PracExtractor: Extracting Configuration Good Practices from Manuals to Detect Server Misconfigurations

 2020 USENIX Annual Technical Conference. July 15–17, 2020 Online virtual conference 

Configuration has become ever so complex and error-prone in today’s server software. To mitigate this problem, software vendors provide user manuals to guide system admins on configuring their systems. Usually, manuals describe not only the meaning of configuration parameters but also good practice recommendations on how to configure certain parameters. Unfortunately, manuals usually also have a large number of pages, which are time-consuming for humans to read and understand. Therefore, system admins often do not refer to manuals but rely on their own guesswork or unreliable sources when setting up systems, which can lead to configuration errors and system failures. 

To understand the characteristics of configuration recommendations in user manuals, this paper first collected and studied 261 recommendations from the manuals of six large open-source systems. Our study shows that 60% of the studied recommendations describe specific and checkable specifications instead of merely general guidance. Moreover, almost all (97%) of such specifications have not been checked in the systems’ source code, and 61% of them are not equivalent to the default settings. This implies that additional checking is needed to ensure the recommendations are correctly applied. 

Based on our characteristic study, we build a tool called PracExtractor, which employs Natural Language Processing (NLP) techniques to automatically extract configuration recommendations from software manuals, converts them into specifications, and then uses the generated specifications to detect violations in system admins’ configuration settings. We evaluate PracExtractor with twelve widely-deployed software systems, including one large commercial system from a public company. In total, PracExtractor automatically extracts 338 recommendations and generates 173 specifications with reasonable accuracy. With these generated specifications, PracExtractor detects 1423 good practice violations from open-source docker images. To this day, we have reported 325 violations and have got 47 of them confirmed as real configuration issues by admins from different organizations.

Resources

The paper, slides, and the presentation video recording can be found at: https://www.usenix.org/conference/atc20/presentation/xiang.