# topic.cheri.bib

@comment{{This file has been generated by bib2bib 1.99}}

@comment{{Command line: bibtex2html-1.99/bib2bib -c 'topic:"cheri" or topictwo:"cheri"' -ob topic.cheri.bib sewellbib2.bib}}

@inproceedings{Cerberus-PLDI16,
author = {
Kayvan Memarian and
Justus Matthiesen and
James Lingard and
Kyndylan Nienhuis and
David Chisnall and
Robert N.M. Watson and
Peter Sewell
},
title = {Into the depths of {C}: elaborating the de facto standards},
abstract = {
C remains central to our computing infrastructure.  It is notionally defined by ISO standards, but in reality the properties of C assumed by systems code and those implemented by compilers have diverged, both from the ISO standards and from each other, and none of these are clearly understood.

We make two contributions to help improve this error-prone situation.  First, we describe an in-depth analysis of the design space for the semantics of pointers and memory in C as it is used in practice.  We articulate many specific questions, build a suite of semantic test cases, gather experimental data from multiple implementations, and survey what C experts believe about the de facto standards.  We identify questions where there is a consensus (either following ISO or differing) and where there are conflicts. We apply all this to an experimental C implemented above capability hardware.  Second, we describe a formal model, Cerberus, for large parts of C.  Cerberus is parameterised on its memory model; it is linkable either with a candidate de facto memory object model, under construction, or with an operational C11 concurrency model; it is defined by elaboration to a much simpler Core language for accessibility, and it is executable as a test oracle on small examples.

This should provide a solid basis for discussion of what mainstream C is now: what programmers and analysis tools can assume and what compilers aim to implement. Ultimately we hope it will be a step towards clear, consistent, and accepted semantics for the various use-cases of C.
},
optcrossref = {},
optkey = {},
conf = {PLDI 2016},
booktitle = {Proceedings of the 37th ACM SIGPLAN conference on Programming Language Design and Implementation},
optpages = {},
year = {2016},
opteditor = {},
optvolume = {},
optnumber = {},
optseries = {},
month = jun,
optorganization = {},
optpublisher = {},
note = {PLDI 2016 Distinguished Paper award},
project = {http://www.cl.cam.ac.uk/~pes20/cerberus},
url = {http://doi.acm.org/10.1145/2908080.2908081},
doi = {10.1145/2908080.2908081},
pdf = {http://www.cl.cam.ac.uk/users/pes20/cerberus/pldi16.pdf},
optannote = {},
topic = {Cerberus},
topictwo = {cheri},
topicthree = {WG14},
cheriformal = {true},
recent = {true}
}

@inproceedings{cerberus-popl2019,
author = {Kayvan Memarian and Victor B. F. Gomes and Brooks Davis and Stephen Kell and Alexander Richardson and Robert N. M. Watson and Peter Sewell},
title = {Exploring {C} Semantics and Pointer Provenance},
optcrossref = {},
optkey = {},
conf = {POPL 2019},
booktitle = {Proceedings of the 46th ACM SIGPLAN Symposium on Principles of Programming Languages},
optbooktitle = {},
year = {2019},
opteditor = {},
optvolume = {},
optnumber = {},
optseries = {},
optpages = {},
month = jan,
optorganization = {},
optpublisher = {},
note = {Proc. ACM Program. Lang. 3, POPL, Article 67. Also available as ISO/IEC JTC1/SC22/WG14 N2311 },
optannote = {},
doi = {10.1145/3290380},
pdf = {http://www.cl.cam.ac.uk/users/pes20/cerberus/cerberus-popl2019.pdf},
supplementarymaterial = {http://www.cl.cam.ac.uk/users/pes20/cerberus/supplementary-material-popl2019},
topic = {Cerberus},
topictwo = {cheri},
topicthree = {WG14},
cheriformal = {true},
project = {http://www.cl.cam.ac.uk/~pes20/cerberus},
abstract = {The semantics of pointers and memory objects in C has been a vexed question for many years.  C values cannot be treated as either purely abstract or purely concrete entities: the language exposes their representations, but compiler optimisations rely on analyses that reason about provenance and initialisation status, not just runtime representations. The ISO WG14 standard leaves much of this unclear, and in some respects differs with de facto standard usage --- which itself is difficult to investigate.

In this paper we explore the possible source-language semantics for memory objects and pointers, in ISO C and in C as it is used and implemented in practice, focussing especially on pointer provenance.  We aim to, as far as possible, reconcile the ISO C standard, mainstream compiler behaviour, and the semantics relied on by the corpus of existing C code.  We present two coherent proposals, tracking provenance via integers and not; both address many design questions. We highlight some pros and cons and open questions, and illustrate the discussion with a library of test cases.  We make our semantics executable as a test oracle, integrating it with the Cerberus semantics for much of the rest of C, which we have made substantially more complete and robust, and equipped with a web-interface GUI.  This allows us to experimentally assess our proposals on those test cases.  To assess their viability with respect to larger bodies of C code, we analyse the changes required and the resulting behaviour for a port of FreeBSD to CHERI, a research architecture supporting hardware capabilities, which (roughly speaking) traps on the memory safety violations which our proposals deem undefined behaviour. We also develop a new runtime instrumentation tool to detect possible provenance violations in normal C code, and apply it to some of the SPEC benchmarks.  We compare our proposal with a source-language variant of the twin-allocation LLVM semantics proposal of Lee et al.  Finally, we describe ongoing interactions with WG14, exploring how our proposals could be incorporated into the ISO standard.
},
recent = {true}
}

@inproceedings{sail-popl2019,
author = {Alasdair Armstrong and Thomas Bauereiss and Brian Campbell and Alastair Reid and Kathryn E. Gray and Robert M. Norton and Prashanth Mundkur and Mark Wassell and Jon French and Christopher Pulte and Shaked Flur and Ian Stark and Neel Krishnaswami and Peter Sewell},
title = {{ISA} Semantics for {ARMv8-A, RISC-V, and CHERI-MIPS}},
optcrossref = {},
optkey = {},
conf = {POPL 2019},
booktitle = {Proceedings of the 46th ACM SIGPLAN Symposium on Principles of Programming Languages},
optbooktitle = {},
year = {2019},
opteditor = {},
optvolume = {},
optnumber = {},
optseries = {},
optpages = {},
month = jan,
optorganization = {},
optpublisher = {},
note = {Proc. ACM Program. Lang. 3, POPL, Article 71},
optnote = {},
optannote = {},
doi = {10.1145/3290384},
abstract = {Architecture specifications notionally define the fundamental interface between hardware and software: the envelope of allowed behaviour for processor implementations, and the basic assumptions for software development and verification.  But in practice, they are typically prose and pseudocode documents, not rigorous or executable artifacts, leaving software and verification on shaky ground.

In this paper, we present rigorous semantic models for the sequential behaviour of large parts of the mainstream ARMv8-A, RISC-V, and MIPS architectures, and the research CHERI-MIPS architecture, that are complete enough to boot operating systems, variously Linux, FreeBSD, or seL4.  Our ARMv8-A models are automatically translated from authoritative ARM-internal definitions, and (in one variant) tested against the ARM Architecture Validation Suite.

We do this using a custom language for ISA semantics, Sail, with a lightweight dependent type system, that supports automatic generation of emulator code in C and OCaml, and automatic generation of proof-assistant definitions for Isabelle, HOL4, and (currently only for MIPS) Coq.  We use the former for validation, and to assess specification coverage.  To demonstrate the usability of the latter, we prove (in Isabelle) correctness of a purely functional characterisation of ARMv8-A address translation.  We moreover integrate the RISC-V model into the RMEM tool for (user-mode) relaxed-memory concurrency exploration.  We prove (on paper) the soundness of the core Sail type system.

We thereby take a big step towards making the architectural abstraction actually well-defined, establishing foundations for verification and reasoning.
},
pdf = {http://www.cl.cam.ac.uk/users/pes20/sail/sail-popl2019.pdf},
supplementarymaterial = {http://www.cl.cam.ac.uk/users/pes20/sail/popl2019.html},
topic = {ISA_semantics},
topictwo = {cheri},
cheriformal = {true},
project = {http://www.cl.cam.ac.uk/~pes20/sail/},
recent = {true}
}

@inproceedings{cheri-arw18,
author = {Kyndylan Nienhuis and Alexandre Joannou and Peter Sewell},
title = {Proving security properties of {CHERI-MIPS}},
optcrossref = {},
optkey = {},
conf = {Automated Reasoning Workshop (ARW) 2018},
booktitle = {Proc. Automated Reasoning Workshop},
year = {2018},
opteditor = {},
optvolume = {},
optnumber = {},
optseries = {},
pages = {18},
month = apr,
optorganization = {},
optpublisher = {},
note = {Two-page abstract},
optnote = {Proceedings available at \url{https://www.cl.cam.ac.uk/events/arw2018/arw2018-proc.pdf}},
optannote = {},
pdf = {http://www.cl.cam.ac.uk/~pes20/cheri/cheri-arw18.pdf},
topic = {cheri},
abstract = { CHERI-MIPS is an instruction set architecture that
provides hardware support for secure encapsulation
and fine-grained memory protection. The guarantees
it intends to offer are described in high-level
prose, which makes it difficult to understand what
they precisely are, whether they are true, and
whether they indeed provide memory protection. We
describe ongoing work on proposing formal
definitions of these guarantees and proving that
they are true.}
}

@inproceedings{cheriABIsub,
optkey = {},
author = {Brooks Davis and
Robert N. M. Watson and
Alexander Richardson and
Peter G. Neumann and
Simon W. Moore and
John Baldwin and
David Chisnall and
James Clarke and
Nathaniel Wesley Filardo and
Khilan Gudka and
Alexandre Joannou and
Ben Laurie and
A. Theodore Markettos and
J. Edward Maste and
Alfredo Mazzinghi and
Edward Tomasz Napierala and
Robert M. Norton and
Michael Roe and
Peter Sewell and
Stacey Son and
Jonathan Woodruff},
title = {{CheriABI}: Enforcing Valid Pointer Provenance and Minimizing
Pointer Privilege in the {POSIX C} Run-time Environment},
opthowpublished = {Submitted for publication},
conf = {ASPLOS 2019},
booktitle = {the 24th ACM International Conference on Architectural Support for Programming Languages and Operating Systems},
month = apr,
year = {2019},
note = {Best paper award},
url = {http://doi.acm.org/10.1145/3297858.3304042},
doi = {10.1145/3297858.3304042},
acmid = {3304042},
publisher = {ACM},
optannote = {},
abstract = {The CHERI architecture allows pointers to be implemented as
capabilities (rather than integer virtual addresses) in a manner that
is compatible with, and strengthens, the
semantics of the C language.
In addition to the spatial protections offered by conventional fat pointers,
CHERI capabilities offer strong integrity, enforced provenance validity, and
access monotonicity.
The stronger guarantees of these architectural capabilities must be reconciled with the real-world behavior of operating systems, run-time environments, and applications.
When the process model, user-kernel interactions, dynamic linking, and memory
management are all considered, we observe that simple derivation of architectural capabilities is insufficient to describe appropriate access to memory.
We bridge this conceptual gap with a notional \emph{abstract capability} that
describes the accesses that should be allowed at a given point in execution,
whether in the kernel or userspace.
To investigate this notion at scale, we describe the first adaptation of a
full C-language operating system (FreeBSD) with an enterprise database
(PostgreSQL) for complete spatial and referential memory safety.
We show that awareness of abstract capabilities, coupled with CHERI
architectural capabilities, can provide more complete protection, strong
compatibility, and acceptable performance overhead compared with the pre-CHERI
baseline and software-only approaches.
Our observations also have potentially significant implications for other
mitigation techniques.},
pdf = {https://www.cl.cam.ac.uk/research/security/ctsrd/pdfs/201904-asplos-cheriabi.pdf},
project = {https://www.cl.cam.ac.uk/research/security/ctsrd/cheri/},
topic = {cheri},
cheriformal = {true},
recent = {true}
}

@techreport{UCAM-CL-TR-927,
author = {Watson, Robert N. M. and Neumann, Peter G. and Woodruff,
Jonathan and Roe, Michael and Almatary, Hesham and
Anderson, Jonathan and Baldwin, John and Chisnall, David
and Davis, Brooks and Filardo, Nathaniel Wesley and
Joannou, Alexandre and Laurie, Ben and Markettos, A.
Theodore and Moore, Simon W. and Murdoch, Steven J. and
Nienhuis, Kyndylan and Norton, Robert and Richardson, Alex
and Rugg, Peter and Sewell, Peter and Son, Stacey and Xia,
Hongyan},
title = {{Capability Hardware Enhanced RISC Instructions: CHERI
Instruction-Set Architecture (Version 7)}},
year = 2019,
month = jun,
pdf = {https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-927.pdf},
institution = {University of Cambridge, Computer Laboratory},
number = {UCAM-CL-TR-927},
note = {496pp},
topic = {CHERI},
abstract = {This technical report describes CHERI ISAv7, the seventh version of the
Capability Hardware Enhanced RISC Instructions (CHERI) Instruction-Set
Architecture (ISA)
being developed by SRI International and the University of Cambridge.
This design captures nine years of research, development, experimentation,
refinement, formal analysis, and validation through hardware and software
implementation.
CHERI ISAv7 is a substantial enhancement to prior ISA versions.
We differentiate an architecture-neutral protection model vs.
architecture-specific instantiations in 64-bit MIPS, 64-bit RISC-V, and
x86-64.
We have defined a new CHERI Concentrate compression model.
CHERI-RISC-V is more substantially elaborated.
A new compartment-ID register assists in resisting microarchitectural
side-channel attacks.
Experimental features include linear capabilities, capability coloring,
temporal memory safety, and 64-bit capabilities for 32-bit architectures.

CHERI is a {\em hybrid capability-system architecture} that adds new
capability-system primitives to commodity 64-bit RISC ISAs, enabling software
to efficiently implement {\em fine-grained memory protection} and {\em
scalable software compartmentalization}.
Design goals include incremental adoptability within current ISAs and
software stacks, low performance overhead for memory protection, significant
performance improvements for software compartmentalization, formal grounding,
and programmer-friendly underpinnings.
We have focused on providing strong, non-probabilistic, efficient
architectural foundations for the principles of \textit{least privilege} and
\textit{intentional use} in the execution of software at multiple levels of
abstraction, preventing and mitigating vulnerabilities.

The CHERI system architecture purposefully addresses known performance and
robustness gaps in commodity ISAs that hinder the adoption of more secure
programming models centered around the principle of least privilege.
To this end, CHERI blends traditional paged virtual memory with an
in-address-space capability model that includes capability registers,
capability instructions, and tagged memory.
CHERI builds on the C-language fat-pointer literature: its capabilities can
describe fine-grained regions of memory, and can be substituted for data or
code pointers in generated code, protecting data and also improving
control-flow robustness.
Strong capability integrity and monotonicity properties allow the CHERI model
to express a variety of protection properties, from enforcing valid C-language
pointer provenance and bounds checking to implementing the isolation and
controlled communication structures required for software
compartmentalization.

CHERI's hybrid capability-system approach, inspired by the Capsicum security
model, allows incremental adoption of capability-oriented design: software
implementations that are more robust and resilient can be deployed where they
are most needed, while leaving less critical software largely unmodified, but
nevertheless suitably constrained to be incapable of having adverse effects.
Potential deployment scenarios include low-level software Trusted Computing
Bases (TCBs) such as separation kernels, hypervisors, and operating-system
kernels, as well as userspace TCBs such as language runtimes and web browsers.
We also see potential early-use scenarios around particularly high-risk
software libraries (such as data compression, protocol parsing, and image
processing), which are concentrations of both complex and historically
vulnerability-prone code exposed to untrustworthy data sources, while leaving
containing applications unchanged.
},
cheriformal = {true},
recent = {true}
}

@misc{cheri-formal-sub,
optkey = {},
author = {
Kyndylan Nienhuis
and Alexandre Joannou
and Anthony Fox
and Michael Roe
and Thomas Bauereiss
and Brian Campbell
and Matthew Naylor
and Robert M. Norton
and Simon W. Moore
and Peter G. Neumann
and Ian Stark
and Robert N. M. Watson
and Peter Sewell
},
title = {Rigorous engineering for hardware security:
Formal modelling and proof in the
{CHERI} design and implementation process},
howpublished = {Draft},
month = aug,
year = {2019},
optnote = {},
optannote = {},
abstract = {The root causes of many security vulnerabilities include a pernicious combination of two problems, often regarded as inescapable aspects of computing.  First, the protection mechanisms provided by the mainstream processor architecture and C/C++ language abstractions, dating back to the 1970s and before, provide only coarse-grain virtual-memory-based protection.  Second, mainstream system engineering relies almost exclusively on test-and-debug methods, with (at best) prose specifications.  These methods have historically sufficed commercially for much of the computer industry, but they fail to prevent large numbers of exploitable bugs, and the security problems that this causes are becoming ever more acute.

In this paper we show how more rigorous engineering methods can be applied to the development of a new security-enhanced processor architecture, with its accompanying hardware implementation and software stack.  We use formal models of the complete instruction-set architecture (ISA) at the heart of the design and engineering process, both in lightweight ways that support and improve normal engineering practice -- as documentation, in emulators used as a test oracle for hardware and for running software, and for test generation -- and for formal verification.  We formalise key intended security properties of the design, and establish that these hold with mechanised proof.  This is for the same complete ISA models (complete enough to boot operating systems), without idealisation.

We do this for CHERI, an architecture with \emph{hardware capabilities} that supports fine-grained memory protection and scalable secure compartmentalisation, while offering a smooth adoption path for existing software.  CHERI is a maturing research architecture, developed since 2010, with work now underway to explore its possible adoption in mass-market commercial processors.  The rigorous engineering work described here has been an integral part of its development to date, enabling more rapid and confident experimentation, and boosting confidence in the design.
},
project = {https://www.cl.cam.ac.uk/research/security/ctsrd/cheri/},
topic = {cheri},
optcheriformal = {true},
pdf = {http://www.cl.cam.ac.uk/~pes20/cheri-formal.pdf},
optrecent = {true}
}

@techreport{UCAM-CL-TR-932,
author = {Davis, Brooks and Watson, Robert N. M. and Richardson,
Alexander and Neumann, Peter G. and Moore, Simon W. and
Baldwin, John and Chisnall, David and Clarke, James and
Filardo, Nathaniel Wesley and Gudka, Khilan and Joannou,
Alexandre and Laurie, Ben and Markettos, A. Theodore and
Maste, J. Edward and Mazzinghi, Alfredo and Napierala,
Edward Tomasz and Norton, Robert M. and Roe, Michael and
Sewell, Peter and Son, Stacey and Woodruff, Jonathan},
title = {{CheriABI: Enforcing valid pointer provenance and
minimizing pointer privilege in the POSIX C run-time
environment}},
year = 2019,
month = jan,
pdf = {https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-932.pdf},
institution = {University of Cambridge, Computer Laboratory},
number = {UCAM-CL-TR-932},
abstract = {The CHERI architecture allows pointers to be implemented as capabilities (rather than integer virtual addresses) in a manner that is compatible with, and strengthens, the semantics of the C language. In addition to the spatial protections offered by conventional fat pointers, CHERI capabilities offer strong integrity, enforced provenance validity, and access monotonicity.

The stronger guarantees of these architectural capabilities must be reconciled with the real-world behavior of operating systems, run-time environments, and applications. When the process model, user-kernel interactions, dynamic linking, and memory management are all considered, we observe that simple derivation of architectural capabilities is insufficient to describe appropriate access to memory. We bridge this conceptual gap with a notional abstract capability that describes the accesses that should be allowed at a given point in execution, whether in the kernel or userspace.

To investigate this notion at scale, we describe the first adaptation of a full C-language operating system (FreeBSD) with an enterprise database (PostgreSQL) for complete spatial and referential memory safety. We show that awareness of abstract capabilities, coupled with CHERI architectural capabilities, can provide more complete protection, strong compatibility, and acceptable performance overhead compared with the pre-CHERI baseline and software-only approaches. Our observations also have potentially significant implications for other mitigation techniques.},
project = {https://www.cl.cam.ac.uk/research/security/ctsrd/cheri/},
topic = {cheri},
cheriformal = {true},
recent = {false}
}

@techreport{UCAM-CL-TR-941,
author = {Watson, Robert N. M. and  Moore, Simon W. and
Sewell, Peter and Neumann, Peter},
title = {An Introduction to {CHERI}},
year = 2019,
month = sep,
pdf = {https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-941.pdf},
institution = {University of Cambridge, Computer Laboratory},
number = {UCAM-CL-TR-941},
abstract = {},
project = {https://www.cl.cam.ac.uk/research/security/ctsrd/cheri/},
topic = {cheri},
cheriformal = {true},
recent = {false}
}