From 1d092172ee12db7f2f525d80588cccc30157749b 2011-08-16 01:34:09
From: Fernando Perez <fperez.net@gmail.com>
Date: 2011-08-16 01:34:09
Subject: [PATCH] Merge pull request #689 from minrk/auth

Protect ipkernel from bad messages: now the kernel logs bad messages as errors instead of crashing.
---

diff --git a/IPython/zmq/ipkernel.py b/IPython/zmq/ipkernel.py
index 1d130ea..bbd6833 100755
--- a/IPython/zmq/ipkernel.py
+++ b/IPython/zmq/ipkernel.py
@@ -121,7 +121,11 @@ class Kernel(Configurable):
     def do_one_iteration(self):
         """Do one iteration of the kernel's evaluation loop.
         """
-        ident,msg = self.session.recv(self.shell_socket, zmq.NOBLOCK)
+        try:
+            ident,msg = self.session.recv(self.shell_socket, zmq.NOBLOCK)
+        except Exception:
+            self.log.warn("Invalid Message:", exc_info=True)
+            return
         if msg is None:
             return
 
@@ -375,7 +379,11 @@ class Kernel(Configurable):
 
     def _abort_queue(self):
         while True:
-            ident,msg = self.session.recv(self.shell_socket, zmq.NOBLOCK)
+            try:
+                ident,msg = self.session.recv(self.shell_socket, zmq.NOBLOCK)
+            except Exception:
+                self.log.warn("Invalid Message:", exc_info=True)
+                continue
             if msg is None:
                 break
             else:
@@ -402,7 +410,13 @@ class Kernel(Configurable):
         msg = self.session.send(self.stdin_socket, u'input_request', content, parent)
 
         # Await a response.
-        ident, reply = self.session.recv(self.stdin_socket, 0)
+        while True:
+            try:
+                ident, reply = self.session.recv(self.stdin_socket, 0)
+            except Exception:
+                self.log.warn("Invalid Message:", exc_info=True)
+            else:
+                break
         try:
             value = reply['content']['value']
         except:
diff --git a/IPython/zmq/session.py b/IPython/zmq/session.py
index 98a573a..bee9396 100644
--- a/IPython/zmq/session.py
+++ b/IPython/zmq/session.py
@@ -588,7 +588,6 @@ class Session(Configurable):
         try:
             return idents, self.unserialize(msg_list, content=content, copy=copy)
         except Exception as e:
-            print (idents, msg_list)
             # TODO: handle it
             raise e
     
@@ -661,6 +660,8 @@ class Session(Configurable):
                 msg_list[i] = msg_list[i].bytes
         if self.auth is not None:
             signature = msg_list[0]
+            if not signature:
+                raise ValueError("Unsigned Message")
             if signature in self.digest_history:
                 raise ValueError("Duplicate Signature: %r"%signature)
             self.digest_history.add(signature)
diff --git a/docs/source/parallel/parallel_security.txt b/docs/source/parallel/parallel_security.txt
index 7b96a93..49f78b7 100644
--- a/docs/source/parallel/parallel_security.txt
+++ b/docs/source/parallel/parallel_security.txt
@@ -132,11 +132,10 @@ owner, just as is common practice with a user's keys in their `.ssh` directory.
 
 .. warning::
 
-    It is important to note that the key authentication, as emphasized by the use of
-    a uuid rather than generating a key with a cryptographic library, provides a 
-    defense against *accidental* messages more than it does against malicious attacks.
-    If loopback is compromised, it would be trivial for an attacker to intercept messages
-    and deduce the key, as there is no encryption.
+    It is important to note that the signatures protect against unauthorized messages,
+    but, as there is no encryption, provide exactly no protection of data privacy.  It is
+    possible, however, to use a custom serialization scheme (via Session.packer/unpacker
+    traits) that does incorporate your own encryption scheme.