Runtime Web Validation via Learned Output Templates
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Solution Overview
Problem
Conventional methods for mitigating Cross-site Scripting (XSS) vulnerabilities in web applications, such as static analysis and sanitization of untrusted data, are difficult to implement effectively and error-prone, leading to prevalent XSS attacks despite existing security measures.
Innovation Solution
A runtime validation apparatus and system that intercepts server requests and responses to apply output validation policies dynamically, comparing response data with predefined templates to ensure compliance and block non-compliant data, thereby preventing XSS attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If static analysis and sanitization are used to mitigate XSS vulnerabilities, then security measures are implemented, but implementation is difficult and error-prone
Solution Approach 1:
The system automatically generates output validation policies by observing and analyzing the web application's own runtime behavior. The training phase captures actual output data during normal operation, and the system autonomously learns the expected output format without requiring manual specification of validation rules, thereby eliminating implementation complexity while maintaining security reliability
Solution Approach 2:
The patent introduces an intermediary validation layer that sits between the web application and the client. This intermediary automatically validates output data against learned policies before transmission, shielding the application from XSS attacks without requiring modifications to the application code itself, thus resolving the contradiction between security effectiveness and implementation ease
2Reliability
If output validators are manually applied to prevent XSS vulnerabilities, then validation can be performed, but the process is difficult and error prone
Solution Approach 1:
The system performs self-service by automatically generating validation policies through observation of the application's runtime output. During the training phase, it captures and analyzes actual output data to learn the expected format, then autonomously creates validation rules without human intervention, making the validation process easy to operate while maintaining high reliability
Solution Approach 2:
The system performs preliminary action by pre-learning the valid output format during a training phase before deployment. This preliminary observation and analysis of normal output data enables the system to establish validation criteria in advance, making subsequent validation operations simple and error-free
3Reliability
If sanitizers are applied to user data to prevent XSS attacks, then dangerous constructs are blocked, but proper placement and ordering is difficult
Solution Approach 1:
The patent introduces an intermediary validation layer that automatically determines the correct placement and ordering of validation operations. The validation policy is applied at the appropriate point in the request-response cycle based on learned patterns, eliminating the complexity of manual sanitizer placement while maintaining effective XSS prevention
Solution Approach 2:
The system self-determines the optimal placement and ordering of validation operations by analyzing the application's runtime behavior during training. It automatically identifies where validation should occur in the data flow and configures the validation pipeline accordingly, removing the need for manual configuration while ensuring reliable XSS prevention
Data Source
AI summary
The embodiments provide a runtime validation apparatus including a runtime interceptor configured to intercept a server request for a requested web resource and a response including response data, and an output validation policy identifier configured to identify an output validation policy from a database storing a plurality of output validation policies based on the requested web resource. The identified output validation policy may represent a template that encompasses allowed responses for the requested web resource. The runtime validation apparatus may further include a validation evaluator configured to compare the response data with the template, and a validation controller configured to permit the response to be transmitted if the response data complies with the template and block the response if at least a portion of the response data does not comply with the template.