Erik Kraft

Martin Schwarzl, Erik Kraft, Moritz Lipp et al.

Memory utilization can be reduced by merging identical memory blocks into copy-on-write mappings. Previous work showed that this so-called memory deduplication can be exploited in local attacks to break ASLR, spy on other programs,and determine the presence of data, i.e., website images. All these attacks exploit memory deduplication across security domains, which in turn was disabled. However, within a security domain or on an isolated system with no untrusted local access, memory deduplication is still not considered a security risk and was recently re-enabled on Windows by default. In this paper, we present the first fully remote memorydeduplication attacks. Unlike previous attacks, our attacks require no local code execution. Consequently, we can disclose memory contents from a remote server merely by sending and timing HTTP/1 and HTTP/2 network requests. We demonstrate our attacks on deduplication both on Windows and Linux and attack widely used server software such as Memcached and InnoDB. Our side channel leaks up to 34.41 B/h over the internet, making it faster than comparable remote memory-disclosure channels. We showcase our remote memory-deduplication attack in three case studies: First, we show that an attacker can disclose the presence of data in memory on a server running Memcached. We show that this information disclosure channel can also be used for fingerprinting and detect the correct libc version over the internet in 166.51 s. Second, in combination with InnoDB, we present an information disclosure attack to leak MariaDB database records. Third, we demonstrate a fully remote KASLR break in less than 4 minutes allowing to derandomize the kernel image of a virtual machine over the Internet, i.e., 14 network hops away. We conclude that memory deduplication must also be considered a security risk if only applied within a single security domain.

Daniel Gruss, Erik Kraft, Trishita Tiwari et al.

We present a new hardware-agnostic side-channel attack that targets one of the most fundamental software caches in modern computer systems: the operating system page cache. The page cache is a pure software cache that contains all disk-backed pages, including program binaries, shared libraries, and other files, and our attacks thus work across cores and CPUs. Our side-channel permits unprivileged monitoring of some memory accesses of other processes, with a spatial resolution of 4KB and a temporal resolution of 2 microseconds on Linux (restricted to 6.7 measurements per second) and 466 nanoseconds on Windows (restricted to 223 measurements per second); this is roughly the same order of magnitude as the current state-of-the-art cache attacks. We systematically analyze our side channel by demonstrating different local attacks, including a sandbox bypassing high-speed covert channel, timed user-interface redressing attacks, and an attack recovering automatically generated temporary passwords. We further show that we can trade off the side channel's hardware agnostic property for remote exploitability. We demonstrate this via a low profile remote covert channel that uses this page-cache side-channel to exfiltrate information from a malicious sender process through innocuous server requests. Finally, we propose mitigations for some of our attacks, which have been acknowledged by operating system vendors and slated for future security patches.