Improving Web Application Security: Threats and - CGISecurity

124 Part II:Designing Secure Web ApplicationsHave You Considered How to Flow Original Caller Identity?Your design should ensure that activity is audited across multiple application tiers.To do so, the identity of the original caller must be available at each tier.●●●Do you audit across application tiers?Examine whether each tier audits activity as it should.How do you synchronize multiple logs?Log files may be needed in legal proceedings to prove crimes committed byindividuals or to settle cases of repudiation. Generally, auditing is considered mostauthoritative if the audits are generated at the time of resource access and by thesame routines that access the resource. Verify that the application design factors inlog file synchronization and logs some form of request identifier to ensure thatmultiple log file entries can be correlated and related back to a single request.How do you flow the original caller identity?If you do not flow the original caller identity at the operating system level, forexample, because of the limited scalability that this approach offers, identify howthe application flows the original caller identity. This is required for cross-tierauditing (and potentially for authorization).Also, if multiple users are mapped to a single application role, check that theapplication logs the identity of the original caller.Have You Considered Secure Log File Management Policies?Check whether your application design factors in how log files are backed up,archived, and analyzed. Log files should be archived regularly to ensure that they donot fill up or start to cycle, and they should be regularly analyzed to detect signs ofintrusion. Also ensure that any accounts used to perform the backup are leastprivileged and that you secure any additional communication channels exposedpurely for the purpose of the backup.SummaryBy spending the time and effort up front to analyze and review your applicationarchitecture and design, you can improve its overall security by eliminating designrelatedvulnerabilities. It is much easier and less expensive to fix vulnerabilities atdesign time than it is later in the development cycle when substantial reengineeringmight be required.By considering your design in relation to the target deployment environment and thesecurity policies defined by that environment, you can help ensure a smooth andsecure application deployment.