Implement extended master secret in tlslite (again)

third_party/tlslite/tlslite/mathtls.py

Index: third_party/tlslite/tlslite/mathtls.py
diff --git a/third_party/tlslite/tlslite/mathtls.py b/third_party/tlslite/tlslite/mathtls.py
index 60a331ab90f66ebe26bb2171b6dad697884bdc15..0a23fe192fa805c27f23fd89d6c38d949328c061 100644
--- a/third_party/tlslite/tlslite/mathtls.py
+++ b/third_party/tlslite/tlslite/mathtls.py
@@ -67,16 +67,20 @@ def PRF_SSL(secret, seed, length):
             index += 1
     return bytes
 
-def calcMasterSecret(version, premasterSecret, clientRandom, serverRandom):
+def calcMasterSecret(version, premasterSecret, clientRandom, serverRandom,
+                     handshakeHash, useExtendedMasterSecret):
+    label = b"master secret"
+    seed = clientRandom + serverRandom
+    if useExtendedMasterSecret:
+        label = b"extended master secret"
+        seed = handshakeHash
+
     if version == (3,0):
-        masterSecret = PRF_SSL(premasterSecret,
-                            clientRandom + serverRandom, 48)
+        masterSecret = PRF_SSL(premasterSecret, seed, 48)
     elif version in ((3,1), (3,2)):
-        masterSecret = PRF(premasterSecret, b"master secret",
-                            clientRandom + serverRandom, 48)
+        masterSecret = PRF(premasterSecret, label, seed, 48)
     elif version == (3,3):
-        masterSecret = PRF_1_2(premasterSecret, b"master secret",
-                            clientRandom + serverRandom, 48)
+        masterSecret = PRF_1_2(premasterSecret, label, seed, 48)
     else:
         raise AssertionError()
     return masterSecret