Network and Security Patterns

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Network and Security Patterns

• Ajoy Kumar

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Introduction

• Network Layer Security is something which has
  become the of prime importance in designing any
  network system.
• We look at the important layers of the network
  and try to identify the different Security
  Patterns associated with each layer. My work will
  be trying to fill the gaps at each layer where
  security patterns are missing or not well
  established.

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VPN Security

• We first look at the available patterns in the
  system.
• And as the next step, we try to understand the
  VPN architecture and we try to develop a Security
  pattern for the VPN Architecture.

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Network Architecture
Security Objects
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Class Diagram for XML FirewallNe06
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Class Diagram for a Packet FWFe06
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Class Diagram for Proxy FireWallFe03
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Class Diagram for IDS.Fer05
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VPN Architecture

• VPN make use of public network resources to
  connect to the private network of the enterprise.
  Within the VPN, the transmission is protected by
  security principles to assure confidentiality of
  the user(s) and data integrity. So a private
  network is established in the public domain.
  Since this network exists in a logical sense, it
  has been termed as virtual private network.

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Features of a good VPN

• Security
• Reliability
• Scalability
• Network management
• Policy management

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Problem

• In the company where I work we have a lot of
  remote employees who log in from different parts
  of the world such as St. Louis, USA or Israel.
  These developers log into a machine in Boca and
  work virtually from Boca. These connections are
  done using an VPN architecture. We need to
  develop the most safe architecture so that the
  work is done most efficiently and with the least
  threats to security.

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Context

• Local networks with applications being executed
  in distributed systems. Access to the network can
  be from the Internet or from other external
  networks using a VPN connection.

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Forces

• There are many remote users trying to connect to
  the same network from different end points. A
  good VPN system must accommodate all these users.
• There may be different end users that may require
  different levels of security. We need to define
  appropriate policies for each of these VPN
  connections.
• The company has various employees joining and
  leaving the company. Hence the security policies
  need to be constantly modified. Hence the VPN
  configuration should be easily configurable.
• The number of users and applications may increase
  significantly adding more users or applications
  should be done transparently and at proper cost.
• A VPN set up should avoid access to the corporate
  network from all harmful external elements
• There are many ways to perform authentication.
  The VPN must support the different methods.

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Pattern Diagram
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Class Diagram for a VPN
End User
Secure Network
VPN Network
Secure Channel
End User Auth Point
Identity Base
Policy Base
Identity
Policy
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Sequence Diagram for a VPN Authentication
End User
VPN
EndUserAuthPT
IdentityBase
Policy Base
SecureCh
SecureN/W
rqstConn
rqstConn
authenticate
authenticated
checkAccess
accessAllowed
openSecConn
Established
Established
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Solution

• Whenever an end user tries to connect to a VPN,
  the network should ask for authorization. An user
  can access a network only if a specific policy
  authorizes it to do.
• Policy enforcing includes authenticating the end
  user who is trying to connect to the network.
• The VPN Tunnel created should maintain its
  confidentiality and data integrity.

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Consequences

• Advantages
• Company can define the policies for VPN end users
  thus centralizing the policies and makes the
  administration better.
• Since authorization is used, company can keep a
  log of end users connected in the present and in
  the past.
• A secure tunnel guarantees data integrity and
  secrecy. Usually a PKI system of encryption is
  used for sending data over the tunnel.
• As authentication of end users are performed,
  users can be held responsible for their actions .
• We can also incorporate RBAC based on the role of
  the end user.
• Usually a Firewall complements a VPN setup..

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Consequences (Contd)

• Liabilities
• If the VPN is compromised, then the attacker gets
  full access to the internal network too.
• VPN traffic is often invisible to IDS
  monitoring.If the IDS probe is outside the VPN
  server, as is often the case, then the IDS cannot
  see the traffic within the VPN tunnel because it
  is encrypted. Therefore if a hacker gains access
  to the VPN, he can attack the internal systems
  without being picked up by the IDS.
• Whatever type of VPN we use, VPN is only as
  secure as the remote computer connected to it.

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• Liabilities (Contd)
• The pattern does not discuss the attack at the
  end points.
• VPN Tunnel is only as strong as the cryptography
  that enables it.

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Known Users

• Citrix. Citrix provides a site to site VPN
  connection for remote users to log into the
  secure network as well as access applications on
  the company (secure) network.

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Related Patterns

• Patterns for Application Firewalls using PEP and
  PAP.
• Nelly Delessy-Gassant, Eduardo B. Fernandez,
  Saeed Rajput,and Maria M. Larrondo Petrie

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Future Work

• Expand on the VPN Pattern and create separate
  patterns for IP, SSL and XML VPNs.
• Developing the patterns missing in the network
  security diagram shown before.

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Thank You

• QA
• Suggestions
• Concerns