Alpenhorn: Bootstrapping Secure Communication without Leaking Metadata

Alpenhorn is the first system for initiating an encrypted connection between two users that provides strong privacy and forward secrecy guarantees for metadata (i.e., information about which users connected to each other) and that does not require out-of-band communication other than knowing the other user's Alpenhorn username (email address). This resolves a significant shortcoming in all prior works on private messaging, which assume an out-of-band key distribution mechanism. Alpenhorn's design builds on three ideas. First, Alpenhorn provides each user with an address book of friends that the user can call to establish a connection. Second, when a user adds a friend for the first time, Alpenhorn ensures the adversary does not learn the friend's identity, by using identity-based encryption in a novel wayto privately determine the friend's public key. Finally, when calling a friend, Alpenhorn ensures forward secrecy of metadata by storing pairwise shared secrets in friends' address books, and evolving them over time, using a new keywheel construction. Alpenhorn relies on a number of servers, but operates in an anytrust model, requiring just one of the servers to be honest. We implemented a prototype of Alpenhorn, and integrated it into the Vuvuzela private messaging system (which did not previously provide privacy or forward secrecy of metadata when initiating conversations). Experimental results show that Alpenhorn can scale to many users, supporting 10 million users on three Alpenhorn servers with an average call latency of 150 seconds and a client bandwidth overhead of 3.7 KB/sec

Making Linux Protection Mechanisms Egalitarian with UserFS

URL to paper on conference site: http://www.usenix.org/events/sec10/tech/UserFS provides egalitarian OS protection mechanisms in Linux. UserFS allows any user—not just the system administrator—to allocate Unix user IDs, to use chroot, and to set up firewall rules in order to confine untrusted code. One key idea in UserFS is representing user IDs as files in a /proc-like file system, thus allowing applications to manage user IDs like any other files, by setting permissions and passing file descriptors over Unix domain sockets. UserFS addresses several challenges in making user IDs egalitarian, including accountability, resource allocation, persistence, and UID reuse. We have ported several applications to take advantage of UserFS; by changing just tens to hundreds of lines of code, we prevented attackers from exploiting application-level vulnerabilities, such as code injection or missing ACL checks in a PHP-based wiki application. Implementing UserFS requires minimal changes to the Linux kernel—a single 3,000-line kernel module—and incurs no performance overhead for most operations, making it practical to deploy on real systems.Quanta Computer (Firm)Samsung Scholarship Foundatio

Cryptographic Treatment of CryptDB's Adjustable Join

In this document, we provide a cryptographic treatment of the adjustable join protocol from CryptDB. We also discuss how our scheme could be used outside of CryptDB because it provides a simple functionality that may be needed in other settings. Intuitively, it is a pseudorandom permutation where an external party not knowing the secret key can nonetheless adjust a ciphertext under one key to a ciphertext under a different key, given an adjustment token from a party that knows the secret key

Tolerating Malicious Device Drivers in Linux

URL to paper from conference siteThis paper presents SUD, a system for running existing Linux device drivers as untrusted user-space processes. Even if the device driver is controlled by a malicious adversary, it cannot compromise the rest of the system. One significant challenge of fully isolating a driver is to confine the actions of its hardware device. SUD relies on IOMMU hardware, PCI express bridges, and message-signaled interrupts to confine hardware devices. SUD runs unmodified Linux device drivers, by emulating a Linux kernel environment in user-space. A prototype of SUD runs drivers for Gigabit Ethernet, 802.11 wireless, sound cards, USB host controllers, and USB devices, and it is easy to add a new device class. SUD achieves the same performance as an in-kernel driver on networking benchmarks, and can saturate a Gigabit Ethernet link. SUD incurs a CPU overhead comparable to existing runtime driver isolation techniques, while providing much stronger isolation guarantees for untrusted drivers. Finally, SUD requires minimal changes to the kernel—just two kernel modules comprising 4,000 lines of code—which may at last allow the adoption of these ideas in practice

Asynchronous intrusion recovery for interconnected web services

Recovering from attacks in an interconnected system is difficult, because an adversary that gains access to one part of the system may propagate to many others, and tracking down and recovering from such an attack requires significant manual effort. Web services are an important example of an interconnected system, as they are increasingly using protocols such as OAuth and REST APIs to integrate with one another. This paper presents Aire, an intrusion recovery system for such web services. Aire addresses several challenges, such as propagating repair across services when some servers may be unavailable, and providing appropriate consistency guarantees when not all servers have been repaired yet. Experimental results show that Aire can recover from four realistic attacks, including one modeled after a recent Facebook OAuth vulnerability; that porting existing applications to Aire requires little effort; and that Aire imposes a 19--30% CPU overhead and 6--9 KB/request storage cost for Askbot, an existing web application.National Science Foundation (U.S.) (NSF award CNS-1053143)United States. Defense Advanced Research Projects Agency (DARPA Clean-slate design of Resilient, Adaptive, Secure Hosts (CRASH) program under contract #N66001-10-2-4089

Optimizing unit test execution in large software programs using dependency analysis

Tao is a system that optimizes the execution of unit tests in large software programs and reduces the programmer wait time from minutes to seconds. Tao is based on two key ideas: First, Tao focuses on efficiency, unlike past work that focused on avoiding false negatives. Tao implements simple and fast function-level dependency tracking that identifies tests to run on a code change; any false negatives missed by this dependency tracking are caught by running the entire test suite on a test server once the code change is committed. Second, to make it easy for programmers to adopt Tao, it incorporates the dependency information into the source code repository. This paper describes an early prototype of Tao and demonstrates that Tao can reduce unit test execution time in two large Python software projects by over 96% while incurring few false negatives.United States. Defense Advanced Research Projects Agency (DARPA Clean-slate design of Resilient, Adaptive, Secure Hosts (CRASH) program under contract #N66001-10-2-4089)National Science Foundation (U.S.) (NSF award CNS-1053143

Retroactive auditing

Retroactive auditing is a new approach for detecting past intrusions and vulnerability exploits based on security patches. It works by spawning two copies of the code that was patched, one with and one without the patch, and running both of them on the same inputs observed during the system's original execution. If the resulting outputs differ, an alarm is raised, since the input may have triggered the patched vulnerability. Unlike prior tools, retroactive auditing does not require developers to write predicates for each vulnerability.United States. Defense Advanced Research Projects Agency. Clean-slate design of Resilient, Adaptive, Secure Hosts (Contract number N66001-10-2-4089)National Natural Science Foundation (CNS-1053143

Separating Web Applications from User Data Storage with BSTORE

URL to paper from conference siteThis paper presents BSTORE, a framework that allows developers to separate their web application code from user data storage. With BSTORE, storage providers implement a standard file system API, and applications access user data through that same API without having to worry about where the data might be stored. A file system manager allows the user and applications to combine multiple file systems into a single namespace, and to control what data each application can access. One key idea in BSTORE’s design is the use of tags on files, which allows applications both to organize data in different ways, and to delegate fine-grained access to other applications. We have implemented a prototype of BSTORE in Javascript that runs in unmodified Firefox and Chrome browsers. We also implemented three file systems and ported three different applications to BSTORE. Our prototype incurs an acceptable performance overhead of less than 5% on a 10Mbps network connection, and porting existing clientside applications to BSTORE required small amounts of source code changes.Quanta Computer (Firm)Google (Firm

CryptDB: A Practical Encrypted Relational DBMS

CryptDB is a DBMS that provides provable and practical privacy in the face of a compromised database server or curious database administrators. CryptDB works by executing SQL queries over encrypted data. At its core are three novel ideas: an SQL-aware encryption strategy that maps SQL operations to encryption schemes, adjustable query-based encryption which allows CryptDB to adjust the encryption level of each data item based on user queries, and onion encryption to efficiently change data encryption levels. CryptDB only empowers the server to execute queries that the users requested, and achieves maximum privacy given the mix of queries issued by the users. The database server fully evaluates queries on encrypted data and sends the result back to the client for final decryption; client machines do not perform any query processing and client-side applications run unchanged. Our evaluation shows that CryptDB has modest overhead: on the TPC-C benchmark on Postgres, CryptDB reduces throughput by 27% compared to regular Postgres. Importantly, CryptDB does not change the innards of existing DBMSs: we realized the implementation of CryptDB using client-side query rewriting/encrypting, user-defined functions, and server-side tables for public key information. As such, CryptDB is portable; porting CryptDB to MySQL required changing 86 lines of code, mostly at the connectivity layer