userkeys.sh

#!/bin/sh

set -e

#############################################################################
# Modify and uncomment one of the examples bellow or your own key repository. 
#############################################################################
# uri="https://s3.amazonaws.com/BUCKET_NAME/devs.keys"
# uri="https://github.com/YOUR_GITHUB_USERNAME.keys"
# if using the examples, make sure you point to your own URL or you might accidently grant access to someone else!
# ideally all keys are in ed25519 format, to make them much smaller compared to RSA2048
# to generate a ed25519 key, run $ ssh-keygen -t ed25519

check_uri=$(curl -4ILs --connect-timeout 30 --max-time 30 "$uri" | grep 'HTTP\/' | grep -o '200' >/dev/null 2>&1; echo $?)

# only run if valid uri remote download location exists
if [[ "$check_uri" -eq '0' ]]; then
  # get's the user trying to authenticate $home path
  userHome=$(getent passwd "$1" | cut -d":" -f6)
  # userHome=$(getent passwd $(whoami) | cut -d":" -f6)
  
  # location of the key cache file
  cacheFile="${userHome}/.ssh/authorized_keys_cache"
  
  # how long do we accept the cached keys before pulling again
  cacheValidity="900"
  
  if [ ! -f "$cacheFile" ] || [ "$(($(date +%s) - $(stat -c %Y "$cacheFile")))" -gt "$cacheValidity" ]
  then
      if ! [ -x "$(command -v curl)" ]; then
          wget -4 -O "$cacheFile" "$uri"
          exit 1
      fi
  
      curl -4 --fail --silent --output "$cacheFile" "$uri"
  fi
  
  cat "$cacheFile"
fi