Script to update SSH keys for a user from a github gist - uses jq or python as a fallback

update-authorized-keys.sh

#!/usr/bin/env bash

USER=''
HOME_DIR=''
DEBUG=false
GIST_ID=''
USE_PYTHON=0

function requirejq {
    which jq

    if [ "$?" -ne "0" ]; then
        debug "jq not installed, attempting install"
        which apt-get
        local APT_GET="$?"
        which apt
        local APT="$?"
        which yum
        local YUM="$?"
        which dnf
        local DNF="$?"
        if [ "$APT_GET" -eq "0" ]; then
            debug "Attempting to install with apt-get"
            apt-get install -y jq
        elif [ "$APT" -eq "0" ]; then
            debug "Attempting to install with apt"
            apt install -y jq
        elif [ "$YUM" -eq "0" ]; then
            debug "Attempting to install with yum"
            yum install -y jq
        elif [ "$DNF" -eq "0" ]; then
            debug "Attempting to install with dnf"
            dnf install -y jq
        else
            echo "Can't proceed, jq needs to be installed"
            exit 1
        fi
        if [ "$?" -ne "0" ]; then
            echo "Failed to install jq"
            exit 1
        fi
    fi
}

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:g:dp" OPTION; do
  case ${OPTION} in
    u ) setuser "${OPTARG}"
        ;;
    g ) GIST_ID="${OPTARG}"
        ;;
    d ) DEBUG=true
        ;;
    p ) USE_PYTHON=1
        ;;
  esac
done

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

if [ -z "${GIST_ID}" ]; then
  echo "MISSING ARGUMENT: Gist ID (-g) required"
  exit 1
fi

if [ "$USE_PYTHON" -ne "0" ]; then
    cat >/tmp/gistparser.py <<EOF
#!/usr/bin/env python

from urllib2 import urlopen
from urllib2 import HTTPError
import json
import sys

url = 'https://api.github.com/gists/$GIST_ID'
try:
    response = urlopen(url)
except HTTPError:
    sys.exit(1)

json_obj = json.loads(response.read())

for i in json_obj['files']:
    print json_obj['files'][i]['content']
EOF

    chmod +x /tmp/gistparser.py

    KEYS="$(/tmp/gistparser.py)"
else
    requirejq
    KEYS="$(curl -s -H 'accept: application/vnd.github.v3+json' https://api.github.com/gists/$GIST_ID | jq -r '.files[].content')"
fi

if [ -n "${KEYS}" ]; then
    addkeys
fi