show us the offending host key

(cherry picked from commit a753df8ea43c26114942147fde2f10f82da5ca29)

paramiko/hostkeys.py

@@ -21,6 +21,7 @@ L{HostKeys}
 """
 
 import base64
+import binascii
 from Crypto.Hash import SHA, HMAC
 import UserDict
 
@@ -29,6 +30,14 @@ from paramiko.dsskey import DSSKey
 from paramiko.rsakey import RSAKey
 
 
+class InvalidHostKey(Exception):
+
+    def __init__(self, line, exc):
+        self.line = line
+        self.exc = exc
+        self.args = (line, exc)
+
+
 class HostKeyEntry:
     """
     Representation of a line in an OpenSSH-style "known hosts" file.
@@ -63,12 +72,15 @@ class HostKeyEntry:
 
         # Decide what kind of key we're looking at and create an object
         # to hold it accordingly.
+        try:
             if keytype == 'ssh-rsa':
                 key = RSAKey(data=base64.decodestring(key))
             elif keytype == 'ssh-dss':
                 key = DSSKey(data=base64.decodestring(key))
             else:
                 return None
+        except binascii.Error, e:
+            raise InvalidHostKey(line, e)
 
         return cls(names, key)
     from_line = classmethod(from_line)