Understanding and Selecting RASP 2019: Technology
It is time to discuss technical facets of RASP products – including how the technology works, how it integrates into an application environment, and the advantages of different integration options. We will also outline important considerations such as platform support which impact the selection process. We will also consider a couple aspects of RASP technology which we expect to evolve over next couple years. How the Technology Works Over the last couple years the RASP market has settled on a couple basic approaches – with a few variations to enhance detection, reliability, or performance. Understanding the technology is important for understanding the strengths and weaknesses of different RASP offerings. Instrumentation: In this deployment model, the RASP system inserts sensors or callbacks at key junctions within the application stack to observe application behavior within and between custom code, application libraries, frameworks, and the underlying operating system. This approach is typically implemented using native application profiler/instrumentation API to monitor runtime application behavior. When a sensor is hit RASP gets a callback, and then evaluates the request against the policies relevant to the request and application context. For example database queries are examined for SQL Injection (SQLi). But they also provide request deserialization ‘sandboxing’ to detect malicious payloads, and what I call ‘checkpointing’ – a request that hits checkpoint A but bypasses checkpoint B can be confidently considered hostile. These approaches provide far more advanced application monitoring than WAF, with nuanced detection of attacks and misuse. But full visibility require monitoring of all relevant interfaces, with a cost to performance and scalability. Customers need to balance thorough coverage against performance. Servlet Filters & Plugins: Some RASP platforms are implemented as web server plugins or Java Servlets, typically installed in Apache Tomcat, JBoss, or Microsoft .NET to process requests. Plugins filter requests before they execute functions such as database queries or transactions, applying detection rules to each request on receipt. Requests which match known attack signatures are blocked. This is effectively the same functionality as a WAF blacklist, with added protections such as lexical analysis of inbound request structures. This is a simple way to retrofit protection into an application environment; it is effective at blocking malicious requests without the deep application understanding possible using other integration approaches Library or JVM Replacement: Some RASP products are installed by replacing standard application libraries and/or JAR files, and at least one vendor offers a full replacement Java Virtual Machine. This method basically hijacks calls to the underlying platform into a custom application. The RASP platform passively ‘sees’ application calls to supporting functions, applying rules as requests are intercepted. For example in the case of JVM replacement, RASP can alter classes as they are loaded into memory, augmenting or patching the application and its stack. Like Instrumentation integration, this approach provides complete visibility into application behaviors and analyzes user requests. Some customers prefer this option as effectively automated platform patching, but most customers we speak with are uncomfortable with dynamic alteration of the production application stack. Instrumentation & Static Hybrid: Like many firewalls, some RASP platforms can deploy as a reverse proxy; several vendors offer this as an option. In one case a novel variant couples a proxy, an Instrumentation module, and parts of a static analysis scan. Essentially it generates a Code-Property-Graph – like a static analysis tool – to build custom security controls for all application and open source functions. This approach requires full integration into the application build pipeline to scan all source code. It then bundles the scan result into the RASP engine as the application is deployed, effectively providing an application-specific functionality whitelist. The security controls are tailored to the application with excellent code coverage – at the expense of full build integration, the need to regularly rebuild the CPG profile, and some added latency for security checks. Several small companies have come and gone over the last couple years, offering a mixture of application logic crawlers (DAST) rule sets, application virtualization to mimic the replacement model listed above, and runtime mirroring in a cloud service. The full virtualization approach was interesting, but being too early to market and being dead wrong in approach are virtually indistinguishable. Still, over time I expect to see new RASP detection variations, possibly in the area of AI, and new cloud services for additional support layers. Detection RASP attack detection is complicated, with multiple techniques employed depending on request type. Most products examine both the request and its parameters, inspecting each component in multiple ways. The good news is that RASP is far more effective at detecting application attacks. Unlike other technologies which use signature-based detection, RASP fully decodes parameters and external references, maps application functions and third-party code usage, maps execution sequences, deserializes payloads, and applies polices accordingly. This not only enables more accurate detection, but improves performance by optimizing which checks are performed based on request context and code execution path. Enforcing rules at the point of use makes it much easier to both understand proper usage and detect misuse. Most RASP platforms employ structural analysis as well. They understand what framework is in use, and which common vulnerabilities it is vulnerable to. As RASP understands the entire application stack, it can detect variations in third-party code libraries — roughly comparable to a vulnerability scan of an open source library — to determine when outdated code is used. RASP can also quickly vet incoming requests and detect injection attacks. There are several approaches – one uses a form of tokenization (replacing parameters with tokens) to quickly verify that a request matches its intended structure. For example tokenizing clauses and parameters in a SQL query can quickly detect when a ‘FROM’ or ‘WHERE’ clause has more tokens than it should, indicating the query has been altered. Blocking When an attack is detected RASP, running within the application, can throw an application error. This prevents the malicious request from being further processed, with the protected application responsible for a graceful response and maintenance of application state.
