Lucas Davi

Privilege escalation attacks on android

Android is a modern and popular software platform for smartphones. Among its predominant features is an advanced security model which is based on application-oriented mandatory access control and sandboxing. This allows developers and users to restrict the execution of an application to the privileges it has (mandatorily) assigned at installation time. The exploitation of vulnerabilities in program code is hence believed to be confined within the privilege boundaries of an applications sandbox. However, in this paper we show that a privilege escalation attack is possible. We show that a genuine application exploited at runtime or a malicious application can escalate granted permissions. Our results immediately imply that Androids security model cannot deal with a transitive permission usage attack and Androids sandbox model fails as a last resort against malware and sophisticated runtime attacks.

Return-oriented programming without returns

We show that on both the x86 and ARM architectures it is possible to mount return-oriented programming attacks without using return instructions. Our attacks instead make use of certain instruction sequences that behave like a return, which occur with sufficient frequency in large libraries on (x86) Linux and (ARM) Android to allow creation of Turing-complete gadget sets. Because they do not make use of return instructions, our new attacks have negative implications for several recently proposed classes of defense against return-oriented programming: those that detect the too-frequent use of returns in the instruction stream; those that detect violations of the last-in, first-out invariant normally maintained for the return-address stack; and those that modify compilers to produce code that avoids the return instruction.

Just-In-Time Code Reuse: On the Effectiveness of Fine-Grained Address Space Layout Randomization

Fine-grained address space layout randomization (ASLR) has recently been proposed as a method of efficiently mitigating runtime attacks. In this paper, we introduce the design and implementation of a framework based on a novel attack strategy, dubbed just-in-time code reuse, that undermines the benefits of fine-grained ASLR. Specifically, we derail the assumptions embodied in fine-grained ASLR by exploiting the ability to repeatedly abuse a memory disclosure to map an applications memory layout on-the-fly, dynamically discover API functions and gadgets, and JIT-compile a target program using those gadgets -- all within a script environment at the time an exploit is launched. We demonstrate the power of our framework by using it in conjunction with a real-world exploit against Internet Explorer, and also provide extensive evaluations that demonstrate the practicality of just-in-time code reuse attacks. Our findings suggest that fine-grained ASLR may not be as promising as first thought.

ROPdefender: a detection tool to defend against return-oriented programming attacks

Modern runtime attacks increasingly make use of the powerful return-oriented programming (ROP) attack techniques and principles such as recent attacks on Apple iPhone and Acrobat products to name some. These attacks even work under the presence of modern memory protection mechanisms such as data execution prevention (DEP). In this paper, we present our tool, ROPdefender, that dynamically detects conventional ROP attacks (that are based on return instructions). In contrast to existing solutions, ROPdefender can be immediately deployed by end-users, since it does not rely on side information (e.g., source code or debugging information) which are rarely provided in practice. Currently, our tool adds a runtime overhead of 2x which is comparable to similar instrumentation-based tools.

Practical and lightweight domain isolation on Android

In this paper, we introduce a security framework for practical and lightweight domain isolation on Android to mitigate unauthorized data access and communication among applications of different trust levels (e.g., private and corporate). We present the design and implementation of our framework, TrustDroid, which in contrast to existing solutions enables isolation at different layers of the Android software stack: (1) at the middleware layer to prevent inter-domain application communication and data access, (2) at the kernel layer to enforce mandatory access control on the file system and on Inter-Process Communication (IPC) channels, and (3) at the network layer to mediate network traffic. For instance, (3) allows network data to be only read by a particular domain, or enables basic context-based policies such as preventing Internet access by untrusted applications while an employee is connected to the companys network. Our approach accurately addresses the demands of the business world, namely to isolate data and applications of different trust levels in a practical and lightweight way. Moreover, our solution is the first leveraging mandatory access control with TOMOYO Linux on a real Android device (Nexus One). Our evaluation demonstrates that TrustDroid only adds a negligible overhead, and in contrast to contemporary full virtualization, only minimally affects the batterys life-time.

Counterfeit Object-oriented Programming: On the Difficulty of Preventing Code Reuse Attacks in C++ Applications

Code reuse attacks such as return-oriented programming (ROP) have become prevalent techniques to exploit memory corruption vulnerabilities in software programs. A variety of corresponding defenses has been proposed, of which some have already been successfully bypassed -- and the arms race continues. In this paper, we perform a systematic assessment of recently proposed CFI solutions and other defenses against code reuse attacks in the context of C++. We demonstrate that many of these defenses that do not consider object-oriented C++ semantics precisely can be generically bypassed in practice. Our novel attack technique, denoted as counterfeit object-oriented programming (COOP), induces malicious program behavior by only invoking chains of existing C++ virtual functions in a program through corresponding existing call sites. COOP is Turing complete in realistic attack scenarios and we show its viability by developing sophisticated, real-world exploits for Internet Explorer 10 on Windows and Fire fox 36 on Linux. Moreover, we show that even recently proposed defenses (CPS, T-VIP, vfGuard, and VTint) that specifically target C++ are vulnerable to COOP. We observe that constructing defenses resilient to COOP that do not require access to source code seems to be challenging. We believe that our investigation and results are helpful contributions to the design and implementation of future defenses against control flow hijacking attacks.

Dynamic integrity measurement and attestation: towards defense against return-oriented programming attacks

Despite the many efforts made in recent years to mitigate runtime attacks such as stack and heap based buffer overflows, these attacks are still a common security concern in todays computing platforms. Attackers have even found new ways to enforce runtime attacks including use of a technique called return-oriented programming. Trusted Computing provides mechanisms to verify the integrity of all executable content in an operating system. But they only provide integrity at load-time and are not able to prevent or detect runtime attacks. To mitigate return-oriented programming attacks, we propose new runtime integrity monitoring techniques that use tracking instrumentation of program binaries based on taint analysis and dynamic tracing. We also describe how these techniques can be employed in a dynamic integrity measurement architecture (DynIMA). In this way we fill the gap between static load-time and dynamic runtime attestation and, in particular, extend trusted computing techniques to effectively defend against return-oriented programming attacks.

Readactor: Practical Code Randomization Resilient to Memory Disclosure

Code-reuse attacks such as return-oriented programming (ROP) pose a severe threat to modern software. Designing practical and effective defenses against code-reuse attacks is highly challenging. One line of defense builds upon fine-grained code diversification to prevent the adversary from constructing a reliable code-reuse attack. However, all solutions proposed so far are either vulnerable to memory disclosure or are impractical for deployment on commodity systems. In this paper, we address the deficiencies of existing solutions and present the first practical, fine-grained code randomization defense, called Read actor, resilient to both static and dynamic ROP attacks. We distinguish between direct memory disclosure, where the attacker reads code pages, and indirect memory disclosure, where attackers use code pointers on data pages to infer the code layout without reading code pages. Unlike previous work, Read actor resists both types of memory disclosure. Moreover, our technique protects both statically and dynamically generated code. We use a new compiler-based code generation paradigm that uses hardware features provided by modern CPUs to enable execute-only memory and hide code pointers from leakage to the adversary. Finally, our extensive evaluation shows that our approach is practical -- we protect the entire Google Chromium browser and its V8 JIT compiler -- and efficient with an average SPEC CPU2006 performance overhead of only 6.4%.

HAFIX: hardware-assisted flow integrity extension

Code-reuse attacks like return-oriented programming (ROP) pose a severe threat to modern software on diverse processor architectures. Designing practical and secure defenses against code-reuse attacks is highly challenging and currently subject to intense research. However, no secure and practical system-level solutions exist so far, since a large number of proposed defenses have been successfully bypassed. To tackle this attack, we present HAFIX (Hardware-Assisted Flow Integrity Extension), a defense against code-reuse attacks exploiting backward edges (returns). HAFIX provides fine-grained and practical protection, and serves as an enabling technology for future control-flow integrity instantiations. This paper presents the implementation and evaluation of HAFIX for the Intel® Siskiyou Peak and SPARC embedded system architectures, and demonstrates its security and efficiency in code-reuse protection while incurring only 2% performance overhead.

It's a TRaP: Table Randomization and Protection against Function-Reuse Attacks

Code-reuse attacks continue to evolve and remain a severe threat to modern software. Recent research has proposed a variety of defenses with differing security, efficiency, and practicality characteristics. Whereas the majority of these solutions focus on specific code-reuse attack variants such as return-oriented programming (ROP), other attack variants that reuse whole functions, such as the classic return-into-libc, have received much less attention. Mitigating function-level code reuse is highly challenging because one needs to distinguish a legitimate call to a function from an illegitimate one. In fact, the recent counterfeit object-oriented programming (COOP) attack demonstrated that the majority of code-reuse defenses can be bypassed by reusing dynamically bound functions, i.e., functions that are accessed through global offset tables and virtual function tables, respectively. In this paper, we first significantly improve and simplify the COOP attack. Based on a strong adversarial model, we then present the design and implementation of a comprehensive code-reuse defense which is resilient against reuse of dynamically-bound functions. In particular, we introduce two novel defense techniques: (i) a practical technique to randomize the layout of tables containing code pointers resilient to memory disclosure and (ii) booby trap insertion to mitigate the threat of brute-force attacks iterating over the randomized tables. Booby traps serve the dual purpose of preventing fault-analysis side channels and ensuring that each table has sufficiently many possible permutations. Our detailed evaluation demonstrates that our approach is secure, effective, and practical. We prevent realistic, COOP-style attacks against the Chromium web browser and report an average overhead of 1.1% on the SPEC CPU2006 benchmarks.