A Cold Fusion Programmers Guide to
Secure Networking
By: Jeremy Brodie, Sr. Developer
12500 Fair Lakes Circle, Suite 150
Farifax, VA
703.815.2500
www.edgewater.com
Overview
Server Environment Best Practices
NAT/Firewalls
IP Environment
Email/Spam/Black Hole Lists
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Why Bother (Care)?
Networking provides the communication
allowing your applications to be accessible
Do it wrong and you place your company
and your applications at risk
Possible Legal Risks?
- Documented legal cases of organizations sued
for poor security
- Can affect your organization’s/department’s
reputation
- Can affect any/all Internet projects
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Typical Environment
Three-tired environment
- Production
- Staging
- Development
Source Control (Development)
Email Relay Server for CF Mail
Several Servers Networked Together
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Typical Environment
Typical Environment Diagram
Router
Firewall
Internet
DMZ
Database Server
Internal
Email Server
Network Server
JRUN Server
w/ Cold Fusion
DNS Server
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Development Env.
Network Environment
Your Corporate Network Will Have Many of These
Components
Your network may include the following items as well
 One or more switches to facilitate communication
within the DMZ or Internal Zones
Diagram
Overview
 Network Address Translation within the Firewall
 Port blocking within the Firewall
 Load Balancers (for high traffic sites)
 Storage Area Network
 Internal DNS
Challenge
Often several employees/ departments will control the functioning of
these network areas. Each will have their own areas of expertise. As a
developer, you need to balance their technical concerns with the
business requirements of your application.
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Diagram Technical Overview
Networking Definitions
Internal
- Workstations
- File and Print Servers
- Outbound communication with outside. Can
pull information from DMZ computers
DMZ or Production
- Location of Servers (web, database, mail)
Hosted
- Location of some production application.
Communication with network available through
FTP and programs such as Terminal Services
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Network Address Translation
Definitions
Business
Challenge
Provide
communication to
servers via a nonroutable IP address
Use Non-Routeable Addresses to
communicate behind the firewall
-
Internal and DMZ
networks are on
separate subnets
-
Example: 192.168.10.3 for a DMZ Server
Example: 192.168.100.3 for a Workstation on
the Internal network
Addresses Reserved for Internet networking
Prevent Outsiders from Knowing the True
Address of Servers.
-
Servers will have non-routable addresses
only.
NAT Table provides reference
Only Exposes to Outside servers needing
Exposing
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Routing Table Example
192.168.100.2
192.168.100.3
192.168.100.4
192.168.100.5
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64.23.122.2
64.32.122.3
65.32.122.4
65.32.122.5
NAT: In Practice
Packet arrives with IP address
Business Challenge
Prevent outsiders
from reaching internal
network resources.
Firewall asks for location of DNS to
translate name
Firewall translates IP address
acceptable list located in DMZ
Reality Check
Insiders need to have
access to corporate
resources on the
road. A VPN solution
allows specified
laptops to have
access to Internal
resources.
Server IP address contain NonRoutable IP address only
Internal users access NAT through
Internal DNS server containing nonroutable IP information.
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NAT: Other Tools
Things to Know
All internal machines communicate via
Non-routable IP address configured by
DHCP
Business Challenge
With a limited pool of
Internal addresses,
allow employees to
access resources on
the Internet.
DHCP uses Internal DNS to locate
router
Internal DNS acts as a gateway between
the Internal and DNZ networks
Set up DHCP, or a
dynamic pool of
internal address with
right to access
resources outside the
Firewall.
Resources
RFC 1631
(http://www.faqs.org/rfcs/rfc1631.html)
NAT Overview
(http://computer.howstuffworks.com/nat1.ht
m)
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Email Spam: Risks and Challanges
The Challenge
CFMAIL Requires a Relay Server
Business Challenge
You need to send
email to external
customers using
your application. You
don’t want to spam,
however.
Spam is a huge problem on the
open Internet
Technology
NAT can be used to
specify who relays
and who does not
-
30-50% of all traffic is spam
-
Spammers use unethical methods to
send email
-
Spam/Virus link?
-
Legal Liability?
Black hole list can prevent your
email from being routed to the right
place
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Successful CFMAIL
Goals of System
Business Challenge
Provide the ability to
use CFMAIL for
external applications,
while preventing
spammers from
having access to Mail
servers.
Factoid
The new versions of
Outlook do not by
default allow customer
to see HTML email.
Spammers were using
external pictures to
validate email
addresses.
Goal 1: Prevent Outsiders from using Email
Server. If not blocked then black hole list
could shut down entire subnet
Goal 2: Only allow Cold Fusion Server to
send out Email
Goal 3: Use an Opt –in Mail list collected
from your site to send public email
Resources
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The Black Hole List
What is a Black Hole List
Email ends up in a black hole: It gets
sent out, but customers never receive
email
Reasons Why
Black hole lists allow
administrators to
block email from
known places.
Employees could be
liable if they did not
filter.
Used by spam filters to reduce the flow
of spam to inboxes
Administrator subscribed
Factoid
Although the MAPS
RBL allows users to
be removed, some
systems do not have
a way to be removed
from a list.
If you receive a new
IP block, check to
see if it has been
listed.
Resources
Realtime Black Hole List
(http://www.mailabuse.org)
Spamcop (http://www.spamcop.net)
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Example in IIS
Router
Business Solution
Only internal servers
can relay. Since mail
server accepts only
Internal addresses,
one must be located in
the DMZ to relay.
Separate server
allows corporate email
server never to relay
Firewall
Internet
IIS Web/ Mail
Server
192.168.10.6
Only allows 192.168.10.5
and other DMZ servers to
relay
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JRUN Server
w/ Cold Fusion
192.168.10.5
SQL Server
192.168.10.7
Solution for Sending CFMAIL
Create a Win-Win Situation
Use a separate server for relaying mail
from applications
Results
Successfully
deliver CFMAIL to
your customers.
-
Opt-In Lists
One way of
ensuring
successful mail is
through the use of
Opt-in Maillists. In
this case, you
specifically ask for
the permission of
the person before
sending out email
from an
application.
New regulations
require companies
to only send out
email for public
applications using
this method.
Relay server only accepts internal IP
addresses from DMZ siubnet
Emails are logged by Cold Fusion
Corporate email server never relays
Configure corporate server to allow HTML
email only from Internal Applications
External Emails Should be Reviewed With
Privacy Policy in Mind
-
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Should be Opt-in list only
Should be text only for external customers
Other Points
Communication is the number one
reasons why projects fail
- The stakes are often higher for the System
admins that your project
- IT pros are naturally conservative outside
their boundaries. IT is the one saying “no”
Your organization requires better
communication or an improved process
- The implementation boundary is stretched
What are your experiences?
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