Abstract:With the general availability of closed-source software for various CPU architectures, there is a need to identify security-critical vulnerabilities at the binary level. Unfortunately, existing bug finding methods fall short in that they i) require source code, ii) only work on a single architecture (typically x86), or iii) rely on dynamic analysis, which is difficult for embedded devices. In this paper, we propose a system to derive bug signatures for known bugs. First, we compute semantic hashes for the basic blocks of the binary. When can then use these semantics to find code parts in the binary that behave similarly to the bug signature, effectively revealing code parts that contain the bug. As a result, we can find vulnerabilities, e.g., the famous Heartbleed vulnerabilities, in buggy binary code for any of the supported architectures (currently, ARM, MIPS and x86).

With the general availability of closed-source software for various CPU architectures, there is a need to identify security-critical vulnerabilities at the binary level to perform a vulnerability assessment. Unfortunately, existing bug finding methods fall short in that they i) require source code, ii) only work on a single architecture (typically x86), or iii) rely on dynamic analysis, which is inherently difficult for embedded devices.In this paper, we propose a system to derive bug signatures for known bugs. We then use these signatures to find bugs in binaries that have been deployed on different CPU architectures (e.g., x86 vs. MIPS). The variety of CPU architectures imposes many challenges, such as the incomparability of instruction set architectures between the CPU models. We solve this by first translating the binary code to an intermediate representation, resulting in assignment formulas with input and output variables. We then sample concrete inputs to observe the I/O behavior of basic blocks, which grasps their semantics. Finally, we use the I/O behavior to find code parts that behave similarly to the bug signature, effectively revealing code parts that contain the bug.We have designed and implemented a tool for crossarchitecture bug search in executables. Our prototype currently supports three instruction set architectures (x86, ARM, and MIPS) and can find vulnerabilities in buggy binary code for any of these architectures. We show that we can find Heartbleed vulnerabilities, regardless of the underlying software instruction set. Similarly, we apply our method to find backdoors in closedsource firmware images of MIPS-and ARM-based routers.

It is a well-known issue that attack primitives which exploit memory corruption vulnerabilities can abuse the ability of processes to automatically restart upon termination. For example, network services like FTP and HTTP servers are typically restarted in case a crash happens and this can be used to defeat Address Space Layout Randomization (ASLR). Furthermore, recently several techniques evolved that enable complete process memory scanning or code-reuse attacks against diversified and unknown binaries based on automated restarts of server applications. Until now, it is believed that client applications are immune against exploit primitives utilizing crashes. Due to their hard crash policy, such applications do not restart after memory corruption faults, making it impossible to touch memory more than once with wrong permissions. In this paper, we show that certain client application can actually survive crashes and are able to tolerate faults, which are normally critical and force program termination. To this end, we introduce a crash-resistance primitive and develop a novel memory scanning method with memory oracles without the need for control-flow hijacking. We show the practicability of our methods for 32-bit Internet Explorer 11 on Windows 8.1, and Mozilla Firefox 64-bit (Windows 8.1 and Linux 3.17.1). Furthermore, we demonstrate the advantages an attacker gains to overcome recent code-reuse defenses. Latest advances propose fine-grained re-randomization of the address space and code layout, or hide sensitive information such as code pointers to thwart tampering or misuse. We show that these defenses need improvements since crash-resistance weakens their security assumptions. To this end, we introduce the concept of Crash-Resistant Oriented Programming (CROP). We believe that our results and the implications of memory oracles will contribute to future research on defensive schemes against code-reuse attacks. Permission to freely reproduce all or part of this paper for noncommercial purposes is granted provided that copies bear this notice and the full citation on the first page. Reproduction for commercial purposes is strictly prohibited without the prior written consent of the Internet Society, the first-named author (for reproduction of an entire paper only), and the author's employer if the paper was prepared within the scope of employment.

Memory disclosure attacks play an important role in the exploitation of memory corruption vulnerabilities. By analyzing recent research, we observe that bypasses of defensive solutions that enforce control-flow integrity or attempt to detect return-oriented programming require memory disclosure attacks as a fundamental first step. However, research lags behind in detecting such information leaks. In this paper, we tackle this problem and present a system for finegrained, automated detection of memory disclosure attacks against scripting engines. The basic insight is as follows: scripting languages, such as JavaScript in web browsers, are strictly sandboxed. They must not provide any insights about the memory layout in their contexts. In fact, any such information potentially represents an ongoing memory disclosure attack. Hence, to detect information leaks, our system creates a clone of the scripting engine process with a re-randomized memory layout. The clone is instrumented to be synchronized with the original process. Any inconsistency in the script contexts of both processes appears when a memory disclosure was conducted to leak information about the memory layout. Based on this detection approach, we have designed and implemented Detile (detection of information leaks), a prototype for the JavaScript engine in Microsoft's Internet Explorer 10/11 on Windows 8.0/8.1. An empirical evaluation shows that our tool can successfully detect memory disclosure attacks even against this proprietary software.

Memory corruption vulnerabilities are still a severe threat for software systems. To thwart the exploitation of such vulnerabilities, many different kinds of defenses have been proposed in the past. Most prominently, Control-Flow Integrity (CFI) has received a lot of attention recently. Several proposals were published that apply coarse-grained policies with a low performance overhead. However, their security remains questionable as recent attacks have shown. To ease the assessment of a given CFI implementation, we introduce a framework to discover code gadgets for code-reuse attacks that conform to coarse-grained CFI policies. For this purpose, binary code is extracted and transformed to a symbolic representation in an architectureindependent manner. Additionally, code gadgets are verified to provide the needed functionality for a security researcher. We show that our framework finds more CFI-compatible gadgets compared to other code gadget discovery tools. Furthermore, we demonstrate that code gadgets needed to bypass CFI solutions on the ARM architecture can be discovered by our framework as well.