BASH script that automates paswordless ssh.

ssh-auth

#!/bin/bash
# Script to create passwordless ssh on remote machine from current host
# requires ssh, naturally
# example usage: ssh-auth foreign.host.com id_dsa.pub myUserName
# @alvaromuir, 6.19.15

set -e
USAGECMD="Usage: $0 <hostname> <public-key.pub> [opt: username]"
SSHHOME=~/.ssh/
if [ "$3" ]
  then
    USER="$3"
  else
    USER=`whoami`
  fi
CONNMSG="connecting to $1 using $2 as $USER"
if [ -z "$1" ]
  then
  echo "ERROR - No hostname supplied." $USAGECMD
  exit
else
  if [ `builtin type -p cat` ]
    then
      CATCMD=`which cat`
      # echo $CATCMD
      if [ `builtin type -p ssh` ]
        then
          SSHCMD=`which ssh`
          if [ -z "$2" ]
            then
              keys=()
              for i in $SSHHOME*.pub
                do
                  keys+=("$i")
              done
              if [ ${#keys[@]} > 1 ]
                then
                echo ''
                echo "${#keys[@]} Keys found in $SSHHOME:"
                printf -- '%s\n' "${keys[@]/"$SSHHOME"}"
                echo ''
                echo $USAGECMD
              else
                echo $CONNMSG
              fi
            else
              if [ ! -e $SSHHOME$2 ]
                then
                  echo "ERROR: $SSHHOME$2 not found"
                else
                  echo $CONNMSG
                  $CATCMD $SSHHOME$2 | $SSHCMD $USER@$1 "mkdir -p ~/.ssh && chmod 700 .ssh && cat >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys"
              fi
          fi
      else echo "ERROR - No openssh executable found in \$PATH";
      fi
  else
    echo "ERROR - No \`cat\` executable found in \$PATH";
  fi
fi