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Security Books Media Book Reviews

SSH, The Secure Shell 174

If you administer remote systems, check your email from the road, or just have a sense of paranoia about your home network, you're probably somewhat familiar with SSH. If you need to know more, though, danny writes "SSH, The Secure Shell will be another 'must have' O'Reilly volume for many system administrators. Read on for my full review."
SSH, The Secure Shell
author Daniel J. Barrett, Richard E. Silverman
pages 540
publisher O'Reilly & Associates
rating 8
reviewer Danny Yee
ISBN 0-596-00011-1
summary Comprehensive look at the ubiquitous SSH protocol, from installation to advanced uses.

A comprehensive study of what is now a key part of many network systems, SSH, The Secure Shell is a valuable resource for system administrators and users. Its explanations are clear and thorough: I'm not sure about the "definitive" claim, but Barrett and Silverman do go into considerable detail, often to the limits of "if you want to play with this you really ought to look at the source code." Perhaps most importantly, The Secure Shell is organised so one can easily skip unwanted detail and find just those portions that are relevant. As a result, it can be used in different ways -- read through to learn about ssh and what it can be used for, or just consulted as necessary to answer particular questions or solve particular problems.

Chapter one puts ssh in context, looking at its history and related technologies, and chapter two introduces basic client operation. Anyone who uses ssh and scp as simple telnet and ftp replacements and isn't curious about how they work can stop reading here -- and doesn't really need their own copy of The Secure Shell. Chapter three is an "under the covers" look at ssh. After a three-page introduction to cryptography (not really suitable for the reader with absolutely no background), it explains the ssh1 protocol and then how ssh2 differs from that and the extra features it offers. There is also a brief overview of the cryptographic algorithms commonly used in ssh implementations, and an explanation what ssh secures and what it doesn't.

The rest of the book is more implementation-specific: the primary implementations covered are SSH, SSH2, and OpenSSH. Being a lazy user of packages, I skipped chapter four, on installation and compile-time configuration. Chapter five is a guide to server configuration, working systematically through the sshd configuration file options.

The next four chapters are aimed at power users, covering client use in much greater depth. Chapter six explains key management: what identities are, how to create them, how to manage them with ssh agents, and how they can be used (to automate logons, most obviously, but fancy things can be done with multiple identities). Chapter seven goes through client configuration in detail, working through the configuration file options, chapter eight covers account configuration on the server-side (including forced commands), and chapter nine looks at port and X11 forwarding.

For those overwhelmed by all of this, chapter ten describes a sample "recommended setup" for everything from compilation to client configuration. Chapter eleven covers some special topics -- unattended SSH, FTP forwarding, mail over SSH, Kerberos, using SSH through a gateway host -- and chapter twelve is a troubleshooting FAQ.

Chapter thirteen is an overview of other implementations, with a table of products, and four short chapters then cover specific Windows and Mac clients. Of the three Windows clients covered here, two are proprietary and the third is only distributed as a bzipped tar file: it would have been good to have a chapter on one of the free and more user-friendly Windows clients, perhaps PuTTY or TTSSH, both of which get a "recommended" tag in the table of products.


You might want to purchase SSH, The Secure Shell from Barnes and Noble or read some of Danny's 600+ other book reviews. Want to be a famous book reviewer? You can read your own book reviews in this space by submitting your reviews after reading the book review guidelines.

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SSH, The Secure Shell

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  • by Anonymous Coward on Thursday May 30, 2002 @11:13AM (#3609454)
    O'Reilly's book is great. OpenSSH is magnificent. But it's SSH Agent [phil.uu.nl] that's the breath of life for all that, bringing it within reach for Joe Moron's grannie too.
  • Re:PuTTY rules (Score:4, Insightful)

    by anthony_dipierro ( 543308 ) on Thursday May 30, 2002 @11:14AM (#3609463) Journal

    It is very small (less than floppy size), is a standalone executable so it doesn't touch your registry, and it handles YAST just fine.

    As was mentioned by someone else, it does touch your registry, but only if it can. What I like about it most is I can put it in my network drive at school and use it from all the computer labs without installing anything. Before I found putty I had to resort to a slow, ugly, broken java applet.

    Just remember, unless you memorize the fingerprint, ssh doesn't protect against man-in-the-middle attacks when you switch client computers.

  • Re:PuTTY rules (Score:4, Insightful)

    by Our Man In Redmond ( 63094 ) on Thursday May 30, 2002 @12:07PM (#3609836)
    is a standalone executable so it doesn't touch your registry

    I beg to differ. It saves its information in HKEY_CURRENT_USER\SimonTatham\PuTTY (at least it does on my Win2000 Pro box).

    And yes, PuTTY does rock. At any given time I have about half a dozen PuTTY sessions open on my desktop, with various connections to my development servers and home box. Not quite as good as having a Linux box to work on, unfortunately, but about as close as you can reasonably get. Like the man says, it's called PuTTY because it makes Windows usable.
  • by Anonymous Coward on Thursday May 30, 2002 @12:39PM (#3610046)
    I have read this book, and I have to say it is virtually useless. Read the draft specification (available on www.ssh.com) and get out your sniffer if you want the real nuts and bolts of the protocol; It's alot cheaper. This book does not detail protocol operation at any length. It insults the reader with analogic descriptions with no detail.

    Read the O'Reilly book if you want to know how to set up specific SSH implementations.
  • by 47PHA60 ( 444748 ) on Thursday May 30, 2002 @01:55PM (#3610691) Journal
    agreed; I am especially happy with the sections on the anatomy of an SSH1 and SSH2 session. For administrative use and documentation, the descriptions are as comprehensive as the draft standard, but much more clearly written.

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