From fad1f1388ea80eb07b4321d1a06e5dd38e81a513 Mon Sep 17 00:00:00 2001
From: Michel Oosterhof <micheloosterhof@users.noreply.github.com>
Date: Mon, 14 Sep 2020 00:08:27 +0800
Subject: [PATCH] Fix nc hang (#1406)

* add libvirt group membership
* stop nc hanging on bad input
---
 docs/BACKEND_POOL.rst     | 11 ++++++++++-
 src/cowrie/commands/nc.py | 10 ++++++++--
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/docs/BACKEND_POOL.rst b/docs/BACKEND_POOL.rst
index 9a4bd528..cd805f9f 100644
--- a/docs/BACKEND_POOL.rst
+++ b/docs/BACKEND_POOL.rst
@@ -19,6 +19,15 @@ libvirt's XML configuration files.
 First of all, install the needed dependencies for the pool, as explained in
 `the installation steps <https://cowrie.readthedocs.io/en/latest/INSTALL.html>`_.
 
+Authorization
+*************
+
+Add your cowrie user to the libvrit group to ensure you have permission to run the VMs on the backend server::
+
+.. code-block:: bash
+
+    sudo usermod -aG "COWRIE_USER_HERE" libvirt
+
 Provided images
 ***************
 
@@ -255,4 +264,4 @@ References
 
 * `libvirt network filter XML syntax <https://libvirt.org/formatnwfilter.html>`_
 
-* `Create a OpenWRT image <https://gist.github.com/extremecoders-re/f2c4433d66c1d0864a157242b6d83f67>`_
\ No newline at end of file
+* `Create a OpenWRT image <https://gist.github.com/extremecoders-re/f2c4433d66c1d0864a157242b6d83f67>`_
diff --git a/src/cowrie/commands/nc.py b/src/cowrie/commands/nc.py
index c47111b7..a6048894 100644
--- a/src/cowrie/commands/nc.py
+++ b/src/cowrie/commands/nc.py
@@ -25,6 +25,7 @@ def makeMask(n):
 def dottedQuadToNum(ip):
     """
     convert decimal dotted quad string to long integer
+    this will throw builtins.OSError on failure
     """
     return struct.unpack('I', socket.inet_aton(ip))[0]
 
@@ -72,7 +73,7 @@ usage: nc [-46bCDdhjklnrStUuvZz] [-I length] [-i interval] [-O length]
         host = args[0]
         port = args[1]
 
-        if not re.match(r'\d+', port):
+        if not re.match(r'^\d+$', port):
             self.errorWrite('nc: port number invalid: {}\n'.format(port))
             self.exit()
             return
@@ -80,10 +81,15 @@ usage: nc [-46bCDdhjklnrStUuvZz] [-I length] [-i interval] [-O length]
         if re.match(r'^\d+$', host):
             address = int(host)
         elif re.match(r'^[\d\.]+$', host):
-            address = dottedQuadToNum(host)
+            try:
+                address = dottedQuadToNum(host)
+            except OSError:
+                self.exit()
+                return
         else:
             # TODO: should do dns lookup
             self.exit()
+            return
 
         for net in local_networks:
             if addressInNetwork(address, net):