60-ssh-keys

#!/bin/sh
# vim: set ts=4 sw=4:
set -eu

update_ssh_keys() {
	local user="$1"
	local keys="$2"

	local homedir="$(getent passwd "$user" | cut -d: -f6)"
	if [ -z "$homedir" ]; then
		echo "ERROR: No home directory found for user $user" >&2
		return 1
	fi

	local auth_file="${homedir:-/root}/.ssh/authorized_keys"
	local group="$(id -gn "$user")"

	if ! [ -f "$auth_file" ]; then
		install -m700 -o "$user" -g "$group" -d "${auth_file%/*}"
		install -m600 -o "$user" -g "$group" /dev/null "$auth_file"
	fi

	printf '%s\n' "$keys" | while read -r key; do
		if ! grep -Fq "$key" "$auth_file"; then
			echo "Adding SSH key to $auth_file" >&2
			printf '%s\n' "$key" >> "$auth_file"
		fi
	done
}

if [ "${ROOT_SSH_KEYS:-}" ]; then
	update_ssh_keys 'root' "$ROOT_SSH_KEYS"
fi

if [ "${ADMIN_SSH_KEYS:-}" ]; then
	if ! id "${ADMIN_USER:-}" >/dev/null 2>&1; then
		ADMIN_USER='root'
	fi
	update_ssh_keys "$ADMIN_USER" "$ADMIN_SSH_KEYS"
fi

exit 0