krb5_runas.sh

# Requires the "kinit" command
#   Fedora: krb5-workstation
#   OpenSUSE: krb5-client
#   Ubuntu: krb5-user

# TODO: allow use of environment variables

USERN="$USER"

while (( "$#" )); do
  case "$1" in
    -D|--domain)
      REALM=$2
      shift 2
      ;;
    -U|--user*)
      USERN=$2
      shift 2
      ;;
    -P|--pass*)
      PASSW=$2
      shift 2
      ;;
    -V|--verbose)
      export KRB5_TRACE=/dev/stdout
      shift 1
      ;;
    -H|--help)
      echo 'TODO: help'
      shift 1
      exit
      ;;
    *)
      break
      ;;
  esac
done

if [ -z "$REALM" ]; then
  if [[ "$USERN" =~ @ ]]; then
    REALM="${USERN#*@}"
  elif [[ "$USERN" =~ \\ ]]; then
    REALM="${USERN%\\*}".local
    USERN="${USERN#*\\}"
  fi
fi

if [ -z "$*" ]; then
  set -- $(xargs -0 < /proc/$$/cmdline)
fi

if [ ! -z "$REALM" ]; then
  export KRB5_CONFIG="$(mktemp)"
  trap "rm -f \"$KRB5_CONFIG\"" EXIT
  echo $'[libdefaults]\ndefault_realm='"${REALM^^}" > "$KRB5_CONFIG"
fi

export KRB5CCNAME="$(mktemp)"
trap "rm -f \"$KRB5CCNAME\"" EXIT

(
  if [ ! -z "$PASSW" ]; then
    echo "$PASSW" | kinit -fVApE "$USERN" > /dev/null
  else
    kinit -fVApE "$USERN" 
  fi
) 2> /dev/null && $@