Nethammer: Inducing Rowhammer Faults through Network Requests (1805.04956v1)

Abstract: 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.

• The paper introduces Nethammer, the first method to induce Rowhammer memory faults remotely through crafted network requests, bypassing the need for local code execution.
• Nethammer exploits systems using uncached memory or performing cache evictions during network processing, such as those with Intel Cache Allocation Technology (CAT), to repeatedly access specific DRAM locations.
• Experiments show Nethammer can cause significant remote damage, including system crashes and file corruption, highlighting the need for new defense strategies in cloud and networked environments.

Nethammer: Inducing Rowhammer Faults through Network Requests

The paper "Nethammer: Inducing Rowhammer Faults through Network Requests" is a significant contribution to the field of systems security, exploring the feasibility of generating Rowhammer-induced faults remotely through network traffic. This paper is a departure from traditional approaches that required local code execution, thus broadening the threat model associated with Rowhammer vulnerabilities and necessitating a re-evaluation of defense mechanisms.

Overview of Nethammer

Nethammer introduces the first truly remote method for exploiting the Rowhammer bug, which relies on network requests to induce memory faults rather than localized code execution. The core of this attack involves sending crafted network packets to a target machine, exploiting patterns of memory access to induce faults in the Dynamic Random Access Memory (DRAM) without executing any attacker-controlled code on the victim system. This approach effectively bypasses previous assumptions and defenses regarding Rowhammer attacks, which were primarily designed to address scenarios where the attacker has local access to the machine.

Technical Approach

The researchers demonstrated that systems utilizing uncached memory or executing flush instructions during the processing of network requests are vulnerable. Furthermore, systems using Intel Cache Allocation Technology (CAT) for quality-of-service guarantees further amplify the vulnerability by facilitating rapid cache eviction. This is particularly true when CAT limits cache availability for applications or virtual machines, leading to frequent DRAM accesses when certain cache lines are flushed during network packet processing.

The methodology employed by the authors leverages the network packet flow to repeatedly access specific memory locations, thereby exploiting Rowhammer's underlying mechanism of inducing bit flips through high-frequency row activation. The paper noted that exploiting these bit flips could compromise system integrity, leading to both temporary and persistent denial-of-service scenarios.

Experimental Evaluation

Through rigorous experimentation on a variety of hardware configurations, including personal computers, servers, and mobile devices, the authors showed that Nethammer could induce an alarming rate of bit flips remotely. They documented attacks that resulted in system crashes, corruption of critical filesystems, and other integrity-compromising outcomes. This illustrates the pervasive nature of the vulnerability and highlights the need for better protective measures.

Implications and Future Directions

The implications of this research are far-reaching, particularly in the context of cloud computing and network-connected devices where remote attacks are a considerable threat. Nethammer necessitates a re-examination of threat models and prompts demand for more robust countermeasures beyond existing software defenses, which are inadequate in addressing the remote aspect of such attacks. Hardware-based solutions, such as those involving error-correcting code (ECC) memory, might provide partial mitigation, but the paper suggests that these too have limitations.

Future research should explore mitigation strategies focusing on the root cause of Rowhammer vulnerabilities and consider novel approaches for detecting and blocking such attacks promptly. An in-depth analysis of memory controller policies and their relationship with access patterns could also offer insights into designing more resistant DRAM architectures.

In conclusion, Nethammer not only expands the scope of Rowhammer attacks but also underscores the critical need for revisiting existing security paradigms. As devices become increasingly interconnected, acknowledging the potential for remote exploits like Nethammer is vital, and this research is an essential step towards enhancing memory reliability and system security in the digital age.