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Program Library HOWTO David A
Program Library HOWTO David A. Wheeler version 1.36, 15 May 2010 This HOWTO for programmers discusses how to create and use program libraries on Linux. This includes static libraries, shared libraries, and dynamically loaded libraries. Table of Contents Introduction...........................................................................................................................3 Static Libraries.......................................................................................................................3 Shared Libraries....................................................................................................................4 Dynamically Loaded (DL) Libraries...............................................................................11 Miscellaneous......................................................................................................................14 More Examples....................................................................................................................18 Other Information Sources...............................................................................................22 Copyright and License.......................................................................................................23 Introduction This HOWTO for programmers discusses how to create and use program libraries on Linux using the GNU toolset. A “program library” is simply a file containing com- piled code (and data) that is to be incorporated later into a program; program libraries allow -
Improving Route Scalability: Nexthops As Separate Objects
Improving Route Scalability: Nexthops as Separate Objects September 2019 David Ahern | Cumulus Networks !1 Agenda Executive Summary ▪ If you remember nothing else about this talk … Driving use case Review legacy route API Dive into Nexthop API Benefits of the new API Cumulus Networks !2 Performance with the Legacy Route API route route route prefix/lenroute prefix/lendev prefix/lendev gatewayprefix/len gatewaydev gatewaydev gateway Cumulus Networks !3 Splitting Next Hops from Routes Routes with separate Nexthop objects Legacy Route API route route prefix/len nexthop route nexthop id dev route gateway prefix/lenroute prefix/lendev prefix/lendev gatewayprefix/len gatewaydev gatewaydev gateway route prefix/len nexthop nexthop nexthop id group nexthopdev nexthop[N] gatewaydev gateway Cumulus Networks !4 Dramatically Improves Route Scalability … Cumulus Networks !5 … with the Potential for Constant Insert Times Cumulus Networks !6 Networking Operating System Using Linux APIs Routing daemon or utility manages switchd ip FRR entries in kernel FIBs via rtnetlink APIs SDK userspace ▪ Enables other control plane software to use Linux networking APIs rtnetlink Data path connections, stats, troubleshooting, … FIB notifications FIB Management of hardware offload is separate kernel upper devices tunnels ▪ Keeps hardware in sync with kernel ... eth0 swp1 swp2 swpN Userspace driver with SDK leveraging driver driver driver kernel notifications NIC switch ASIC H / W Cumulus Networks !7 NOS with switchdev Driver In-kernel switchdev driver ip FRR Leverages -
Chrooting All Services in Linux
LinuxFocus article number 225 http://linuxfocus.org Chrooting All Services in Linux by Mark Nielsen (homepage) About the author: Abstract: Mark works as an independent consultant Chrooted system services improve security by limiting damage that donating time to causes like someone who broke into the system can possibly do. GNUJobs.com, writing _________________ _________________ _________________ articles, writing free software, and working as a volunteer at eastmont.net. Introduction What is chroot? Chroot basically redefines the universe for a program. More accurately, it redefines the "ROOT" directory or "/" for a program or login session. Basically, everything outside of the directory you use chroot on doesn't exist as far a program or shell is concerned. Why is this useful? If someone breaks into your computer, they won't be able to see all the files on your system. Not being able to see your files limits the commands they can do and also doesn't give them the ability to exploit other files that are insecure. The only drawback is, I believe it doesn't stop them from looking at network connections and other stuff. Thus, you want to do a few more things which we won't get into in this article too much: Secure your networking ports. Have all services run as a service under a non-root account. In addition, have all services chrooted. Forward syslogs to another computer. Analyze logs files Analyze people trying to detect random ports on your computer Limit cpu and memory resources for a service. Activate account quotas. The reason why I consider chroot (with a non-root service) to be a line of defense is, if someone breaks in under a non-root account, and there are no files which they can use to break into root, then they can only limit damage to the area they break in. -
The Kernel Report
The kernel report (ELC 2012 edition) Jonathan Corbet LWN.net [email protected] The Plan Look at a year's worth of kernel work ...with an eye toward the future Starting off 2011 2.6.37 released - January 4, 2011 11,446 changes, 1,276 developers VFS scalability work (inode_lock removal) Block I/O bandwidth controller PPTP support Basic pNFS support Wakeup sources What have we done since then? Since 2.6.37: Five kernel releases have been made 59,000 changes have been merged 3069 developers have contributed to the kernel 416 companies have supported kernel development February As you can see in these posts, Ralink is sending patches for the upstream rt2x00 driver for their new chipsets, and not just dumping a huge, stand-alone tarball driver on the community, as they have done in the past. This shows a huge willingness to learn how to deal with the kernel community, and they should be strongly encouraged and praised for this major change in attitude. – Greg Kroah-Hartman, February 9 Employer contributions 2.6.38-3.2 Volunteers 13.9% Wolfson Micro 1.7% Red Hat 10.9% Samsung 1.6% Intel 7.3% Google 1.6% unknown 6.9% Oracle 1.5% Novell 4.0% Microsoft 1.4% IBM 3.6% AMD 1.3% TI 3.4% Freescale 1.3% Broadcom 3.1% Fujitsu 1.1% consultants 2.2% Atheros 1.1% Nokia 1.8% Wind River 1.0% Also in February Red Hat stops releasing individual kernel patches March 2.6.38 released – March 14, 2011 (9,577 changes from 1198 developers) Per-session group scheduling dcache scalability patch set Transmit packet steering Transparent huge pages Hierarchical block I/O bandwidth controller Somebody needs to get a grip in the ARM community. -
The Linux Kernel Module Programming Guide
The Linux Kernel Module Programming Guide Peter Jay Salzman Michael Burian Ori Pomerantz Copyright © 2001 Peter Jay Salzman 2007−05−18 ver 2.6.4 The Linux Kernel Module Programming Guide is a free book; you may reproduce and/or modify it under the terms of the Open Software License, version 1.1. You can obtain a copy of this license at http://opensource.org/licenses/osl.php. This book is distributed in the hope it will be useful, but without any warranty, without even the implied warranty of merchantability or fitness for a particular purpose. The author encourages wide distribution of this book for personal or commercial use, provided the above copyright notice remains intact and the method adheres to the provisions of the Open Software License. In summary, you may copy and distribute this book free of charge or for a profit. No explicit permission is required from the author for reproduction of this book in any medium, physical or electronic. Derivative works and translations of this document must be placed under the Open Software License, and the original copyright notice must remain intact. If you have contributed new material to this book, you must make the material and source code available for your revisions. Please make revisions and updates available directly to the document maintainer, Peter Jay Salzman <[email protected]>. This will allow for the merging of updates and provide consistent revisions to the Linux community. If you publish or distribute this book commercially, donations, royalties, and/or printed copies are greatly appreciated by the author and the Linux Documentation Project (LDP). -
Oracle® Linux Administrator's Solutions Guide for Release 6
Oracle® Linux Administrator's Solutions Guide for Release 6 E37355-64 August 2017 Oracle Legal Notices Copyright © 2012, 2017, Oracle and/or its affiliates. All rights reserved. This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license agreement or allowed by law, you may not use, copy, reproduce, translate, broadcast, modify, license, transmit, distribute, exhibit, perform, publish, or display any part, in any form, or by any means. Reverse engineering, disassembly, or decompilation of this software, unless required by law for interoperability, is prohibited. The information contained herein is subject to change without notice and is not warranted to be error-free. If you find any errors, please report them to us in writing. If this is software or related documentation that is delivered to the U.S. Government or anyone licensing it on behalf of the U.S. Government, then the following notice is applicable: U.S. GOVERNMENT END USERS: Oracle programs, including any operating system, integrated software, any programs installed on the hardware, and/or documentation, delivered to U.S. Government end users are "commercial computer software" pursuant to the applicable Federal Acquisition Regulation and agency-specific supplemental regulations. As such, use, duplication, disclosure, modification, and adaptation of the programs, including any operating system, integrated software, any programs installed on the hardware, and/or documentation, shall be subject to license terms and license restrictions applicable to the programs. No other rights are granted to the U.S. -
Rootless Containers with Podman and Fuse-Overlayfs
CernVM Workshop 2019 (4th June 2019) Rootless containers with Podman and fuse-overlayfs Giuseppe Scrivano @gscrivano Introduction 2 Rootless Containers • “Rootless containers refers to the ability for an unprivileged user (i.e. non-root user) to create, run and otherwise manage containers.” (https://rootlesscontaine.rs/ ) • Not just about running the container payload as an unprivileged user • Container runtime runs also as an unprivileged user 3 Don’t confuse with... • sudo podman run --user foo – Executes the process in the container as non-root – Podman and the OCI runtime still running as root • USER instruction in Dockerfile – same as above – Notably you can’t RUN dnf install ... 4 Don’t confuse with... • podman run --uidmap – Execute containers as a non-root user, using user namespaces – Most similar to rootless containers, but still requires podman and runc to run as root 5 Motivation of Rootless Containers • To mitigate potential vulnerability of container runtimes • To allow users of shared machines (e.g. HPC) to run containers without the risk of breaking other users environments • To isolate nested containers 6 Caveat: Not a panacea • Although rootless containers could mitigate these vulnerabilities, it is not a panacea , especially it is powerless against kernel (and hardware) vulnerabilities – CVE 2013-1858, CVE-2015-1328, CVE-2018-18955 • Castle approach : it should be used in conjunction with other security layers such as seccomp and SELinux 7 Podman 8 Rootless Podman Podman is a daemon-less alternative to Docker • $ alias -
GNU Readline Library
GNU Readline Library Edition 2.1, for Readline Library Version 2.1. March 1996 Brian Fox, Free Software Foundation Chet Ramey, Case Western Reserve University This do cument describ es the GNU Readline Library, a utility which aids in the consistency of user interface across discrete programs that need to provide a command line interface. Published by the Free Software Foundation 675 Massachusetts Avenue, Cambridge, MA 02139 USA Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this p ermission notice are preserved on all copies. Permission is granted to copy and distribute mo di ed versions of this manual under the con- ditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a p ermission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another lan- guage, under the ab ove conditions for mo di ed versions, except that this p ermission notice may b e stated in a translation approved by the Foundation. c Copyright 1989, 1991 Free Software Foundation, Inc. Chapter 1: Command Line Editing 1 1 Command Line Editing This chapter describ es the basic features of the GNU command line editing interface. 1.1 Intro duction to Line Editing The following paragraphs describ e the notation used to representkeystrokes. i h i h C-k is read as `Control-K' and describ es the character pro duced when the k The text key is pressed while the Control key is depressed. h i The text M-k is read as `Meta-K' and describ es the character pro duced when the meta h i key if you have one is depressed, and the k key is pressed. -
Troubleshooting Passwords
Troubleshooting Passwords The following procedures may be used to troubleshoot password problems: • Performing Password Recovery with an Existing Administrator, page 1 • Performing Password Recovery with No Existing Administrator, page 1 • Performing Password Recovery for the Linux Grapevine User Account, page 2 Performing Password Recovery with an Existing Administrator To perform password recovery for a user (administrator, installer or observer) where there exists at least one controller administrator (ROLE_ADMIN) user account, take the following steps: 1 Contact the existing administrator to set up a temporary password for the user that requires password recovery. Note The administrator can set up a temporary password by deleting the user's account and then recreating it with the lost password. The user can then log back into the controller to regain access and change the password once again to whatever he or she desires. 2 The user then needs to log into the controller with the temporary password and change the password. Note Passwords are changed in the controller GUI using the Change Password window. For information about changing passwords, see Chapter 4, Managing Users and Roles in the Cisco Application Policy Infrastructure Controller Enterprise Module Configuration Guide. Performing Password Recovery with No Existing Administrator The following procedure describes how to perform password recovery where there exists only one controller administrator (ROLE_ADMIN) user account and this account cannot be successfully logged into. Cisco Application Policy Infrastructure Controller Enterprise Module Troubleshooting Guide, Release 1.3.x 1 Troubleshooting Passwords Performing Password Recovery for the Linux Grapevine User Account Note We recommend that you create at least two administrator accounts for your deployment. -
Version 7.8-Systemd
Linux From Scratch Version 7.8-systemd Created by Gerard Beekmans Edited by Douglas R. Reno Linux From Scratch: Version 7.8-systemd by Created by Gerard Beekmans and Edited by Douglas R. Reno Copyright © 1999-2015 Gerard Beekmans Copyright © 1999-2015, Gerard Beekmans All rights reserved. This book is licensed under a Creative Commons License. Computer instructions may be extracted from the book under the MIT License. Linux® is a registered trademark of Linus Torvalds. Linux From Scratch - Version 7.8-systemd Table of Contents Preface .......................................................................................................................................................................... vii i. Foreword ............................................................................................................................................................. vii ii. Audience ............................................................................................................................................................ vii iii. LFS Target Architectures ................................................................................................................................ viii iv. LFS and Standards ............................................................................................................................................ ix v. Rationale for Packages in the Book .................................................................................................................... x vi. Prerequisites -
Mesalock Linux: Towards a Memory-Safe Linux Distribution
MesaLock Linux Towards a memory-safe Linux distribution Mingshen Sun MesaLock Linux Maintainer | Baidu X-Lab, USA Shanghai Jiao Tong University, 2018 whoami • Senior Security Research in Baidu X-Lab, Baidu USA • PhD, The Chinese University of Hong Kong • System security, mobile security, IoT security, and car hacking • MesaLock Linux, TaintART, Pass for iOS, etc. • mssun @ GitHub | https://mssun.me !2 MesaLock Linux • Why • What • How !3 Why • Memory corruption occurs in a computer program when the contents of a memory location are unintentionally modified; this is termed violating memory safety. • Memory safety is the state of being protected from various software bugs and security vulnerabilities when dealing with memory access, such as buffer overflows and dangling pointers. !4 Stack Buffer Overflow • https://youtu.be/T03idxny9jE !5 Types of memory errors • Access errors • Buffer overflow • Race condition • Use after free • Uninitialized variables • Memory leak • Double free !6 Memory-safety in user space • CVE-2017-13089 wget: Stack-based buffer overflow in HTTP protocol handling • A stack-based buffer overflow when processing chunked, encoded HTTP responses was found in wget. By tricking an unsuspecting user into connecting to a malicious HTTP server, an attacker could exploit this flaw to potentially execute arbitrary code. • https://bugzilla.redhat.com/show_bug.cgi?id=1505444 • POC: https://github.com/r1b/CVE-2017-13089 !7 What • Linux distribution • Memory-safe user space !8 Linux Distribution • A Linux distribution (often abbreviated as distro) is an operating system made from a software collection, which is based upon the Linux kernel and, often, a package management system. !9 Linux Distros • Server: CentOS, Federa, RedHat, Debian • Desktop: Ubuntu • Mobile: Android • Embedded: OpenWRT, Yocto • Hard-core: Arch Linux, Gentoo • Misc: ChromeOS, Alpine Linux !10 Security and Safety? • Gentoo Hardened: enables several risk-mitigating options in the toolchain, supports PaX, grSecurity, SELinux, TPE and more. -
Kdump, a Kexec-Based Kernel Crash Dumping Mechanism
Kdump, A Kexec-based Kernel Crash Dumping Mechanism Vivek Goyal Eric W. Biederman Hariprasad Nellitheertha IBM Linux NetworkX IBM [email protected] [email protected] [email protected] Abstract important consideration for the success of a so- lution has been the reliability and ease of use. Kdump is a crash dumping solution that pro- Kdump is a kexec based kernel crash dump- vides a very reliable dump generation and cap- ing mechanism, which is being perceived as turing mechanism [01]. It is simple, easy to a reliable crash dumping solution for Linux R . configure and provides a great deal of flexibility This paper begins with brief description of what in terms of dump device selection, dump saving kexec is and what it can do in general case, and mechanism, and plugging-in filtering mecha- then details how kexec has been modified to nism. boot a new kernel even in a system crash event. The idea of kdump has been around for Kexec enables booting into a new kernel while quite some time now, and initial patches for preserving the memory contents in a crash sce- kdump implementation were posted to the nario, and kdump uses this feature to capture Linux kernel mailing list last year [03]. Since the kernel crash dump. Physical memory lay- then, kdump has undergone significant design out and processor state are encoded in ELF core changes to ensure improved reliability, en- format, and these headers are stored in a re- hanced ease of use and cleaner interfaces. This served section of memory. Upon a crash, new paper starts with an overview of the kdump de- kernel boots up from reserved memory and pro- sign and development history.