Merge pull request #527 from tlsfuzzer/correct-int-to-bytes

make int_to_bytes and numberToByteArray encode 0 as b'\x00'

tlslite/messages.py

@@ -1738,7 +1738,10 @@ def parse(self, parser):
             else:
                 raise AssertionError()
         elif self.cipherSuite in CipherSuite.dhAllSuites:
-            self.dh_Yc = bytesToNumber(parser.getVarBytes(2))
+            val = parser.getVarBytes(2)
+            if len(val) < 1:
+                raise DecodeError("DH key share too short")
+            self.dh_Yc = bytesToNumber(val)
         elif self.cipherSuite in CipherSuite.ecdhAllSuites:
             self.ecdh_Yc = parser.getVarBytes(1)
         else:

tlslite/utils/compat.py

@@ -106,7 +106,10 @@ def bit_length(val):
     def int_to_bytes(val, length=None, byteorder="big"):
         """Return number converted to bytes"""
         if length is None:
-            length = byte_length(val)
+            if val:
+                length = byte_length(val)
+            else:
+                length = 1
         # for gmpy we need to convert back to native int
         if type(val) != int:
             val = int(val)
@@ -206,7 +209,10 @@ def bytes_to_int(val, byteorder):
     def int_to_bytes(val, length=None, byteorder="big"):
         """Return number converted to bytes"""
         if length is None:
-            length = byte_length(val)
+            if val:
+                length = byte_length(val)
+            else:
+                length = 1
         if byteorder == "big":
             return bytearray((val >> i) & 0xff
                              for i in reversed(range(0, length*8, 8)))

unit_tests/test_tlslite_utils_cryptomath.py

@@ -100,6 +100,12 @@ def test_numberToByteArray(self):
         self.assertEqual(numberToByteArray(0x00000000000001),
                          bytearray(b'\x01'))
 
+    def test_numberToByteArray_zero_bigendian(self):
+        self.assertEqual(numberToByteArray(0, endian="big"), bytearray(b'\x00'))
+
+    def test_numberToByteArray_zero_littleendian(self):
+        self.assertEqual(numberToByteArray(0, endian="little"), bytearray(b'\x00'))
+
     def test_numberToByteArray_with_MSB_number(self):
         self.assertEqual(numberToByteArray(0xff),
                          bytearray(b'\xff'))