Null-byte Injection Detection via Finite-State Machine
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Solution Overview
Problem
Existing solutions are inadequate in detecting and preventing null-byte injection attacks, which can lead to service outages and business-logic exploits due to the interpretation of null-bytes as end-of-string sentinels, causing buffer overflows and code-injection attacks, especially when null-bytes are encoded using various methods.
Innovation Solution
A system that uses directed graphs to generate an output finite-state machine to model detection of multiply encoded null-bytes across multiple character encoding methods, interposing a single system for detecting and blocking all cases of null-byte injection in received text data before it reaches vulnerable services, employing finite-state machines to identify and decode null-bytes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple character encoding methods are used to encode null-bytes, then the ability to bypass validation checks improves, but the difficulty of detecting and measuring increases
Solution Approach 1:
The patent applies preliminary action by performing decoding operations before validation checks. The system proactively decodes input data using multiple character encoding methods (URL decoding, XML entity decoding, C escape sequence decoding) before the validation phase, ensuring that encoded null-bytes are revealed and can be detected by subsequent validation logic. This prevents attackers from bypassing checks through encoding obfuscation.
Solution Approach 2:
The patent introduces intermediary decoding functions that act as mediators between the raw input data and the validation checks. These decoding intermediaries (URL decoder, XML entity decoder, C escape sequence decoder) transform encoded data into its original form, allowing validation logic to operate on decoded content rather than having to handle multiple encoding formats directly.
2Reliability
If comprehensive validation is applied at all entry points, then security against null-byte injection improves, but the complexity of the system increases
Solution Approach 1:
The patent applies universality by creating a multi-functional validation component that handles multiple character encoding methods within a single unified structure. The validation logic can process URL-encoded data, XML entity-encoded data, and C escape sequence-encoded data through the same component, eliminating the need for separate validation mechanisms for each encoding type and reducing overall system complexity.
Solution Approach 2:
The patent segments the validation process into distinct decoding stages (URL decoding, XML entity decoding, C escape sequence decoding) that can be applied independently and in sequence. This segmentation allows each decoding function to be tested and maintained separately while providing comprehensive protection when combined, making the overall system more manageable despite handling multiple encoding methods.
3Object-affected harmful factors
If encoding methods are applied to disguise null-bytes, then the ability to smuggle malicious payloads improves, but the ease of operation for detection worsens
Solution Approach 1:
The system performs preliminary decoding operations on all incoming data before validation, proactively converting encoded representations (URL encoding, XML entities, C escape sequences) into their original forms. This ensures that malicious null-bytes disguised through encoding are revealed before the validation phase, making detection straightforward without requiring complex analysis of encoded formats.
Data Source
AI summary
A single system for detecting and blocking all cases of null-byte injection in all text data received for a network, before the text reaches potentially vulnerable services in the network. A set of directed graphs is received, each one of the directed graphs corresponding to a singly encoded null-byte that is encoded according to a corresponding character encoding method contained within a set of character encoding methods. The set of directed graphs is used to generate an output finite-state machine that models detection of at least one multiply encoded null-byte that is encoded according to at least one of the character encoding methods contained in the set of character encoding methods. The output finite-state machine is loaded into an attack detection and prevention system that receives input text, and that detects null-bytes, including multiply encoded null-bytes, within the input text.