Differentiating Between Access Control Terms WP
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Role Based Access Control on MLS Systems Without Kernel Changes
Role Based Access Control on For example, roles in a bank may include the role of teller or accountant. Each of these roles has a set of MLS Systems without Kernel privileges or transactions that they can p erform, includ- Changes ing some privileges that are available to b oth roles. Roles can b e hierarchical. For example, some roles in a hospital D. Richard Kuhn may b e health care provider, nurse, and do ctor. The do c- National Institute of Standards and Technology tor role may include all privileges available to the nurse Gaithersburg, Maryland 20899 role, which in turn includes all the privileges available to the health care provider role. Roles have b een used in a variety of forms for com- Abstract puter system security for at least 20 years, and several prop osals for incorp orating roles into existing access con- Role based access control (RBAC) is attracting increas- trol mechanisms have b een published [2], [3], [4]. More ing attention as a security mechanism for b oth commer- recently, formal defnitions for general-purp ose RBAC no- cial and many military systems. This pap er shows how tions have b een prop osed [5], [6], [7]. RBAC can b e implemented using the mechanisms avail- This pap er shows how RBAC can b e implemented able on traditional multi-level security systems that im- using the controls available on traditional lattice-based plement information fow p olicies. The construction from multi-level secure systems. This approach presents a MLS to RBAC systems is signifcant b ecause it shows that number of advantages: the enormous investment in MLS systems can b e lever- aged to pro duce RBAC systems. -
Administrative Role-Based Access Control on Top of Security Enhanced Linux
Administrative Role-Based Access Control on Top of Security Enhanced Linux Ayla Solomon Submitted in Partial Fulfillment of the Prerequisite for Honors in Computer Science June 2009 Copyright Ayla Solomon, 2009 Abstract In a time when the Internet is increasingly dangerous and software is increasingly com- plex, properly securing one’s system has become a widespread concern, especially for system administrators. There are a number of ways to secure a Linux system; these methods vary in effectiveness and usability. Regular Linux discretionary access control is suitable for most mundane tasks and is easy to use, but it fails to confine insecure programs that run with administrative powers and is difficult to scale. Security Enhanced Linux (SELinux) is an extension to the Linux kernel that provides fine-grained controls for preventing malicious agents from exploiting software vulnerabilities. It can be very effective, but its policy lan- guage is extremely low-level and its paradigm difficult to understand and use. This makes it difficult to map a high-level idea of a security policy to what needs to be done in SELinux, which rules out its use to a vast majority of people with Linux systems, including system administrators, though many attempts have been made to make it more usable. I have designed and partially implemented a system on top of SELinux to implement administrative role-based access control (ARBAC), which is not available on any Linux system. ARBAC is an intuitive, flexible, and scalable security paradigm well suited for user confinement, especially for very large systems with many users. ARBAC’s main advan- tages are not only in its intuitive structure but also its built-in administrator confinement mechanism: its very structure promotes separation of privilege amongst administrators. -
File Permissions Do Not Restrict Root
Filesystem Security 1 General Principles • Files and folders are managed • A file handle provides an by the operating system opaque identifier for a • Applications, including shells, file/folder access files through an API • File operations • Access control entry (ACE) – Open file: returns file handle – Allow/deny a certain type of – Read/write/execute file access to a file/folder by – Close file: invalidates file user/group handle • Access control list (ACL) • Hierarchical file organization – Collection of ACEs for a – Tree (Windows) file/folder – DAG (Linux) 2 Discretionary Access Control (DAC) • Users can protect what they own – The owner may grant access to others – The owner may define the type of access (read/write/execute) given to others • DAC is the standard model used in operating systems • Mandatory Access Control (MAC) – Alternative model not covered in this lecture – Multiple levels of security for users and documents – Read down and write up principles 3 Closed vs. Open Policy Closed policy Open Policy – Also called “default secure” • Deny Tom read access to “foo” • Give Tom read access to “foo” • Deny Bob r/w access to “bar” • Give Bob r/w access to “bar • Tom: I would like to read “foo” • Tom: I would like to read “foo” – Access denied – Access allowed • Tom: I would like to read “bar” • Tom: I would like to read “bar” – Access allowed – Access denied 4 Closed Policy with Negative Authorizations and Deny Priority • Give Tom r/w access to “bar” • Deny Tom write access to “bar” • Tom: I would like to read “bar” – Access -
Access Control and Operating System
Outline (may not finish in one lecture) Access Control and Operating Access Control Concepts Secure OS System Security • Matrix, ACL, Capabilities • Methods for resisting • Multi-level security (MLS) stronger attacks OS Mechanisms Assurance • Multics • Orange Book, TCSEC John Mitchell – Ring structure • Common Criteria • Amoeba • Windows 2000 – Distributed, capabilities certification • Unix Some Limitations – File system, Setuid • Information flow • Windows • Covert channels – File system, Tokens, EFS • SE Linux – Role-based, Domain type enforcement Access control Access control matrix [Lampson] Common Assumption Objects • System knows who the user is File 1 File 2 File 3 … File n – User has entered a name and password, or other info • Access requests pass through gatekeeper User 1 read write - - read – OS must be designed monitor cannot be bypassed User 2 write write write - - Reference Subjects monitor User 3 - - - read read User process ? Resource … User m read write read write read Decide whether user can apply operation to resource Two implementation concepts Capabilities Access control list (ACL) File 1 File 2 … Operating system concept • “… of the future and always will be …” • Store column of matrix User 1 read write - Examples with the resource User 2 write write - • Dennis and van Horn, MIT PDP-1 Timesharing Capability User 3 - - read • Hydra, StarOS, Intel iAPX 432, Eros, … • User holds a “ticket” for … • Amoeba: distributed, unforgeable tickets each resource User m read write write • Two variations References – store -
Making Linux Security Frameworks Available to Containers
Security Namespace : Making Linux Security Frameworks Available to Containers Yuqiong Sun, David Safford, Mimi Zohar, Dimitrios Pendarakis, Zhongshu Gu and Trent Jaeger Container vs. Virtual Machines • Containers are operating system level virtualization environment for running multiple isolated Linux systems on a single Linux control host Image credit: Docker Inc. and RightScale Inc. Is Kernel Sharing All Good? • Container owners cannot leverage kernel security frameworks to protect their containers • I.e., cannot apply local security policies to govern integrity measurement, code execution, mandatory access control, etc. Integrity Attestation for Container • On a container cloud, can a container owner attest integrity of his/her containers to his/her customers? • Exactly what Linux Integrity subsystem (a.k.a. IMA) is designed for kernel mmap() extend Process Measure record Policy Measurements Integrity Attestation for Container (Cont.) • But… • Mixed measurements from different containers and host Process mmap() kernel extend Container1 Measure mmap() record Process Policy Measurements Container2 Integrity Attestation for Container (Cont.) • But… • Mixed measurements from different containers and host • Different versions of policies Process mmap() kernel extend Container1 Measure mmap() record Process Policy1 Policy2 Measurements Container2 Integrity Attestation for Container (Cont.) • But… • Mixed measurements from different containers and host • Different versions of policies • And policies do not always agree with each other Me: -
Operating Systems & Virtualisation Security Knowledge Area
Operating Systems & Virtualisation Security Knowledge Area Issue 1.0 Herbert Bos Vrije Universiteit Amsterdam EDITOR Andrew Martin Oxford University REVIEWERS Chris Dalton Hewlett Packard David Lie University of Toronto Gernot Heiser University of New South Wales Mathias Payer École Polytechnique Fédérale de Lausanne The Cyber Security Body Of Knowledge www.cybok.org COPYRIGHT © Crown Copyright, The National Cyber Security Centre 2019. This information is licensed under the Open Government Licence v3.0. To view this licence, visit: http://www.nationalarchives.gov.uk/doc/open-government-licence/ When you use this information under the Open Government Licence, you should include the following attribution: CyBOK © Crown Copyright, The National Cyber Security Centre 2018, li- censed under the Open Government Licence: http://www.nationalarchives.gov.uk/doc/open- government-licence/. The CyBOK project would like to understand how the CyBOK is being used and its uptake. The project would like organisations using, or intending to use, CyBOK for the purposes of education, training, course development, professional development etc. to contact it at con- [email protected] to let the project know how they are using CyBOK. Issue 1.0 is a stable public release of the Operating Systems & Virtualisation Security Knowl- edge Area. However, it should be noted that a fully-collated CyBOK document which includes all of the Knowledge Areas is anticipated to be released by the end of July 2019. This will likely include updated page layout and formatting of the individual Knowledge Areas KA Operating Systems & Virtualisation Security j October 2019 Page 1 The Cyber Security Body Of Knowledge www.cybok.org INTRODUCTION In this Knowledge Area, we introduce the principles, primitives and practices for ensuring se- curity at the operating system and hypervisor levels. -
Discretionary Access Control (DAC)
CS 5323 Discretionary Access Control (DAC) Prof. Ravi Sandhu Executive Director and Endowed Chair Lecture 7 [email protected] www.profsandhu.com © Ravi Sandhu World-Leading Research with Real-World Impact! 1 Authentication, Authorization, Audit AAA Authentication Authorization Audit Who are You? What are You What Did You Do? Allowed to Do? siloed integrated © Ravi Sandhu World-Leading Research with Real-World Impact! 2 Access Control Fixed policy Discretionary Access Control Mandatory Access Control (DAC), 1970 (MAC), 1970 Role Based Access Control (RBAC), 1995 Attribute Based Access Control (ABAC), ???? Flexible policy © Ravi Sandhu World-Leading Research with Real-World Impact! 3 Access Matrix Model © Ravi Sandhu World-Leading Research with Real-World Impact! 4 Access Matrix Model Objects (and Subjects) F G S U r w r u own b j r w e V c own t s rights © Ravi Sandhu World-Leading Research with Real-World Impact! 5 Access Matrix Model Basic Abstractions Subjects Objects Rights The rights in a cell specify the access of the subject (row) to the object (column) © Ravi Sandhu World-Leading Research with Real-World Impact! 6 Users and Subjects A subject is a program (application) executing on behalf of a user A user may at any time be idle, or have one or more subjects executing on its behalf User-subject distinction is important if subject’s rights are different from a user’s rights Usually a subset In many systems a subject has all the rights of a user A human user may manifest as multiple users (accounts, principals) in the system © Ravi Sandhu World-Leading Research with Real-World Impact! 7 Users and Subjects JOE.TOP-SECRET JOE.SECRET JOE JOE.CONFIDENTIAL JOE.UNCLASSIFIED USER SUBJECTS © Ravi Sandhu World-Leading Research with Real-World Impact! 8 Users and Subjects JANE.CHAIRPERSON JANE.FACULTY JANE JANE. -
Role Hierarchies and Constraints for Lattice-Based Access Controls
Role Hierarchies and Constraints for Lattice-Based Access Controls Ravi Sandhu* George Mason University & SETA Corporation~* Abstract Role-based access control (RBAC) is a promising alternative to traditional discretionary and mandatory access controls. In RBAC permis- sions are associated with roles, and users are made members of appropriate roles thereby acquiring the roles' permissions. In this paper we formally show that lattice-based mandatory access controls can be enforced by appropriate configuration of RBAC components. Our constructions demonstrate that role hierarchies and constraints are required to effectively achieve this result. We show that variations of the lattice-based *-property, such as write-up (liberal *-property) and no-write-up (strict ,-property), can be easily accommodated in RBAC. Our results attest to the flexibility of RBAC and its ability to ac- commodate different policies by suitable configuration of role hierarchies and constraints. 1 INTRODUCTION Role-based access control (RBAC) has recently received considerable attention as a promising alternative to traditional discretionary and mandatory access controls (see, for example, [FK92, SCY96, SCFY96]). In RBAC permissions are associated with roles, and users are made members of appropriate roles thereby acquiring the roles' permissions. This greatly simplifies management of permissions. Roles are created for the various job functions in an organization and users are assigned roles based on their responsibilities and qualifications. Users can be easily reassigned from one role to another. Roles can be granted new permissions as new applications and systems are incorporated, and permissions can be revoked from roles as needed. An important characteristic of RBAC is that by itself it is policy neutral. -
Linux OS-Level Security Nikitas Angelinas
Linux OS-Level Security Nikitas Angelinas MSST 2015 Agenda ● SELinux ● SELinux issues ● Audit subsystem ● Audit issues ● Further OS hardening 2 SELinux ● Security-Enhanced Linux ● Is NOT a Linux distribution ● A kernel feature ● A Linux Security Module (LSM) ● security fields in kernel data structures — processes, files, directories, sockets, IPC, and other OS objects ● hooks on all paths from userspace — return a binary predicate: allowed or not allowed (e.g. EACCES) 3 SELinux ● SELinux is a labeling system ● Every process has a label ● Every OS object has a label ● Policy rules control access between processes and objects, based on their labels ● Policy rules are enforced by the kernel ● The objective is to contain misbehaving/compromised userspace applications 4 SELinux policy management application interface userspace open(2) kernel error checks selinuxfs DAC checks cache Allowed? miss? Security Server LSM hook Access Vector Cache (Policy Rules and Access Decision Logic) Yes/No return SELinux 5 SELinux ● Mandatory Access Control ● vs. Discretionary Access Control (file ownership, permissions) ● Labels are of the form user:role:type:level ● e.g. process: /usr/sbin/sshd → system_u:object_r:sshd_exec_t:s0 ● e.g. file: /root/ssh/* → root:object_r:ssh_home_t ● SELinux implements LSM hooks and offers: ● Role-based Access Control ● Type Enforcement ● Multi-Level Security 6 SELinux labels and rules ● ls -Z /usr/sbin/sshd -rwxr-xr-x. root root system_u:object_r:sshd_exec_t:s0 /usr/sbin/sshd ● ls -Z /root/.ssh/id_rsa -rw-------. root root root:object_r:ssh_home_t /root/.ssh/id_rsa ● ls -Z /etc/ssh/sshd_config -rw-------. root root system_u:object_r:etc_t /etc/ssh/sshd_config ● ls -Z /var/run/sshd.pid -rw-------. -
Security Architecture
COVER STORY RSBAC Architecture of Rule Set Based Access Control (RSBAC) Security Architecture inux security holes typically occur Integrating multiple security models simultaneously in the kernel and in Server programs and S bit tools. LThe best approach would be to detailed logs of any access:The free Rule Set Based Access Control avoid mistakes and update programs immediately if a bug occurs. This is not (RSBAC) security System offers customized protection for a wide range always possible, the next best thing is to of requirements. BY AMON OTT restrict potential damage, and this is where access control systems such as RSBAC come into play [1]. If an attacker exploits the security holes in servers or s bit tools, access to the system should be restricted to a minimum. In this case, even a successful compromise will cause only limited damage, and protective mechanisms can be implemented directly in the operating system kernel. The standard Linux kernel prevents access to various resources such as files, directories or system configurations, but unfortunately the standard mechanisms are fraught with weaknesses: •Poor granularity Ro • Discretionary access control nald Raefle , visipix.com • An all-powerful root user Linux access controls only offer the standard privileges read, write and execute; additionally they only allow distinct privileges to be defined for the owner of a file, the members of a group and all others. Restrictions typically do account used to run that process. kernel a while back, allow a program not apply to the root user. The Thus, an attacker, if fortunate, can launched by root to drop some granularity of these privileges is thus manipulate any files belonging to the privileges, but this is left up to the insufficient for many tasks. -
I. RSBAC Theory
The RSBAC library The RSBAC library Copyright © 2003 Amon Ott, Stanislav Ievlev and Henk Klöpping The RSBAC introduction Amon Ott Stanislav Ievlev Heinrich W. Klöpping The RSBAC introduction by Amon Ott, Stanislav Ievlev, and Heinrich W. Klöpping Audience: This book is intended for use by experienced and skilled Unix professionals who wish to install, configure and use RSBAC. Approach: This book resulted from a project founded on June 28th, 2002 by Amon Ott, Stanislav Ievlev and Henk Klöpping. It provides an introduction to Rule Set Based Access control (RSBAC). If you are new to RSBAC, this book is the place to start reading. It provides an overview of what RSBAC is and how it can be employed. It is aimed at both potential users of RSBAC and programmers that would like to enhance the software by writing their own modules - or even changing the software itself. This book also introduces its companions: The RSBAC cookbook, The RSBAC reference manual, The RSBAC programmers cookbook and The RSBAC programmers reference manual. To learn where the latest version of this book can be downloaded or read please refer to Section 6.2. Sources: Our sources of information were (Open Source) material on the Internet, several books, practical experience of the authors , research and programming work done by the authors and others. We try to give credit where due, but are fallible. We apologize. Caution While every precaution was made in the preparation of this book, we can assume no responsibility for errors or omissions. When you feel we have not given you proper credit or feel we may have violated your rights or when you have suggestions how we may improve our work please notify us immediately so we can take corrective actions. -
Case Study: Building a Secure Operating System for Linux
121 C H A P T E R 9 Case Study: Building a Secure Operating System for Linux The Linux operating system is a complete reimplementation of the POSIX interface initiated by Linus Torvalds [187]. Linux gained popularity throughout the 1990s, resulting in the promotion of Linux as a viable alternative to Windows, particularly for server systems (e.g., web servers). As Linux achieved acceptance, variety of efforts began to address the security problems of traditional UNIX systems (see Chapter 4). In this chapter, we describe the resulting approach for enforcing mandatory access control, the Linux Security Modules (LSM) framework. The LSM framework defines a reference monitor interface for Linux behind which a variety of reference monitor imple- mentations are possible. We also examine one of the LSM reference monitors, Security-enhanced Linux (SELinux), and evaluate how it uses the LSM framework to implement the reference monitor guarantees of Chapter 2. 9.1 LINUX SECURITY MODULES The Linux Security Modules (LSM) framework is a reference monitor system for the Linux ker- nel [342]. The LSM framework consists of two parts, a reference monitor interface integrated into the mainline Linux kernel (since version 2.6) and a reference monitor module, called an LSM, that implements reference monitor function (i.e., authorization module and policy store, see Chapter 2 for the reference monitor concept definition) behind that interface. Several independent modules have been developed for the LSM framework [228, 183, 127, 229] to implement different forms of reference monitor function (e.g., different policy modules). We examine the LSM reference monitor interface in this section, and one of its LSMs, Security-Enhanced Linux (SELinux) [229] in the subsequent section.