1. 02/03/14 Copyright © 2002 WireX Communications, Inc. 1 Autonomix: Autonomic Defenses for Vulnerable Software Crispin Cowan, Ph.D WireX Communications, Inc wirex.com

2. 02/03/14 Copyright © 2002 WireX Communications, Inc. 2 Phase I and Phase II Phase I: WireX and OGI WireX: Component Autonomy –Defend software implementation against common vulnerabilities OGI: Network and Systemic Autonomy –IDS notification translation –IDS response “orchestrate” Phase II: Just WireX More component Autonomy LSM: Linux Security Module

3. 02/03/14 Copyright © 2002 WireX Communications, Inc. 3 Autonomix Technical Objectives Tools to guard legacy components against common software vulnerabilities StackGuard: protection from “stack smashing” buffer overflows SubDomain: lightweight mandatory access controls FormatGuard: protection from printf format bugs RaceGuard: protection from temp file races PointGuard: generalized StackGuard CryptoMark: kernel-enforced digital signatures for programs Linux Security Module: facilitate kernel loadable security extensions Objective: vulnerability tolerance

4. 02/03/14 Copyright © 2002 WireX Communications, Inc. 4 Technical Approach: Abstract Approach –Local intrusion response –Catch intrusion in process –Halt exploited component The Canary Technique Detect attacks in progress: –Make symptoms of attack mode obvious –Place a sacrificial canary where an attack will show tampering –Monitor canary If canary destroyed, then attack is happening

5. 02/03/14 Copyright © 2002 WireX Communications, Inc. 5 Quick Review Results previous to this project StackGuard: protection from “stack smashing” buffer overflows SubDomain: lightweight mandatory access controls Last Year’s Autonomix results FormatGuard: protection from printf format bugs USENIX Security 2001 paper Open source In Immunix 7.0 products RaceGuard: protection from temp file races USENIX Security 2001 paper Didn’t quite make the product cut; in next drop Relative Invulnerability: empirical measurement of effectiveness of these tools, individually and in combination

6. 02/03/14 Copyright © 2002 WireX Communications, Inc. 6 Major Achievement: Low-Effort Protection These tools are highly transparent: –Performance overhead: under 2% across the board, usually lower –Compatibility issues: minimal Under 5% of all Linux programs need trivial source patches to compile with StackGuard and FormatGuard RaceGuard works on binary code, breaks nothing –Administrative overhead: nil

7. 02/03/14 Copyright © 2002 WireX Communications, Inc. 7 Proposed Metric: Relative Invulnerability Compare a “base” system against a system protected with Immunix tools Count the number of known vulnerabilities stopped by the technology “Relative Invulnerability”: % of vulnerabilities stopped

8. 02/03/14 Copyright © 2002 WireX Communications, Inc. 8 Immunix Relative Invulnerability Immunix System 7: –Based on Red Hat 7.0 –Compare Immunix vulnerability to Red Hat’s Errata page (plus a few they don’t talk about :-) October 1, 2000 - May 25, 2001 –57 vulnerabilities total –16 remote, 41 local –53 penetration, 4 DoS –13 remote penetration

9. 02/03/14 Copyright © 2002 WireX Communications, Inc. 9 Immunix Relative Invulnerability

10. 02/03/14 Copyright © 2002 WireX Communications, Inc. 10 New Stuff Incremental work: FormatGuard: refinement to improve coverage RaceGuard: refinement to close hole New Autonomix Component Technologies PointGuard: generalized StackGuard CryptoMark: kernel-enforced digital signatures for programs Linux Security Module: facilitate kernel loadable security extensions

11. 02/03/14 Copyright © 2002 WireX Communications, Inc. 11 New Stuff Incremental work: FormatGuard: refinement to improve coverage RaceGuard: refinement to close hole New Autonomix Component Technologies PointGuard: generalized StackGuard CryptoMark: kernel-enforced digital signatures for programs Linux Security Module: facilitate kernel loadable security extensions Today’s Focus

12. 02/03/14 Copyright © 2002 WireX Communications, Inc. 12 LSM: Linux Security Module Standard Linux kernel limited to classical UNIX security model: –root is everything –POSIX.1e Capabilities Linux kernel a common target for security research –Immunix: SubDomain, RaceGuard –Others: SELinux, RSBAC, LIDS, LOMAC, DTE, NAI Wrappers, Janus, SGI CAPP, etc.

13. 02/03/14 Copyright © 2002 WireX Communications, Inc. 13 LSM: Linux Security Module Unfortunately, none are standard to Linux –Maintained as kernel patches –To deploy them, must acquire a custom kernel Linus would like to support advanced security policy, but not willing to endorse one project. –Too political… “My security policy is better than yours.” –Linus is not a security expert, and doesn’t want to be –Linux is about choice anyway Solution: enrich Linux’s module interface to support security policy modules

14. 02/03/14 Copyright © 2002 WireX Communications, Inc. 14 LSM - Design Goal Create a general purpose framework to enable pluggable security modules –Be general enough to support existing security projects –Work with community to define each project's needs –Continue to support root/Capabilities, perhaps as a module

15. 02/03/14 Copyright © 2002 WireX Communications, Inc. 15 LSM Community 470 people subscribed to LSM mailing list Active participation (code :-) from: –WireX –SELinux (NAI) –SGI –IBM (at least three different locations) –Janus (David Wagner, UC Berkeley)

16. 02/03/14 Copyright © 2002 WireX Communications, Inc. 16 Constrained Design Space LSM needs to be: –generic enough for existing security modules –simple enough to be acceptable to the Linux core maintainers minimally intrusive patch easy to understand code –able to support POSIX.1e capabilities

17. 02/03/14 Copyright © 2002 WireX Communications, Inc. 17 LSM Design syscall interposition, i.e. wrappers at the syscall interface –not appropriate: leads to module bloat –already available by re-writing Linux syscall table Instead, we mediate access to internal kernel objects “May subject X access object Y for operation Z?”

18. 02/03/14 Copyright © 2002 WireX Communications, Inc. 18 LSM - Architecture User-level process Kernel LSM Module Open syscall Std. error checks Std. Security checks LSM hook: Complete request Policy engine examine context does request pass policy? grant or deny

19. 02/03/14 Copyright © 2002 WireX Communications, Inc. 19 LSM - Architecture User-level process Kernel LSM Module Open syscall Std. error checks Std. Security checks LSM hook: Complete request Policy engine examine context does request pass policy? grant or deny

20. 02/03/14 Copyright © 2002 WireX Communications, Inc. 20 LSM - Architecture User-level process Kernel LSM Module Open syscall Std. error checks Std. Security checks LSM hook: Complete request Policy engine examine context does request pass policy? grant or deny “ok with you?”

21. 02/03/14 Copyright © 2002 WireX Communications, Inc. 21 LSM - Architecture User-level process Kernel LSM Module Open syscall Std. error checks Std. Security checks LSM hook: Complete request Policy engine examine context does request pass policy? grant or deny “ok with you?” Yes or no

22. 02/03/14 Copyright © 2002 WireX Communications, Inc. 22 Hook Style Restrictive: module may only reject a request about to be granted Permissive: module may only permit a request about to be rejected Authoritative: module may totally over-rule standard kernel logic We chose restrictive hooks only, except for capabilities –Simplifies LSM patch for maximum acceptability to Linux community

23. 02/03/14 Copyright © 2002 WireX Communications, Inc. 23 Module Stacking Strong desire to compose modules However, composition in general is intractable Solution: stacking left to modules that want to stack –Stackable module must export an LSM-like interface “out the back” –Stackable module responsible for composing policy by taking down-chain module’s results under advisement

24. 02/03/14 Copyright © 2002 WireX Communications, Inc. 24 Hook Location

25. 02/03/14 Copyright © 2002 WireX Communications, Inc. 25 LSM System Call Many modules need a syscall interface for applications to talk directly to the module LSM provides a generic syscall interface, and makes the module MUX it –lsm(unsigned int id, unsigned int call, unsigned long *args)

26. 02/03/14 Copyright © 2002 WireX Communications, Inc. 26 Kinds of Hooks task hooks program loading hooks IPC hooks FS hooks network hooks meta-hooks

27. 02/03/14 Copyright © 2002 WireX Communications, Inc. 27 Performance Overhead Microbenchmark: lmbench –Tests various critical kernel functions, e.g. open, read/write, context switch, etc. –Worst case: 7% for trivial calls Macro: Khernelstone, i.e. time to make Linux kernel –overhead not measurable –LSM version actually measured faster, but we don’t claim LSM is an optimization :-)

28. 02/03/14 Copyright © 2002 WireX Communications, Inc. 28 Related Work Extensible kernels –Microkernels, SPIN, SCOUT, Synthetix, etc. All about safety: –prevent extensions from corrupting the kernel Insight: LSM doesn’t need that safety –System is completely at the mercy of security policy anyway –Go ahead and just trust LSM modules –Use simple dynamic linking technologies

29. 02/03/14 Copyright © 2002 WireX Communications, Inc. 29 Status & Modules LSM interface implemented & stable –Linux 2.4.16 and 2.5.1, actively tracking Modules: SELinux: NSA & NAI project to add RBAC and DTE to Linux DTE: GPL re-implementation of the classic Openwall: prevents various attacks involving symbolic and hard links POSIX.1e capabilities

30. 02/03/14 Copyright © 2002 WireX Communications, Inc. 30 OASIS Projects SCC: using SELinux via LSM Bob Balzer wants to do LSM for Windows Wrappers might consider porting to LSM –restrictive hooks may be a problem Others?

31. 02/03/14 Copyright © 2002 WireX Communications, Inc. 31 LSM - What's next Paper submitted; pending response Phase 1: –Submit to Linux 2.5 kernel –Pending on VFS reorg by Linux people Phase 2: –Consider extended support for Audit –More permissive hooks beyond Capabilities? –See if Linus is interested

32. 02/03/14 Copyright © 2002 WireX Communications, Inc. 32 Transition of Technology Open source: StackGuard, FormatGuard, and RaceGuard are all GPL’d Commercial: –All being incorporated into WireX Server Appliance products Server appliance: a server for dummies Thus the need for dummy-proof security For sale through eLinux.com, FlexiServe (UK) –Immunix OS 7.0: hardened Linux distribution Available for purchase through wirex.com and eLinux.com Licensed by Counterpane

33. 02/03/14 Copyright © 2002 WireX Communications, Inc. 33 Summary Component Autonomy: –Largely working software –Running this laptop: StackGuard, FormatGuard, RaceGuard, and SubDomain –Available piece wise, or integrated into Immunix OS and Immunix server appliances, at wirex.com, eLinux.com

34. 02/03/14 Copyright © 2002 WireX Communications, Inc. 34 LSM Web site: http://lsm.immunix.org Mailing list: on the web site BOF at USENIX? USENIX Security?