Improving Web Application Security: Threats and - CGISecurity

Chapter 4: Design Guidelines for Secure Web Applications 73Security Policies and ProceduresSecurity policy determines what your applications are allowed to do and what theusers of the application are permitted to do. More importantly, they definerestrictions to determine what applications and users are not allowed to do. Identifyand work within the framework defined by your corporate security policy whiledesigning your applications to make sure you do not breach policy that mightprevent the application being deployed.Network Infrastructure ComponentsMake sure you understand the network structure provided by your targetenvironment and understand the baseline security requirements of the network interms of filtering rules, port restrictions, supported protocols, and so on.Identify how firewalls and firewall policies are likely to affect your application’sdesign and deployment. There may be firewalls to separate the Internet-facingapplications from the internal network. There may be additional firewalls in front ofthe database. These can affect your possible communication ports and, therefore,authentication options from the Web server to remote application and databaseservers. For example, Windows authentication requires additional ports.At the design stage, consider what protocols, ports, and services are allowed to accessinternal resources from the Web servers in the perimeter network. Also identify theprotocols and ports that the application design requires and analyze the potentialthreats that occur from opening new ports or using new protocols.Communicate and record any assumptions made about network and applicationlayer security and which component will handle what. This prevents securitycontrols from being missed when both development and network teams assume thatthe other team is addressing the issue. Pay attention to the security defenses that yourapplication relies upon the network to provide. Consider the implications of a changein network configuration. How much security have you lost if you implement aspecific network change?Deployment TopologiesYour application’s deployment topology and whether you have a remote applicationtier is a key consideration that must be incorporated in your design. If you have aremote application tier, you need to consider how to secure the network betweenservers to address the network eavesdropping threat and to provide privacy andintegrity for sensitive data.