[LLVMdev] Proposal for GSOC : KCoFI

Aditya Verma IDD M Tech Computer Sc & Engg., IIT(BHU), Varanasi (U.P.) aditya.verma.cse12 at iitbhu.ac.in
Fri Mar 27 07:54:54 PDT 2015

can anyone please review my proposal. I need suggestions on timeline on the
PNaCL improvements and also its improvements.

*Project Goals:*
The primary objective of this project is to implement stronger SFI
mechanism in existing kernel of KCoFI.The following are three broad
improvements I aim to implement in KCoFI:
      1 .Implement a stronger call graph using libLTO tool.
      2.To replace KCoFI's SFI instrumehntation with that found in Portable
Native Client (PNaCL).

CFI is a compiler based security mechanism that protects against the
malicious programs that hijack the flow of control of the program*[1]*.
KCoFI *[2]* is a security mechanism for operating system kernel that
extends the CFI technique to os kernel. Thus KCoFI is a security mechanism
that protects commodity operating systems from classical control- flow
hijack attacks, return-to-user attacks, and code segment modification
KCoFI uses traditional label-based protection for programmed indirect jumps
*[1] *but adds a thin run-time layer linked into the OS that protects some
key OS data structures like thread stacks and monitors all low-level state
manipulations performed by the OS.
KCoFI is an LLVM based kernel. In this project I aim to undertake the
improvements in the KCoFI mechanism to make it stronger against ever
growing future attacks.
Software Fault Isolation(SFI) is the act of separating distrusted
extensions that are possibly faulty.

This project is organized as a two part project in which the first part
aims to implement a stronger call graph and the second part integrates the
SFI Instrumentation found in PNaCl(Portable Native Client) to KCoFI and
replace the older SFI Instrumentations.

*Portable Native Client* extends that technology of sandboxing used by
Native CLlent with architecture independence, letting developers compile
their code once to run in any website and on any architecture with
ahead-of-time (AOT) translation.
This project will make use of Software Fault Isolation(SFI)
Instrumentations of PNaCL and integrate them with KCoFI while replacing the
older SFI Instrumentations of KCoFI.

The following is the things to do in the project:
*1. Implementing a stronger call graph:* in this part of the project the
FreeBSD kernel will be compiled using the libTO tool. This will involve
writing patches that build to IR, use llvm-link to run LTO and then link
the resulting binary. This project will involve delving further into the
llvm bundle. It will requires modifying the CFI MachineFunctionPass to
support multiple labels.
Since, KCoFI currently uses a really weak call-graph (all functions and
call sites are equivalence-classed), thus after compiling the FreeBSD
kernel with libLTO, first task to do is to improve the CFI instrumentation
to enforce a more accurate call graph. This implementation will be done by
using libLTO to compute a whole-kernel call graph and then using different
CFI labels for different nodes in the call graph.
 It could be improved by using libLTO to compute a whole-kernel call graph
and then using different CFI labels for different nodes in the call graph.

A second improvement would be to remove CFI labels that are unnecessary.
Any function that is only called directly does not need a CFI label.
Again, to make this optimization work, a whole-kernel analysis will be done
via libLTO.

Another improvement to undertake is to implement Forward Edge Call graph

*2.Replace KCoFI's SFI instrumentation with the Instrumentation  found in
Portable Native Client (PNaCL): *
The PNaCL implementation should be much better than KCoFI's. PNacl and NaCL
both are open source.The SFI approach NaCl takes expects a single sandbox
per process, which doesn't seem very suitable to kernel use. It can be made
to support multiple sandboxes in the same address space, which is the work
that I will undertake as a part of the project.

This project will require modifying the CFI MachineFunctionPass and using
either the LLVM CallGraphAnalysis pass or the DSA CallGraph pass.  It will
also require modification of the low-level KCoFI run-time library (i.e.,
the implementation of the SVA-OS instructions, as some of them need to do
CFI checks).

*Timeline and Roadmap:*
Since it is a big project and I will be using the existing code of KCoFI I
will be going ahead with the Iterative Enhancement model of Software
Development Process
*Week 1:*Discussion with my mentor on documentation style and the code.
*Week 2 to Week 3:* Writing the patches that build to IR and use llvm- link
to run LTO with FreeBSD
*Week 4 to Week 6:* Compiling the kernel with libLTO tool. In this week I
will write the methods to build a strong call graph.
*Week 7:* Testing the call graphs with proper benchmarking.
*Week 8 to Week 9:* using the PNaCl and NaCL SFI techniques and
implementing them in the kernel.
*Week 10:* using the NaCl to support multiple sandboxing in same address
space for for multiple processes in an os kernel.
*Week 11:* testing the new sandboxing techniques together with the previous
techniques of stronger call graph imlemntation with proper benchmarking of
the compile time.
*WEEK 12:* Evaluating the performance of the improvements.

*Criteria of Success:*
1. Newer stronger call graph implementation. Evaluation done using proper
2.Implmentation of SFI Instrumentation of PNaCl,

Thus by the end of the summer improving the call graph, replacing the SFI
instrumentation, and evaluating the performance will be the work that I
will complete.

*Brief Bio:*
I am a third year undergraduate in Computer Science and Engineering. My
interests lie in Computer Architecture and Operating System. I like working
with the machinistic aspects of computer science. My rigorous programming
experience has spanned across fields such as Database Management System,
Operating Systems, Networking , Artificial Intelligence and Machine
Learning. I see myself as a hardworking and sincere, at the same time
passionate about building newer software. I also have experience programing
the Microprocessor 8085 and 8086.
I am proficient in C and C++.

[1] M. Abadi, M. Budiu, U. Erlingsson, and J. Ligatti, “Control-flow
integrity principles, implementations, and applications,” ACM Trans. Inf.
Syst. Secur. , vol. 13, pp. 4:1–4:40, November 2009.
[2] KCoFI: Complete Control-Flow Integrity for Commodity Operating System
[3] M. Zhang and R. Sekar, “Control flow integrity for COTS binaries,” in
Proceedings of the 22nd USENIX conference on Security , ser. SEC’13.
Berkeley, CA, USA: USENIX Association, 2013, pp. 337–352.
[4] J. Criswell, A. Lenharth, D. Dhurjati, and V. Adve, “Secure Virtual
Architecture: A Safe Execution Environment for Commodity Operating
Systems,” in Proc. ACM SIGOPS Symp. on Op. Sys. Principles
[5] Caroline Tice , Tom Roeder , Peter Collingbourne , Stephen Checkoway ,
Úlfar Erlingsson , Luis Lozano , Geoff Pike, Enforcing forward-edge
control-flow integrity in GCC & LLVM, Proceedings of the 23rd USENIX
conference on Security Symposium, p.941-955, August 20-22, 2014, San Diego,
Aditya Verma
Junior Undergraduate
IDD Computer Sc & Engg
IIT(BHU), Varanasi(UP)
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