Remote attestation of system integrity is an essential part of trusted computing. However, current remote attestation techniques only provide integrity proofs of static properties of the system. To address this problem we present a novel remote dynamic attestation system named ReDAS (Remote Dynamic Attestation System) that provides integrity evidence for dynamic system properties. Such dynamic system properties represent the runtime behavior of the attested system, and enable an attester to prove its runtime integrity to a remote party. ReDAS currently provides two types of dynamic system properties for running applications: structural integrity and global data integrity. In this work, we present the challenges of remote dynamic attestation, provide an in-depth security analysis and introduce a first step towards providing a complete runtime dynamic attestation framework. Our prototype implementation and evaluation with real-world applications show that we can improve on current static attestation techniques with an average performance overhead of 8%.

In biology, a vaccine is a weakened strain of a virus or bacterium that is intentionally injected into the body for the purpose of stimulating antibody production. Inspired by this idea, we propose a packet vaccine mechanism that randomizes address-like strings in packet payloads to carry out fast exploit detection and signature generation. An exploit with a randomized jump address behaves like a vaccine: it will likely cause an exception in a vulnerable program’s process when attempting to hijack the control flow, and thereby expose itself. Taking that exploit as a template, our signature generator creates a set of new vaccines to probe the program in an attempt to uncover the necessary conditions for the exploit to happen. A signature is built upon these conditions to shield the underlying vulnerability from further attacks. In this way, packet vaccine detects exploits and generates signatures in a black-box fashion, that is, not relying on the knowledge of a vulnerable program’s source and binary code. Therefore, it even works on the commodity software obfuscated for the purpose of copyright protection. In addition, since our approach avoids the expense of tracking the program’s execution flow, it performs almost as fast as a normal run of the program and is capable of generating a signature of high quality within seconds or even subseconds. We present the design of the packet vaccine mechanism and an example of its application. We also describe our proof-of-concept implementation and the evaluation of our technique using real exploits.

Understanding security bugs in a vulnerable program is a non-trivial task, even if the target program is known to be vulnerable. Though there exist debugging tools that facilitate the vulnerability analysis and debugging process, human developers still need to manually trace the program execution most of the times. This makes security debugging a difficult and tiresome task even for experienced programmers. In this paper, we present the development of a novel security debugging tool called CBones (SeeBones, where bones is an analogy of program structures). CBones is intended to fully automate the analysis of a class of security vulnerabilities in C programs, the exploits of which would compromise the integrity of program structures satisfied by all legitimate binaries compiled from C source code. In other words, CBones automatically discovers how unknown vulnerabilities in C programs are exploited based on program structural constraints. Unlike the previous approaches, CBones can automatically identify exploit points of unknown security bugs without requiring a training phase, source code access (analysis or instrumentation), or additional hardware supports. To validate the effectiveness of this approach, we evaluate CBones with 12 real-world applications that contain a wide range of vulnerabilities. Our results show that CBones can discover all security bugs with no false alarms, pinpoint the corrupting instructions, and provide information to facilitate the understanding of how an attack exploits a security bug.

Software vulnerabilities have been the main contributing factor to the Internet security problems such as fast spreading worms. Among these software vulnerabilities, memory corruption vulnerabilities such as buffer overflow and format string bugs have been the most common ones exploited by network-based attacks. Many security countermeasures (e.g., patching, automatic signature generation for intrusion detection systems) require vulnerability information to function correctly. However, despite many years of research, automatically identifying unknown software vulnerabilities still remains an open problem.In this paper, we present the development of a security debugging tool named MemSherlock, which can automatically identify unknown memory corruption vulnerabilities upon the detection of malicious payloads that exploit such vulnerabilities. MemSherlock provides critical information for unknown memory corruption vulnerabilities, including (1) the corruption point in the source code (i.e., the statement that allows the exploitation of memory corruption vulnerability), (2) the slice of source code that helps the malicious input to reach the corruption point, and (3) the description of how the malicious input exploits the unknown vulnerability. We evaluate MemSherlock with a set of 11 real-world applications that have buffer overflow, heap overflow, and format string vulnerabilities. The evaluation results indicate that MemSherlock is a useful tool to facilitate the automatic vulnerability analysis process.

Address space randomization is an emerging and promising method for stopping a broad range of memory corruption attacks. By randomly shifting critical memory regions at process initialization time, address space randomization converts an otherwise successful malicious attack into a benign process crash. However, existing approaches either introduce insufficient randomness, or require source code modification. While insufficient randomness allows successful brute-force attacks, as shown in recent studies, the required source code modification prevents this effective method from being used for commodity software, which is the major source of exploited vulnerabilities on the Internet. We propose Address Space Layout Permutation (ASLP) that introduces high degree of randomness (or high entropy) with minimal performance overhead. Essential to ASLP is a novel binary rewriting tool that can place the static code and data segments of a compiled executable to a randomly specified location and performs fine-grained permutation of procedure bodies in the code segment as well as static data objects in the data segment. We have also modified the Linux operating system kernel to permute stack, heap, and memory mapped regions. Together, ASLP completely permutes memory regions in an application. Our security and performance evaluation shows minimal performance overhead with orders of magnitude improvement in randomness (e.g., up to 29 bits of randomness on a 32-bit architecture).

In biology,a vaccine is a weakened strain of a virus or bacterium that is intentionally injected into the body for the purpose of stimulating antibody production.Inspired by this idea, we propose a packet vaccine mechanism that randomizes address-like strings in packet payloads to carry out fast exploit detection, vulnerability diagnosis and signature generation. An exploit with a randomized jump address behaves like a vaccine: it will likely cause an exception in a vulnerable program's process when attempting to hijack the control flow,and thereby expose itself. Taking that exploit as a template, our signature generator creates a set of new vaccines to probe the program, in an attempt to uncover the necessary conditions for the exploit to happen. A signature is built upon these conditions to shield the underlying vulnerability from further attacks. In this way, packet vaccine detects and fllters exploits in a black-box fashion,i.e., avoiding the expense of tracking the program's execution flow. We present the design of the packet vaccine mechanism and an example of its application. We also describe our proof-of-concept implementation and the evaluation of our technique using real exploits.

Cyber attacks against networked computers have become relentless in recent years. The most common attack method is to exploit memory corruption vulnerabilities such as buffer overflow and format string bugs. This paper presents a technique to automatically identify both known and unknown memory corruption vulnerabilities. Based on the observation that a randomized program usually crashes upon a memory corruption attack, this technique uses the crash as a trigger to initiate an automatic diagnosis algorithm. The output of the diagnosis includes the instruction that is tricked to corrupt data, the call stack at the time of corruption, and the propagation history of corrupted data. These results provide useful information in fixing the vulnerabilities. Moreover, the diagnosis process also generates a signature of the attack using data/address values embedded in the malicious input message, and is used to block future attacks. Such a signature is further associated with the program execution state to reduce false positives without decreasing the detection rate. The proposed techniques enable the development of a decentralized self-diagnosing and self-protecting defense mechanism for networked computers. We report the implementation experience and experimental evaluation of a prototype system on Linux.