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特定主机/动态 DNS 的 UFW 规则

tag-icon • tag-icon linux firewall ufw rules ddns
特定主机/动态 DNS 的 UFW 规则

如何设置 UFW（简单防火墙）来为特定主机添加规则？例如，我只想允许来自 yourpc.no-ip.org 的 SSH？

答案1

我发现了一个非常有用的脚本，可以为特定主机动态创建规则在这篇博客中。该脚本需要使用 cron 运行，这样它才能在 IP 发生变化时查找主机名并添加/删除规则。

#!/bin/bash


HOSTS_ALLOW=/etc/ufw-dynamic-hosts.allow
IPS_ALLOW=/var/tmp/ufw-dynamic-ips.allow

add_rule() {
  local proto=$1
  local port=$2
  local ip=$3
  local regex="${port}\/${proto}.*ALLOW.*IN.*${ip}"
  local rule=$(ufw status numbered | grep $regex)
  if [ -z "$rule" ]; then
      ufw allow proto ${proto} from ${ip} to any port ${port}
  else
      echo "rule already exists. nothing to do."
  fi
}

delete_rule() {
  local proto=$1
  local port=$2
  local ip=$3
  local regex="${port}\/${proto}.*ALLOW.*IN.*${ip}"
  local rule=$(ufw status numbered | grep $regex)
  if [ -n "$rule" ]; then
      ufw delete allow proto ${proto} from ${ip} to any port ${port}
  else
      echo "rule does not exist. nothing to do."
  fi
}


sed '/^[[:space:]]*$/d' ${HOSTS_ALLOW} | sed '/^[[:space:]]*#/d' | while read line
do
    proto=$(echo ${line} | cut -d: -f1)
    port=$(echo ${line} | cut -d: -f2)
    host=$(echo ${line} | cut -d: -f3)

    if [ -f ${IPS_ALLOW} ]; then
      old_ip=$(cat ${IPS_ALLOW} | grep ${host} | cut -d: -f2)
    fi

    ip=$(dig +short $host | tail -n 1)

    if [ -z ${ip} ]; then
        if [ -n "${old_ip}" ]; then
            delete_rule $proto $port $old_ip
        fi
        echo "Failed to resolve the ip address of ${host}." 1>&2
        exit 1
    fi

    if [ -n "${old_ip}" ]; then
        if [ ${ip} != ${old_ip} ]; then
            delete_rule $proto $port $old_ip
        fi
    fi
    add_rule $proto $port $ip
    if [ -f ${IPS_ALLOW} ]; then
      sed -i.bak /^${host}*/d ${IPS_ALLOW}
    fi
    echo "${host}:${ip}" >> ${IPS_ALLOW}
done

的内容/etc/ufw-dynamic-hosts.allow可能看起来像这样：

tcp:22:yourpc.no-ip.org

每五分钟执行一次脚本的 crontab 条目可能如下所示：

*/5 * * * * /usr/local/sbin/ufw-dynamic-host-update > /dev/null

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