EROS (
The Extremely Reliable Operating System) is an
operating systemAn operating system is an interface between hardware and user which is responsible for the management and coordination of activities and the sharing of the resources of the computer that acts as a host for computing applications run on the machine. As a host, one of the purposes of an operating...
developed by The EROS Group, LLC., the
Johns Hopkins UniversityThe Johns Hopkins University, commonly referred to as Johns Hopkins, JHU, or simply Hopkins, is a private research university located in Baltimore, Maryland, United States. Johns Hopkins also maintains full-time campuses elsewhere in Maryland, Washington, D.C., Italy, China, and Singapore...
, and the
University of PennsylvaniaThe University of Pennsylvania is a private research university located in Philadelphia, Pennsylvania, USA. Penn is the fourth-oldest institution of higher education in the United States, and is one of several institutions that claims to have been the first university in America...
. Features include automatic data and process persistence, some preliminary
real-timeA real-time operating system is a multitasking operating system intended for real-time applications. Such applications include embedded systems , industrial robots, spacecraft, industrial control , and scientific research equipment.A RTOS facilitates the creation of a real-time system, but does not...
support, and
capability-based securityCapability-based security is a concept in the design of secure computing systems. A capability is a communicable, unforgeable token of authority. It refers to a value that references an object along with an associated set of access rights. A user program on a capability-based operating system must...
. EROS is purely a research operating system, and was never deployed in real world use. , development has stopped in favor of two successor systems,
CapROSCapROS is an open source operating system. It is a pure capability-based system that features automatic persistence of data and processes, even across system reboots...
and
CoyotosCoyotos is a capability-based security-focused microkernel operating system being developed by The EROS Group, LLC. It is a successor to the EROS system that was created at the University of Pennsylvania and Johns Hopkins University.- History :...
.
The overriding goal of the EROS system (and its relatives) is to provide strong support at the operating system level for the efficient restructuring of critical applications into small communicating components.
EROS (
The Extremely Reliable Operating System) is an
operating systemAn operating system is an interface between hardware and user which is responsible for the management and coordination of activities and the sharing of the resources of the computer that acts as a host for computing applications run on the machine. As a host, one of the purposes of an operating...
developed by The EROS Group, LLC., the
Johns Hopkins UniversityThe Johns Hopkins University, commonly referred to as Johns Hopkins, JHU, or simply Hopkins, is a private research university located in Baltimore, Maryland, United States. Johns Hopkins also maintains full-time campuses elsewhere in Maryland, Washington, D.C., Italy, China, and Singapore...
, and the
University of PennsylvaniaThe University of Pennsylvania is a private research university located in Philadelphia, Pennsylvania, USA. Penn is the fourth-oldest institution of higher education in the United States, and is one of several institutions that claims to have been the first university in America...
. Features include automatic data and process persistence, some preliminary
real-timeA real-time operating system is a multitasking operating system intended for real-time applications. Such applications include embedded systems , industrial robots, spacecraft, industrial control , and scientific research equipment.A RTOS facilitates the creation of a real-time system, but does not...
support, and
capability-based securityCapability-based security is a concept in the design of secure computing systems. A capability is a communicable, unforgeable token of authority. It refers to a value that references an object along with an associated set of access rights. A user program on a capability-based operating system must...
. EROS is purely a research operating system, and was never deployed in real world use. , development has stopped in favor of two successor systems,
CapROSCapROS is an open source operating system. It is a pure capability-based system that features automatic persistence of data and processes, even across system reboots...
and
CoyotosCoyotos is a capability-based security-focused microkernel operating system being developed by The EROS Group, LLC. It is a successor to the EROS system that was created at the University of Pennsylvania and Johns Hopkins University.- History :...
.
Key concepts
The overriding goal of the EROS system (and its relatives) is to provide strong support at the operating system level for the efficient restructuring of critical applications into small communicating components. Each component can communicate with the others only through protected interfaces, and is isolated from the rest of the system. A "protected interface", in this context, is one that is enforced by the lowest level part of the operating system (the kernel). The kernel is the only portion of the system that can move information from one process to another. It also has complete control of the machine and (if properly constructed) cannot be bypassed. In EROS, the kernel-provided mechanism by which one component names and invokes the services of another is capabilities using
inter-process communicationInter-process communication is a set of techniques for the exchange of data among multiple threads in one or more processes. Processes may be running on one or more computers connected by a network. IPC techniques are divided into methods for message passing, synchronization, shared memory, and...
(IPC). By enforcing capability-protected interfaces, the kernel ensures that all communications to a process arrive via an intentionally exported interface. It also ensures that
no invocation is possible unless the invoking component holds a valid capability to the invokee. Protection in capability systems is achieved by restricting the propagation of capabilities from one component to another, often through a security policy known as confinement.
Capability systems naturally promote component-based software structure. This organizational approach is similar to the programming language concept of
object-oriented programmingObject-oriented programming is a programming paradigm that uses "objects" – data structures consisting of datafields and methods together with their interactions – to design applications and computer programs. Programming techniques may include features such as information hiding, data...
, but occurs at larger granularity and does not include the concept of
inheritanceIn object-oriented programming, inheritance is a way to form new classes using classes that have already been defined. Inheritance is intended to help reuse existing code with little or no modification...
. When software is restructured in this way, several benefits emerge:
- The individual components are most naturally structured as event loops
In computer programming, event-driven programming or event-based programming is a programming paradigm in which the flow of the program is determined by events—i.e., sensor outputs or user actions or messages from other programs or threads.Event-driven programming can also be defined as an...
. Examples of systems that are commonly structured this way include flight control systems (see also DO-178B Software Considerations in Airborne Systems and Equipment CertificationDO-178B, Software Considerations in Airborne Systems and Equipment Certification is the title of a document published by RTCA, Incorporated. Development was a joint effort with EUROCAE...
), and telephone switching systems (see 5ESS switchThe 5ESS Switch is the Class 5 telephone electronic switching system sold by Alcatel-Lucent. This digital central office telephone circuit switching system is used by many telecommunications service providers.-History:...
). Event-driven programming is chosen for these systems primarily because of simplicity and robustness, which are essential attributes in life-critical and mission-critical systems.
- Components become smaller and individually testable, which helps the implementor to more readily identify flaws and bugs.
- The isolation of each component from the others limits the scope of the damage that may occur when something goes wrong or the software misbehaves.
Collectively, these benefits lead to measurably more robust and secure systems. The
SDS Sigma 7Scientific Data Systems, or SDS, was an American computer company founded in September 1961 by Max Palevsky, a veteran of Packard Bell and Bendix, along with eleven other computer scientists. SDS was an early adopter of integrated circuits in computer design and the first to employ silicon...
was a hardware-based capability system originally designed for use in telephony switches. A capability-based design was chosen specifically for reasons of robustness.
In contrast to many earlier systems, capabilities are the
only mechanism for naming and using resources in EROS. Such a system is sometimes referred to as a
pure capability system. The IBM AS/400 is an example of a commercially successful capability system, but it is not a pure capability system.
Pure capability architectures are supported by well-tested and mature mathematical security models. These have been used to formally demonstrate that capability-based systems can be made secure if implemented correctly. The so-called "safety property" has been shown to be decidable for pure capability systems (see Lipton). Confinement, which is the fundamental building block of isolation, has been formally verified to be enforceable by pure capability systems, and is reduced to practical implementation by the EROS "constructor" and the KeyKOS "factory". No comparable verification exists for any other primitive protection mechanism. There is a fundamental result in the literature showing that "safety" is mathematically undecidable in the general case (see
HRUThe HRU security model is an operating system level computer security model which deals with the integrity of access rights in the system...
, but note that it is of course provable for an unbounded set of restricted cases). Of greater practical importance, safety has been shown to be
false for all of the primitive protection mechanisms shipping in current commodity operating systems (see
HRUThe HRU security model is an operating system level computer security model which deals with the integrity of access rights in the system...
). Safety is a necessary precondition to successful enforcement of
any security policy. In practical terms, this result means that it is not possible
in principle to secure current commodity systems, but it is potentially possible to secure capability-based systems
provided they are implemented with sufficient care. Neither system has ever been successfully penetrated, and their isolation mechanisms have never been successfully defeated by any inside attacker, but it is not known whether the EROS or KeyKOS implementations was careful enough. One goal of the
CoyotosCoyotos is a capability-based security-focused microkernel operating system being developed by The EROS Group, LLC. It is a successor to the EROS system that was created at the University of Pennsylvania and Johns Hopkins University.- History :...
project is to demonstrate that component isolation and security has been definitively achieved by apply software verification techniques.
The L4.sec system, which is a successor to the
L4 microkernel familyL4 is a family of second-generation microkernels based on theoriginal designs and implementations by German computer scientist Jochen Liedtke. Originally implemented as highly tuned Intel i386-specific assembly language code, the API has seen extensive development in a number of directions, both in...
, is a capability-based system, and has been significantly influenced by the results of the EROS project. The influence is mutual, since the EROS work on high-performance invocation was motivated strongly by
Jochen LiedtkeJochen Liedtke was a German computer scientist, noted for his work on microkernels, especially the creation of the L4 microkernel family....
's successes with the
L4 microkernel familyL4 is a family of second-generation microkernels based on theoriginal designs and implementations by German computer scientist Jochen Liedtke. Originally implemented as highly tuned Intel i386-specific assembly language code, the API has seen extensive development in a number of directions, both in...
.
History
The primary developer of EROS was Jonathan S. Shapiro. He is also the driving force behind
CoyotosCoyotos is a capability-based security-focused microkernel operating system being developed by The EROS Group, LLC. It is a successor to the EROS system that was created at the University of Pennsylvania and Johns Hopkins University.- History :...
, which is a "evolutionary step" beyond the EROS operating system.
The EROS project started in 1991 as a clean-room reconstruction of an earlier system,
KeyKOSKeyKOS is a persistent, pure capability-based operating system for the IBM S/370 mainframe computers. It allows emulating the VM, MVS, and POSIX environments. It is a predecessor of the Extremely Reliable Operating System , and its successors, the CapROS and Coyotos operating systems.- External...
. KeyKOS was an operating system developed by Key Logic, Inc., and was a direct continuation of work on the earlier
GNOSIS (Great New Operating System In the Sky) system created by Tymshare, Inc. The KeyKOS system offered a degree of security and reliability that remains unduplicated today (2006). The circumstances surrounding Key Logic's unfortunate demise in 1991 made licensing KeyKOS impractical. Since KeyKOS did not run on popular commodity processors in any case, the decision was made to reconstruct it from the publicly available documentation.
By late 1992, it had become clear that processor architecture had changed significantly since the introduction of the capability idea, and it was no longer obvious that component-structured systems were practical.
MicrokernelIn computer science, a microkernel is a computer kernel that provides the mechanisms needed to implement an operating system, such as low-level address space management, thread management, and inter-process communication...
-based systems, which similarly favor large numbers of processes and IPC, were facing severe performance challenges, and it was uncertain if these could be successfully resolved. The
x86 architectureThe term x86 refers to a family of instruction set architectures based on the Intel 8086. The term derived from the fact that many early processors backward compatible with the 8086 also had names ending in "86". Many additions and extensions have been added to the x86 instruction set over the...
was clearly emerging as the dominant architecture but the expensive user/supervisor transition latency on the
386-Roman Empire:* Theodosius I concludes peace with Persia, dividing Armenia between them.* Theodosius I begins to rebuild the present-day Basilica of Saint Paul Outside the Walls....
and
486-Europe:*Roman rule in Gaul ends with the defeat at Soissons of the Roman governor Syagrius by the Franks under Clovis I. The land between the Loire and the Somme becomes a part of the Frankish realm....
presented serious challenges for process-based isolation. The EROS project was turning into a research effort, and moved to the
University of PennsylvaniaThe University of Pennsylvania is a private research university located in Philadelphia, Pennsylvania, USA. Penn is the fourth-oldest institution of higher education in the United States, and is one of several institutions that claims to have been the first university in America...
to become the focus of Shapiro's dissertation research. By 1999, a high performance implementation for the
PentiumThe original Pentium processor was a 32-bit microprocessor produced by Intel. The first superscalar x86 architecture processor, it was introduced on March 22, 1993. Its microarchitecture was a direct extension of the 80486 architecture with dual integer pipelines, a faster FPU, wider data bus, and...
processor had been demonstrated that was directly performance competitive with the
L4 microkernel familyL4 is a family of second-generation microkernels based on theoriginal designs and implementations by German computer scientist Jochen Liedtke. Originally implemented as highly tuned Intel i386-specific assembly language code, the API has seen extensive development in a number of directions, both in...
, which is known for its exceptional speed in IPC. The EROS confinement mechanism had been formally verified, in the process creating a general formal model for secure capability systems.
In 2000, Shapiro joined the faculty of Computer Science at Johns Hopkins University. At Hopkins, the goal was to show how to
use the facilities provided by the EROS kernel to construct secure and defensible servers at application level. Funded by the
Defense Advanced Research Projects AgencyThe Defense Advanced Research Projects Agency is an agency of the United States Department of Defense responsible for the development of new technology for use by the military...
and the
Air Force Research LaboratoryThe Air Force Research Laboratory is a scientific research organization operated by the United States Air Force Materiel Command dedicated to leading the discovery, development, and integration of affordable aerospace warfighting technologies; planning and executing the Air Force science and...
, EROS was used as the basis for a trusted window system, a high-performance, defensible network stack, and the beginnings of a secure web browser. It was also used to explore the effectiveness of lightweight static checking. In 2003, some very challenging security issues were discovered that are intrinsic to
any system architecture based on synchronous IPC primitives (notably including EROS and L4). Work on EROS halted in favor of Coyotos, which resolves these issues.
, EROS and its successors are the only widely available capability systems that run on commodity hardware.
Status
Work on EROS by the original group has halted, but there are two successor systems. The
CapROSCapROS is an open source operating system. It is a pure capability-based system that features automatic persistence of data and processes, even across system reboots...
system is building directly from the EROS code base, while the
CoyotosCoyotos is a capability-based security-focused microkernel operating system being developed by The EROS Group, LLC. It is a successor to the EROS system that was created at the University of Pennsylvania and Johns Hopkins University.- History :...
system is a successor system that addresses some of the architectural deficiencies of
EROS, and is exploring (as research) the possibility of a fully verified operating system. Both CapROS and Coyotos are expected to be released in various commercial deployments.
Journals
- R. J. Lipton and L. Snyder. "A Linear Time Algorithm for Deciding Subject Security." Journal of the ACM, 24(3):455--464, 1977.
- M. A. Harrison, W. L. Ruzzo and J. D. Ullman. "Protection in Operating Systems". Communications of ACM. 19(8):461--471, August 1976.
External links