Thwarting Advanced Code-reuse Attacks

Code-reuse attacks are the leading mechanism by which attackers infiltrate systems. Various mitigation techniques have been proposed to defend against these attacks, the most prominent one being control-flow integrity (CFI). CFI is a principled approach that restricts all indirect control flows to adhere to a statically determined control-flow graph (CFG). CFI has gained widespread adoption in industry -- such as Microsoft Control Flow Guard and Intel Control-flow Enforcement Technology. However, recent attacks dubbed CFG mimicry attacks, like control flow bending and counterfeit object-oriented programming, have shown that code-reuse attacks are still possible without violating CFI. Furthermore, data-oriented programming (DOP) has generalized non-control data attacks to achieve Turing-complete computation; it accomplishes this by repeatedly corrupting non-control data to execute a sequence of instructions within the legitimate control flow of the program. In this dissertation, we present techniques to mitigate these advanced code-reuse attacks. First, this dissertation presents a novel approach to thwart advanced control flow attacks called ProxyCFI. ProxyCFI replaces all code pointers in a program with a less powerful construct: pointer proxies. Pointer proxies are random identifiers associated with each legitimate control flow edge in the program. Pointer proxy values are defined per-function and are re-randomized at program load time to mitigate their disclosure. To ensure that the approach covers the entire control flow of the program, we have a load-time verifier built-in the program loader that performs reachability analyses of the code and verify that there is no vulnerable control flow transfer. ProxyCFI delivers these protections incurring minimal performance overhead, while stopping a broad range of real-world attacks and achieving a 100% coverage of the RIPE x86-64 attack suite. Second, this dissertation evaluates the effectiveness of previously proposed stack layout randomization techniques against attacks that only utilize relative offset between allocations (e.g., data-oriented programming) and demonstrate that they are ineffective at stopping real-world DOP exploits. We then propose Smokestack, a runtime stack-layout randomization technique that addresses the problems with prior approaches. Smokestack instruments programs to randomize their stack layout at runtime for each invocation of a function. By doing so, Smokestack minimizes the utility of information gained in the probes of chained DOP attacks for later attack stages. Our evaluation on SPEC benchmarks and various real-world applications shows that Smokestack, with a cryptographically secure pseudo random generator, can stop DOP attacks with an average slowdown of 8.7%. Lastly, we present a technique to randomize heap allocations at runtime to prevent attackers from orchestrating advanced control flow attacks as well as DOP attacks through heap-resident variables. To this end, we explored the use of multi-variant execution (MVX) with each variant having uniquely seeded random heap allocators. This capability enables our system to automatically track heap allocation pointers without the need for storing explicit meta-data. We then re-randomize heap allocations to thwart attacks that perform runtime probes to discover allocations. This technique will provide modular heap allocation protection while maintaining compatibility with legacy binaries. In all, this thesis presents novel techniques that carve out a new space in advanced code-reuse attack protections, offering a protection strength as good or better than prior solutions. These techniques provide additional protections for advanced control flow attacks and DOP attacks, while incurring minimal performance overheads.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/155142/1/misiker_1.pd

Nethammer: Inducing Rowhammer Faults through Network Requests

A fundamental assumption in software security is that memory contents do not change unless there is a legitimate deliberate modification. Classical fault attacks show that this assumption does not hold if the attacker has physical access. Rowhammer attacks showed that local code execution is already sufficient to break this assumption. Rowhammer exploits parasitic effects in DRAM to modify the content of a memory cell without accessing it. Instead, other memory locations are accessed at a high frequency. All Rowhammer attacks so far were local attacks, running either in a scripted language or native code. In this paper, we present Nethammer. Nethammer is the first truly remote Rowhammer attack, without a single attacker-controlled line of code on the targeted system. Systems that use uncached memory or flush instructions while handling network requests, e.g., for interaction with the network device, can be attacked using Nethammer. Other systems can still be attacked if they are protected with quality-of-service techniques like Intel CAT. We demonstrate that the frequency of the cache misses is in all three cases high enough to induce bit flips. We evaluated different bit flip scenarios. Depending on the location, the bit flip compromises either the security and integrity of the system and the data of its users, or it can leave persistent damage on the system, i.e., persistent denial of service. We investigated Nethammer on personal computers, servers, and mobile phones. Nethammer is a security landslide, making the formerly local attack a remote attack

Nethammer: Inducing Rowhammer Faults through Network Requests

International audienceIn this paper, we present Nethammer, a remote Rowhammer attack without a single attacker-controlled line of code on the targeted system, i.e., not even JavaScript. Nethammer works on commodity consumer-grade systems that either are protected with quality-of-service techniques like Intel CAT or that use uncached memory, flush instructions, or non-temporal instructions while handling network requests (e.g., for interaction with the network device). We demonstrate that the frequency of the cache misses is in all three cases high enough to induce bit flips. Our evaluation showed that depending on the location, the bit flip compromises either the security and integrity of the system and the data of its users, or it can leave persistent damage on the system, i.e., persistent denial of service. We invalidate threat models of Rowhammer defenses building upon the assumption of a local attacker. Consequently, we show that most state-of-the-art defenses do not affect our attack. In particular, we demonstrate that target-row-refresh (TRR) implemented in DDR4 has no aggravating effect on local or remote Rowhammer attacks