Lecture 7: Introduction to Sockets
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Network/Socket Programming in Java
Network/Socket Programming in Java Rajkumar Buyya Elements of C-S Computing a client, a server, and network Request Client Server Network Result Client machine Server machine java.net n Used to manage: c URL streams c Client/server sockets c Datagrams Part III - Networking ServerSocket(1234) Output/write stream Input/read stream Socket(“128.250.25.158”, 1234) Server_name: “manjira.cs.mu.oz.au” 4 Server side Socket Operations 1. Open Server Socket: ServerSocket server; DataOutputStream os; DataInputStream is; server = new ServerSocket( PORT ); 2. Wait for Client Request: Socket client = server.accept(); 3. Create I/O streams for communicating to clients is = new DataInputStream( client.getInputStream() ); os = new DataOutputStream( client.getOutputStream() ); 4. Perform communication with client Receiive from client: String line = is.readLine(); Send to client: os.writeBytes("Hello\n"); 5. Close sockets: client.close(); For multithreade server: while(true) { i. wait for client requests (step 2 above) ii. create a thread with “client” socket as parameter (the thread creates streams (as in step (3) and does communication as stated in (4). Remove thread once service is provided. } Client side Socket Operations 1. Get connection to server: client = new Socket( server, port_id ); 2. Create I/O streams for communicating to clients is = new DataInputStream( client.getInputStream() ); os = new DataOutputStream( client.getOutputStream() ); 3. Perform communication with client Receiive from client: String line = is.readLine(); Send to client: os.writeBytes("Hello\n"); -
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 . -
Retrofitting Privacy Controls to Stock Android
Saarland University Faculty of Mathematics and Computer Science Department of Computer Science Retrofitting Privacy Controls to Stock Android Dissertation zur Erlangung des Grades des Doktors der Ingenieurwissenschaften der Fakultät für Mathematik und Informatik der Universität des Saarlandes von Philipp von Styp-Rekowsky Saarbrücken, Dezember 2019 Tag des Kolloquiums: 18. Januar 2021 Dekan: Prof. Dr. Thomas Schuster Prüfungsausschuss: Vorsitzender: Prof. Dr. Thorsten Herfet Berichterstattende: Prof. Dr. Michael Backes Prof. Dr. Andreas Zeller Akademischer Mitarbeiter: Dr. Michael Schilling Zusammenfassung Android ist nicht nur das beliebteste Betriebssystem für mobile Endgeräte, sondern auch ein ein attraktives Ziel für Angreifer. Um diesen zu begegnen, nutzt Androids Sicher- heitskonzept App-Isolation und Zugangskontrolle zu kritischen Systemressourcen. Nutzer haben dabei aber nur wenige Optionen, App-Berechtigungen gemäß ihrer Bedürfnisse einzuschränken, sondern die Entwickler entscheiden über zu gewährende Berechtigungen. Androids Sicherheitsmodell kann zudem nicht durch Dritte angepasst werden, so dass Nutzer zum Schutz ihrer Privatsphäre auf die Gerätehersteller angewiesen sind. Diese Dissertation präsentiert einen Ansatz, Android mit umfassenden Privatsphäreeinstellun- gen nachzurüsten. Dabei geht es konkret um Techniken, die ohne Modifikationen des Betriebssystems oder Zugriff auf Root-Rechte auf regulären Android-Geräten eingesetzt werden können. Der erste Teil dieser Arbeit etabliert Techniken zur Durchsetzung von Sicherheitsrichtlinien -
Libioth (Slides)
libioth The definitive API for the Internet of Threads Renzo Davoli – Michael Goldweber "niversit$ o% Bolo&na '(taly) – *avier "niver#it$ (Cin!innati, "SA) ,irt-alS.-are Micro/ernel DevRoo0 1 © 2021 Davoli-Goldweber libioth. CC-BY-SA 4.0 (nternet of Thread# (IoTh) service1.company.com → 2001:1:2::1 service2.company.com → 2001:1:2::2 host.company.com→11.12.13.14 processes service3.company.com → 2001:1:2::3 2 © 2021 Davoli-Goldweber libioth. CC-BY-SA 4.0 IoTh vs Iold What is an end-node o% the (nternet4 (t depends on what is identified b$ an (P addre##. ● (nternet o% 1hreads – (oTh – 7roce##e#8threads are a-tonomou# nodes of the (nternet ● (nternet o% 9e&ac$ Devi!es 'in brie% (-old in this presentation) – (nternet o% :ost# – Internet of ;etwork Controller#. – (nternet o% ;a0e#5a!e# 2 © 2021 Davoli-Goldweber libioth. CC-BY-SA 4.0 7,M – IoTh - </ernel 4 © 2021 Davoli-Goldweber libioth. CC-BY-SA 4.0 7,M – IoTh - </ernel ● icro/ernel, Internet o% Threads, Partial Virtual a!hines have the co00on goal to create independent code units i05lementing services ● 1hey are all against monolithic i05lementation# ● 1he challenge o% this talk is to !reate !ontacts, e>5loit paralleli#0#+ that allow to share res-lts, A7I, code. = © 2021 Davoli-Goldweber libioth. CC-BY-SA 4.0 Network Sta!/ ● API to application layer TCP-IP stack TCP UDP IPv4 IPv6 ICMP(v4,v6) ● API (NPI) to data-link – (e.g. libioth uses VDE: libvdeplug) ? © 2021 Davoli-Goldweber libioth. CC-BY-SA 4.0 IoTh & </ernel User process User process TCP-IP stack TCP UDP TCP/IP stack process IPv4 IPv6 ICMP(v4,v6) TCP-IP stack TCP UDP IPv4 IPv6 ICMP(v4,v6) Data-link network server Data-link network server @ © 2021 Davoli-Goldweber libioth. -
Beej's Guide to Unix IPC
Beej's Guide to Unix IPC Brian “Beej Jorgensen” Hall [email protected] Version 1.1.3 December 1, 2015 Copyright © 2015 Brian “Beej Jorgensen” Hall This guide is written in XML using the vim editor on a Slackware Linux box loaded with GNU tools. The cover “art” and diagrams are produced with Inkscape. The XML is converted into HTML and XSL-FO by custom Python scripts. The XSL-FO output is then munged by Apache FOP to produce PDF documents, using Liberation fonts. The toolchain is composed of 100% Free and Open Source Software. Unless otherwise mutually agreed by the parties in writing, the author offers the work as-is and makes no representations or warranties of any kind concerning the work, express, implied, statutory or otherwise, including, without limitation, warranties of title, merchantibility, fitness for a particular purpose, noninfringement, or the absence of latent or other defects, accuracy, or the presence of absence of errors, whether or not discoverable. Except to the extent required by applicable law, in no event will the author be liable to you on any legal theory for any special, incidental, consequential, punitive or exemplary damages arising out of the use of the work, even if the author has been advised of the possibility of such damages. This document is freely distributable under the terms of the Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License. See the Copyright and Distribution section for details. Copyright © 2015 Brian “Beej Jorgensen” Hall Contents 1. Intro................................................................................................................................................................1 1.1. Audience 1 1.2. Platform and Compiler 1 1.3. -
How to XDP (With Snabb)
How to XDP (with Snabb) Max Rottenkolber <[email protected]> Tuesday, 21 January 2020 Table of Contents Intro 1 Creating an XDP socket 2 Mapping the descriptor rings 4 Binding an XDP socket to an interface 7 Forwarding packets from a queue to an XDP socket 8 Creating a BPF map . 9 Assembling a BPF program . 9 Attaching a BPF program to an interface . 12 Packet I/O 14 Deallocating the XDP socket 18 Intro Networking in userspace is becoming mainstream. Recent Linux kernels ship with a feature called eXpress Data Path (XDP) that intends to con- solidate kernel-bypass packet processing applications with the kernel’s networking stack. XDP provides a new kind of network socket that al- lows userspace applications to do almost direct I/O with network device drivers while maintaining integration with the kernel’s native network stack. To Snabb XDP looks like just another network I/O device. In fact the XDP ABI/API is so similar to a typical hardware interfaces that it feels a bit like driving a NIC, and not by accident. I think it is fair to describe XDP as a generic interface to Linux network drivers that also 1 has a virtual backend it integrates with: the Linux network stack. In that sense, XDP can be seen as a more hardware centric sibling of AF_PACKET. I can think of two reasons why XDP might be interesting for Snabb users: • While the Snabb community prefers NICs with open hardware interface specifications there are a lot of networking devices out there that lack open specifications. -
Improving Networking
IMPERIAL COLLEGE LONDON FINALYEARPROJECT JUNE 14, 2010 Improving Networking by moving the network stack to userspace Author: Matthew WHITWORTH Supervisor: Dr. Naranker DULAY 2 Abstract In our modern, networked world the software, protocols and algorithms involved in communication are among some of the most critical parts of an operating system. The core communication software in most modern systems is the network stack, but its basic monolithic design and functioning has remained unchanged for decades. Here we present an adaptable user-space network stack, as an addition to my operating system Whitix. The ideas and concepts presented in this report, however, are applicable to any mainstream operating system. We show how re-imagining the whole architecture of networking in a modern operating system offers numerous benefits for stack-application interactivity, protocol extensibility, and improvements in network throughput and latency. 3 4 Acknowledgements I would like to thank Naranker Dulay for supervising me during the course of this project. His time spent offering constructive feedback about the progress of the project is very much appreciated. I would also like to thank my family and friends for their support, and also anybody who has contributed to Whitix in the past or offered encouragement with the project. 5 6 Contents 1 Introduction 11 1.1 Motivation.................................... 11 1.1.1 Adaptability and interactivity.................... 11 1.1.2 Multiprocessor systems and locking................ 12 1.1.3 Cache performance.......................... 14 1.2 Whitix....................................... 14 1.3 Outline...................................... 15 2 Hardware and the LDL 17 2.1 Architectural overview............................. 17 2.2 Network drivers................................. 18 2.2.1 Driver and device setup....................... -
Sockets in the Kernel
Linux Kernel Networking – advanced topics (6) Sockets in the kernel Rami Rosen [email protected] Haifux, August 2009 www.haifux.org All rights reserved. Linux Kernel Networking (6)- advanced topics ● Note: ● This lecture is a sequel to the following 5 lectures I gave in Haifux: 1) Linux Kernel Networking lecture – http://www.haifux.org/lectures/172/ – slides:http://www.haifux.org/lectures/172/netLec.pdf 2) Advanced Linux Kernel Networking - Neighboring Subsystem and IPSec lecture – http://www.haifux.org/lectures/180/ – slides:http://www.haifux.org/lectures/180/netLec2.pdf Linux Kernel Networking (6)- advanced topics 3) Advanced Linux Kernel Networking - IPv6 in the Linux Kernel lecture ● http://www.haifux.org/lectures/187/ – Slides: http://www.haifux.org/lectures/187/netLec3.pdf 4) Wireless in Linux http://www.haifux.org/lectures/206/ – Slides: http://www.haifux.org/lectures/206/wirelessLec.pdf 5) Sockets in the Linux Kernel ● http://www.haifux.org/lectures/217/ – Slides: http://www.haifux.org/lectures/217/netLec5.pdf Note ● Note: This is the second part of the “Sockets in the Linux Kernel” lecture which was given in Haifux in 27.7.09. You may find some background material for this lecture in its slides: ● http://www.haifux.org/lectures/217/netLec5.pdf TOC ● TOC: – RAW Sockets – UNIX Domain Sockets – Netlink sockets – SCTP sockets. – Appendices ● Note: All code examples in this lecture refer to the recent 2.6.30 version of the Linux kernel. RAW Sockets ● There are cases when there is no interface to create sockets of a certain protocol (ICMP protocol, NETLINK protocol) => use Raw sockets. -
Post Sockets - a Modern Systems Network API Mihail Yanev (2065983) April 23, 2018
Post Sockets - A Modern Systems Network API Mihail Yanev (2065983) April 23, 2018 ABSTRACT In addition to providing native solutions for problems, es- The Berkeley Sockets API has been the de-facto standard tablishing optimal connection with a Remote point or struc- systems API for networking. However, designed more than tured data communication, we have identified that a com- three decades ago, it is not a good match for the networking mon issue with many of the previously provided networking applications today. We have identified three different sets of solutions has been leaving the products vulnerable to code problems in the Sockets API. In this paper, we present an injections and/or buffer overflow attacks. The root cause implementation of Post Sockets - a modern API, proposed by for such problems has mostly proved to be poor memory Trammell et al. that solves the identified limitations. This or resource management. For this reason, we have decided paper can be used for basis of evaluation of the maturity of to use the Rust programming language to implement the Post Sockets and if successful to promote its introduction as new API. Rust is a programming language, that provides a replacement API to Berkeley Sockets. data integrity and memory safety guarantees. It uses region based memory, freeing the programmer from the responsibil- ity of manually managing the heap resources. This in turn 1. INTRODUCTION eliminates the possibility of leaving the code vulnerable to Over the years, writing networked applications has be- resource management errors, as this is handled by the lan- come increasingly difficult. -
Introduction to RAW-Sockets Jens Heuschkel, Tobias Hofmann, Thorsten Hollstein, Joel Kuepper
Introduction to RAW-sockets Jens Heuschkel, Tobias Hofmann, Thorsten Hollstein, Joel Kuepper 16.05.2017 Technical Report No. TUD-CS-2017-0111 Technische Universität Darmstadt Telecooperation Report No. TR-19, The Technical Reports Series of the TK Research Division, TU Darmstadt ISSN 1864-0516 http://www.tk.informatik.tu-darmstadt.de/de/publications/ Introduction to RAW-sockets by Heuschkel, Jens Hofmann, Tobias Hollstein, Thorsten Kuepper, Joel May 17, 2017 Abstract This document is intended to give an introduction into the programming with RAW-sockets and the related PACKET-sockets. RAW-sockets are an additional type of Internet socket available in addition to the well known DATAGRAM- and STREAM-sockets. They do allow the user to see and manipulate the information used for transmitting the data instead of hiding these details, like it is the case with the usually used STREAM- or DATAGRAM sockets. To give the reader an introduction into the subject we will first give an overview about the different APIs provided by Windows, Linux and Unix (FreeBSD, Mac OS X) and additional libraries that can be used OS-independent. In the next section we show general problems that have to be addressed by the programmer when working with RAW-sockets. We will then provide an introduction into the steps necessary to use the APIs or libraries, which functionality the different concepts provide to the programmer and what they provide to simplify using RAW and PACKET-sockets. This section includes examples of how to use the different functions provided by the APIs. Finally in the additional material we will give some complete examples that show the concepts and can be used as a basis to write own programs. -
Flatpak a Desktop Version of Containers
Flatpak a desktop version of containers Alexander Larsson, Red Hat What is Flatpak? A distribution-independent, Linux-based application distribution and deployment mechanism for desktop applications distribution-independent ● run on any distribution ● build on any distribution ● Any version of the distribution Linux-based ● Flatpak runs only on Linux ● Uses linux-specific features ● However, needs to run on older kernel ● Current minimum target – RHEL 7 – Ubuntu 16.04 (Xenial) – Debian 9 (Stretch) Distribution mechanism ● Built in support for install ● Built in support for updates ● Anyone can set up a repository Deployment mechanism ● Run apps in a controlled environment – “container” ● Sandbox for improved security – Default sandbox is very limited – Apps can ask for more permissions Desktop application ● Focus on GUI apps ● No root permissions ● Automatically integrates with desktop ● App lifetimes are ad-hoc and transient ● Nothing assumes a “sysadmin” being available How is flatpak different from containers Filesystem layout Docker requirements ● Examples: – REST API micro-service – Website back-end ● Few dependencies, all hand-picked ● Runs as a daemon user ● Writes to nonstandard locations in file-system ● Not a lot of integration with host – DNS – Port forwarding – Volumes for data ● No access to host filesystem ● Updates are managed Docker layout ● One image for the whole fs – Bring your own dependencies – Layout up to each app ● Independent of host filesystem layout Flatpak requirements ● Examples – Firefox – Spotify – gedit -
Lesson-3 Case Study of Coding for Sending Application Layer Byte Streams on a TCP/IP Network Router Using RTOS Vxworks
Design Examples and Case Studies of Program Modeling and Programming with RTOS: Lesson-3 Case Study Of Coding For Sending Application Layer Byte Streams on a TCP/IP Network Router Using RTOS VxWorks Chapter-13 L03: "Embedded Systems - Architecture, Programming and Design" , 2015 1 Raj Kamal, Publs.: McGraw-Hill Education 1. Specifications Chapter-13 L03: "Embedded Systems - Architecture, Programming and Design" , 2015 2 Raj Kamal, Publs.: McGraw-Hill Education TCP/IP Stack In TCP/IP suite of protocols, application layer transfers the data with appropriate header words to transport layer. At transport layer, either UDP or TCP protocol is used and additional header words placed. Chapter-13 L03: "Embedded Systems - Architecture, Programming and Design" , 2015 3 Raj Kamal, Publs.: McGraw-Hill Education TCP/IP Stack transmitting subsystem Chapter-13 L03: "Embedded Systems - Architecture, Programming and Design" , 2015 4 Raj Kamal, Publs.: McGraw-Hill Education TCP/IP Stack UDP is connection-less protocol for datagram transfer of total size including headers of less than 216 Byte. TCP is connection oriented protocol, in which data of unlimited size can be transferred in multiple sequences to the internet layer At internet layer, the IP protocol is used and IP packets are formed, each packet with an IP header transfers to the network through network driver subsystem. Chapter-13 L03: "Embedded Systems - Architecture, Programming and Design" , 2015 5 Raj Kamal, Publs.: McGraw-Hill Education TCP/IP stack A TCP/IP stack network driver is available in the RTOSes It has a library, sockLib for socket programming. The reader may refer to VxWorks Programmer’s Guide when using these APIs and sockLib.