From e9842dc6bec50adcfc5277f4425cb52e0dfb2953 Mon Sep 17 00:00:00 2001
From: Erick Vermot <erick.vermot@gmail.com>
Date: Fri, 7 Jul 2017 16:51:06 -0300
Subject: [PATCH 1/2] introduce general unpack method (comes from
 of_core.utils)

---
 pyof/utils.py | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 pyof/utils.py

diff --git a/pyof/utils.py b/pyof/utils.py
new file mode 100644
index 000000000..a71d8945d
--- /dev/null
+++ b/pyof/utils.py
@@ -0,0 +1,37 @@
+"""General Unpack utils for python-openflow."""
+import pyof.v0x01.common.header
+import pyof.v0x01.common.utils
+import pyof.v0x04.common.header
+import pyof.v0x04.common.utils
+from pyof.foundation.exceptions import UnpackException
+
+pyof_version_libs = {0x01: pyof.v0x01,
+                     0x04: pyof.v0x04}
+
+
+def unpack(packet):
+    """Unpack the OpenFlow Packet and returns a message."""
+    try:
+        version = packet[0]
+    except IndexError:
+        raise UnpackException('null packet')
+
+    try:
+        pyof_lib = pyof_version_libs[version]
+    except KeyError:
+        raise UnpackException('Version not supported')
+
+    try:
+        header = pyof_lib.common.header.Header()
+        header.unpack(packet[:8])
+        message = pyof_lib.common.utils.new_message_from_header(header)
+        binary_data = packet[8:]
+        if binary_data:
+            if len(binary_data) == header.length - 8:
+                message.unpack(binary_data)
+            else:
+                raise UnpackException(
+                    'packet size does not match packet length field')
+        return message
+    except (UnpackException, ValueError) as e:
+        raise UnpackException(e)

From a2d4480810f5ae4a96b8a5f372d5b41b827f2642 Mon Sep 17 00:00:00 2001
From: Erick Vermot <erick.vermot@gmail.com>
Date: Fri, 14 Jul 2017 15:17:14 -0300
Subject: [PATCH 2/2] separate packet validation from unpack

---
 pyof/utils.py | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/pyof/utils.py b/pyof/utils.py
index a71d8945d..179e2c2cf 100644
--- a/pyof/utils.py
+++ b/pyof/utils.py
@@ -9,13 +9,30 @@
                      0x04: pyof.v0x04}
 
 
+def validate_packet(packet):
+    """Check if packet is valid OF packet."""
+    if not isinstance(packet, bytes):
+        raise UnpackException('invalid packet')
+
+    packet_length = len(packet)
+
+    if packet_length < 8 or packet_length > 2**16:
+        raise UnpackException('invalid packet')
+
+    if packet_length != int.from_bytes(packet[2:4],
+                                       byteorder='big'):
+        raise UnpackException('invalid packet')
+
+    version = packet[0]
+    if version == 0 or version >= 128:
+        raise UnpackException('invalid packet')
+
+
 def unpack(packet):
     """Unpack the OpenFlow Packet and returns a message."""
-    try:
-        version = packet[0]
-    except IndexError:
-        raise UnpackException('null packet')
+    validate_packet(packet)
 
+    version = packet[0]
     try:
         pyof_lib = pyof_version_libs[version]
     except KeyError:
@@ -27,11 +44,7 @@ def unpack(packet):
         message = pyof_lib.common.utils.new_message_from_header(header)
         binary_data = packet[8:]
         if binary_data:
-            if len(binary_data) == header.length - 8:
-                message.unpack(binary_data)
-            else:
-                raise UnpackException(
-                    'packet size does not match packet length field')
+            message.unpack(binary_data)
         return message
     except (UnpackException, ValueError) as e:
         raise UnpackException(e)