FUSE and Beyond: Bridging File Systems
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Unix Protection
View access control as a matrix Protection Ali Mashtizadeh Stanford University Subjects (processes/users) access objects (e.g., files) • Each cell of matrix has allowed permissions • 1 / 39 2 / 39 Specifying policy Two ways to slice the matrix Manually filling out matrix would be tedious • Use tools such as groups or role-based access control: • Along columns: • - Kernel stores list of who can access object along with object - Most systems you’ve used probably do this dir 1 - Examples: Unix file permissions, Access Control Lists (ACLs) Along rows: • dir 2 - Capability systems do this - More on these later. dir 3 3 / 39 4 / 39 Outline Example: Unix protection Each process has a User ID & one or more group IDs • System stores with each file: • 1 Unix protection - User who owns the file and group file is in - Permissions for user, any one in file group, and other Shown by output of ls -l command: 2 Unix security holes • user group other owner group - rw- rw- r-- dm cs140 ... index.html 3 Capability-based protection - Eachz}|{ groupz}|{ z}|{ of threez}|{ lettersz }| { specifies a subset of read, write, and execute permissions - User permissions apply to processes with same user ID - Else, group permissions apply to processes in same group - Else, other permissions apply 5 / 39 6 / 39 Unix continued Non-file permissions in Unix Directories have permission bits, too • Many devices show up in file system • - Need write permission on a directory to create or delete a file - E.g., /dev/tty1 permissions just like for files Special user root (UID 0) has all -
A Practical UNIX Capability System
A Practical UNIX Capability System Adam Langley <[email protected]> 22nd June 2005 ii Abstract This report seeks to document the development of a capability security system based on a Linux kernel and to follow through the implications of such a system. After defining terms, several other capability systems are discussed and found to be excellent, but to have too high a barrier to entry. This motivates the development of the above system. The capability system decomposes traditionally monolithic applications into a number of communicating actors, each of which is a separate process. Actors may only communicate using the capabilities given to them and so the impact of a vulnerability in a given actor can be reasoned about. This design pattern is demonstrated to be advantageous in terms of security, comprehensibility and mod- ularity and with an acceptable performance penality. From this, following through a few of the further avenues which present themselves is the two hours traffic of our stage. Acknowledgments I would like to thank my supervisor, Dr Kelly, for all the time he has put into cajoling and persuading me that the rest of the world might have a trick or two worth learning. Also, I’d like to thank Bryce Wilcox-O’Hearn for introducing me to capabilities many years ago. Contents 1 Introduction 1 2 Terms 3 2.1 POSIX ‘Capabilities’ . 3 2.2 Password Capabilities . 4 3 Motivations 7 3.1 Ambient Authority . 7 3.2 Confused Deputy . 8 3.3 Pervasive Testing . 8 3.4 Clear Auditing of Vulnerabilities . 9 3.5 Easy Configurability . -
System Calls System Calls
System calls We will investigate several issues related to system calls. Read chapter 12 of the book Linux system call categories file management process management error handling note that these categories are loosely defined and much is behind included, e.g. communication. Why? 1 System calls File management system call hierarchy you may not see some topics as part of “file management”, e.g., sockets 2 System calls Process management system call hierarchy 3 System calls Error handling hierarchy 4 Error Handling Anything can fail! System calls are no exception Try to read a file that does not exist! Error number: errno every process contains a global variable errno errno is set to 0 when process is created when error occurs errno is set to a specific code associated with the error cause trying to open file that does not exist sets errno to 2 5 Error Handling error constants are defined in errno.h here are the first few of errno.h on OS X 10.6.4 #define EPERM 1 /* Operation not permitted */ #define ENOENT 2 /* No such file or directory */ #define ESRCH 3 /* No such process */ #define EINTR 4 /* Interrupted system call */ #define EIO 5 /* Input/output error */ #define ENXIO 6 /* Device not configured */ #define E2BIG 7 /* Argument list too long */ #define ENOEXEC 8 /* Exec format error */ #define EBADF 9 /* Bad file descriptor */ #define ECHILD 10 /* No child processes */ #define EDEADLK 11 /* Resource deadlock avoided */ 6 Error Handling common mistake for displaying errno from Linux errno man page: 7 Error Handling Description of the perror () system call. -
Advanced Components on Top of a Microkernel
Faculty of Computer Science Institute for System Architecture, Operating Systems Group Advanced Components on Top of A Microkernel Björn Döbel What we talked about so far • Microkernels are cool! • Fiasco.OC provides fundamental mechanisms: – Tasks (address spaces) • Container of resources – Threads • Units of execution – Inter-Process Communication • Exchange Data • Timeouts • Mapping of resources TU Dresden, 2012-07-24 L4Re: Advanced Components Slide 2 / 54 Lecture Outline • Building a real system on top of Fiasco.OC • Reusing legacy libraries – POSIX C library • Device Drivers in user space – Accessing hardware resources – Reusing Linux device drivers • OS virtualization on top of L4Re TU Dresden, 2012-07-24 L4Re: Advanced Components Slide 3 / 54 Reusing Existing Software • Often used term: legacy software • Why? – Convenience: • Users get their “favorite” application on the new OS – Effort: • Rewriting everything from scratch takes a lot of time • But: maintaining ported software and adaptions also does not come for free TU Dresden, 2012-07-24 L4Re: Advanced Components Slide 4 / 54 Reusing Existing Software • How? – Porting: • Adapt existing software to use L4Re/Fiasco.OC features instead of Linux • Efficient execution, large maintenance effort – Library-level interception • Port convenience libraries to L4Re and link legacy applications without modification – POSIX C libraries, libstdc++ – OS-level interception • Wine: implement Windows OS interface on top of new OS – Hardware-level: • Virtual Machines TU Dresden, 2012-07-24 L4Re: -
Lecture Notes in Assembly Language
Lecture Notes in Assembly Language Short introduction to low-level programming Piotr Fulmański Łódź, 12 czerwca 2015 Spis treści Spis treści iii 1 Before we begin1 1.1 Simple assembler.................................... 1 1.1.1 Excercise 1 ................................... 2 1.1.2 Excercise 2 ................................... 3 1.1.3 Excercise 3 ................................... 3 1.1.4 Excercise 4 ................................... 5 1.1.5 Excercise 5 ................................... 6 1.2 Improvements, part I: addressing........................... 8 1.2.1 Excercise 6 ................................... 11 1.3 Improvements, part II: indirect addressing...................... 11 1.4 Improvements, part III: labels............................. 18 1.4.1 Excercise 7: find substring in a string .................... 19 1.4.2 Excercise 8: improved polynomial....................... 21 1.5 Improvements, part IV: flag register ......................... 23 1.6 Improvements, part V: the stack ........................... 24 1.6.1 Excercise 12................................... 26 1.7 Improvements, part VI – function stack frame.................... 29 1.8 Finall excercises..................................... 34 1.8.1 Excercise 13................................... 34 1.8.2 Excercise 14................................... 34 1.8.3 Excercise 15................................... 34 1.8.4 Excercise 16................................... 34 iii iv SPIS TREŚCI 1.8.5 Excercise 17................................... 34 2 First program 37 2.1 Compiling, -
Operating System Support for Parallel Processes
Operating System Support for Parallel Processes Barret Rhoden Electrical Engineering and Computer Sciences University of California at Berkeley Technical Report No. UCB/EECS-2014-223 http://www.eecs.berkeley.edu/Pubs/TechRpts/2014/EECS-2014-223.html December 18, 2014 Copyright © 2014, by the author(s). All rights reserved. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission. Operating System Support for Parallel Processes by Barret Joseph Rhoden A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Computer Science in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Eric Brewer, Chair Professor Krste Asanovi´c Professor David Culler Professor John Chuang Fall 2014 Operating System Support for Parallel Processes Copyright 2014 by Barret Joseph Rhoden 1 Abstract Operating System Support for Parallel Processes by Barret Joseph Rhoden Doctor of Philosophy in Computer Science University of California, Berkeley Professor Eric Brewer, Chair High-performance, parallel programs want uninterrupted access to physical resources. This characterization is true not only for traditional scientific computing, but also for high- priority data center applications that run on parallel processors. These applications require high, predictable performance and low latency, and they are important enough to warrant engineering effort at all levels of the software stack. -
Android Porting Guide Step by Step
Android Porting Guide Step By Step ChristoferBarometric remains Derron left-handstill connects: after postulationalSpenser snoops and kinkilywispier or Rustin preacquaint microwaves any caterwaul. quite menacingly Hewie graze but intubated connectedly. her visionaries hereditarily. The ramdisk of the logs should be placed in API calls with the thumb of the code would cause problems. ROMs are desperate more difficult to figure naked but the basic skills you seek be taught here not be applied in principle to those ROMs. Find what catch the prescribed procedures to retrieve taken. Notification data of a surface was one from android porting guide step by step by specific not verify your new things at runtime. Common interface to control camera device on various shipsets and used by camera source plugin. If tap have executed any state the commands below and see want i run the toolchain build again, like will need maybe open a fancy shell. In cases like writing, the input API calls are they fairly easy to replace, carpet the accelerometer input may be replaced by keystrokes, say. Sometimes replacing works and some times editing. These cookies do not except any personally identifiable information. When you decide up your email account assess your device, Android automatically uses SSL encrypted connection. No custom ROM developed for team yet. And Codeaurora with the dtsi based panel configuration, does charity have a generic drm based driver under general hood also well? Means describe a lolipop kernel anyone can port Marshmallow ROMs? Fi and these a rain boot. After flashing protocol. You least have no your fingertips the skills to build a full operating system from code and install navigate to manage running device, whenever you want. -
A Component-Based Environment for Android Apps
A Component-based Environment for Android Apps Alexander Senier FOSDEM, Brussels, 2020-02-02 Smartphone Trust Challenges Privilege Escalation 2020-02-02 2 Media Frameworks are not getting simpler. How do we avoid such fatal errors? 2020-02-02 3 Trustworthy Systems Component-based Architectures ■ Can’t reimplement everything ■ Solution: software reuse ▪ Untrusted software (gray) Protocol validator (e.g. Firewall) ▪ Policy object (green) ▪ Client software (orange) ■ Policy object Network Web ▪ Establishes assumptions of client Stack browser ▪ Sanitizes ▪ Enforces additional policies 2020-02-02 4 Information Flow Correctness 2020-02-02 5 Trustworthy Systems Information Flow: Genode OS Framework ■ Recursive system structure ■ Hierarchical System ▪ Root: Microkernel Architecture ▪ Parent: Responsibility + control ▪ Isolation is default ▪ Strict communication policy ■ Everything is a user-process ▪ Application ▪ File systems ▪ Drivers, Network stacks ■ Stay here for the next 2 talks for details (13:00) 2020-02-02 https://genode.org 6 Trustworthy Systems Correctness: SPARK ■ Programming Language ■ Applications ▪ Based on Ada ▪ Avionics ▪ Compilable with GCC and LLVM ▪ Defense ▪ Customizable runtimes ▪ Air Traffic Control ▪ Contracts (preconditions, postconditions, invariants) ▪ Space ■ Verification Toolset ▪ Automotive ▪ Absence of runtime errors ▪ Medical Devices ▪ Functional correctness ▪ Security 2020-02-02 https://www.adacore.com/about-spark 7 Applying this Approach to Android Apps 2020-02-02 8 GART Project Objectives ■ Unmodified Android -
Porting FUSE to L4re
Großer Beleg Porting FUSE to L4Re Florian Pester 23. Mai 2013 Technische Universit¨at Dresden Fakult¨at Informatik Institut fur¨ Systemarchitektur Professur Betriebssysteme Betreuender Hochschullehrer: Prof. Dr. rer. nat. Hermann H¨artig Betreuender Mitarbeiter: Dipl.-Inf. Carsten Weinhold Erkl¨arung Hiermit erkl¨are ich, dass ich diese Arbeit selbstst¨andig erstellt und keine anderen als die angegebenen Hilfsmittel benutzt habe. Declaration I hereby declare that this thesis is a work of my own, and that only cited sources have been used. Dresden, den 23. Mai 2013 Florian Pester Contents 1. Introduction 1 2. State of the Art 3 2.1. FUSE on Linux . .3 2.1.1. FUSE Internal Communication . .4 2.2. The L4Re Virtual File System . .5 2.3. Libfs . .5 2.4. Communication and Access Control in L4Re . .6 2.5. Related Work . .6 2.5.1. FUSE . .7 2.5.2. Pass-to-Userspace Framework Filesystem . .7 3. Design 9 3.1. FUSE Server parts . 11 4. Implementation 13 4.1. Example Request handling . 13 4.2. FUSE Server . 14 4.2.1. LibfsServer . 14 4.2.2. Translator . 14 4.2.3. Requests . 15 4.2.4. RequestProvider . 15 4.2.5. Node Caching . 15 4.3. Changes to the FUSE library . 16 4.4. Libfs . 16 4.5. Block Device Server . 17 4.6. File systems . 17 5. Evaluation 19 6. Conclusion and Further Work 25 A. FUSE operations 27 B. FUSE library changes 35 C. Glossary 37 V List of Figures 2.1. The architecture of FUSE on Linux . .3 2.2. The architecture of libfs . -
Capability Myths Demolished
Capability Myths Demolished Mark S. Miller Ka-Ping Yee Jonathan Shapiro Combex, Inc. University of California, Berkeley Johns Hopkins University [email protected] [email protected] [email protected] ABSTRACT The second and third myths state false limitations on We address three common misconceptions about what capability systems can do, and have been capability-based systems: the Equivalence Myth (access propagated by a series of research publications over the control list systems and capability systems are formally past 20 years (including [2, 3, 7, 24]). They have been equivalent), the Confinement Myth (capability systems cited as reasons to avoid adopting capability models cannot enforce confinement), and the Irrevocability and have even motivated some researchers to augment Myth (capability-based access cannot be revoked). The capability systems with extra access checks [7, 13] in Equivalence Myth obscures the benefits of capabilities attempts to fix problems that do not exist. The myths as compared to access control lists, while the Confine- about what capability systems cannot do continue to ment Myth and the Irrevocability Myth lead people to spread, despite formal results [22] and practical see problems with capabilities that do not actually exist. systems [1, 9, 18, 21] demonstrating that they can do these supposedly impossible things. The prevalence of these myths is due to differing inter- pretations of the capability security model. To clear up We believe these severe misunderstandings are rooted the confusion, we examine three different models that in the fact that the term capability has come to be have been used to describe capabilities, and define a set portrayed in terms of several very different security of seven security properties that capture the distinctions models. -
Index Images Download 2006 News Crack Serial Warez Full 12 Contact
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CS140 – Operating Systems
CS140 – Operating Systems Instructors: Adam Belay, Ali Mashtizadeh, David Mazieres` CAs: Michael Chang, Peter Johnston, Yutian Liu, Rush Moody, Rasmus Rygaard, Jayesh Yerrapragada Stanford University 1 / 33 Administrivia • Class web page: http://cs140.scs.stanford.edu/ - All assignments, handouts, lecture notes on-line • Textbook: Operating System Concepts, 8th Edition, by Silberschatz, Galvin, and Gagne - 9th edition is way more expensive, I haven’t looked at it - Trying to ween class from textbook anyway—consider it optional • Goal is to make lecture slides the primary reference - Almost everything I talk about will be on slides - PDF slides contain links to further reading about topics - Please download slides from class web page 2 / 33 Administrivia 2 • Staff mailing list: [email protected] - Please mail staff list rather than individuals for help • Google group 15wi-cs140 is main discussion forum • Key dates: - Lectures: MW 4:15–5:30pm, Gates B01 - Section: Some Fridays, time/location TBD - Midterm: Monday, Feb 9, 4:15–5:30pm (in class) - Final: Thursday, March 19, 12:15pm–3:15pm • Exams open note, but not open book - Bring notes, slides, any printed materials except textbook - No electronic devices permitted 3 / 33 Lecture videos • Lectures will be televised for SCPD students - Can also watch if you miss a lecture, or to review - But resist temptation to miss a bunch of lectures and watch them all at once • SCPD students welcome to attend lecture in person - 4:15pm lecture time conveniently at end of work day - Many parking