Replacing Telnet; OpenSSH, a secure alternative
The Internet is built with communication in mind. You will routinely move
around the Web from one site to the other or telnet to another machine to
check your mail or to administer that machine. The trouble with most of
these protocols is that they are not encrypted. Over a telnet connection,
your passwords are sent as plain-text, which can be read by anyone.
Using sophisticated programs called packet sniffers, even a amateur hacker
can spy on your connection and grab your data.
Secure Shell (SSH) was built to address these faults and provide a more
secure environment to work in. SSH encrypts all your traffic including
your passwords when you connect to another machine over the net. SSH also
replaces telnet, ftp, rsh, rlogin and rexec.
Let's take a look at OpenSSH, an excellent and more importantly open
source implementation of SSH. It is very well supported by the OpenBSD
team and includes rock-solid SSH2 support. Versions are available for
nearly all the Unices including Linux, which is what we are using here.
OpenSSH can be downloaded from www.openssh.com. The latest version as of
writing this article is 2.3.0. It is available as source tarballs
or in RPM format. If you are downloading the RPM's, then you need to get
the following files.
Zlib - This is an open source and patent free lossless data compression
library. This should already have been installed as part of your standard
Linux installation. If not then you can download it from
http://www.freesoftware.com/pub/infozip/zlib/. Source is available as
also RPMs. Take your pick.
OpenSSL - Another open source effort, aimed at creating a commercial grade
toolkit implementing Secure Socket Layer (SSL), Transport Layer Security
(TLS) and a strong cryptography library. This is also available as source
or RPM packages. The RPM packages are available right where the OpenSSH
RPMs are. The source packages are available at www.openssl.org
RPM: rpm -ivh zlib-1.1.3-i386.rpm
For the tar.gz
tar zxvf zlib-1.1.3.tar.gz
su -c "make install"
RPM: rpm -ivh openssl-0.9.5a-i386.rpm
For the tar.gz