automatically authorize a remote host (SSH key swap) (See related posts)

#!/bin/bash
# kumar.mcmillan -at- farmdev.com

function usage()
{
    echo ""
    echo "Authorizes a host for automatic SSH use by sending your key to the remote host ..."
    echo "Usage: $0 remote_host_to_authorize [username:=defaults to current username]"
    echo ""
}

function cleanup()
{
    if [ -f $TEMP_PUB_KEY_XFER ]
    then
        rm $TEMP_PUB_KEY_XFER
    fi
}

function exit_on_error()
{
    cleanup
    exit 1
}

if [ $# -lt 1 -o "$1" = "-h" -o "$1" = "--help" ]
then
    usage
    exit 0
fi

PUB_KEY=~/.ssh/id_dsa.pub
if [ $# -eq 2 ]; then
    USER=$2
else
    USER=`whoami`
fi
HOST_TO_AUTH=$1
TEMP_PUB_KEY_XFER=/tmp/$USER"_TEMP_KEY"

echo "checking for $PUB_KEY ..."
if [ ! -f $PUB_KEY ]; then
    echo "generating your dsa public key (leave passphrase blank and save to $PUB_KEY when prompted) ..."
    ssh-keygen -t dsa
    if [ $? -ne 0 ]; then
        echo "ssh-keygen failed"
        exit_on_error
    fi
fi
echo "OK"

echo "for the following commands you will be asked to supply your password for $HOST_TO_AUTH :"

echo "copying a temp pub key to $HOST_TO_AUTH ..."
cat $PUB_KEY > $TEMP_PUB_KEY_XFER
chmod 700 $TEMP_PUB_KEY_XFER
echo "OK"

remote_key=`basename $TEMP_PUB_KEY_XFER`
scp $TEMP_PUB_KEY_XFER $USER@$HOST_TO_AUTH:~/$remote_key
if [ $? -ne 0 ]; then
    echo "scp failed"
    exit_on_error
fi
    
echo "authorizing $HOST_TO_AUTH for automatic SSH use ..."
ssh $USER@$HOST_TO_AUTH "cat ~/$remote_key >> ~/.ssh/authorized_keys; rm ~/$remote_key"
if [ $? -ne 0 ]; then
    echo "ssh failed"
    exit_on_error
fi
echo "OK"

cleanup
echo "authorization successful!  you can now login automatically to $HOST_TO_AUTH"
exit 0