How to perform a security architecture review at Level 2

If you are performing an application security verification according to the OWASP Application Security Verification Standard (ASVS) verification requirements, then you will need to perform an analysis of the application’s security architecture. The ASVS Level 2 security architecture requirements read in part:

''“... the web application shall be defined by grouping its components into a high-level architecture … Components may be defined in terms of either individual or groups of source files, libraries, and/or executables. At Level 2, the relationship between components or groups of components need not be defined… At Level 2, the path or paths a given end user request may take within the application must be documented…”''

The level of detail, and corresponding depth and breadth of analysis, is the same for ASVS Levels 2, 2A, and 2B. The above requirements can be met by performing three basic steps.

The first step is to identify web application and IT environment components. Please see the ASVS article How to perform a security architecture review at Level 1.

The next step is to organize web application and IT environment components identified into the previous step into a high-level architecture. One way to accomplish this is to draw a block diagram that can be understood without having know for example UML.
 * Draw blocks that correspond to web application components, possibly omitting IT environment components for clarity
 * Arrange blocks such that a line can be drawn through the blocks to depict an application request without lifting your pen from the paper
 * Arrange blocks such that a line can be drawn through the blocks to depict an application response without lifting your pen from the paper

The last step is to identify call stacks for application requests, using the block diagram from the previous step as guidance.

Helpful hints:
 * If you’re working from code without the assistance of documentation or the application developers, the second and third steps may be reversed.
 * Keep in mind that security architecture analysis is an iterative, on-going process.
 * Learning how to identify and group components to obtain a desired level of abstractions is an art form in and of itself.
 * Corrections and additional detail are typically added as more information about the implementation is discovered over the course of the verification.