.closed:
+                try_once = False
                 try:
                     for result in self._getMsg(allowedTypes,
                                                allowedHsTypes,
@@ -338,21 +345,19 @@ def readAsync(self, max=None, min=1):
                     if isinstance(result, NewSessionTicket):
                         result.time = time.time()
                         self.tickets.append(result)
-                        continue
                     elif isinstance(result, KeyUpdate):
                         for result in self._handle_keyupdate_request(result):
                             yield result
-                        continue
                     elif isinstance(result, Certificate):
                         for result in self._handle_srv_pha(result):
                             yield result
-                        continue
                     elif isinstance(result, CertificateRequest):
                         for result in self._handle_pha(result):
                             yield result
-                        continue
-                    applicationData = result
-                    self._readBuffer += applicationData.write()
+                    else:
+                        assert isinstance(result, ApplicationData)
+                        applicationData = result
+                        self._readBuffer += applicationData.write()
                 except TLSRemoteAlert as alert:
                     if alert.description != AlertDescription.close_notify:
                         raise