Almost every web application employs a database to store the various kinds of information that it needs in order to operate. For example, a web application deployed by an online retailer might use a database to store the following information: ■ User accounts, credentials, and personal information ■ Descriptions and prices of goods for sale … Read more
The topic of code injection is a huge one, encompassing dozens of different languages and environments, and a wide variety of different attacks. It would be possible to write an entire book on any one of these areas, exploring all of the theoretical subtleties of how vulnerabilities can arise and be exploited. Because this is … Read more
Issues relating to access apply not only to the web application itself but also to the other infrastructure tiers which lie beneath it — in particular, the application server, the database, and the operating system. Taking a defense-in-depth approach to security entails implementing access controls at each of these layers to create several layers of … Read more
Access controls are one of the easiest areas of web application security to understand, although a well-informed, thorough methodology must be carefully applied when implementing them. First, there are several obvious pitfalls to avoid. These usually arise from ignorance about the essential requirements of effective access control or flawed assumptions about the kinds of requests that … Read more
Before starting to probe the application to detect any actual access control vulnerabilities, you should take a moment to review the results of your application mapping exercises, to understand what the application’s actual requirements are in terms of access control, and therefore where it will probably be most fruitful to focus your attention. The easiest … Read more
Common Vulnerabilities Access controls can be divided into two broad categories: vertical and horizontal. Vertical access controls allow different types of users to access different parts of the application’s functionality. In the simplest case, this typically involves a division between ordinary users and administrators. In more complex cases, vertical access controls may involve fine-grained user … Read more
The application’s session management functionality should be closely integrated with its mechanisms for logging, monitoring, and alerting, in order to provide suitable records of anomalous activity and enable administrators to take defensive actions where necessary: ■ The application should monitor requests that contain invalid tokens. Except in the most trivially predictable cases, a successful attack … Read more
The usual simple summary of how cookies work is that the server issues a cookie using the HTTP response header Set-cookie , and the browser then resubmits this cookie in subsequent requests to the same server using the Cookie header. In fact, matters are rather more subtle than this. The cookie mechanism allows a server … Read more
Aside from the clear-text transmission of session tokens in network communications, the most common place where tokens are simply disclosed to unauthorized view is in system logs of various kinds. Although it is a rarer occurrence, the consequences of this kind of disclosure are usually more serious because those logs may be viewed by a … Read more
No matter how effective an application is at ensuring that the session tokens it generates do not contain any meaningful information and are not susceptible to analysis or prediction, its session mechanism will be wide open to attack if those tokens are not handled carefully after generation. For example, if tokens are disclosed to an … Read more