7,849 research outputs found
Synthesizing Certified Code
Code certification is a lightweight approach for formally demonstrating software quality. Its basic idea is to require code producers to provide formal proofs that their code satisfies certain quality properties. These proofs serve as certificates that can be checked independently. Since code certification uses the same underlying technology as program verification, it requires detailed annotations (e.g., loop invariants) to make the proofs possible. However, manually adding annotations to the code is time-consuming and error-prone. We address this problem by combining code certification with automatic program synthesis. Given a high-level specification, our approach simultaneously generates code and all annotations required to certify the generated code. We describe a certification extension of AutoBayes, a synthesis tool for automatically generating data analysis programs. Based on built-in domain knowledge, proof annotations are added and used to generate proof obligations that are discharged by the automated theorem prover E-SETHEO. We demonstrate our approach by certifying operator- and memory-safety on a data-classification program. For this program, our approach was faster and more precise than PolySpace, a commercial static analysis tool
CONFLLVM: A Compiler for Enforcing Data Confidentiality in Low-Level Code
We present an instrumenting compiler for enforcing data confidentiality in
low-level applications (e.g. those written in C) in the presence of an active
adversary. In our approach, the programmer marks secret data by writing
lightweight annotations on top-level definitions in the source code. The
compiler then uses a static flow analysis coupled with efficient runtime
instrumentation, a custom memory layout, and custom control-flow integrity
checks to prevent data leaks even in the presence of low-level attacks. We have
implemented our scheme as part of the LLVM compiler. We evaluate it on the SPEC
micro-benchmarks for performance, and on larger, real-world applications
(including OpenLDAP, which is around 300KLoC) for programmer overhead required
to restructure the application when protecting the sensitive data such as
passwords. We find that performance overheads introduced by our instrumentation
are moderate (average 12% on SPEC), and the programmer effort to port OpenLDAP
is only about 160 LoC.Comment: Technical report for CONFLLVM: A Compiler for Enforcing Data
Confidentiality in Low-Level Code, appearing at EuroSys 201
CUP: Comprehensive User-Space Protection for C/C++
Memory corruption vulnerabilities in C/C++ applications enable attackers to
execute code, change data, and leak information. Current memory sanitizers do
no provide comprehensive coverage of a program's data. In particular, existing
tools focus primarily on heap allocations with limited support for stack
allocations and globals. Additionally, existing tools focus on the main
executable with limited support for system libraries. Further, they suffer from
both false positives and false negatives.
We present Comprehensive User-Space Protection for C/C++, CUP, an LLVM
sanitizer that provides complete spatial and probabilistic temporal memory
safety for C/C++ program on 64-bit architectures (with a prototype
implementation for x86_64). CUP uses a hybrid metadata scheme that supports all
program data including globals, heap, or stack and maintains the ABI. Compared
to existing approaches with the NIST Juliet test suite, CUP reduces false
negatives by 10x (0.1%) compared to the state of the art LLVM sanitizers, and
produces no false positives. CUP instruments all user-space code, including
libc and other system libraries, removing them from the trusted code base
Embedded Program Annotations for WCET Analysis
We present __builtin_ais_annot(), a user-friendly, versatile way to transfer annotations (also known as flow facts) written on the source code level to the machine code level. To do so, we couple two tools often used during the development of safety-critical hard real-time systems, the formally verified C compiler CompCert and the static WCET analyzer aiT. CompCert stores the AIS annotations given via __builtin_ais_annot() in a special section of the ELF binary, which can later be extracted automatically by aiT
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