Trusted Compilation Server for Kernel Module Signing
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Solution Overview
Problem
Unprivileged users lack a mechanism to safely access a limited subset of introspection tool functionality, as existing solutions fail to enforce safety constraints during kernel module generation and loading, and are vulnerable to tampering and corruption.
Innovation Solution
A trusted compilation server translates and compiles user scripts to generate a safe client kernel module, adding safety constraints and signing it to ensure only authorized, tamper-proof modules can be loaded and executed by unprivileged users.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an unprivileged user is allowed to create and load kernel modules with full system-wide instrumentation, then the user can access comprehensive introspection functionality, but system security and stability are compromised due to lack of safety constraints
Solution Approach 1:
The patent segments the kernel module functionality into safe and unsafe operations. A security manager component divides introspection capabilities into privileged and unprivileged subsets, allowing unprivileged users to access only the safe subset while preventing access to potentially harmful kernel operations. This segmentation resolves the contradiction by providing adequate functionality while maintaining security boundaries.
Solution Approach 2:
The patent introduces a security manager as an intermediary component between unprivileged users and the kernel module loading system. This intermediary verifies safety constraints, signs kernel modules to prove their safety, and mediates the loading process. The security manager acts as a trusted mediator that enables unprivileged users to safely access introspection functionality without compromising system security.
2Reliability
If safety checks are performed during translation and compilation of user scripts, then potentially unsafe operations can be blocked, but an unprivileged user can interfere with these processes to weaken the checks
Solution Approach 1:
The patent performs safety verification as a preliminary action during the kernel module generation process. The security manager checks for unsafe operations during translation and compilation before the module is finalized. By performing safety checks preliminarily and incorporating them into the generated module code, the system ensures safety constraints are enforced before the user can interfere with the process.
Solution Approach 2:
The patent creates a verified copy of the user script with safety constraints embedded during the translation and compilation process. The security manager generates a new version of the script that includes safety checks and constraints, replacing potentially harmful operations with safe alternatives. This copying approach allows the original user intent to be preserved while eliminating security risks.
3Adaptability or versatility
If the system loads and runs kernel modules created by unprivileged users, then introspection functionality is provided, but the module may have been corrupted or tampered with by the time it reaches the loading system
Solution Approach 1:
The patent performs preliminary signing of the kernel module during the generation process, before the module leaves the creating system. The security manager signs the module with a cryptographic signature that proves its safety and integrity. This preliminary action ensures that the module is authenticated before transmission, preventing tampering detection issues at loading time.
Solution Approach 2:
The patent implements a feedback mechanism where the loading system verifies the cryptographic signature of the kernel module before loading it. The security manager provides feedback about the module's safety status through the signature, and the loading system uses this feedback to decide whether to load the module. This feedback loop ensures that only verified safe modules are loaded, maintaining integrity throughout the process.
Data Source
AI summary
A module building system, hosted by a server, receives a user script to be run to monitor software on a client using an introspection tool. The server adds safety constraints to the user script and generates a client kernel module using the user script which includes the safety constraints. The server signs the client kernel module and sends the signed client kernel module to the client. The signed client kernel module allows a user to use the introspection tool to load and execute the client module on the client for monitoring the software on the client.