patch from james bardin: bail early if the high byte is zero.

paramiko/message.py

@@ -111,7 +111,7 @@ class Message (object):
         """
         b = self.packet.read(n)
         if len(b) < n:
-            return '\x00'*n
+            return b + '\x00' * (n - len(b))
         return b
 
     def get_byte(self):

paramiko/util.py

@@ -135,6 +135,8 @@ def safe_string(s):
 def bit_length(n):
     norm = deflate_long(n, 0)
     hbyte = ord(norm[0])
+    if hbyte == 0:
+        return 1
     bitlen = len(norm) * 8
     while not (hbyte & 0x80):
         hbyte <<= 1