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User-Level Sandboxing with FUSE for File System Protection

This project aims to safeguard the file system from abuse using transparency, isolation, and user input principles. By employing system call interposition, intercepting, analyzing, and rerouting activities, it logs and commits post-execution operations. Key components include FUSE, syscall interposition, sandbox, and logging mechanisms to handle file operations effectively. Three main cases - writing a new file, writing an existing file, and reading system calls - are addressed through log recording and virtual file lists. The performance evaluation compares logging, sandboxing, and disk caching methods across different environments.

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User-Level Sandboxing with FUSE for File System Protection

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  1. University of Notre DameCSE 60641 User-Level Sandboxing with FUSE Brandon RichAndrew Blaich

  2. Problem • Protect the file system from abuse. • Guiding Principles: • Transparency • Isolation • User input

  3. Solution • System Call Interposition • Intercept • Analyze • Re-route and log activity • Return • Post-execution commit • Using log and execution cache

  4. Components • FUSE • Syscall interposition (free) • Logger • Sandbox • Whole-file copy • Virtual File List • Commit process • Uses log and .sandbox files

  5. 3 Cases: 1) Writing a new file2) Writing an existing file3) Reading System-Call USER-Space log call in: log.log OpenReadWriteClose FUSE Kernel /tmp file1.txt file1.txt.sandbox file2.doc

  6. Virtual File List

  7. Sandboxing Writes

  8. Sandboxing Writes

  9. Sandboxing Deletes • No deletes ever take place • VFL entry can be designated “deleted” • Version numbers keep track of future generations of a file

  10. Hiding Sandbox Files

  11. Logging

  12. Committer

  13. Performance Evaluation • Tests • Andrew Benchmark • Chirp Benchmark • Custom Benchmarks • Three Environments • Unmodified ext3 file system • “Clean” FUSE • Sandboxing FUSE

  14. Andrew Benchmark (Compile Phase 5: Am-utils)

  15. Chirp Benchmark

  16. Overhead of Logging vs Sandboxing Chirp Benchmark

  17. Custom Benchmark

  18. Conclusions • System call interposition at the user level is expensive • Disk-based caching is simple but robust • Our approach is effective but could be improved

  19. Questions?

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