Kali Linux Revealed.pdf

Kali Linux Revealed Mastering the Penetration Testing Distribution Kali Linux Revealed Mastering the Penetration Testing Distribution by Raphaël Hertzog, Jim O’Gorman, and Mati Aharoni Kali Linux Revealed Copyright © 2017 Raphaël Hertzog, Jim O’Gorman, and Mati Aharoni This book is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License. ➨ http://creativecommons.org/licenses/by-sa/3.0/ Some sections of this book borrow content from the “Debian Administrator’s Handbook, Debian Jessie from Discovery to Mastery” written by Raphaël Hertzog and Roland Mas, which is available here: ➨ https://debian-handbook.info/browse/stable/ For the purpose of the CC-BY-SA license, Kali Linux Revealed is an Adaptation of the Debian Administrator’s Handbook. “Kali Linux” is a trademark of Offensive Security. Any use or distribution of this book, modified or not, must comply with the trademark policy defined here: ➨ https://www.kali.org/trademark-policy/ All Rights Not Explicitly Granted Above Are Reserved. ISBN: 978-0-9976156-0-9 (paperback) Offsec Press 19701 Bethel Church Road, #103-253 Cornelius NC 28031 USA www.offensive-security.com Library of Congress Control Number: 2017905895 The information in this book is distributed on an “As Is” basis, without warranty. While every precaution has been taken in the preparation of this work, neither the authors nor Offsec Press shall have any liabil- ity to any person or entity with respect to any loss or damage caused or alleged to be caused directly or indirectly by the information contained in it. Because of the dynamic nature of the Internet, any Web addresses or links contained in this book may have changed since publication and may no longer be valid. 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In 1998, I was an up-and-coming hacker, co-founding one of the earliest professional white hat hacking teams. We were kids, really, with dream jobs, paid to break into some of the most secure computer systems, networks, and buildings on the planet. It sounds pretty sexy, but in reality, we spent most of our time hovering over a keyboard, armed with the digital tools of our trade. We wielded a sordid collection of programs, designed to map networks and locate targets; then scan, exploit, and pivot through them. In some cases, one of us (often Jim Chapple) would write custom tools to do wicked things like scan a Class A network (something no other tool could do, at the time), but most often we would use or modify tools written by the hacker community. In those pre-Google days, we frequented BugTraq, AstaLaVista, Packet Storm, w00w00, SecurityFocus, X-Force, and other resources to conduct research and build our arsenal. Since we had limited time on each gig, we had to move quickly. That meant we couldn’t spend a lot of time fiddling with tools. It meant we had to learn the core tools inside and out, and keep the ancillary ones on tap, just in case. It meant we had to have our tools well-organized, documented, and tested so there would be few surprises in the field. After all, if we didn’t get in, we lost face with our clients and they would take our recommendations far less seriously. Because of this, I spent a lot of time cataloging tools. When a tool was released or updated, I’d go through a routine. I had to figure out if it would run on the attack platform (some didn’t), and whether it was worthwhile (some weren’t); I had to update any scripts that relied on it, document it, and test it, including carrying over any changes made to the previous version. Then, I would shake out all the tools and put them in directories based on their purpose during an assessment. I’d write wrapper scripts for certain tools, chain some tools together, and correlate all that into a separate CD that we could take into sensitive areas, when customers wouldn’t let us take in attack machines or remove media from their labs. This process was painful, but it was necessary. We knew that we had the ability to break into any network—if we applied our skills and expertise properly, stayed organized, and worked efficiently. Although remaining undefeated was a motivator, it was about providing a service to clients who needed us to break into networks, so they could plug gaps and move money toward critical-but- neglected information security programs. We spent years sharpening our skills and expertise but we wouldn’t have been successful without organization and efficiency. We would have failed if we couldn’t put our hands on the proper tool when needed. That’s why I spent so much time researching, documenting, testing, and cataloging tools, and at the turn of the 21st Century, it was quickly becoming an overwhelming, full-time job. Thanks to the Internet, the worldwide attack surface exploded and the variety and number of attack tools increased exponentially, as did the workload required to maintain them. Starting in 2004, the Internet exploded not only as a foundation for business but also as a social platform. Computers were affordable, more consumer-friendly and ubiquitous. Storage technol- ogy expanded from megabytes to gigabytes. Ethernet jumped from hundreds of kilobits to tens of megabits per second, and Internet connections were faster and cheaper than ever before. E- commerce was on the rise, social media sites like Facebook (2004) and Twitter (2006) came online and Google (1998) had matured to the point that anyone (including criminals) could find just about anything online. Research became critical for teams like ours because we had to keep up with new attacks and toolsets. We responded to more computer crimes, and forensic work demanded that we tread lightly as we mucked through potential evidence. The concept of a live CD meant that we could perform live forensics on a compromised machine without compromising evidence. Now our little team had to manage attack tools, forensic tools, and a sensitive area tool distribu- tion; we had to keep up with all the latest attack and exploit methodologies; and we had to, you know, actually do what we were paid for—penetration tests, which were in high demand. Things were spinning out of control, and before long, we were spending less time in battle and much more time researching, sharpening our tools, and planning. We were not alone in this struggle. In 2004, Mati “Muts” Aharoni, a hacker and security profes- sional released “WHoppiX” (White Hat Knoppix), a live Linux CD that he billed as “the ultimate pen testing live CD,” It included “all the exploits from SecurityFocus, Packet Storm and k-otik, Metasploit Framework 2.2, and much, much more.” I remember downloading WHoppiX and thinking it was a great thing to have around. I downloaded other live CDs, thinking that if I were ever in a real pinch, live CDs could save my bacon in the field. But I wasn’t about to rely on WHoppiX or any other CD for real work. I didn’t trust any of them to fulfill the majority of my needs; none of them felt right for my workflow; they were not full, installable distributions; and the moment I downloaded them they were out of date. An aged toolset is the kiss of death in our industry. I simply added these CD images, despite their relatively massive size, to our arsenal and kept up the painful process of maintaining our “real” toolkit. But despite my personal opinions at the time, and perhaps despite Muts’ expectations, WHoppiX and its descendants had a seismic impact on his life, our industry, and our community. 9** ,BMJ -JOVY 3FWFBMFE In 2005, WHoppiX evolved into WHAX, with an expanded and updated toolset, based on “the more modular SLAX (Slackware) live CD.” Muts and a growing team of volunteers from the hacker com- munity seemed to realize that no matter how insightful they were, they could never anticipate all the growth and fluctuation of our industry and that users of their CD would have varied needs in the field. It was obvious that Muts and his team were actually using WHAX in the field, and they seemed dedicated to making it work. This was encouraging to me. In 2006, Muts, Max Moser, and their teams consolidated Auditor Security Linux and WHAX into a single distribution called BackTrack. Still based on SLAX, BackTrack continued to grow, adding more tools, more frameworks, extended language support, extensive wireless support, a menu structure catering to both novice and pro users, and a heavily modified kernel. BackTrack became the leading security distribution, but many like me still used it as a backup for their ”real tools.” By early 2009, Muts and his team had extended BackTrack significantly to BackTrack 4. Now a full- time job for Muts, BackTrack was no longer a live CD but a full-blown Ubuntu-based distribution leveraging the Ubuntu software repositories. The shift marked a serious evolution: BackTrack 4 had an update mechanism. In Muts’ own words: “When syncing with our BackTrack repositories, you will regularly get security tool updates soon after they are released.” This was a turning point. The BackTrack team had tuned into the struggles facing pen testers, forensic analysts and others working in our industry. Their efforts would save us countless hours and provide a firm foundation, allowing us to get back into the fight and spend more time doing the important (and fun) stuff. As a result, the community responded by flocking to the forums and wiki; and by pitching in on the dev team. BackTrack was truly a community effort, with Muts still leading the charge. BackTrack 4 had finally become an industrial-strength platform and I, and others like me, breathed a sigh of relief. We knew firsthand the “pain and sufferance” Muts and his team were bearing, because we had been there. As a result, many of us began using BackTrack as a primary foundation for our work. Yes, we still fiddled with tools, wrote our own code, and developed our own exploits and techniques; and we researched and experimented; but we did not spend all our time collecting, updating, validating, and organizing tools. BackTrack 4 R1 and R2 were further revisions in 2010, leading to the ground-up rebuild of Back- Track 5 in 2011. Still based on Ubuntu, and picking up steam with every release, BackTrack was now a massive project that required a heroic volunteer and community effort but also funding. Muts launched Offensive Security (in 2006) not only to provide world-class training and penetra- tion testing services but also to provide a vehicle to keep BackTrack development rolling, and ensure that BackTrack remained open-source and free to use. BackTrack continued to grow and improve through 2012 (with R1, R2, and R3), maintaining an Ubuntu core and adding hundreds of new tools, including physical and hardware exploitation tools, VMware support, countless wireless and hardware drivers, and a multitude of stability im- provements and bug fixes. However, after the release of R3, BackTrack development went rela- tively, and somewhat mysteriously, quiet. 1SFGBDF 9*** There was some speculation in the industry. Some thought that BackTrack was getting “bought out”, selling its soul to a faceless evil corporate overlord for a massive payout. Offensive Secu- rity was growing into one of the most respected training companies and a thought leader in our industry, and some speculated that its success had gobbled up and sidelined the key BackTrack developers. However, nothing could be farther from the truth. In 2013, Kali Linux 1.0 was released. From the release notes: “After a year of silent development, Offensive Security is proud to announce the release and public availability of Kali Linux, the most advanced, robust, and stable penetration-testing distribution to date. Kali is a more mature, se- cure, and enterprise-ready version of BackTrack.” Kali Linux was not a mere rebranding of BackTrack. Sporting more than 600 completely repack- aged tools, it was clearly an amazing toolset, but there was still more to it than that. Kali had been built, from the ground up, on a Debian core. To the uninformed, this might not seem like a big deal. But the ripple effects were staggering. Thanks to a massive repackaging effort, Kali users could download the source for every single tool; they could modify and rebuild a tool as needed, with only a few keystrokes. Unlike other mainstream operating systems of the day, Kali Linux synchronized with the Debian repositories four times a day, which meant Kali users could get wickedly current package updates and security fixes. Kali developers threw themselves into the fray, packaging and maintaining upstream versions of many tools so that users were constantly kept on the bleeding edge. Thanks to its Debian roots, Kali’s users could bootstrap an installation or ISO directly from the repositories, which opened the door for completely customized Kali in- stallations or massive enterprise deployments, which could be further automated and customized with preseed files. To complete the customization trifecta, Kali Users could modify the desktop environment, alter menus, change icons, and even replace windowing environments. A massive ARM development push opened the door for installation of Kali Linux on a wide range of hardware platforms including access points, single-board computers (Raspberry Pi, ODROID, BeagleBone, and CubieBoard, for example), and ARM-based Chromebook computers. And last but certainly not least, Kali Linux sported seamless minor and major upgrades, which meant devotees would never have to re-install customized Kali Linux setups. The community took notice. In the first five days, 90,000 of us downloaded Kali 1.0. This was just the beginning. In 2015, Kali 2.0 was released, followed by the 2016 rolling releases. In summary, “If Kali 1.0 was focused on building a solid infrastructure, then Kali 2.0 is focused on overhauling the user experience and maintaining updated packages and tool repositories.” The current version of Kali Linux is a rolling distribution, which marks the end of discrete ver- sions. Now, users are up to date continuously and receive updates and patches as they are created. Core tools are updated more frequently thanks to an upstream version tagging system, ground- breaking accessibility improvements for the visually impaired have been implemented, and the Linux kernels are updated and patched to continue wireless 802.11 injection support. Software De- fined Radio (SDR) and Near-Field Communication (NFC) tools add support for new fields of security testing. Full Linux encrypted disk installation and emergency self-destruct options are available, 9*7 ,BMJ -JOVY 3FWFBMFE thanks to LVM and LUKS respectively, USB persistence options have been added, allowing USB- based Kali installs to maintain changes between reboots, whether the USB drive is encrypted or not. Finally, the latest revisions of Kali opened the door for NetHunter, an open-source world-class operating system running on mobile devices based on Kali Linux and Android. Kali Linux has evolved not only into the information security professional’s platform of choice, but truly into an industrial-grade, world-class, mature, secure, and enterprise-ready operating system distribution. Through the decade-long development process, Muts and his team, along with the tireless dedi- cation of countless volunteers from the hacker community, have taken on the burden of stream- lining and organizing our work environment, freeing us from much of the drudgery of our work and providing a secure and reliable foundation, allowing us to concentrate on driving the industry forward to the end goal of securing our digital world. And interestingly, but not surprisingly, an amazing community has built up around Kali Linux. Each and every month, three to four hundred thousand of us download a version of Kali. We come together on the Kali forums, some forty-thousand strong, and three to four hundred of us at a time can be found on the Kali IRC channel. We gather at conferences and attend Kali Dojos to learn how to best leverage Kali from the developers themselves. Kali Linux has changed the world of information security for the better, and Muts and his team have saved each of us countless hours of toil and frustration, allowing us to spend more time and energy driving the industry forward, together. But despite its amazing acceptance, support, and popularity, Kali has never released an official manual. Well, now that has changed. I’m thrilled to have come alongside the Kali development team and specifically Mati Aharoni, Raphaël Hertzog, Devon Kearns, and Jim O’Gorman to offer this, the first in perhaps a series of official publications focused on Kali Linux. In this book, we will focus on the Kali Linux platform itself, and help you understand and maximize the usage of Kali from the ground up. We won’t yet delve into the arsenal of tools contained in Kali Linux, but whether you’re a veteran or an absolute n00b, this is the best place to start, if you’re ready to dig in and get serious with Kali Linux. Regardless of how long you’ve been at the game, your decision to read this book connects you to the growing Kali Linux community, one of the oldest, largest, most active, and most vibrant in our industry. On behalf of Muts and the rest of the amazing Kali team, congratulations on taking the first step to mastering Kali Linux! Johnny Long February 2017 1SFGBDF 97 'PSFXPSE The sixteen high-end laptops ordered for your pentesting team just arrived, and you have been tasked to set them up—for tomorrow’s offsite engagement. You install Kali and boot up one of the laptops only to find that it is barely usable. Despite Kali’s cutting-edge kernel, the network cards and mouse aren’t working, and the hefty NVIDIA graphics card and GPU are staring at you blankly, because they lack properly installed drivers. You sigh. In Kali Live mode, you quickly type lspci into a console, then squint. You scroll through the hardware listing: “PCI bridge, USB controller, SATA controller. Aha! Ethernet and Network con- trollers.” A quick Google search for their respective model numbers, cross referenced with the Kali kernel version, reveals that these cutting-edge drivers haven’t reached the mainline kernel yet. But all is not lost. A plan is slowly formulating in your head, and you thank the heavens for the Kali Linux Revealed book that you picked up a couple of weeks ago. You could use the Kali Live- Build system to create a custom Kali ISO, which would have the needed drivers baked into the installation media. In addition, you could include the NVIDIA graphics drivers as well as the CUDA libraries needed to get that beast of a GPU to talk nicely to hashcat, and have it purr while cracking password hashes at blistering speeds. Heck, you could even throw in a custom wallpaper with a Microsoft Logo on it, to taunt your team at work. Since the hardware profiles for your installations are identical, you add a preseeded boot option to the ISO, so that your team can boot off a USB stick and have Kali installed with no user interaction— the installation takes care of itself, full disk encryption and all. Perfect! You can now generate an updated version of Kali on demand, specifically designed and optimized for your hardware. You saved the day. Mission complete! With the deluge of hardware hitting the market, this scenario is becoming more common for those of us who venture away from mainstream operating systems, in search of something leaner, meaner, or more suitable to our work and style. This is especially applicable to those attracted to the security field, whether it be an alluring hobby, fascination, or line of work. As newcomers, they often find themselves stumped by the environ- ment or the operating system. For many newcomers Kali is their first introduction to Linux. We recognized this shift in our user base a couple of years back, and figured that we could help our community by creating a structured, introductory book that would guide users into the world of security, while giving them all the Linux sophistication they would need to get started. And so, the Kali book was born—now available free over the Internet for the benefit of anyone interested in entering the field of security through Kali Linux. As the book started taking shape, however, we quickly realized that there was untapped potential. This would be a great opportunity to go further than an introductory Kali Linux book and explore some of the more interesting and little-known features. Hence, the name of the book: Kali Linux Revealed. By the end, we were chuffed with the result. The book answered all our requirements and I’m proud to say it exceeded our expectations. We came to the realization that we had inadvertently enlarged the book’s potential user base. It was no longer intended only for newcomers to the security field, but also included great information for experienced penetration testers who needed to improve and polish their control of Kali Linux—allowing them to unlock the full potential of our distribution. Whether they were fielding a single machine or thousands across an enterprise, making minor configuration changes or completely customizing down to the kernel level, building their own repositories, touching the surface or delving deep into the amazing Debian package management system, Kali Linux Revealed provides the roadmap. With your map in hand, on behalf of myself and the entire Kali Linux team, I wish you an exciting, fun, fruitful, and “revealing” journey! Muts, February 2017 97*** ,BMJ -JOVY 3FWFBMFE *OUSPEVDUJPO Kali Linux is the world’s most powerful and popular penetration testing platform, used by security professionals in a wide range of specializations, including penetration testing, forensics, reverse engineering, and vulnerability assessment. It is the culmination of years of refinement and the result of a continuous evolution of the platform, from WHoppiX to WHAX, to BackTrack, and now to a complete penetration testing framework leveraging many features of Debian GNU/Linux and the vibrant open source community worldwide. Kali Linux has not been built to be a simple collection of tools, but rather a flexible framework that professional penetration testers, security enthusiasts, students, and amateurs can customize to fit their specific needs. 8IZ 5IJT #PPL Kali Linux is not merely a collection of various information security tools that are installed on a standard Debian base and preconfigured to get you up and running right away. To get the most out of Kali, it is important to have a thorough understanding of its powerful Debian GNU/Linux underpinnings (which support all those great tools) and learning how you can put them to use in your environment. Although Kali is decidedly multi-purpose, it is primarily designed to aid in penetration testing. The objective of this book is not only to help you feel at home when you use Kali Linux, but also to help improve your understanding and streamline your experience so that when you are engaged in a penetration test and time is of the essence, you won’t need to worry about losing precious minutes to install new software or enable a new network service. In this book, we will introduce you first to Linux, then we will dive deeper as we introduce you to the nuances specific to Kali Linux so you know exactly what is going on under the hood. This is invaluable knowledge to have, particularly when you are trying to work under tight time constraints. It is not uncommon to require this depth of knowledge when you are getting set up, troubleshooting a problem, struggling to bend a tool to your will, parsing output from a tool, or leveraging Kali in a larger-scale environment. *T 5IJT #PPL GPS :PV If you are eager to dive into the intellectually rich and incredibly fascinating field of information security, and have rightfully selected Kali Linux as a primary platform, then this book will help you in that journey. This book is written to help first-time Linux users, as well as current Kali users seeking to deepen their knowledge about the underpinnings of Kali, as well as those who have used Kali for years but who are looking to formalize their learning, expand their use of Kali, and fill in gaps in their knowledge. In addition, this book can serve as a roadmap, technical reference, and study guide for those pur- suing the Kali Linux Certified Professional certification. (FOFSBM "QQSPBDI BOE #PPL 4USVDUVSF This book has been designed so that you can put your hands on Kali Linux right from the start. You don’t have to read half of the book to get started. Every topic is covered in a very pragmatic manner, and the book is packed with samples and screenshots to help make the explanations more concrete. In chapter 1, “About Kali Linux” [page 2], we define some basic terminology and explain the pur- pose of Kali Linux. In chapter 2, “Getting Started with Kali Linux” [page 14], we guide you step-by- step from the download of the ISO image to getting Kali Linux running on your computer. Next comes chapter 3, “Linux Fundamentals” [page 48] which supplies the basic knowledge that you need to know about any Linux system, such as its architecture, installation process, file system hierarchy, permissions, and more. At this point, you have been using Kali Linux as live system for a while. With chapter 4, “Installing Kali Linux” [page 66] you will learn how to make a permanent Kali Linux installation (on your hard disk) and with chapter 5, “Configuring Kali Linux” [page 104] how to tweak it to your liking. As a regular Kali user, it is time to get familiar with the important resources available to Kali users: chapter 6, “Helping Yourself and Getting Help” [page 124] gives you the keys to deal with the unexpected problems that you will likely face. With the basics well covered, the rest of the book dives into more advanced topics: chapter 7, “Securing and Monitoring Kali Linux” [page 150] gives you tips to ensure that your Kali Linux installation meets your security requirements. Next, chapter 8, “Debian Package Management” [page 170] explains how to leverage the full potential of the Debian packaging ecosystem. And in chapter 9, “Advanced Usage” [page 222], you learn how to create a fully customized Kali Linux ISO image. All those topics are even more relevant when you deploy Kali Linux at scale in an enterprise as documented in chapter 10, “Kali Linux in the Enterprise” [page 252]. 99 ,BMJ -JOVY 3FWFBMFE The last chapter, chapter 11, “Introduction to Security Assessments” [page 280], makes the link between everything that you have learned in this book and the day-to-day work of security pro- fessionals. "DLOPXMFEHNFOUT PG 3BQIB«M )FSU[PH I would like to thank Mati Aharoni: in 2012, he got in touch with me because I was one out of dozens of Debian consultants and he wanted to build a successor to BackTrack that would be based on Debian. That is how I started to work on Kali Linux, and ever since I have enjoyed my journey in the Kali world. Over the years, Kali Linux got closer to Debian GNU/Linux, notably with the switch to Kali Rolling, based on Debian Testing. Now most of my work, be it on Kali or on Debian, provides benefits to the entire Debian ecosystem. And this is exactly what keeps me so motivated to continue, day after day, month after month, year after year. Working on this book is also a great opportunity that Mati offered me. It is not the same kind of work but it is equally rewarding to be able to help people and share with them my expertise of the Debian/Kali operating system. Building on my experience with the Debian Administrator’s Handbook, I hope that my explanations will help you to get started in the fast-moving world of computer security. I would also like to thank all the Offensive Security persons who were involved in the book: Jim O’Gorman (co-author of some chapters), Devon Kearns (reviewer), Ron Henry (technical editor), Joe Steinbach and Tony Cruse (project managers). And thank you to Johnny Long who joined to write the preface but ended up reviewing the whole book. "DLOPXMFEHNFOUT PG +JN 0‫(ڔ‬PSNBO I would like to thank everyone involved in this project for their contributions, of which mine were only a small part. This book, much like Kali Linux itself was a collaborative project of many hands making light work. Special thanks to Raphaël, Devon, Mati, Johnny, and Ron for taking on the lion’s share of the effort. Without them, this book would not have come together. "DLOPXMFEHNFOUT PG.BUJ "IBSPOJ It has been a few years since Kali Linux was first released, and since day one, I have always dreamt of publishing an official book which covers the Kali operating system as a whole. It is therefore a great privilege for me to finally see such a book making it out to the public. I would like to sincerely thank everyone involved in the creation of this project—including Jim, Devon, Johnny, *OUSPEVDUJPO 99* and Ron. A very special thanks goes to Raphaël for doing most of the heavy lifting in this book, and bringing in his extensive expertise to our group. 99** ,BMJ -JOVY 3FWFBMFE ,FZXPSET -JOVY EJTUSJCVUJPO %FCJBO EFSJWBUJWF 1VSQPTF 'FBUVSFT 1PMJDJFT $IBQUFS "CPVU ,BMJ -JOVY $POUFOUT " #JU PG )JTUPSZ 3FMBUJPOTIJQ XJUI %FCJBO 1VSQPTF BOE 6TF $BTFT .BJO ,BMJ -JOVY 'FBUVSFT ,BMJ -JOVY 1PMJDJFT 4VNNBSZ Kali Linux1 is an enterprise-ready security auditing Linux distribution based on Debian GNU/Linux. Kali is aimed at security professionals and IT administrators, enabling them to con- duct advanced penetration testing, forensic analysis, and security auditing. 8IBU JT B -JOVY "MUIPVHI JU JT DPNNPOMZ VTFE BT B OBNF GPS UIF FOUJSF PQFSBUJOH TZTUFN -JOVY JT %JTUSJCVUJPO KVTU UIF OBNF PG UIF LFSOFM B QJFDF PG TPࡺ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ࡺXBSF QSPKFDU QSPWJEJOH NVMUJQMF WFSTJPOT PG JUT PQFSBUJOH TZTUFN BOE XF PࡺFO VTF UIF UFSN EJTUSJCVUJPO UP SFGFS UP B TQFDJGJD WFSTJPO PG JU GPS FYBN QMF UIF %FCJBO 4UBCMF PS %FCJBO 5FTUJOH EJTUSJCVUJPOT 5IF TBNF BMTP BQQMJFT UP ,BMJ -JOVY‫ن‬XJUI UIF ,BMJ 3PMMJOH EJTUSJCVUJPO GPS FYBNQMF " #JU PG )JTUPSZ The Kali Linux project began quietly in 2012, when Offensive Security decided that they wanted to replace their venerable BackTrack Linux project, which was manually maintained, with something that could become a genuine Debian derivative3 , complete with all of the required infrastructure and improved packaging techniques. The decision was made to build Kali on top of the Debian dis- tribution because it is well known for its quality, stability, and wide selection of available software. That is why I (Raphaël) got involved in this project, as a Debian consultant. The first release (version 1.0) happened one year later, in March 2013, and was based on Debian 7 “Wheezy”, Debian’s stable distribution at the time. In that first year of development, we pack- aged hundreds of pen-testing-related applications and built the infrastructure. Even though the number of applications is significant, the application list has been meticulously curated, drop- ping applications that no longer worked or that duplicated features already available in better programs. During the two years following version 1.0, Kali released many incremental updates, expanding the range of available applications and improving hardware support, thanks to newer kernel re- leases. With some investment in continuous integration, we ensured that all important packages 1 https://www.kali.org 2 https://www.debian.org 3 https://wiki.debian.org/Derivatives/Census ,BMJ -JOVY 3FWFBMFE were kept in an installable state and that customized live images (a hallmark of the distribution) could always be created. In 2015, when Debian 8 “Jessie” came out, we worked to rebase Kali Linux on top of it. While Kali Linux 1.x avoided the GNOME Shell (relying on GNOME Fallback instead), in this version we decided to embrace and enhance it: we added some GNOME Shell extensions to acquire missing features, most notably the Applications menu. The result of that work became Kali Linux 2.0, published in August 2015. (/0.& JT ,BMJ -JOVY‫ڔ‬T " EFTLUPQ FOWJSPONFOU JT B DPMMFDUJPO PG HSBQIJDBM BQQMJDBUJPOT UIBU TIBSF B DPNNPO %FGBVMU %FTLUPQ HSBQIJDBM UPPMLJU BOE UIBU BSF NFBOU UP CF VTFE UPHFUIFS PO VTFS XPSLTUBUJPOT %FTL &OWJSPONFOU UPQ FOWJSPONFOUT BSF HFOFSBMMZ OPU VTFE JO TFSWFST 5IFZ VTVBMMZ QSPWJEF BO BQQMJDB UJPO MBVODIFS B GJMF NBOBHFS B XFC CSPXTFS BO FNBJM DMJFOU BO Pख़JDF TVJUF FUD (/0.&4 JT POF PG UIF NPTU QPQVMBS EFTLUPQ FOWJSPONFOUT UPHFUIFS XJUI ,%&5 9GDF6 -9%&7."5&8 BOE JT JOTUBMMFE PO UIF NBJO *40 JNBHFT QSPWJEFE CZ ,BMJ -JOVY *G ZPV EJTMJLF (/0.& JU JT FBTZ UP CVJME B DVTUPN *40 JNBHF XJUI UIF EFTLUPQ FO WJSPONFOU PG ZPVS DIPPTJOH *OTUSVDUJPOT UP EP TP BSF DPWFSFE MBUFS JO UIJT CPPL JO DIBQUFS` َ"EWBODFE 6TBHFُ In parallel, we increased our efforts to ensure that Kali Linux always has the latest version of all pen-testing applications. Unfortunately, that goal was a bit at odds with the use of Debian Stable as a base for the distribution, because it required us to backport many packages. This is due to the fact that Debian Stable puts a priority on the stability of the software, often causing a long delay from the release of an upstream update to when it is integrated into the distribution. Given our investment in continuous integration, it was quite a natural move to rebase Kali Linux on top of Debian Testing so that we could benefit from the latest version of all Debian packages as soon as they were available. Debian Testing has a much more aggressive update cycle, which is more compatible with the philosophy of Kali Linux. This is, in essence, the concept of Kali Rolling. While the rolling distribution has been available for quite a while, Kali 2016.1 was the first release to officially embrace the rolling nature of that distribution: when you install the latest Kali release, your system actually tracks the Kali Rolling distribution and every single day you get new updates. In the past, Kali releases were snapshots of the underlying Debian distribution with Kali-specific packages injected into it. A rolling distribution has many benefits but it also comes with multiple challenges, both for those of us who are building the distribution and for the users who have to cope with a never-ending flow of updates and sometimes backwards-incompatible changes. This book aims to give you the knowledge required to deal with everything you may encounter while managing your Kali Linux installation. 4 https://www.gnome.org 5 https://www.kde.org 6 http://www.xfce.org 7 http://lxde.org 8 http://mate-desktop.org $IBQUFS ‫" ن‬CPVU ,BMJ -JOVY 3FMBUJPOTIJQ XJUI %FCJBO The Kali Linux distribution is based on Debian Testing9. Therefore, most of the packages available in Kali Linux come straight from this Debian repository. While Kali Linux relies heavily on Debian, it is also entirely independent in the sense that we have our own infrastructure and retain the freedom to make any changes we want. 5IF 'MPX PG 1BDLBHFT On the Debian side, the contributors are working every day on updating packages and uploading them to the Debian Unstable distribution. From there, packages migrate to the Debian Testing distribution once the most troublesome bugs have been taken out. The migration process also ensures that no dependencies are broken in Debian Testing. The goal is that Testing is always in a usable (or even releasable!) state. Debian Testing’s goals align quite well with those of Kali Linux so we picked it as the base. To add the Kali-specific packages in the distribution, we follow a two-step process. First, we take Debian Testing and force-inject our own Kali packages (located in our kali-dev-only repository) to build the kali-dev repository. This repository will break from time to time: for in- stance, our Kali-specific packages might not be installable until they have been recompiled against newer libraries. In other situations, packages that we have forked might also have to be updated, either to become installable again, or to fix the installability of another package that depends on a newer version of the forked package. In any case, kali-dev is not for end-users. kali-rolling is the distribution that Kali Linux users are expected to track and is built out of kali-dev in the same way that Debian Testing is built out of Debian Unstable. Packages migrate only when all dependencies can be satisfied in the target distribution. .BOBHJOH UIF %Jख़FSFODF XJUI %FCJBO As a design decision, we try to minimize the number of forked packages as much as possible. How- ever, in order to implement some of Kali’s unique features, some changes must be made. To limit the impact of these changes, we strive to send them upstream, either by integrating the feature di- rectly, or by adding the required hooks so that it is straightforward to enable the desired features without further modifying the upstream packages themselves. The Kali Package Tracker10 helps us to keep track of our divergence with Debian. At any time, we can look up which package has been forked and whether it is in sync with Debian, or if an update 9 https://www.debian.org/releases/testing/ 10 http://pkg.kali.org/derivative/kali-dev/ ,BMJ -JOVY 3FWFBMFE is required. All our packages are maintained in Git repositories11 hosting a Debian branch and a Kali branch side-by-side. Thanks to this, updating a forked package is a simple two-step process: update the Debian branch and then merge it into the Kali branch. While the number of forked packages in Kali is relatively low, the number of additional packages is rather high: in April 2017 there were almost 400. Most of these packages are free software complying with the Debian Free Software Guidelines12 and our ultimate goal would be to maintain those packages within Debian whenever possible. That is why we strive to comply with the Debian Policy13 and to follow the good packaging practices used in Debian. Unfortunately, there are also quite a few exceptions where proper packaging was nearly impossible to create. As a result of time being scarce, few packages have been pushed to Debian. 1VSQPTF BOE 6TF $BTFT While Kali’s focus can be quickly summarized as “penetration testing and security auditing”, there are many different tasks involved behind those activities. Kali Linux is built as a framework, be- cause it includes many tools covering very different use cases (though they may certainly be used in combination during a penetration test). For example, Kali Linux can be used on various types of computers: obviously on the laptops of penetration testers, but also on servers of system administrators wishing to monitor their net- work, on the workstations of forensic analysts, and more unexpectedly, on stealthy embedded de- vices, typically with ARM CPUs, that can be dropped in the range of a wireless network or plugged in the computer of target users. Many ARM devices are also perfect attack machines due to their small form factors and low power requirements. Kali Linux can also be deployed in the cloud to quickly build a farm of password-cracking machines and on mobile phones and tablets to allow for truly portable penetration testing. But that is not all; penetration testers also need servers: to use collaboration software within a team of pen-testers, to set up a web server for use in phishing campaigns, to run vulnerability scanning tools, and other related activities. Once you have booted Kali, you will quickly discover that Kali Linux’s main menu is organized by theme across the various kind of tasks and activities that are relevant for pen-testers and other information security professionals as shown in Figure 1.1, “Kali Linux’s Applications Menu” [page 6]. 11 http://git.kali.org 12 https://www.debian.org/social_contract 13 https://www.debian.org/doc/debian-policy/ $IBQUFS ‫" ن‬CPVU ,BMJ -JOVY 'JHVSF ,BMJ -JOVY٥T "QQMJDBUJPOT.FOV These tasks and activities include: Information Gathering: Collecting data about the target network and its structure, identify- ing computers, their operating systems, and the services that they run. Identifying poten- tially sensitive parts of the information system. Extracting all sorts of listings from running directory services. Vulnerability Analysis: Quickly testing whether a local or remote system is affected by a number of known vulnerabilities or insecure configurations. Vulnerability scanners use databases containing thousands of signatures to identify potential vulnerabilities. Web Application Analysis: Identifying misconfigurations and security weaknesses in web applications. It is crucial to identify and mitigate these issues given that the public avail- ability of these applications makes them ideal targets for attackers. Database Assessment: From SQL injection to attacking credentials, database attacks are a very common vector for attackers. Tools that test for attack vectors ranging from SQL in- jection to data extraction and analysis can be found here. Password Attacks: Authentication systems are always a go-to attack vector. Many useful tools can be found here, from online password attack tools to offline attacks against the encryption or hashing systems. Wireless Attacks: The pervasive nature of wireless networks means that they will always be a commonly attacked vector. With its wide range of support for multiple wireless cards, Kali is an obvious choice for attacks against multiple types of wireless networks. Reverse Engineering: Reverse engineering is an activity with many purposes. In support of offensive activities, it is one of the primary methods for vulnerability identification and ,BMJ -JOVY 3FWFBMFE exploit development. On the defensive side, it is used to analyze malware employed in tar- geted attacks. In this capacity, the goal is to identify the capabilities of a given piece of tradecraft. Exploitation Tools: Exploiting, or taking advantage of a (formerly identified) vulnerability, allows you to gain control of a remote machine (or device). This access can then be used for further privilege escalation attacks, either locally on the compromised machine, or on other machines accessible on its local network. This category contains a number of tools and utilities that simplify the process of writing your own exploits. Sniffing & Spoofing: Gaining access to the data as they travel across the network is often ad- vantageous for an attacker. Here you can find spoofing tools that allow you to impersonate a legitimate user as well as sniffing tools that allow you to capture and analyze data right off the wire. When used together, these tools can be very powerful. Post Exploitation: Once you have gained access to a system, you will often want to maintain that level of access or extend control by laterally moving across the network. Tools that assist in these goals are found here. Forensics: Forensic Linux live boot environments have been very popular for years now. Kali contains a large number of popular Linux-based forensic tools allowing you to do ev- erything from initial triage, to data imaging, to full analysis and case management. Reporting Tools: A penetration test is only complete once the findings have been reported. This category contains tools to help collate the data collected from information-gathering tools, discover non-obvious relationships, and bring everything together in various reports. Social Engineering Tools: When the technical side is well-secured, there is often the possi- bility of exploiting human behavior as an attack vector. Given the right influence, people can frequently be induced to take actions that compromise the security of the environment. Did the USB key that the secretary just plugged in contain a harmless PDF? Or was it also a Trojan horse that installed a backdoor? Was the banking website the accountant just logged into the expected website or a perfect copy used for phishing purposes? This category con- tains tools that aid in these types of attacks. System Services: This category contains tools that allow you to start and stop applications that run in the background as system services. .BJO ,BMJ -JOVY 'FBUVSFT Kali Linux is a Linux distribution that contains its own collection of hundreds of software tools specifically tailored for their target users—penetration testers and other security professionals. It also comes with an installation program to completely setup Kali Linux as the main operating system on any computer. $IBQUFS ‫" ن‬CPVU ,BMJ -JOVY This is pretty much like all other existing Linux distributions but there are other features that differentiate Kali Linux, many of which are tailored to the specific needs of penetration testers. Let’s have a look at some of those features. " -JWF 4ZTUFN Contrary to most Linux distributions, the main ISO image that you download is not simply ded- icated to installing the operating system; it can also be used as a bootable live system. In other words, you can use Kali Linux without installing it, just by booting the ISO image (usually after having copied the image onto a USB key). The live system contains the tools most commonly used by penetration testers so even if your day- to-day system is not Kali Linux, you can simply insert the disk or USB key and reboot to run Kali. However, keep in mind that the default configuration will not preserve changes between reboots. If you configure persistence with a USB key (see section 9.4, “Adding Persistence to the Live ISO with a USB Key” [page 239]), then you can tweak the system to your liking (modify config files, save reports, upgrade software, and install additional packages, for example), and the changes will be retained across reboots. 'PSFOTJDT.PEF In general, when doing forensic work on a system, you want to avoid any activity that would alter the data on the analyzed system in any way. Unfortunately, modern desktop environments tend to interfere with this objective by trying to auto-mount any disk(s) they detect. To avoid this behavior, Kali Linux has a forensics mode that can be enabled from the boot menu: it will disable all such features. The live system is particularly useful for forensics purposes, because it is possible to reboot any computer into a Kali Linux system without accessing or modifying its hard disks. " $VTUPN -JOVY ,FSOFM Kali Linux always provides a customized recent Linux kernel, based on the version in Debian Un- stable. This ensures solid hardware support, especially for a wide range of wireless devices. The kernel is patched for wireless injection support since many wireless security assessment tools rely on this feature. Since many hardware devices require up-to-date firmware files (found in /lib/firmware/), Kali installs them all by default—including the firmware available in Debian’s OPOGSFF section. Those are not installed by default in Debian, because they are closed-source and thus not part of Debian proper. ,BMJ -JOVY 3FWFBMFE $PNQMFUFMZ $VTUPNJ[BCMF Kali Linux is built by penetration testers for penetration testers but we understand that not ev- eryone will agree with our design decisions or choice of tools to include by default. With this in mind, we always ensure that Kali Linux is easy to customize based on your own needs and prefer- ences. To this end, we publish the live-build configuration used to build the official Kali images so you can customize it to your liking. It is very easy to start from this published configuration and implement various changes based on your needs thanks to the versatility of live-build. Live-build includes many features to modify the installed system, install supplementary files, in- stall additional packages, run arbitrary commands, and change the values pre-seeded to debconf. " 5SVTUBCMF 0QFSBUJOH 4ZTUFN Users of a security distribution rightfully want to know that it can be trusted and that it has been developed in plain sight, allowing anyone to inspect the source code. Kali Linux is developed by a small team of knowledgeable developers working transparently and following the best security practices: they upload signed source packages, which are then built on dedicated build daemons. The packages are then checksummed and distributed as part of a signed repository. The work done on the packages can be fully reviewed through the packaging Git repositories14 (which contain signed tags) that are used to build the Kali source packages. The evolution of each package can also be followed through the Kali package tracker15. 6TBCMF PO B 8JEF 3BOHF PG "3. %FWJDFT Kali Linux provides binary packages for the armel, armhf, and arm64 ARM architectures. Thanks to the easily installable images provided by Offensive Security, Kali Linux can be deployed on many interesting devices, from smartphones and tablets to Wi-Fi routers and computers of various shapes and sizes. ,BMJ -JOVY 1PMJDJFT While Kali Linux strives to follow the Debian policy whenever possible, there are some areas where we made significantly different design choices due to the particular needs of security profession- als. 14 http://git.kali.org 15 http://pkg.kali.org $IBQUFS ‫" ن‬CPVU ,BMJ -JOVY 4JOHMF 3PPU 6TFS CZ %FGBVMU Most Linux distributions encourage, quite sensibly, the use of a non-privileged account while run- ning the system and the use of a utility like sudo when administrative privileges are needed. This is sound security advice, providing an extra layer of protection between the user and any poten- tially disruptive or destructive operating system commands or operations. This is especially true for multiple user systems, where user privilege separation is a requirement—misbehavior by one user can disrupt or destroy the work of many users. Since many tools included in Kali Linux can only be executed with SPPU privileges, this is the de- fault Kali user account. Unlike other Linux distributions, you will not be prompted to create a non-privileged user when installing Kali. This particular policy is a major deviation from most Linux systems and tends to be very confusing for less experienced users. Beginners should be es- pecially careful when using Kali since most destructive mistakes occur when operating with root privileges. /FUXPSL 4FSWJDFT %JTBCMFE CZ %FGBVMU In contrast to Debian, Kali Linux disables any installed service that would listen on a public net- work interface by default, such as HTTP and SSH. The rationale behind this decision is to minimize exposure during a penetration test when it is detrimental to announce your presence and risk detection because of unexpected network inter- actions. You can still manually enable any services of your choosing by running systemctl enable service. We will get back to this in chapter 5, “Configuring Kali Linux” [page 104] later in this book. " $VSBUFE $PMMFDUJPO PG "QQMJDBUJPOT Debian aims to be the universal operating system and puts very few limits on what gets packaged, provided that each package has a maintainer. By way of contrast, Kali Linux does not package every penetration testing tool available. Instead, we aim to provide only the best freely-licensed tools covering most tasks that a penetration tester might want to perform. Kali developers working as penetration testers drive the selection process and we leverage their experience and expertise to make enlightened choices. In some cases this is a matter of fact, but there are other, more difficult choices that simply come down to personal preference. Here are some of the points considered when a new application gets evaluated: The usefulness of the application in a penetration testing context ,BMJ -JOVY 3FWFBMFE The unique functionality of the application’s features The application’s license The application’s resource requirements Maintaining an updated and useful penetration testing tool repository is a challenging task. We welcome tool suggestions within a dedicated category (New Tool Requests) in the Kali Bug Tracker16. New tool requests are best received when the submission is well-presented, including an explana- tion of why the tool is useful, how it compares to other similar applications, and so on. 4VNNBSZ In this chapter we have introduced you to Kali Linux, provided a bit of history, run through some of the primary features, and presented several use cases. We have also discussed some of the policies we have adopted when developing Kali Linux. Summary Tips: Kali Linux17 is an enterprise-ready security auditing Linux distribution based on Debian GNU/Linux. Kali is aimed at security professionals and IT administrators, enabling them to conduct advanced penetration testing, forensic analysis, and security auditing. Unlike most mainstream operating systems, Kali Linux is a rolling distribution, which means that you will receive updates every single day. The Kali Linux distribution is based on Debian Testing18. Therefore, most of the packages available in Kali Linux come straight from this Debian repository. While Kali’s focus can be quickly summarized with “penetration testing and security audit- ing”, there are several use cases including system administrators wishing to monitor their networks, forensic analysis, embedded device installations, wireless monitoring, installa- tion on mobile platforms, and more. Kali’s menus make it easy to get to tools for various tasks and activities including: vulnera- bility analysis, web application analysis, database assessment, password attacks, wireless at- tacks, reverse engineering, exploitation tools, sniffing and spoofing, post exploitation tools, forensics, reporting tools, social engineering tools, and system services. Kali Linux has many advanced features including: use as a live (non-installed) system, a ro- bust and safe forensics mode, a custom Linux kernel, ability to completely customize the system, a trusted and secure base operating system, ARM installation capability, secure de- fault network policies, and a curated set of applications. In the next chapter, we will jump in and try out Kali Linux thanks to its live mode. 16 http://bugs.kali.org 17 https://www.kali.org 18 https://www.debian.org/releases/testing/ $IBQUFS ‫" ن‬CPVU ,BMJ -JOVY ,FZXPSET %PXOMPBE *40 JNBHF -JWF CPPU $IBQUFS (FࡻJOH 4UBSUFE XJUI ,BMJ -JOVY $POUFOUT %PXOMPBEJOH B ,BMJ *40 *NBHF #PPUJOH B ,BMJ *40 *NBHF JO -JWF.PEF 4VNNBSZ Unlike some other operating systems, Kali Linux makes getting started easy, thanks to the fact that its disk images are live ISOs, meaning that you can boot the downloaded image without following any prior installation procedure. This means you can use the same image for testing, for use as a bootable USB or DVD-ROM image in a forensics case, or for installing as a permanent operating system on physical or virtual hardware. Because of this simplicity, it is easy to forget that certain precautions must be taken. Kali users are often the target of those with ill intentions, whether state sponsored groups, elements of orga- nized crime, or individual hackers. The open-source nature of Kali Linux makes it relatively easy to build and distribute fake versions, so it is essential that you get into the habit of downloading from original sources and verifying the integrity and the authenticity of your download. This is especially relevant to security professionals who often have access to sensitive networks and are entrusted with client data. %PXOMPBEJOH B ,BMJ *40 *NBHF 8IFSF UP %PXOMPBE The only official source of Kali Linux ISO images is the Downloads section of the Kali website. Due to its popularity, numerous sites offer Kali images for download, but they should not be considered trustworthy and indeed may be infected with malware or otherwise cause irreparable damage to your system. ➨ https://www.kali.org/downloads/ The website is available over HTTPS, making it difficult to impersonate. Being able to carry out a man-in-the-middle attack is not sufficient as the attacker would also need a XXXLBMJPSH cer- tificate signed by a Transport Layer Security (TLS) certificate authority that is trusted by the vic- tim’s browser. Because certificate authorities exist precisely to prevent this type of problem, they deliver certificates only to people whose identities have been verified and who have provided evidence that they control the corresponding website. DEJNBHFLBMJPSH 5IF MJOLT GPVOE PO UIF EPXOMPBE QBHF QPJOU UP UIF cdimage.kali.org EPNBJO XIJDI SFEJSFDUT UP B NJSSPS DMPTF UP ZPV JNQSPWJOH ZPVS USBOTGFS TQFFE XIJMF SFEVDJOH UIF CVSEFO PO ,BMJًT DFOUSBM TFSWFST " MJTU PG BWBJMBCMF NJSSPST DBO CF GPVOE IFSF ➨ http://cdimage.kali.org/README.mirrorlist 8IBU UP %PXOMPBE The official download page shows a short list of ISO images, as shown in Figure 2.1, “List of Images Offered for Download” [page 15]. ,BMJ -JOVY 3FWFBMFE 'JHVSF -JTU PG *NBHFT 0८FSFE GPS %PXOMPBE All disk images labeled 32- or 64-bit refer to images suitable for CPUs, found in most modern desk- top and laptop computers. If you are downloading for use on a fairly modern machine, it most likely contains a 64-bit processor. If you are unsure, rest assured that all 64-bit processors can run 32-bit instructions. You can always download and run the 32-bit image. The reverse is not true, however. Refer to the sidebar for more detailed information. If you are planning to install Kali on an embedded device, smartphone, Chromebook, access point, or any other device with an ARM processor, you must use the Linux armel or armhf images. $IBQUFS ‫( ن‬FࡻJOH 4UBSUFE XJUI ,BMJ -JOVY *T.Z $16 PS CJU 6OEFS 8JOEPXT ZPV DBO GJOE UIJT JOGPSNBUJPO CZ SVOOJOH UIF 4ZTUFN *OGPSNBUJPO BQQMJDBUJPO GPVOE JO UIF "DDFTTPSJFT 4ZTUFN 5PPMT GPMEFS 0O UIF 4ZTUFN 4VNNBSZ TDSFFO ZPV DBO JOTQFDU UIF 4ZTUFN 5ZQF GJFME JU XJMM DPOUBJO ُYCBTFE 1$ُ GPS B CJU $16 PS َYCBTFE 1$ُ GPS B CJU $16 6OEFS 04 9NBD04 UIFSF JT OP TUBOEBSE BQQMJDBUJPO TIPXJOH UIJT JOGPSNBUJPO CVU ZPV DBO TUJMM JOGFS JU GSPN UIF PVUQVU PG UIF uname -m DPNNBOE SVO PO UIF UFSNJOBM *U XJMM SFUVSO x86_64 PO B TZTUFN XJUI B CJU LFSOFM XIJDI DBO POMZ SVO PO B CJU $16 BOE PO TZTUFNT XJUI B CJU LFSOFM JU XJMM SFUVSO i386 PS TPNFUIJOH TJNJMBS i486 i586 PS i686 "OZ CJU LFSOFM DBO SVO PO B CJU $16 CVU TJODF "QQMF DPOUSPMT UIF IBSEXBSF BOE UIF TPࡺXBSF JU JT VOMJLFMZ ZPV XJMM GJOE UIJT DPOGJHVSBUJPO 6OEFS -JOVY ZPV DBO JOTQFDU UIF GMBHT GJFME JO UIF /proc/cpuinfo WJSUVBM GJMF *G JU DPOUBJOT UIF lm BࡻSJCVUF UIFO ZPVS $16 JT B CJU PUIFSXJTF JU JT B CJU 5IF GPMMPXJOH DPNNBOE MJOF XJMM UFMM ZPV XIBU LJOE PG $16 ZPV IBWF $ grep -qP ’^flags\s*:.*\blm\b’ /proc/cpuinfo && echo 64-bit ➥ || echo 32-bit 64-bit Now that you know whether you need a 32-bit or 64-bit image, there is only one step left: selecting the kind of image. The default Kali Linux image and the Kali Linux Light variant are both live ISOs that can be used to run the live system or to start the installation process. They differ only by the set of pre-installed applications. The default image comes with the GNOME desktop and a large collection of packages found to be appropriate for most penetration testers, while the light image comes with the Xfce desktop, (which is much less demanding on system resources), and a limited collection of packages, allowing you to choose only the apps you need. The remaining images use alternate desktop environments but come with the same large package collection as the main image. Once you have decided on the image you need, you can download the image by clicking on ”ISO” in the respective row. Alternatively, you can download the image from the BitTorrent peer-to-peer network by clicking on ”Torrent,” provided that you have a BitTorrent client associated with the.torrent extension. While your chosen ISO image is downloading, you should take note of the checksum written in the sha256sum column. Once you have downloaded your image, use this checksum to verify that the downloaded image matches the one the Kali development team put online (see next section). 7FSJGZJOH *OUFHSJUZ BOE "VUIFOUJDJUZ Security professionals must verify the integrity of their tools to not only protect their data and networks but also those of their clients. While the Kali download page is TLS-protected, the actual download link points to an unencrypted URL that offers no protection against potential man-in- the-middle attacks. The fact that Kali relies on a network of external mirrors to distribute the ,BMJ -JOVY 3FWFBMFE image means that you should not blindly trust what you download. The mirror you were directed to may have been compromised, or you might be the victim of an attack yourself. To alleviate this, the Kali project always provides checksums of the images it distributes. But to make such a check effective, you must be sure that the checksum you grabbed is effectively the checksum published by the Kali Linux developers. You have different ways to ascertain this. 3FMZJOH PO UIF 5-41SPUFDUFE 8FCTJUF When you retrieve the checksum from the TLS-protected download webpage, its origin is indi- rectly guaranteed by the X.509 certificate security model: the content you see comes from a web site that is effectively under the control of the person who requested the TLS certificate. Now you should generate the checksum of your downloaded image and ensure that it matches what you recorded from the Kali website: $ sha256sum kali-linux-2017.1-amd64.iso 49b1c5769b909220060dc4c0e11ae09d97a270a80d259e05773101df62e11e9d kali-linux-2016.2-amd64.iso If your generated checksum matches the one on the Kali Linux download page, you have the cor- rect file. If the checksums differ, there is a problem, although this does not indicate a compromise or an attack; downloads occasionally get corrupted as they traverse the Internet. Try your down- load again, from another official Kali mirror, if possible (see “cdimage.kali.org” [page 14] for more information about available mirrors). 3FMZJOH PO 1(1٥T 8FC PG 5SVTU If you don’t trust HTTPS for authentication, you are a bit paranoid but rightfully so. There are many examples of badly managed certificate authorities that issued rogue certificates, which ended up being misused. You may also be the victim of a “friendly” man-in-the-middle at- tack implemented on many corporate networks, using a custom, browser-implanted trust store that presents fake certificates to encrypted websites, allowing corporate auditors to monitor en- crypted traffic. For cases like this, we also provide a GnuPG key that we use to sign the checksums of the images we provide. The key’s identifiers and its fingerprints are shown here: pub rsa4096/0xED444FF07D8D0BF6 2012-03-05 [SC] [expires: 2018-02-02] Key fingerprint = 44C6 513A 8E4F B3D3 0875 F758 ED44 4FF0 7D8D 0BF6 uid [ full ] Kali Linux Repository sub rsa4096/0xA8373E18FC0D0DCB 2012-03-05 [E] [expires: 2018-02-02] This key is part of a global web of trust because it has been signed at least by me (Raphaël Hertzog) and I am part of the web of trust due to my heavy GnuPG usage as a Debian developer. $IBQUFS ‫( ن‬FࡻJOH 4UBSUFE XJUI ,BMJ -JOVY The PGP/GPG security model is very unique. Anyone can generate any key with any identity, but you would only trust that key if it has been signed by another key that you already trust. When you sign a key, you certify that you met the holder of the key and that you know that the associated identity is correct. And you define the initial set of keys that you trust, which obviously includes your own key. This model has its own limitations so you can opt to download Kali’s public key over HTTPS (or from a keyserver) and just decide that you trust it because its fingerprint matches what we an- nounced in multiple places, including just above in this book: $ wget -q -O - https://www.kali.org/archive-key.asc | gpg --import [ or ] $ gpg --keyserver hkp://keys.gnupg.net --recv-key ED444FF07D8D0BF6 gpg: key 0xED444FF07D8D0BF6: public key ”Kali Linux Repository ” imported gpg: Total number processed: 1 gpg: imported: 1 (RSA: 1) [...] $ gpg --fingerprint 7D8D0BF6 [...] Key fingerprint = 44C6 513A 8E4F B3D3 0875 F758 ED44 4FF0 7D8D 0BF6 [...] After you have retrieved the key, you can use it to verify the checksums of the distributed im- ages. Let’s download the file with the checksums (SHA256SUMS) and the associated signature file (SHA256SUMS.gpg) and verify the signature: $ wget http://cdimage.kali.org/current/SHA256SUMS [...] $ wget http://cdimage.kali.org/current/SHA256SUMS.gpg [...] $ gpg --verify SHA256SUMS.gpg SHA256SUMS gpg: Signature made Thu 16 Mar 2017 08:55:45 AM MDT gpg: using RSA key ED444FF07D8D0BF6 gpg: Good signature from ”Kali Linux Repository ” If you get that “Good signature” message, you can trust the content of the SHA256SUMS file and use it to verify the files you downloaded. Otherwise, there is a problem. You should review whether you downloaded the files from a legitimate Kali Linux mirror. Note that you can use the following command line to verify that the downloaded file has the same checksum that is listed in SHA256SUMS, provided that the downloaded ISO file is in the

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