SSH SUDO passwordless to run commands on remote server

Question

Hi Experts,
We are running various OS/Network and Database related commands and scripts on Local and Remote Server to perform/compare the results
As part of this activity, we have bottleneck on running commands/scripts on the remote server as we need to provide password everytime whenever we use SSH command
Also, we need to run command as ssh sudo su - oracle for security purpose which prompts password two times.
we would like to automate this process in order to save password securely(temporarily) while running ssh sudo commands/scripts.
I see, there are various solutions using SSHPASS,EXPECT commands, however we dont have anything available to use within our group.
We may not be able to use SSHPASS as this component not installed during VM build, so we left with only option to use EXPECT.
So, Need your help to get any example working script using EXPECT for ssh sudo passwordless connection.
Appreciate if anybody can share ideas or working scripts
Thanks in advance

Answer 1

FWIW, here is a small script that I wrote several years ago that may help you to automate the password less ssh setup with a remote system. I just verified it and changed it to create a RSA key. The script still works and runs fine under Oracle Linux and Mac OS X.
Simply create a script called "passwordless-ssh" with the content shown below.
Assign execute privileges: chmod u+x passwordless-ssh
Then run the script as following:
./passwordless-ssh user@target_hostname_or_ip
The script will create a ssh RSA private and public key, prompt for the remote host password and the copy the pubic key to the remote host. A subsequent ssh login to the remote host should no longer prompt for the password. It is essential however that the scrips runs in an interactive session, which is verified.
#!/bin/bash
# Creating SSH public RSA key if non exist and copying it to remote target
# for passwordless SSH login.
# Author: Catch 22, Oracle OTN, 28-APR-2015
# Arguments: $1 (ssh login to remote target)
ME=passwordless-ssh
LOGFILE="/tmp/$ME.log"
f-mode()
# Check if session is interactive (terminal) or non-interactive (UDEV).
# Output: 0 = interactive, 1 = non-interactive
   [[ -t 0 || -p /dev/stdin ]] && return 0 || return 1
f-log()
# Display messages in interactive mode, or write output to syslog
# (/var/log/messages) when in non-interactive mode. Write the messages
# to a logfile if the syslog logger interface command is not available.
# Input: $1 = text
   if f-mode; then
      echo "$ME: $1"
   elif hash logger; then
      logger "$ME: $1"
   else
      echo "$ME:`date`: [logger] Cannot execute, aborting" >> $LOGFILE
      echo "$ME:`date`: $1" >> $LOGFILE
   fi     
# Exit and show error if current session is not interactive.
[ ! f-mode ] && f-log "[session] non-interactive, aborting" && exit 1
keyfile="$HOME/.ssh/id_rsa"
[ -z "$1" ] && echo "Missing 'user@target_host' argument. Aborted." && exit 1
if [ ! -f $keyfile ]; then
   mkdir -p $HOME/.ssh
   ssh-keygen -t rsa -f $keyfile -N ''
fi
keycode=`cat $keyfile.pub`
remote_cmd2="echo "$keycode" >> $remote_ssh_file; chmod 644 $remote_ssh_file;"
remote_ssh_dir="~/.ssh"
remote_ssh_file="$remote_ssh_dir/authorized_keys"
ssh -q $1 "mkdir -p $remote_ssh_dir; chmod 700 $remote_ssh_dir
echo "$keycode" >> $remote_ssh_file; chmod 644 $remote_ssh_file"
unset ME LOGFILE keyfile keycode remote_ssh_dir remote_ssh_file
#END