CommCSL: Proving Information Flow Security for Concurrent Programs using Abstract Commutativity

Information flow security ensures that the secret data manipulated by a program does not influence its observable output. Proving information flow security is especially challenging for concurrent programs, where operations on secret data may influence the execution time of a thread and, thereby, the interleaving between different threads. Such internal timing channels may affect the observable outcome of a program even if an attacker does not observe execution times. Existing verification techniques for information flow security in concurrent programs attempt to prove that secret data does not influence the relative timing of threads. However, these techniques are often restrictive (for instance because they disallow branching on secret data) and make strong assumptions about the execution platform (ignoring caching, processor instructions with data-dependent runtime, and other common features that affect execution time). In this paper, we present a novel verification technique for secure information flow in concurrent programs that lifts these restrictions and does not make any assumptions about timing behavior. The key idea is to prove that all mutating operations performed on shared data commute, such that different thread interleavings do not influence its final value. Crucially, commutativity is required only for an abstraction of the shared data that contains the information that will be leaked to a public output. Abstract commutativity is satisfied by many more operations than standard commutativity, which makes our technique widely applicable. We formalize our technique in CommCSL, a relational concurrent separation logic with support for commutativity-based reasoning, and prove its soundness in Isabelle/HOL. We implemented CommCSL in HyperViper, an automated verifier based on the Viper verification infrastructure, and demonstrate its ability to verify challenging examples

HasTEE: Programming Trusted Execution Environments with Haskell

Trusted Execution Environments (TEEs) are hardware-enforced memory isolation units, emerging as a pivotal security solution for security-critical applications. TEEs, like Intel SGX and ARM TrustZone, allow the isolation of confidential code and data within an untrusted host environment, such as the cloud and IoT. Despite strong security guarantees, TEE adoption has been hindered by an awkward programming model. This model requires manual application partitioning and the use of error-prone, memory-unsafe, and potentially information-leaking low-level C/C++ libraries. We address the above with \textit{HasTEE}, a domain-specific language (DSL) embedded in Haskell for programming TEE applications. HasTEE includes a port of the GHC runtime for the Intel-SGX TEE. HasTEE uses Haskell's type system to automatically partition an application and to enforce \textit{Information Flow Control} on confidential data. The DSL, being embedded in Haskell, allows for the usage of higher-order functions, monads, and a restricted set of I/O operations to write any standard Haskell application. Contrary to previous work, HasTEE is lightweight, simple, and is provided as a \emph{simple security library}; thus avoiding any GHC modifications. We show the applicability of HasTEE by implementing case studies on federated learning, an encrypted password wallet, and a differentially-private data clean room.Comment: To appear in Haskell Symposium 202

Complexity and Unwinding for Intransitive Noninterference

The paper considers several definitions of information flow security for intransitive policies from the point of view of the complexity of verifying whether a finite-state system is secure. The results are as follows. Checking (i) P-security (Goguen and Meseguer), (ii) IP-security (Haigh and Young), and (iii) TA-security (van der Meyden) are all in PTIME, while checking TO-security (van der Meyden) is undecidable, as is checking ITO-security (van der Meyden). The most important ingredients in the proofs of the PTIME upper bounds are new characterizations of the respective security notions, which also lead to new unwinding proof techniques that are shown to be sound and complete for these notions of security, and enable the algorithms to return simple counter-examples demonstrating insecurity. Our results for IP-security improve a previous doubly exponential bound of Hadj-Alouane et al

Beyond Over-Protection: A Targeted Approach to Spectre Mitigation and Performance Optimization

Since the advent of Spectre attacks, researchers and practitioners have developed a range of hardware and software measures to counter transient execution attacks. A prime example of such mitigation is speculative load hardening in LLVM, which protects against leaks by tracking the speculation state and masking values during misspeculation. LLVM relies on static analysis to harden programs using slh that often results in over-protection, which incurs performance overhead. We extended an existing side-channel model validation framework, Scam-V, to check the vulnerability of programs to Spectre-PHT attacks and optimize the protection of programs using the slh approach. We illustrate the efficacy of Scam-V by first demonstrating that it can automatically identify Spectre vulnerabilities in real programs, e.g., fragments of crypto-libraries. We then develop an optimization mechanism that validates the necessity of slh hardening w.r.t. the target platform. Our experiments showed that hardening introduced by LLVM in most cases could be significantly improved when the underlying microarchitecture properties are considered.Comment: The paper will appear in ACM AsiaCCS 202

Non-Interference with What-Declassification in Component-Based Systems

Component-based design is a method for modular design of systems. The structure of component-based systems follows specific rules and single components make assumptions on the environment that they run in. In this paper, we provide a noninterference property for component-based systems that allows for a precise specification of what-declassification of information and takes assumptions on the environment into consideration in order to allow a modular, precise and re-usable information-flow analysis. For precise analysis, components can be analyzed by separately analysing services provided by a component, and from our compositionality theorem non-interference of components follows

EDSL en Haskell para la programaci ́on segura respecto a la propiedad Delimited Release

La confidencialidad de la información manipulada por sistemas informáticos ha tomado mayor importancia con el uso creciente de aplicaciones a través de internet. Los mecanismos de seguridad tradicionales como control de acceso o criptografía no proveen protección punta a punta de los datos: funcionan eficientemente en limitar su acceso, pero no pueden hacer nada para evitar su propagación. Para complementar estos mecanismos de seguridad, surgen las técnicas de control de flujo de información (IFC, Information-Flow Control), las cuales permiten establecer garantías sobre la confidencialidad e integridad de los datos. analizando cómo fluye la información dentro del programa. En este contexto surgen políticas de confidencialidad que garantizan que la información confidencial no puede ser inferida a partir de los datos públicos. No-interferencia es un ejemplo de una política de seguridad. Lo interesante de esta propiedad es que puede ser chequeada de manera estática mediante un sistema de tipos, por lo tanto, cuando un programa tipa en ese sistema de tipos, significa que satisface la propiedad de seguridad. Para que los lenguajes de seguridad tengan utilidad práctica necesitamos mecanismos de desclasificación, en los cuales el flujo de información sea controlado y al mismo tiempo se permita liberar información confidencial a canales públicos, pero solo de manera permitida y controlada, la cual la propiedad de no-interferencia resulta ser demasiado restrictiva. Delimited Release es una propiedad de seguridad que garantiza que la desclasificación no puede ser usada para filtrar información de manera no deseada. El objetivo de esta tesina es desarrollar un lenguaje de dominio específico embebido en Haskell para escribir programas seguros respecto a la propiedad Delimited Release

Glass-Vault: A Generic Transparent Privacy-preserving Exposure Notification Analytics Platform

The highly transmissible COVID-19 disease is a serious threat to people’s health and life. To automate tracing those who have been in close physical contact with newly infected people and/or to analyse tracing-related data, researchers have proposed various ad-hoc programs that require being executed on users’ smartphones. Nevertheless, the existing solutions have two primary limitations: (1) lack of generality: for each type of analytic task, a certain kind of data needs to be sent to an analyst; (2) lack of transparency: parties who provide data to an analyst are not necessarily infected individuals; therefore, infected individuals’ data can be shared with others (e.g., the analyst) without their fine-grained and direct consent. In this work, we present Glass-Vault, a protocol that addresses both limitations simultaneously. It allows an analyst to run authorised programs over the collected data of infectious users, without learning the input data. Glass-Vault relies on a new variant of generic Functional Encryption that we propose in this work. This new variant, called DD-Steel, offers these two additional properties: dynamic and decentralised. We illustrate the security of both Glass-Vault and DD-Steel in the Universal Composability setting. Glass-Vault is the first UC-secure protocol that allows analysing the data of Exposure Notification users in a privacy-preserving manner. As a sample application, we indicate how it can be used to generate “infection heatmaps”