Efficient and provable local capability revocation using uninitialized capabilities

Georges, Aïna Linn; Guéneau, Armaël; Strydonck, Thomas Van; Timany, Amin; Trieu, Alix; Huyghebaert, Sander; Devriese, Dominique; Birkedal, Lars

doi:10.1145/3434287

Cited by 17 publications

(30 citation statements)

References 47 publications

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“…The other most closely related work, proving properties of capability architectures, establishes stronger results but for highly idealised architecture definitions. While our monotonicity theorem is about arbitrary machine execution up to a domain crossing, Skorstengaard et al and Georges et al [46,47,49,48,24] establish logical-relation methods for reasoning about combinations of arbitrary and known code, the latter mechanised in Iris [28], but for idealised machines rather than full architectures. These add new features to help enforcing strong properties, but with unclear hardware implementation cost.…”

Section: Related Workmentioning

confidence: 99%

Verified Security for the Morello Capability-enhanced Prototype Arm Architecture

Bauereiss

Campbell

Sewell

et al. 2022

Lecture Notes in Computer Science

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Memory safety bugs continue to be a major source of security vulnerabilities in our critical infrastructure. The CHERI project has proposed extending conventional architectures with hardware-supported capabilities to enable fine-grained memory protection and scalable compartmentalisation, allowing historically memory-unsafe C and C++ to be adapted to deterministically mitigate large classes of vulnerabilities, while requiring only minor changes to existing system software sources. Arm is currently designing and building Morello, a CHERI-enabled prototype architecture, processor, SoC, and board, extending the high-performance Neoverse N1, to enable industrial evaluation of CHERI and pave the way for potential mass-market adoption. However, for such a major new security-oriented architecture feature, it is important to establish high confidence that it does provide the intended protections, and that cannot be done with conventional engineering techniques.In this paper we put the Morello architecture on a solid mathematical footing from the outset. We define the fundamental security property that Morello aims to provide, reachable capability monotonicity, and prove that the architecture definition satisfies it. This proof is mechanised in Isabelle/HOL, and applies to a translation of the official Arm specification of the Morello instruction-set architecture (ISA) into Isabelle. The main challenge is handling the complexity and scale of a production architecture: 62,000 lines of specification, translated to 210,000 lines of Isabelle. We do so by factoring the proof via a narrow abstraction capturing essential properties of arbitrary CHERI ISAs, expressed above a monadic intra-instruction semantics. We also develop a model-based test generator, which generates instruction-sequence tests that give good specification coverage, used in early testing of the Morello implementation and in Morello QEMU development, and we use Arm’s internal test suite to validate our model.This gives us machine-checked mathematical proofs of whole-ISA security properties of a full-scale industry architecture, at design-time. To the best of our knowledge, this is the first demonstration that that is feasible, and it significantly increases confidence in Morello.

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Section: Related Workmentioning

confidence: 99%

Verified Security for the Morello Capability-enhanced Prototype Arm Architecture

Bauereiss

Campbell

Sewell

et al. 2022

Lecture Notes in Computer Science

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“…Building on related work in high-level languages [7], [8], [9], Skorstengaard et al and Georges et al have developed a methodology for robust modular verification of software running on capability machines [10], [11] that supports proving (security) properties in the presence of untrusted code. The idea is to formalize the hardware-provided security guarantees in the form of a universal contract: a separation logic contract that holds for arbitrary, untrusted code on the machine.…”

Section: Introductionmentioning

confidence: 99%

“…For now, this work has remained restricted to proving artificial security properties: for example the fact that an assertion failure flag will never be set [11], [15] or equitermination of programs [?]. In this paper, we extend this robust modular verification approach to a capability machine with memory-mapped I/O (MMIO).…”

Section: Introductionmentioning

confidence: 99%

Proving full-system security properties under multiple attacker models on capability machines

Strydonck

Georges

Guéneau

et al. 2022

2022 IEEE 35th Computer Security Foundations Symposium (CSF)

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Assembly-level protection mechanisms (virtual memory, trusted execution environments, virtualization) make it possible to guarantee security properties of a full system in the presence of arbitrary attacker provided code. However, they typically only support a single trust boundary: code is either trusted or untrusted, and protection cannot be nested. Capability machines provide protection mechanisms that are more finegrained and that do support arbitrary nesting of protection. We show in this paper how this enables the formal verification of full-system security properties under multiple attacker models: different security objectives of the full system can be verified under a different choice of trust boundary (i.e. under a different attacker model). The verification approach we propose is modular, and is robust: code outside the trust boundary for a given security objective can be arbitrary, unverified attacker-provided code. It is based on the use of universal contracts for untrusted adversarial code: sound, conservative contracts which can be combined with manual verification of trusted components in a compositional program logic. Compositionality of the program logic also allows us to reuse common parts in the analyses for different attacker models. We instantiate the approach concretely by extending an existing capability machine model with support for memorymapped I/O and we obtain full system, machine-verified security properties about external effect traces while limiting the manual verification effort to a small trusted computing base relevant for the specific property under study.inv P (F x , P x , tp x ) read spec(d r pr(x) , d e pr(x) , d r pr(x) , False) inv st (d r pr(x) , d w pr(x) , d e pr(x) , d r x , d w x , d e x , F x , P x ) read spec(d r x , d e x , d r x , tp x )

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“…In this respect, password capabilities are an important improvement over the capability concept [12]. In a classical capability environment, the specification of the access authorization is part of the capability [7], [17], [22]. Consequently, capabilities should be segregated, into reserved memory regions [11], or by taking advantage of memory tagging techniques [2], [3], [18], [28].…”

Section: Introductionmentioning

confidence: 99%

Password Systems: Problems and Solutions

Lopriore¹

2022

IJACSA

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In a security environment featuring subjects and objects, we consider an alternative to the classical password paradigm. In this alternative, a key includes a password, an object identifier, and an authorization. A master password is associated with each object. A key is valid if the password in that key descends from the master password by using a validity relation expressed in terms of a symmetric-key algorithm. We analyse a number of security problems. For each problem, a solution is presented and discussed. In certain cases, extensions to the original key paradigm are introduced. The problems considered include the revocation of access authorizations; bounded keys expressing limitations on the number of iterated utilizations of the same key to access the corresponding object; repositories, which are objects aimed at storing keys, possibly organized into hierarchical structures; and the merging of two keys into a single key featuring a composite authorization that includes the access rights in the two keys.

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Efficient and provable local capability revocation using uninitialized capabilities

Cited by 17 publications

References 47 publications

Verified Security for the Morello Capability-enhanced Prototype Arm Architecture

Verified Security for the Morello Capability-enhanced Prototype Arm Architecture

Proving full-system security properties under multiple attacker models on capability machines

Password Systems: Problems and Solutions

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