There is a good reason why people write superficial messages on post cards: post cards afford no confidentiality and there is no expectation of privacy. The Internet can be compared to a post card; it is one large system where data is freely interchanged. While common sense tells us that post cards are open to the public, there is a misperception among non-technical Internet users that Internet data is kept private. However, nothing could be further from the truth; on the Wild West net,
all data is inherently open and unregulated.
There are solutions to this predicament. One solution is called SSH (Secure Shell). SSH provides a way to take that "postcard" and have it securely delivered by a courier.
In a nutshell, the book SSH, the Secure Shell: The Definitive Guide expands on two basic ideas: - Privacy is a basic human right, but on today's computer networks, privacy isn't guaranteed. - SSH is a simple idea, but it has many complex parts.
But the truth is that the need for privacy and security on today's networks is far too important to be encapsulated in two bullets. This book is so loaded with valuable and important information that anyone using or administering SSH should read it thoroughly.
As an introduction, SSH is a protocol that enables secure communications between computer systems that are communicating over insecure channels. SSH is more than simply a point-to-point encryption process such as a VPN. SSH allows users to authenticate themselves to remote hosts. After authentication, users can securely execute commands on a remote machine. SSH fills in for the security deficiencies that are inherent in applications such as telnet, ftp, rlogin, rsh, and rcp. The book also shows how SSH can be used to secure other protocols, such as POP, SMTP, IMAP, and others.
SSH was developed in response to the Unix "r" commands' (rsh, rlogin, rcp) vulnerability to attack. Some of these vulnerabilities include password and protocol sniffing, spoofing, eavesdropping and connection hijacking.
SSH, the Secure Shell: The Definitive Guide is everything you need to know about SSH and lives up to its bold claim of being a definitive guide. After an introduction to SSH -- why it came to be needed and its features and history -- the book goes into the core of the administration and use of SSH. The authors explain that SSH is in reality, not a true shell. The two versions of secure shell are SSH1 and SSH2; the book distinguishes between the two and describes when to use each version.
Chapter 2 details the basic client use of SSH. It shows how remote sessions are managed by the program and the various ways a user can authenticate to an SSH server.
Subsequent chapters cover the aspects of installing and compiling SSH. A myriad of different configuration possibilities are discussed. As the authors maintain, SSH is at its foundation a simple idea, but it has countless complex parts. SSH allows for a highly configurable architecture and provides both strong encryption and public-key authentication, but this comes at the price of complexity. The book allows an SSH administrator to understand the various versions and implementations of SSH (SSH1, SSH2, OpenSSH, F-Secure SSH, in addition to ports for Unix, Windows and Macintosh).
Chapter 9 provides in-depth coverage of a powerful feature of SSH -- port forwarding and X forwarding. Forwarding enables SSH to intercept service requests from another software program on one side of the SSH connection, send it across the encrypted connection, and then deliver it to the intended recipient on the other side. X Forwarding enables a user to securely run remote X Window applications by securing the X protocol traffic.
The authors demonstrate their extensive real-world experience with SSH throughout the book. The book includes many technical tips that could only have been obtained through extensive and widespread use. This attention to detail is especially useful considering the documentation provided with the free SSH implementation is often inaccessible for those without extensive SSH experience. Chapter 11 -- Case Studies, available on-line at Unix Review's book excerpt's -- details examples of real-world use of SSH. Two examples are how to integrate SSH with Pine or IMAP and the use of Kerberos with SSH. Anyone attempting such installations and configurations can attest to the difficulties involved.
For anyone who has had occasion to troubleshoot SSH, Chapter 12 -- Troubleshooting and Frequently Asked Questions -- will be a real boon. Many of the common (and some not so common) issues that have left many SSH systems administrators scratching their heads are addressed in this chapter.
For the SSH aficionado on a tight budget, the comprehensive SSH FAQ can be downloaded from various sites on the Web. For everyone else who needs to understand the often-undocumented inner-workings of SSH, this book is required reading.
