Replacing Telnet; OpenSSH, a secure alternative
tar zxvf openssl-0.9.5a.tar.gz
cd openssl-0.9.5a
./configure
make
su -c "make install"
OpenSSH
RPM: rpm -ivh openssh-2.3.0p1-1.i386.rpm <- Should be installed first
rpm -ivh openssh-clients-2.3.0p1-1.i386.rpm
rpm -ivh openssh-server-2.3.0p1-1.i386.rpm
For the tar.gz
tar zxvf openssh-2.3.0p1.tar.gz
cd openssh-2.3.0p1
./configure --sysconfdir=/etc/ssh
By default OpenSSH places the configuration files under /usr/local/etc. Using
the --sysconfdir allows you to set your own.
make
su -c "make install"
su -c "make host-key"
This will create the RSA and DSA host keys for your system. SSH works on
the public/private key pair method. RSA is the older format whereas DSA is
the new format and the one used by SSH2.
Enter the contrib sub-directory. There are a few files of importance here.
First is ssh.pam.generic. Most new Linux distributions use PAM for
authentication. This is a generic file that suits most distributions. A
version for Red Hat can be found in the redhat sub-directory. Copy this
file to /etc/pam.d as sshd.
cp sshd.pam.generic /etc/pam.d/sshd
Also provided here are init script for use with SuSE and Red Hat. The SuSE
directory also contains a configuration file that you should copy to
/etc/rc.config.d
cat rc.config.sshd >> /etc/rc.config
You can use these scripts across most distributions with a few changes.
One of the changes that we needed to make to the SuSE script was to change
the path from /usr/sbin to /usr/local/sbin. Copy the startup script to
/etc/rc.d/init.d (Red Hat) /sbin/init.d (SuSE).
Now you can start the ssh daemon by
/etc/rc.d/init.d/sshd start (Red Hat)
or
/sbin/init.d/sshd start (SuSE)
To check whether SSH is running, telnet to port 22 on your machine. You
should see the following.
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
SSH-1.99-OpenSSH_2.3.0p1
Usage
First thing that each user needs to do is create a public/private key
pair. This is done using the ssh-keygen program.
ssh-keygen -d
The command ssh-keygen is enough to prepare an RSA key for usage. The '-d'
bit makes a DSA key instead for use with SSH2. You will be asked for the
filename to store the key as. This allows you to have different
private/public key pairs for the various hosts that you will be connecting
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