A simple shell script function for retrieving the fingerprint of a certificate. Useful for determining whether a certificate is already present in a keychain on macOS.

get_certificate_fingerprint.sh

write_error() {
  MSG=$2
  echo -e "\033[1;31m$1\033[0m \033[0;37m${MSG}\033[0m" 1>&2
  return 0
}

get_certificate_fingerprint() {
  if [ -z "$1" ]; then
    write_error "shared_functions" "The certificate file path was not defined."
    return 1
  fi
  if [ ! -e "$1" ]; then
    write_error "shared_functions" "The certificate could not be found or does not exist. (\"$1\")"
    return 2
  fi
  # echo $(openssl x509 -inform der -in $1 | openssl dgst -sha256 | awk '{print toupper($0)}')
  echo $(openssl x509 -inform der -in $1 -sha256 -fingerprint -noout | sed -e 's/SHA256 Fingerprint=//' | tr -d ':' | xargs)
  return 0
}

get_certificate_fingerprint certificate_goes_here.cer