Implement extended master secret in tlslite

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..ba8cd5fba7b6bc875a39f0491c8a06bb5b166026 100644
--- a/third_party/tlslite/tlslite/mathtls.py
+++ b/third_party/tlslite/tlslite/mathtls.py
@@ -10,6 +10,7 @@
 from .utils.compat import *
 from .utils.cryptomath import *
 
+import hashlib
 import hmac
 
 #1024, 1536, 2048, 3072, 4096, 6144, and 8192 bit groups]
@@ -67,16 +68,31 @@ def PRF_SSL(secret, seed, length):
             index += 1
     return bytes
 
-def calcMasterSecret(version, premasterSecret, clientRandom, serverRandom):
+def calcMasterSecret(version, premasterSecret, clientRandom, serverRandom,
+                     handshakeMessages, useExtendedMasterSecret):
+    label = b"master secret"
+    seed = clientRandom + serverRandom
+    if useExtendedMasterSecret:
+        label = b"extended master secret"
+
     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)
+        if useExtendedMasterSecret:
+            seed_md5 = hashlib.md5()
+            seed_sha1 = hashlib.sha1()
+            for msg in handshakeMessages:
+                seed_md5.update(msg)
+                seed_sha1.update(msg)
+            seed = seed_md5.digest() + seed_sha1.digest()
+        masterSecret = PRF(premasterSecret, label, seed, 48)
     elif version == (3,3):
-        masterSecret = PRF_1_2(premasterSecret, b"master secret",
-                            clientRandom + serverRandom, 48)
+        if useExtendedMasterSecret:
+            seed_sha256 = hashlib.sha256()
+            for msg in handshakeMessages:
+                seed_sha256.update(msg)
+            seed = seed_sha256.digest()
+        masterSecret = PRF_1_2(premasterSecret, label, seed, 48)
     else:
         raise AssertionError()
     return masterSecret