Script to update SSH keys for a user

update-authorized-keys.sh

#!/usr/bin/env bash

USER=''
HOME_DIR=''
DEBUG=false
KEY_FILE=''

function setuser {
  if [ -z "$1" ]; then
    echo "RUNTIME EXCEPTION: No user supplied"
    exit 1
  fi
  debug "Setting user $1"
  USER="$1"
  HOME_DIR="$(eval echo ~$USER)"
  debug "Set home dir to: ${HOME_DIR}"
  return 0
}

function debug {
  ${DEBUG} && echo "$@"
  return 0
}

function addkeys {
  # ensure the user has an ~/.ssh/ dir
  debug "Adding .ssh dir for user"
  mkdir -p -m 700 "${HOME_DIR}/.ssh/"
  # If the authorized keys file exists, remove our managed keys
  if [ -f "${HOME_DIR}/.ssh/authorized_keys" ]; then
    debug "authorized keys file exists, removing automatically managed keys"
    sed -i '/### AUTOMATICALLY MANAGED KEYS ###/,/### END OF AUTOMATICALLY MANAGED KEYS ###/d' "${HOME_DIR}/.ssh/authorized_keys"
  else
    debug "Authorized keys file doesn't exist, adding it"
    touch "${HOME_DIR}/.ssh/authorized_keys"
  fi
  debug "Adding automatically managed keys"
  # Add our keys to the authorized keys file
  echo '### AUTOMATICALLY MANAGED KEYS ###' >> "${HOME_DIR}/.ssh/authorized_keys"
  
  #loop over lines in file
  # This is looping over each word and not each line
  while read -r line; do
    if [[ "${line}" == \#*  ]]; then
      continue
    fi
    debug "Adding key: ${line}"
    echo "${line}" >> "${HOME_DIR}/.ssh/authorized_keys"
  done <<< "${KEYS}"
  
  echo '### END OF AUTOMATICALLY MANAGED KEYS ###' >> "${HOME_DIR}/.ssh/authorized_keys"
  debug "finished adding keys"
  debug "Ensuring ownership of .ssh is correct"
  # ensure ownership and permissions are correct
  chown -R "${USER}:" "${HOME_DIR}/.ssh"
  debug "Making sure authorized keys file permissions are set correctly"
  chmod 0600 "${HOME_DIR}/.ssh/authorized_keys"
  
  return 0

}

while getopts "u:k:d" OPTION; do
  case ${OPTION} in
    u ) setuser "${OPTARG}"
        ;;
    k ) KEY_FILE="${OPTARG}"
        ;;
    d ) DEBUG=true
        ;;
  esac
done

if [ -z ${USER} ]; then
  setuser `whoami`
fi

if [ -z ${KEY_FILE} ]; then
  echo "MISSING ARGUMENT: Key file (-k) required"
  exit 1
fi

KEYS=$(wget -q -O - ${KEY_FILE})

addkeys