关于linux内核防火墙netfilter详解
信息流经过linux主机时的一般处理流程：
信息流报文---->报文到达主机时---->做一些预处理prerouting-----> 路由转换，--->审核--->postrouting--->路由选择---->转发出去--->
原理netfilter能实现防火墙功能是基于linux内核调度实现。
[root@lib ~]# systemctl status firewalld
● firewalld.service - firewalld - dynamic firewall daemon
Loaded: loaded (/usr/lib/systemd/system/firewalld.service; disabled; vendor preset: enabled)
Active: inactive (dead)
Docs: man:firewalld(1)
[root@lib ~]# systemctl start firewalld
查看其全部默认规则
[root@lib ~]# iptables -vnL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
79 5656 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
0 0 ACCEPT all -- lo 0.0.0.0/0 0.0.0.0/0
3 390 INPUT_direct all -- 0.0.0.0/0 0.0.0.0/0
3 390 INPUT_ZONES_SOURCE all -- 0.0.0.0/0 0.0.0.0/0
3 390 INPUT_ZONES all -- 0.0.0.0/0 0.0.0.0/0
0 0 DROP all -- 0.0.0.0/0 0.0.0.0/0 ctstate INVALID
2 286 REJECT all -- * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
0 0 ACCEPT all -- lo 0.0.0.0/0 0.0.0.0/0
0 0 FORWARD_direct all -- 0.0.0.0/0 0.0.0.0/0
0 0 FORWARD_IN_ZONES_SOURCE all -- 0.0.0.0/0 0.0.0.0/0
0 0 FORWARD_IN_ZONES all -- 0.0.0.0/0 0.0.0.0/0
0 0 FORWARD_OUT_ZONES_SOURCE all -- 0.0.0.0/0 0.0.0.0/0
0 0 FORWARD_OUT_ZONES all -- 0.0.0.0/0 0.0.0.0/0
0 0 DROP all -- 0.0.0.0/0 0.0.0.0/0 ctstate INVALID
0 0 REJECT all -- * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited
Chain OUTPUT (policy ACCEPT 42 packets, 4480 bytes)
pkts bytes target prot opt in out source destination
42 4480 OUTPUT_direct all -- 0.0.0.0/0 0.0.0.0/0
Chain FORWARD_IN_ZONES (1 references)
pkts bytes target prot opt in out source destination
0 0 FWDI_public all -- ens33 0.0.0.0/0 0.0.0.0/0 [goto]
0 0 FWDI_public all -- + 0.0.0.0/0 0.0.0.0/0 [goto]
Chain FORWARD_IN_ZONES_SOURCE (1 references)
pkts bytes target prot opt in out source destination
Chain FORWARD_OUT_ZONES (1 references)
pkts bytes target prot opt in out source destination
0 0 FWDO_public all -- ens33 0.0.0.0/0 0.0.0.0/0 [goto]
0 0 FWDO_public all -- + 0.0.0.0/0 0.0.0.0/0 [goto]
Chain FORWARD_OUT_ZONES_SOURCE (1 references)
pkts bytes target prot opt in out source destination
Chain FORWARD_direct (1 references)
pkts bytes target prot opt in out source destination
Chain FWDI_public (2 references)
pkts bytes target prot opt in out source destination
0 0 FWDI_public_log all -- 0.0.0.0/0 0.0.0.0/0
0 0 FWDI_public_deny all -- 0.0.0.0/0 0.0.0.0/0
0 0 FWDI_public_allow all -- 0.0.0.0/0 0.0.0.0/0
0 0 ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0
Chain FWDI_public_allow (1 references)
pkts bytes target prot opt in out source destination
Chain FWDI_public_deny (1 references)
pkts bytes target prot opt in out source destination
Chain FWDI_public_log (1 references)
pkts bytes target prot opt in out source destination
Chain FWDO_public (2 references)
pkts bytes target prot opt in out source destination
0 0 FWDO_public_log all -- 0.0.0.0/0 0.0.0.0/0
0 0 FWDO_public_deny all -- 0.0.0.0/0 0.0.0.0/0
0 0 FWDO_public_allow all -- 0.0.0.0/0 0.0.0.0/0
Chain FWDO_public_allow (1 references)
pkts bytes target prot opt in out source destination
Chain FWDO_public_deny (1 references)
pkts bytes target prot opt in out source destination
Chain FWDO_public_log (1 references)
pkts bytes target prot opt in out source destination
Chain INPUT_ZONES (1 references)
pkts bytes target prot opt in out source destination
3 390 IN_public all -- ens33 0.0.0.0/0 0.0.0.0/0 [goto]
0 0 IN_public all -- + 0.0.0.0/0 0.0.0.0/0 [goto]
Chain INPUT_ZONES_SOURCE (1 references)
pkts bytes target prot opt in out source destination
Chain INPUT_direct (1 references)
pkts bytes target prot opt in out source destination
Chain IN_public (2 references)
pkts bytes target prot opt in out source destination
3 390 IN_public_log all -- 0.0.0.0/0 0.0.0.0/0
3 390 IN_public_deny all -- 0.0.0.0/0 0.0.0.0/0
3 390 IN_public_allow all -- 0.0.0.0/0 0.0.0.0/0
0 0 ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0
Chain IN_public_allow (1 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 ctstate NEW
1 104 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:22 ctstate NEW
0 0 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:443 ctstate NEW
Chain IN_public_deny (1 references)
pkts bytes target prot opt in out source destination
Chain IN_public_log (1 references)
pkts bytes target prot opt in out source destination
Chain OUTPUT_direct (1 references)
pkts bytes target prot opt in out source destination
[root@lib ~]#
[root@lib ~]# yum install firewall-config
打开图形防火墙配置命令
[root@lib ~]# firewall-config
neifilter功能模块详解
报文经过的过程：
hook function：
prerouting
input
output
forward
postrouting
链（内置）： chian
PREROUTING
INPUT
FORWARD
OUTPUT
POSTROUTING
功能：
filter：过滤，防火墙；
nat：network address translation；用于修改源IP或目标IP，也可以改端口；
mangle：拆解报文，做出修改，并重新封装起来；
raw：关闭nat表上启用的连接追踪机制；
功能<--链：
高 raw：PREROUTING， OUTPUT
| mangle：PREROUTING，INPUT，FORWARD，OUTPUT，POSTROUTING
nat：PREROUTING，[INPUT，]OUTPUT，POSTROUTING
低 filter：INPUT，FORWARD，OUTPUT
报文流向：
流入本机：PREROUTING --> INPUT
由本机流出：OUTPUT --> POSTROUTING
转发：PREROUTING --> FORWARD --> POSTROUTING
netfilter 防火墙规则可以通过iptables命令去管理
访问量多的放前面
规范小的放前面
iptables/netfilter
规则：
组成部分：根据规则匹配条件来尝试匹配报文，一旦匹配成功，就由规则定义的处理动作作出处理；
匹配条件：
基本匹配条件：内建
扩展匹配条件：由扩展模块定义；
处理动作：
基本处理动作：内建
扩展处理动作：由扩展模块定义；
自定义处理机制：自定义链
iptables的链：内置链和自定义链
内置链：对应于hook function
自定义链接：用于内置链的扩展和补充，可实现更灵活的规则管理机制；
添加规则时的考量点：
(1) 要实现哪种功能：判断添加到哪个表上；
(2) 报文流经的路径：判断添加到哪个链上；
链：链上的规则次序，即为检查的次序；因此，隐含一定的应用法则：
(1) 同类规则（访问同一应用），匹配范围小的放上面；
(2) 不同类的规则（访问不同应用），匹配到报文频率较大的放在上面；
(3) 将那些可由一条规则描述的多个规则合并起来；
(4) 设置默认策略；
iptables命令：
高度模块化，由诸多扩展模块实现其检查条件或处理动作的定义；
/usr/lib64/xtables/
IPv6：libip6t_
IPv4：libipt_, libxt_
iptables命令：
iptables [-t table] COMMAND chain [rulenum] [-m machename [per-match-options]] [-j targetname [per-target-options]] [options]
匹配条件：
基本匹配条件：
-s, -d, -p, -i, -o
扩展匹配条件：
-m matchname per-match-options
处理动作:
基本处理动作：ACCEPT， DROP
扩展处理动作：REJECT，RETURN，LOG，REDIRECT，...
用户自定义链：
COMMAND：
链管理：-N，-X，-E，-P，-F，-Z
规则管理：-A，-I，-R，-D
查看：-L，-n, -v, -x, --line-numbers
iptables/netfilter
规则：
组成部分：根据规则匹配条件来尝试匹配报文，一旦匹配成功，就由规则定义的处理动作作出处理；
匹配条件：
基本匹配条件：内建
扩展匹配条件：由扩展模块定义；
处理动作：
基本处理动作：内建
扩展处理动作：由扩展模块定义；
自定义处理机制：自定义链
iptables的链：内置链和自定义链
内置链：对应于hook function
自定义链接：用于内置链的扩展和补充，可实现更灵活的规则管理机制；
添加规则时的考量点：
(1) 要实现哪种功能：判断添加到哪个表上；
(2) 报文流经的路径：判断添加到哪个链上；
链：链上的规则次序，即为检查的次序；因此，隐含一定的应用法则：
(1) 同类规则（访问同一应用），匹配范围小的放上面；
(2) 不同类的规则（访问不同应用），匹配到报文频率较大的放在上面；
(3) 将那些可由一条规则描述的多个规则合并起来；
(4) 设置默认策略；
iptables命令：
高度模块化，由诸多扩展模块实现其检查条件或处理动作的定义；
/usr/lib64/xtables/
IPv6：libip6t_
IPv4：libipt_, libxt_
iptables [-t table] {-A|-C|-D} chain rule-specification
iptables [-t table] -I chain [rulenum] rule-specification
iptables [-t table] -R chain rulenum rule-specification
iptables [-t table] -D chain rulenum
iptables [-t table] -S [chain [rulenum]]
iptables [-t table] {-F|-L|-Z} [chain [rulenum]] [options...]
iptables [-t table] -N chain
iptables [-t table] -X [chain]
iptables [-t table] -P chain target
iptables [-t table] -E old-chain-name new-chain-name
rule-specification = [matches...] [target]
match = -m matchname [per-match-options]
target = -j targetname [per-target-options]
规则格式：iptables [-t table] COMMAND chain [-m matchname [per-match-options]] -j targetname [per-target-options]
-t table：
raw, mangle, nat, [filter]
COMMAND：
链管理：
-N：new, 自定义一条新的规则链；[root@lib ~]# iptables -vnL in_web_rules
Chain in_web_rules (0 references) 引用计数为0
pkts bytes target prot opt in out source destination
[root@lib ~]#
-X： delete，删除自定义的规则链；
注意：仅能删除 用户自定义的 引用计数为0的 空的 链；[root@lib ~]# iptables -X in_web_rules
[root@lib ~]# iptables -vnL in_web_rules
iptables: No chain/target/match by that name.
[root@lib ~]#
-P：Policy，设置默认策略；对filter表中的链而言，其默认策略有：
ACCEPT：接受
DROP：丢弃
REJECT：拒绝[root@lib ~]# iptables -vnL FORWARD | head -1
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
[root@lib ~]# iptables -P FORWARD DROP
[root@lib ~]# iptables -vnL FORWARD | head -1
Chain FORWARD (policy DROP 0 packets, 0 bytes)
[root@lib ~]# iptables -P FORWARD ACCEPT
[root@lib ~]# iptables -vnL FORWARD | head -1
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
[root@lib ~]#
-E：重命名自定义链；引用计数不为0的自定义链不能够被重命名，也不能被删除；
规则管理：[root@lib ~]# iptables -vnL in_web_rules
Chain in_web_rules (0 references)
pkts bytes target prot opt in out source destination
[root@lib ~]# iptables -E in_web_rules in_web_rules_new1
[root@lib ~]# iptables -vnL in_web_rules_new1
Chain in_web_rules_new1 (0 references)
pkts bytes target prot opt in out source destination
[root@lib ~]# iptables -vnL in_web_rules
iptables: No chain/target/match by that name.
[root@lib ~]#
-A：append，追加；
-I：insert, 插入，要指明位置，省略时表示第一条；
-D：delete，删除；
(1) 指明规则序号；
(2) 指明规则本身；[root@lib ~]# iptables -vnL FORWARD --line-numbers
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 0 0 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
2 0 0 ACCEPT all -- lo 0.0.0.0/0 0.0.0.0/0
3 0 0 FORWARD_direct all -- 0.0.0.0/0 0.0.0.0/0
4 0 0 FORWARD_IN_ZONES_SOURCE all -- 0.0.0.0/0 0.0.0.0/0
5 0 0 FORWARD_IN_ZONES all -- 0.0.0.0/0 0.0.0.0/0
6 0 0 FORWARD_OUT_ZONES_SOURCE all -- 0.0.0.0/0 0.0.0.0/0
7 0 0 FORWARD_OUT_ZONES all -- 0.0.0.0/0 0.0.0.0/0
8 0 0 DROP all -- 0.0.0.0/0 0.0.0.0/0 ctstate INVALID
9 0 0 REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited
[root@lib ~]# iptables -D FORWARD 8 删除第8条forward规则
[root@lib ~]# iptables -vnL FORWARD --line-numbers
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 0 0 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
2 0 0 ACCEPT all -- lo 0.0.0.0/0 0.0.0.0/0
3 0 0 FORWARD_direct all -- 0.0.0.0/0 0.0.0.0/0
4 0 0 FORWARD_IN_ZONES_SOURCE all -- 0.0.0.0/0 0.0.0.0/0
5 0 0 FORWARD_IN_ZONES all -- 0.0.0.0/0 0.0.0.0/0
6 0 0 FORWARD_OUT_ZONES_SOURCE all -- 0.0.0.0/0 0.0.0.0/0
7 0 0 FORWARD_OUT_ZONES all -- 0.0.0.0/0 0.0.0.0/0
8 0 0 REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited
[root@lib ~]#
-R：replace，替换指定链上的指定规则；
-F：flush，清空指定的规则链；[root@lib ~]# iptables -vnL INPUT 查看INPUT链路规则
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
77 5976 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
0 0 ACCEPT all -- lo 0.0.0.0/0 0.0.0.0/0
7 1087 INPUT_direct all -- 0.0.0.0/0 0.0.0.0/0
7 1087 INPUT_ZONES_SOURCE all -- 0.0.0.0/0 0.0.0.0/0
7 1087 INPUT_ZONES all -- 0.0.0.0/0 0.0.0.0/0
0 0 DROP all -- 0.0.0.0/0 0.0.0.0/0 ctstate INVALID
7 1087 REJECT all -- * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited
[root@lib ~]#
[root@lib ~]# iptables -F INPUT
[root@lib ~]# iptables -vnL INPUT
Chain INPUT (policy ACCEPT 7 packets, 575 bytes)
pkts bytes target prot opt in out source destination
[root@lib ~]#
-Z：zero，置零；
iptables的每条规则都有两个计数器：
(1) 匹配到的报文的个数；
(2) 匹配到的所有报文的大小之和； [root@lib ~]# iptables -Z INPUT
查看：
-L：list, 列出指定鏈上的所有规则；
-n：numberic，以数字格式显示地址和端口号；
-v：verbose，详细信息；
-vv, -vvv
-x：exactly，显示计数器结果的精确值；
--line-numbers：显示规则的序号；[root@lib ~]# iptables -L -n
[root@lib ~]# iptables -L --line-numbers -v -n
[root@lib ~]# iptables -L --line-numbers -vv -n
[root@lib ~]# iptables -L --line-numbers -v -n -x
[root@lib ~]# iptables -vnxL --line-number
[root@lib ~]# iptables -vnxL INPUT
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
8539 737755 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
0 0 ACCEPT all -- lo 0.0.0.0/0 0.0.0.0/0
1175 174348 INPUT_direct all -- 0.0.0.0/0 0.0.0.0/0
1175 174348 INPUT_ZONES_SOURCE all -- 0.0.0.0/0 0.0.0.0/0
1175 174348 INPUT_ZONES all -- 0.0.0.0/0 0.0.0.0/0
0 0 DROP all -- 0.0.0.0/0 0.0.0.0/0 ctstate INVALID
1168 173260 REJECT all -- * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited
[root@lib ~]#
[root@lib ~]# iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT all -- anywhere anywhere ctstate RELATED,ESTABLISHED
ACCEPT all -- anywhere anywhere
INPUT_direct all -- anywhere anywhere
INPUT_ZONES_SOURCE all -- anywhere anywhere
INPUT_ZONES all -- anywhere anywhere
DROP all -- anywhere anywhere ctstate INVALID
REJECT all -- anywhere anywhere reject-with icmp-host-prohibited
Chain FORWARD (policy ACCEPT)
target prot opt source destination
ACCEPT all -- anywhere anywhere ctstate RELATED,ESTABLISHED
ACCEPT all -- anywhere anywhere
FORWARD_direct all -- anywhere anywhere
FORWARD_IN_ZONES_SOURCE all -- anywhere anywhere
FORWARD_IN_ZONES all -- anywhere anywhere
FORWARD_OUT_ZONES_SOURCE all -- anywhere anywhere
FORWARD_OUT_ZONES all -- anywhere anywhere
DROP all -- anywhere anywhere ctstate INVALID
REJECT all -- anywhere anywhere reject-with icmp-host-prohibited
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
OUTPUT_direct all -- anywhere anywhere
Chain FORWARD_IN_ZONES (1 references)
target prot opt source destination
FWDI_public all -- anywhere anywhere [goto]
FWDI_public all -- anywhere anywhere [goto]
Chain FORWARD_IN_ZONES_SOURCE (1 references)
target prot opt source destination
Chain FORWARD_OUT_ZONES (1 references)
target prot opt source destination
FWDO_public all -- anywhere anywhere [goto]
FWDO_public all -- anywhere anywhere [goto]
Chain FORWARD_OUT_ZONES_SOURCE (1 references)
target prot opt source destination
Chain FORWARD_direct (1 references)
target prot opt source destination
Chain FWDI_public (2 references)
target prot opt source destination
FWDI_public_log all -- anywhere anywhere
FWDI_public_deny all -- anywhere anywhere
FWDI_public_allow all -- anywhere anywhere
ACCEPT icmp -- anywhere anywhere
Chain FWDI_public_allow (1 references)
target prot opt source destination
Chain FWDI_public_deny (1 references)
target prot opt source destination
Chain FWDI_public_log (1 references)
target prot opt source destination
Chain FWDO_public (2 references)
target prot opt source destination
FWDO_public_log all -- anywhere anywhere
FWDO_public_deny all -- anywhere anywhere
FWDO_public_allow all -- anywhere anywhere
Chain FWDO_public_allow (1 references)
target prot opt source destination
Chain FWDO_public_deny (1 references)
target prot opt source destination
Chain FWDO_public_log (1 references)
target prot opt source destination
Chain INPUT_ZONES (1 references)
target prot opt source destination
IN_public all -- anywhere anywhere [goto]
IN_public all -- anywhere anywhere [goto]
Chain INPUT_ZONES_SOURCE (1 references)
target prot opt source destination
Chain INPUT_direct (1 references)
target prot opt source destination
Chain IN_public (2 references)
target prot opt source destination
IN_public_log all -- anywhere anywhere
IN_public_deny all -- anywhere anywhere
IN_public_allow all -- anywhere anywhere
ACCEPT icmp -- anywhere anywhere
Chain IN_public_allow (1 references)
target prot opt source destination
ACCEPT tcp -- anywhere anywhere tcp dpt:http ctstate NEW
ACCEPT tcp -- anywhere anywhere tcp dpt:ssh ctstate NEW
ACCEPT tcp -- anywhere anywhere tcp dpt:https ctstate NEW
Chain IN_public_deny (1 references)
target prot opt source destination
Chain IN_public_log (1 references)
target prot opt source destination
Chain OUTPUT_direct (1 references)
target prot opt source destination
[root@lib ~]#
chain：
PREROUTING，INPUT，FORWARD，OUTPUT，POSTROUTING
匹配条件：
基本匹配条件：无需加载任何模块，由iptables/netfilter自行提供；
[!] -s, --source address[/mask][,...]：检查报文中的源IP地址是否符合此处指定的地址或范围；
[!] -d, --destination address[/mask][,...]：检查报文中的目标IP地址是否符合此处指定的地址或范围；
所有地址：0.0.0.0/0
[!] -p, --protocol protocol
protocol: tcp, udp, udplite, icmp, icmpv6,esp, ah, sctp, mh or "all"
{tcp|udp|icmp}
[!] -i, --in-interface name：数据报文流入的接口；只能应用于数据报文流入的环节，只能应用于PREROUTING，INPUT和FORWARD链；
[!] -o, --out-interface name：数据报文流出的接口；只能应用于数据报文流出的环节，只能应用于FORWARD、OUTPUT和POSTROUTING链；
处理动作：
-j targetname [per-target-options]
ACCEPT
DROP
REJECTcentos 7 有7张表
[root@lib ~]# iptables -L 默认filter表
[root@lib ~]# iptables -t filter -L
[root@lib ~]# iptables -t mangle -L
[root@lib ~]# iptables -t raw -L
[root@lib ~]# iptables -t nat -L
[root@lib ~]# iptables -t security -L
[root@lib ~]# systemctl stop firewalld
[root@lib ~]# iptables -vnL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
[root@lib ~]#
例如允许192.168.0.0/24 网访问本机
[root@lib ~]# iptables -t filter -A INPUT -s 192.168.0.0/24 -d 192.168.0.103 -p tcp -j ACCEPT
[root@lib ~]# iptables -vnL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
6 432 ACCEPT tcp -- 192.168.0.0/24 192.168.0.103
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 4 packets, 592 bytes)
pkts bytes target prot opt in out source destination
[root@lib ~]#
允许本机访问192.168.0.0/24网段
[root@lib ~]# iptables -t filter -A OUTPUT -s 192.168.0.103 -d 192.168.0.0/24 -p tcp -j ACCEPT
[root@lib ~]# iptables -vnL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
254 18424 ACCEPT tcp -- 192.168.0.0/24 192.168.0.103
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
4 592 ACCEPT tcp -- 192.168.0.103 192.168.0.0/24
[root@lib ~]#
-d , -p 不写代表所有
[root@lib ~]# iptables -P INPUT DROP
[root@lib ~]# iptables -P FORWARD DROP
[root@lib ~]# iptables -P OUTPUT DROP
DROP后建立起了白名单
[root@lib ~]# iptables -vnL
Chain INPUT (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
381 27776 ACCEPT tcp -- 192.168.0.0/24 192.168.0.103
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
79 9064 ACCEPT tcp -- 192.168.0.103 192.168.0.0/24
[root@lib ~]#
192.168.0.101ping 不通了192.168.0.103 ,英文其INPUT只开放了tcp 协议流经过，ping是ICMP协议
C:\Users\kerberos>ping 192.168.0.103
Pinging 192.168.0.103 with 32 bytes of data:
Request timed out.
放其进来
[root@lib ~]# iptables -t filter -A INPUT -s 192.168.0.101 -d 192.168.0.103 -p icmp -j ACCEPT
[root@lib ~]# iptables -vnL
Chain INPUT (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
766 57344 ACCEPT tcp -- 192.168.0.0/24 192.168.0.103
0 0 ACCEPT icmp -- 192.168.0.101 192.168.0.103
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
320 36208 ACCEPT tcp -- 192.168.0.103 192.168.0.0/24
[root@lib ~]#
还是ping不通，因为没有放其出去
C:\Users\kerberos>ping 192.168.0.103
Pinging 192.168.0.103 with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Ping statistics for 192.168.0.103:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
C:\Users\kerberos>
抓包可以看的出
[root@lib ~]# tcpdump -i ens33 -nn icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on ens33, link-type EN10MB (Ethernet), capture size 262144 bytes
16:18:21.075645 IP 192.168.0.101 > 192.168.0.103: ICMP echo request, id 1, seq 347, length 40
16:18:26.077079 IP 192.168.0.101 > 192.168.0.103: ICMP echo request, id 1, seq 348, length 40
16:18:31.079188 IP 192.168.0.101 > 192.168.0.103: ICMP echo request, id 1, seq 349, length 40
加一条规则，放其出去
[root@lib ~]# iptables -t filter -A OUTPUT -s 192.168.0.103 -d 192.168.0.101 -p icmp -j ACCEPT
[root@lib ~]# iptables -vnL
Chain INPUT (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1070 79152 ACCEPT tcp -- 192.168.0.0/24 192.168.0.103
6 360 ACCEPT icmp -- 192.168.0.101 192.168.0.103
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
484 53984 ACCEPT tcp -- 192.168.0.103 192.168.0.0/24
0 0 ACCEPT icmp -- 192.168.0.103 192.168.0.101
[root@lib ~]#
再ping
C:\Users\kerberos>ping 192.168.0.103
Pinging 192.168.0.103 with 32 bytes of data:
Reply from 192.168.0.103: bytes=32 time<1ms TTL=64
Reply from 192.168.0.103: bytes=32 time<1ms TTL=64
Reply from 192.168.0.103: bytes=32 time<1ms TTL=64
Reply from 192.168.0.103: bytes=32 time<1ms TTL=64
Ping statistics for 192.168.0.103:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms
C:\Users\kerberos>
抓包
[root@lib ~]# tcpdump -i ens33 -nn icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on ens33, link-type EN10MB (Ethernet), capture size 262144 bytes
16:21:09.433967 IP 192.168.0.101 > 192.168.0.103: ICMP echo request, id 1, seq 352, length 40
16:21:09.434011 IP 192.168.0.103 > 192.168.0.101: ICMP echo reply, id 1, seq 352, length 40
16:21:10.442321 IP 192.168.0.101 > 192.168.0.103: ICMP echo request, id 1, seq 353, length 40
16:21:10.442357 IP 192.168.0.103 > 192.168.0.101: ICMP echo reply, id 1, seq 353, length 40
防火墙定制机制： 一般使用白名单机制，拒绝所有，允许特定。
[root@lib ~]# systemctl status firewalld
练习：本机地址172.16.0.67
1、开放本机的所有tcp服务给所有主机；
# iptables -I INPUT -d 172.16.0.67 -p tcp -j ACCEPT
# iptables -I OUTPUT -s 172.16.0.67 -p tcp -j ACCEPT
2、开放本机的所有udp服务给172.16.0.0/16网络中的主机，但不包含172.16.0.200；
# iptables -I INPUT 2 -d 172.16.0.67 -s 172.16.0.200 -p udp -j REJECT
# iptables -I INPUT 3 -d 172.16.0.67 -s 172.16.0.0/16 -p udp -j ACCEPT
# iptables -I OUTPUT 2 -s 172.16.0.67 -d 172.16.0.0/16 -p udp -j ACCEPT
3、默认策略为REJECT；
扩展：
1、仅开放本机的ssh服务给172.16.0.0/16中的主机，而且不包含172.16.0.200; iptables/netfilter
framework: netfilter
五链：
PREROUTING，INPUT，FORWARD，OUTPUT，POSTROUTING
filter：包过滤；
nat：地址转换；
mangle：报文修改；
raw：关闭nat表上启用的连接追踪机制；
security：
filter：INPUT，FORWARD，OUTPUT
nat：PREROUTING，INPUT，OUTPUT，POSTROUTING
mangle：PREROUTING，INPUT，FORWARD，OUTPUT，POSTROUTING
raw：OUTPUT，PREROUTING
iptables命令：
iptables [-t table] COMMAND chain [rulenum] [-m machename [per-match-options]] [-j targetname [per-target-options]] [options]
匹配条件：
基本匹配条件：
-s, -d, -p, -i, -o
扩展匹配条件：
-m matchname per-match-options
处理动作:
基本处理动作：ACCEPT， DROP
扩展处理动作：REJECT，RETURN，LOG，REDIRECT，...
用户自定义链：
COMMAND：
链管理：-N，-X，-E，-P，-F，-Z
规则管理：-A，-I，-R，-D
查看：-L，-n, -v, -x, --line-numbers大写处理
小写条件匹配
[root@lib ~]# rpm -ql iptables | grep -i -E 'tcp|icmp|upd'
/usr/lib64/xtables/libip6t_icmp6.so
/usr/lib64/xtables/libipt_icmp.so
/usr/lib64/xtables/libxt_TCPMSS.so
/usr/lib64/xtables/libxt_TCPOPTSTRIP.so
/usr/lib64/xtables/libxt_tcp.so
/usr/lib64/xtables/libxt_tcpmss.so
[root@lib ~]#
iptables（2）
iptables [-t table] COMMAND [chain] [PARAMETERS] [-m matchname [per-match-options]] [-j targetname [per-target-options]]
匹配条件：
基本匹配条件：PARAMETERS
扩展匹配条件：
隐式扩展：在使用-p选项指明了特定的协议时，无需再同时使用-m选项指明扩展模块的扩展机制；
显式扩展：必须使用-m选项指明要调用的扩展模块的扩展机制；
隐式扩展：不需要手动加载扩展模块；因为它们是对协议的扩展，所以，但凡使用-p指明了协议，就表示已经指明了要扩展的模块；
tcp：
[!] --source-port, --sport port[:port]：匹配报文的源端口；可以是端口范围；
[!] --destination-port,--dport port[:port]：匹配报文的目标端口；可以是端口范围；
[!] --tcp-flags mask comp
mask is the flags which we should examine, written as a comma-separated list，例如 SYN,ACK,FIN,RST
comp is a comma-separated list of flags which must be set，例如SYN
例如：“--tcp-flags SYN,ACK,FIN,RST SYN”表示，要检查的标志位为SYN,ACK,FIN,RST四个，其中SYN必须为1，余下的必须为0；
[!] --syn：用于匹配第一次握手，相当于”--tcp-flags SYN,ACK,FIN,RST SYN“； 允许 192.168.0.0/24访问192.168.0.103 22端口服务
[root@lib ~]# iptables -I INPUT -s 192.168.0.0/24 -d 192.168.0.103 -p tcp --dport 22 -j ACCEPT I表示插入
[root@lib ~]# iptables -I OUTPUT -s 192.168.0.103 -d 192.168.0.0/24 -p tcp --dport 22 -j ACCEPT
[root@lib ~]# iptables -vnL
Chain INPUT (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
127 9148 ACCEPT tcp -- 192.168.0.0/24 192.168.0.103 tcp dpt:22
2221 175K ACCEPT tcp -- 192.168.0.0/24 192.168.0.103
10 600 ACCEPT icmp -- 192.168.0.101 192.168.0.103
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- 192.168.0.103 192.168.0.0/24 tcp dpt:22
1391 152K ACCEPT tcp -- 192.168.0.103 192.168.0.0/24
4 240 ACCEPT icmp -- 192.168.0.103 192.168.0.101
[root@lib ~]#
ssh 无法连接了，有问题，貌似是客户端连接ssh显示端口不是22，而是一个随机端口，不是这个原因，是上面OUTPUT 出口应该是--sport 22
删除重新配置
[root@lib ~]#iptables -D OUTPUT 1
[root@lib ~]# iptables -I OUTPUT -s 192.168.0.103 -d 192.168.0.0/24 -p tcp --sport 22 -j ACCEPT
此时如果执行 [root@lib ~]# iptables -F 就清理策略，就只剩默认策略了，也就是 policy DROP
ssh 就连不上了
为了去除上面风险
指定下面规则，相当于默认策略 DROP ，但又没有上面 iptables —F的风险
[root@lib ~]#iptables -A INPUT -d 192.168.0.103 -j REJECT
[root@lib ~]#iptables -A OUTPUT -s 192.168.0.103 -j REJECT
[root@lib ~]#iptables -P INPUT ACCEPT
[root@lib ~]#iptables -P OUTPUT ACCEPT
相当于默认策略的DROP
[root@lib ~]# iptables -vnL --line-numbers
Chain INPUT (policy ACCEPT 18 packets, 2660 bytes)
num pkts bytes target prot opt in out source destination
1 619 52768 ACCEPT tcp -- 192.168.0.0/24 192.168.0.103 tcp dpt:22
2 31 1860 ACCEPT icmp -- 192.168.0.101 192.168.0.103
3 0 0 REJECT all -- 0.0.0.0/0 192.168.0.103 reject-with icmp-port-unreachable
Chain FORWARD (policy DROP 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 215 39652 ACCEPT tcp -- 192.168.0.103 192.168.0.0/24 tcp spt:22
2 4 240 ACCEPT icmp -- 192.168.0.103 192.168.0.101
3 30 2460 REJECT all -- 192.168.0.103 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
ping 自己 可以通
[root@lib ~]# ping 127.0.0.1
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.035 ms
64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0.027 ms
^C
--- 127.0.0.1 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 999ms
rtt min/avg/max/mdev = 0.027/0.031/0.035/0.004 ms
回到之前的默认策略
[root@lib ~]# iptables -P INPUT DROP
[root@lib ~]# iptables -P OUTPUT DROP
[root@lib ~]# iptables -D INPUT 3
[root@lib ~]# iptables -D OUTPUT 3
[root@lib ~]# iptables -vnL --line-numbers
Chain INPUT (policy DROP 1 packets, 143 bytes)
num pkts bytes target prot opt in out source destination
1 953 77040 ACCEPT tcp -- 192.168.0.0/24 192.168.0.103 tcp dpt:22
2 31 1860 ACCEPT icmp -- 192.168.0.101 192.168.0.103
Chain FORWARD (policy DROP 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
Chain OUTPUT (policy DROP 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 396 60380 ACCEPT tcp -- 192.168.0.103 192.168.0.0/24 tcp spt:22
2 4 240 ACCEPT icmp -- 192.168.0.103 192.168.0.101
ping自己，ping不同，过分紧张了
[root@lib ~]# ping 127.0.0.1
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
ping: sendmsg: Operation not permitted
ping: sendmsg: Operation not permitted
^C
--- 127.0.0.1 ping statistics ---
2 packets transmitted, 0 received, 100% packet loss, time 999ms
[root@lib ~]#
再回到production 模式
[root@lib ~]# iptables -A INPUT -d 192.168.0.103 -j REJECT
[root@lib ~]# iptables -A OUTPUT -s 192.168.0.103 -j REJECT
[root@lib ~]#
[root@lib ~]# iptables -P INPUT ACCEPT
[root@lib ~]# iptables -P OUTPUT ACCEPT
[root@lib ~]# iptables -vnL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1902 148K ACCEPT tcp -- 192.168.0.0/24 192.168.0.103 tcp dpt:22
31 1860 ACCEPT icmp -- 192.168.0.101 192.168.0.103
0 0 REJECT all -- 0.0.0.0/0 192.168.0.103 reject-with icmp-port-unreachable
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
955 132K ACCEPT tcp -- 192.168.0.103 192.168.0.0/24 tcp spt:22
4 240 ACCEPT icmp -- 192.168.0.103 192.168.0.101
0 0 REJECT all -- 192.168.0.103 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
又或者可以这样设置，对网卡进行设置
[root@lib ~]# iptables -A INPUT -i ens33 -j REJECT
[root@lib ~]# iptables -A OUTPUT -o ens33 -j REJECT
[root@lib ~]# iptables -vnL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
2135 165K ACCEPT tcp -- 192.168.0.0/24 192.168.0.103 tcp dpt:22
31 1860 ACCEPT icmp -- 192.168.0.101 192.168.0.103
0 0 REJECT all -- 0.0.0.0/0 192.168.0.103 reject-with icmp-port-unreachable
1 143 REJECT all -- ens33 * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1082 147K ACCEPT tcp -- 192.168.0.103 192.168.0.0/24 tcp spt:22
4 240 ACCEPT icmp -- 192.168.0.103 192.168.0.101
0 0 REJECT all -- 192.168.0.103 0.0.0.0/0 reject-with icmp-port-unreachable
0 0 REJECT all -- * ens33 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
此时可以把第三条配置删了
[root@lib ~]# iptables -D INPUT 3
[root@lib ~]# iptables -D OUTPUT 3
[root@lib ~]# iptables -vnL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
2217 171K ACCEPT tcp -- 192.168.0.0/24 192.168.0.103 tcp dpt:22
31 1860 ACCEPT icmp -- 192.168.0.101 192.168.0.103
3 429 REJECT all -- ens33 * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1127 153K ACCEPT tcp -- 192.168.0.103 192.168.0.0/24 tcp spt:22
4 240 ACCEPT icmp -- 192.168.0.103 192.168.0.101
0 0 REJECT all -- * ens33 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
[root@lib ~]# ping 127.0.0.1
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.031 ms
64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0.052 ms
^C
--- 127.0.0.1 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1000ms
rtt min/avg/max/mdev = 0.031/0.041/0.052/0.012 ms
[root@lib ~]#
samba 137,138 udp dns tcp53或者upd53
139,445 tcp
udp
[!] --source-port, --sport port[:port]：匹配报文的源端口；可以是端口范围；
[!] --destination-port,--dport port[:port]：匹配报文的目标端口；可以是端口范围；
icmp
[!] --icmp-type {type[/code]|typename}
echo-request：8
echo-reply：0[root@lib ~]# iptables -D INPUT 2
[root@lib ~]# iptables -D OUTPUT 2
[root@lib ~]# iptables -vnL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
2453 187K ACCEPT tcp -- 192.168.0.0/24 192.168.0.103 tcp dpt:22
38 5520 REJECT all -- ens33 * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1299 188K ACCEPT tcp -- 192.168.0.103 192.168.0.0/24 tcp spt:22
462 42904 REJECT all -- * ens33 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
[root@lib ~]# ping 192.168.0.101
PING 192.168.0.101 (192.168.0.101) 56(84) bytes of data.
From 192.168.0.103 icmp_seq=1 Destination Port Unreachable
ping: sendmsg: Operation not permitted
From 192.168.0.103 icmp_seq=2 Destination Port Unreachable
ping: sendmsg: Operation not permitted
^C
--- 192.168.0.101 ping statistics ---
2 packets transmitted, 0 received, +2 errors, 100% packet loss, time 1000ms
[root@lib ~]#
添加规则
放其出去
[root@lib ~]# iptables -I OUTPUT 2 -s 192.168.0.103 -p icmp --icmp-type 8 -j ACCEPT
[root@lib ~]# iptables -vnL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
3041 236K ACCEPT tcp -- 192.168.0.0/24 192.168.0.103 tcp dpt:22
55 9273 REJECT all -- ens33 * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1715 235K ACCEPT tcp -- 192.168.0.103 192.168.0.0/24 tcp spt:22
0 0 ACCEPT icmp -- 192.168.0.103 0.0.0.0/0 icmptype 8
486 50288 REJECT all -- * ens33 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
试着ping,可以ping出去，只是收不到reply而已，因为没有配置
[root@lib ~]# ping 192.168.0.100
PING 192.168.0.100 (192.168.0.100) 56(84) bytes of data.
[root@lamp ~]# tcpdump -i ens33 -nn icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on ens33, link-type EN10MB (Ethernet), capture size 262144 bytes
20:21:25.826655 IP 192.168.0.103 > 192.168.0.100: ICMP echo request, id 6301, seq 81, length 64
20:21:25.826691 IP 192.168.0.100 > 192.168.0.103: ICMP echo reply, id 6301, seq 81, length 64
20:21:26.826886 IP 192.168.0.103 > 192.168.0.100: ICMP echo request, id 6301, seq 82, length 64
20:21:26.826909 IP 192.168.0.100 > 192.168.0.103: ICMP echo reply, id 6301, seq 82, length 64
在给一条配置，可以接受reply
[root@lib ~]# iptables -I INPUT 2 -d 192.168.0.103 -p icmp --icmp-type 0/0 -j ACCEPT
[root@lib ~]# iptables -vnL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
3412 266K ACCEPT tcp -- 192.168.0.0/24 192.168.0.103 tcp dpt:22
1 84 ACCEPT icmp -- 0.0.0.0/0 192.168.0.103 icmptype 0 code 0
240 27642 REJECT all -- ens33 * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1923 271K ACCEPT tcp -- 192.168.0.103 192.168.0.0/24 tcp spt:22
161 13524 ACCEPT icmp -- 192.168.0.103 0.0.0.0/0 icmptype 8
679 79464 REJECT all -- * ens33 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
[root@lib ~]# ping 192.168.0.100
PING 192.168.0.100 (192.168.0.100) 56(84) bytes of data.
64 bytes from 192.168.0.100: icmp_seq=1 ttl=64 time=0.526 ms
64 bytes from 192.168.0.100: icmp_seq=2 ttl=64 time=0.325 ms
^C
--- 192.168.0.100 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 999ms
rtt min/avg/max/mdev = 0.325/0.425/0.526/0.102 ms
[root@lib ~]#
成功
别人ping其实不通的，因为没有配置
[root@lamp ~]# ping 192.168.0.103
PING 192.168.0.103 (192.168.0.103) 56(84) bytes of data.
^C
--- 192.168.0.103 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2000ms
[root@lamp ~]#
再配置
[root@lib ~]# iptables -I INPUT 3 -d 192.168.0.103 -p icmp --icmp-type 8 -j ACCEPT
[root@lib ~]# iptables -I OUTPUT 3 -s 192.168.0.103 -p icmp --icmp-type 0/0 -j ACCEPT
[root@lib ~]# iptables -vnL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
4417 349K ACCEPT tcp -- 192.168.0.0/24 192.168.0.103 tcp dpt:22
1 84 ACCEPT icmp -- 0.0.0.0/0 192.168.0.103 icmptype 0 code 0
2 168 ACCEPT icmp -- 0.0.0.0/0 192.168.0.103 icmptype 8
264 30983 REJECT all -- ens33 * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
2599 346K ACCEPT tcp -- 192.168.0.103 192.168.0.0/24 tcp spt:22
161 13524 ACCEPT icmp -- 192.168.0.103 0.0.0.0/0 icmptype 8
2 168 ACCEPT icmp -- 192.168.0.103 0.0.0.0/0 icmptype 0 code 0
712 89640 REJECT all -- * ens33 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
[root@lamp ~]# ping 192.168.0.103
PING 192.168.0.103 (192.168.0.103) 56(84) bytes of data.
64 bytes from 192.168.0.103: icmp_seq=1 ttl=64 time=0.341 ms
64 bytes from 192.168.0.103: icmp_seq=2 ttl=64 time=0.317 ms
^C
--- 192.168.0.103 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1000ms
rtt min/avg/max/mdev = 0.317/0.329/0.341/0.012 ms
[root@lamp ~]#
配置samba 共享服务器规则
[root@lib ~]# iptables -I INPUT -d 192.168.0.103 -p udp --dport 137:138 -j ACCEPT
[root@lib ~]# iptables -I OUTPUT -s 192.168.0.103 -p udp --sport 137:138 -j ACCEPT
[root@lib ~]# iptables -vnL
Chain INPUT (policy ACCEPT 1 packets, 356 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT udp -- 0.0.0.0/0 192.168.0.103 udp dpts:137:138
5246 420K ACCEPT tcp -- 192.168.0.0/24 192.168.0.103 tcp dpt:22
1 84 ACCEPT icmp -- 0.0.0.0/0 192.168.0.103 icmptype 0 code 0
2 168 ACCEPT icmp -- 0.0.0.0/0 192.168.0.103 icmptype 8
857 119K REJECT all -- ens33 * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 1 packets, 356 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT udp -- 192.168.0.103 0.0.0.0/0 udp spts:137:138
3057 430K ACCEPT tcp -- 192.168.0.103 192.168.0.0/24 tcp spt:22
161 13524 ACCEPT icmp -- 192.168.0.103 0.0.0.0/0 icmptype 8
2 168 ACCEPT icmp -- 192.168.0.103 0.0.0.0/0 icmptype 0 code 0
1257 253K REJECT all -- * ens33 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
配置后还是无法telnet
[root@lamp ~]# telnet 192.168.0.103 137
Trying 192.168.0.103...
^C
[root@lamp ~]# telnet 192.168.0.103 138
Trying 192.168.0.103...
^C
[root@lamp ~]#
[root@lamp ~]# smbclient //192.168.0.103/HRDept -U smbuser4
Connection to 192.168.0.103 failed (Error NT_STATUS_IO_TIMEOUT)
[root@lamp ~]#
139 和445端口
显式扩展：必须要手动加载扩展模块， [-m matchname [per-match-options]]；
显式扩展：必须使用-m选项指明要调用的扩展模块的扩展机制；
1、multiport
This module matches a set of source or destination ports. Up to 15 ports can be specified. A port range (port:port) counts as two ports. It can only be used in conjunction with one of the following protocols: tcp, udp, udplite, dccp and sctp.
以离散或连续的 方式定义多端口匹配条件，最多15个；
[!] --source-ports,--sports port[,port|,port:port]...：指定多个源端口；
[!] --destination-ports,--dports port[,port|,port:port]...：指定多个目标端口；
# iptables -I INPUT -d 172.16.0.7 -p tcp -m multiport --dports 22,80,139,445,3306 -j ACCEPT-R, --replace chain rulenum rule-specification
Replace a rule in the selected chain. If the source and/or destination names resolve
to multiple addresses, the command will fail. Rules are numbered starting at 1.
[root@lib ~]# iptables -R INPUT 2 -d 192.168.0.103 -p tcp -m multiport --dports 22,80,139,445 -j ACCEPT
[root@lib ~]# iptables -R OUTPUT 2 -s 192.168.0.103 -p tcp -m multiport --sport 22,80,139,445 -j ACCEPT
[root@lib ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT udp -- 0.0.0.0/0 192.168.0.103 udp dpts:137:138
152 10960 ACCEPT tcp -- 0.0.0.0/0 192.168.0.103 multiport dports 22,80,139,445
1 84 ACCEPT icmp -- 0.0.0.0/0 192.168.0.103 icmptype 0 code 0
2 168 ACCEPT icmp -- 0.0.0.0/0 192.168.0.103 icmptype 8
3609 557K REJECT all -- ens33 * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
249 54072 ACCEPT udp -- 192.168.0.103 0.0.0.0/0 udp spts:137:138
9 1480 ACCEPT tcp -- 192.168.0.103 0.0.0.0/0 multiport sports 22,80,139,445
1 84 ACCEPT icmp -- 192.168.0.103 0.0.0.0/0 icmptype 8
2 168 ACCEPT icmp -- 192.168.0.103 0.0.0.0/0 icmptype 0 code 0
2645 863K REJECT all -- * ens33 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
[root@lamp ~]# smbclient -L 192.168.0.103
Enter SAMBA\root's password:
Anonymous login successful
Sharename Type Comment
--------- ---- -------
print$ Disk Printer Drivers
HRDept Disk HR share file
IPC$ IPC IPC Service (Samba 4.8.3)Reconnecting with SMB1 for workgroup listing.
Anonymous login successful
Server Comment
--------- -------
Workgroup Master
--------- -------
SAMBA LIB[root@lamp ~]#
2、iprange
以连续地址块的方式来指明多IP地址匹配条件；
[!] --src-range from[-to]
[!] --dst-range from[-to]
# iptables -I INPUT -d 172.16.0.7 -p tcp -m multiport --dports 22,80,139,445,3306 -m iprange --src-range 172.16.0.61-172.16.0.70 -j REJECT
# iptables -I OUTPUT -s 172.16.0.7 -p tcp -m multiport --sports 22,80,139,445,3306 -m iprange --src-range 172.16.0.61-172.16.0.70 -j REJECT
3、time
This matches if the packet arrival time/date is within a given range.
--timestart hh:mm[:ss]
--timestop hh:mm[:ss]
[!] --weekdays day[,day...]
[!] --monthdays day[,day...]
--datestart YYYY[-MM[-DD[Thh[:mm[:ss]]]]]
--datestop YYYY[-MM[-DD[Thh[:mm[:ss]]]]]
--kerneltz：使用内核配置的时区而非默认的UTC； 4、string 检查字符编码后的字符是否匹配
This modules matches a given string by using some pattern matching strategy.
--algo {bm|kmp} 算法
[!] --string pattern
[!] --hex-string pattern
--from offset
--to offset
~]# iptables -I OUTPUT -m string --algo bm --string "gay" -j REJECT iptables -A INPUT -p tcp --dport 80 -m string --algo bm --string 'GET /index.html' -j LOG
# The hex string pattern can be used for non-printable characters, like |0D 0A| or |0D0A|.
iptables -p udp --dport 53 -m string --algo bm --from 40 --to 57 --hex-string '|03|www|09|net‐
filter|03|org|00|'
5、connlimit 拒绝服务***，限制单客户端访问并发数
Allows you to restrict the number of parallel connections to a server per client IP address (or client address block).
--connlimit-upto n
--connlimit-above n
防火墙的默认规则是拒绝的，所以低于就允许，
~]# iptables -I INPUT -d 172.16.0.7 -p tcp --syn --dport 22 -m connlimit --connlimit-above 2 -j REJECT[root@lib ~]# systemctl start mariadb
[root@lib ~]#
[root@lib ~]# mysql
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 2
Server version: 5.5.60-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]>
MariaDB [(none)]> create user 'test'@'%' IDENTIFIED BY 'test';
Query OK, 0 rows affected (0.00 sec)
MariaDB [(none)]> flush privileges;
Query OK, 0 rows affected (0.00 sec)
MariaDB [(none)]> select user,host from mysql.user where user = 'test';
+------+------+
| user | host |
+------+------+
| test | % |
+------+------+
1 row in set (0.00 sec)
MariaDB [(none)]>
访问不了
[root@lamp ~]# mysql -u test -h 192.168.0.103 -p
Enter password:
ERROR 2003 (HY000): Can't connect to MySQL server on '192.168.0.103' (110)
[root@lamp ~]#
添加防火墙规则
[root@lib ~]# iptables -I INPUT 2 -s 192.168.0.0/24 -d 192.168.0.103 -p tcp --dport 3306 -j ACCEPT
[root@lib ~]# iptables -I OUTPUT 2 -d 192.168.0.0/24 -s 192.168.0.103 -p tcp --sport 3306 -j ACCEPT
[root@lib ~]# iptables -vnL | grep 3306
1 60 ACCEPT tcp -- 192.168.0.0/24 192.168.0.103 tcp dpt:3306
0 0 ACCEPT tcp -- 192.168.0.103 192.168.0.0/24 tcp spt:3306
[root@lib ~]#
[root@lamp ~]# mysql -u test -h 192.168.0.103 -p
Enter password:
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 5
Server version: 5.5.60-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]>
修改第一条进站规则，同一个客户端连接大于2条，就拒绝多余的连接，就是检查其TCP3次握手次数
[root@lib ~]# iptables -R INPUT 2 -d 192.168.0.103 -s 192.168.0.0/24 -p tcp --dport 3306 -m connlimit --connlimit-upto 2 -j ACCEPT
[root@lib ~]# iptables -vnL | grep 3306
0 0 ACCEPT tcp -- 192.168.0.0/24 192.168.0.103 tcp dpt:3306 #conn src/32 <= 2
11 952 ACCEPT tcp -- 192.168.0.103 192.168.0.0/24 tcp spt:3306
[root@lib ~]#
6、limit 从报文发包速率来限制，令牌方式
This module matches at a limited rate using a token bucket filter.
--limit rate[/second|/minute|/hour|/day]
--limit-burst number 可以收集多少个令牌环
~]# iptables -I OUTPUT -s 172.16.0.7 -p icmp --icmp-type 0 -j ACCEPT
限制本机某tcp服务接收新请求的速率：--syn, -m limit[root@lamp ~]# wget ftp://ftp.pbone.net/mirror/ftp5.gwdg.de/pub/opensuse/repositories/home%3A/matthewdva%3A/build%3A/EPEL%3A/el7/CentOS_7/x86_64/hping3-0.0.20051105-24.el7.x86_64.rpm
[root@lamp ~]# yum intall hping3-0.0.20051105-24.el7.x86_64.rpm
[root@lamp ~]# rpm -ql hping3
/usr/sbin/hping
/usr/sbin/hping2
/usr/sbin/hping3
#iptables -I INPUT 6 -d 192.168.0.103 -p icmp --icmp-type 8 -m limit --limit-burst 5 --limit 20/minute -j ACCEPT
#iptables -I OUTPUT 6 -s 192.168.0.103 -p icmp --icmp-type 0 -j ACCEPT
对于web 新请求数进行限制 限制本机某tcp服务接收新请求的速率：--syn, -m limit
7、state
The "state" extension is a subset of the "conntrack" module. "state" allows access to the connection tracking state for this packet.
[!] --state state
INVALID, ESTABLISHED, NEW, RELATED or UNTRACKED.
NEW: 新连接请求；
ESTABLISHED：已建立的连接；
INVALID：无法识别的连接；
RELATED：相关联的连接，当前连接是一个新请求，但附属于某个已存在的连接；
UNTRACKED：未追踪的连接；链接追踪，查询在内存中记录
state扩展：
内核模块装载：
nf_conntrack
nf_conntrack_ipv4
手动装载：
nf_conntrack_ftp
追踪到的连接： 在并发访问量大的模式中，不建议开启
/proc/net/nf_conntrack[root@lib ~]# cat /proc/net/nf_conntrack
ipv4 2 tcp 6 299 ESTABLISHED src=192.168.0.103 dst=192.168.0.101 sport=22 dport=56005 src=192.168.0.101 dst=192.168.0.103 sport=56005 dport=22 [ASSURED] mark=0 zone=0 use=2
ipv4 2 tcp 6 117 TIME_WAIT src=192.168.0.101 dst=192.168.0.103 sport=53484 dport=80 src=192.168.0.103 dst=192.168.0.101 sport=80 dport=53484 [ASSURED] mark=0 zone=0 use=2
ipv4 2 tcp 6 117 TIME_WAIT src=192.168.0.101 dst=192.168.0.103 sport=53483 dport=80 src=192.168.0.103 dst=192.168.0.101 sport=80 dport=53483 [ASSURED] mark=0 zone=0 use=2
[root@lib ~]#
调整可记录的连接数量最大值：
/proc/sys/net/nf_conntrack_max[root@lib ~]# cat /proc/sys/net/nf_conntrack_max
25432
[root@lib ~]#
超时时长： 不同协议，超时时长不同
/proc/sys/net/netfilter/*timeout*[root@lib ~]# cat /proc/sys/net/netfilter/timeout
15
600
30
10
60
432000
120
30
300
60
120
120
300
30
180
[root@lib ~]# ls -lt /proc/sys/net/netfilter/
total 0
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_acct
-r--r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_buckets
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_checksum
-r--r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_count
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_events
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_events_retry_timeout
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_expect_max
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_generic_timeout
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_helper
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_icmp_timeout
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_log_invalid
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_max
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_tcp_be_liberal
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_tcp_loose
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_tcp_max_retrans
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_tcp_timeout_close
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_tcp_timeout_close_wait
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_tcp_timeout_established
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_tcp_timeout_fin_wait
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_tcp_timeout_last_ack
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_tcp_timeout_max_retrans
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_tcp_timeout_syn_recv
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_tcp_timeout_syn_sent
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_tcp_timeout_time_wait
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_tcp_timeout_unacknowledged
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_timestamp
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_udp_timeout
-rw-r--r-- 1 root root 0 Aug 4 21:53 nf_conntrack_udp_timeout_stream
dr-xr-xr-x 1 root root 0 Aug 4 21:53 nf_log
[root@lib ~]#
清空所有规则
[root@lib ~]# iptables -F
[root@lib ~]# iptables -vnL
Chain INPUT (policy ACCEPT 6 packets, 432 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 4 packets, 432 bytes)
pkts bytes target prot opt in out source destination
[root@lib ~]#
-I 默认插入第一规则, -A 在前面规则后追加规则
建立规则
[root@lib ~]# iptables -A INPUT -d 192.168.0.103 -p tcp -m multiport --dports 22:23,80,139,445,3306 -m state --state NEW -j ACCEPT
[root@lib ~]# iptables -I INPUT -d 192.168.0.103 -m state --state ESTABLISHED -j ACCEPT
[root@lib ~]# iptables -A OUTPUT -s 192.168.0.103 -m state --state ESTABLISHED -j ACCEPT
[root@lib ~]# iptables -A INPUT -d 192.168.0.103 -j REJECT
[root@lib ~]# iptables -A OUTPUT -s 192.168.0.103 -j REJECT
[root@lib ~]# iptables -vnL --line-numbers
Chain INPUT (policy ACCEPT 1 packets, 143 bytes)
num pkts bytes target prot opt in out source destination
1 1339 109K ACCEPT all -- 0.0.0.0/0 192.168.0.103 state ESTABLISHED
2 0 0 ACCEPT tcp -- 0.0.0.0/0 192.168.0.103 multiport dports 22:23,80,139,445,3306 state NEW
3 3 164 ACCEPT tcp -- 0.0.0.0/0 192.168.0.103 multiport dports 22:23,80,137,138,139,445,3306 state NEW
4 52 2992 REJECT all -- 0.0.0.0/0 192.168.0.103 reject-with icmp-port-unreachable
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 773 116K ACCEPT all -- 192.168.0.103 0.0.0.0/0 state ESTABLISHED
2 50 4472 REJECT all -- 192.168.0.103 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
NTP出站同步时间服务器
[root@lib ~]# iptables -I OUTPUT 2 -s 192.168.0.103 -p udp -m multiport --dports 123,323 -m state --state NEW -j ACCEPT
[root@lib ~]# iptables -vnL --line-numbers
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 2146 181K ACCEPT all -- 0.0.0.0/0 192.168.0.103 state ESTABLISHED
2 2 120 ACCEPT tcp -- 0.0.0.0/0 192.168.0.103 multiport dports 22:23,80,139,445,3306 state NEW
3 3 164 ACCEPT tcp -- 0.0.0.0/0 192.168.0.103 multiport dports 22:23,80,137,138,139,445,3306 state NEW
4 52 2992 REJECT all -- 0.0.0.0/0 192.168.0.103 reject-with icmp-port-unreachable
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 1321 191K ACCEPT all -- 192.168.0.103 0.0.0.0/0 state ESTABLISHED
2 0 0 ACCEPT udp -- 192.168.0.103 0.0.0.0/0 multiport dports 123,323 state NEW
3 50 4472 REJECT all -- 192.168.0.103 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
[root@lib ~]# iptables -I INPUT 2 -d 192.168.0.103 -p udp --dport 137:138 -m state --state NEW -j ACCEPT
[root@lib ~]# iptables -vnL --line-numbers
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 247 22635 ACCEPT all -- 0.0.0.0/0 192.168.0.103 state ESTABLISHED
2 0 0 ACCEPT udp -- 0.0.0.0/0 192.168.0.103 udp dpts:137:138 state NEW
3 6 312 ACCEPT tcp -- 0.0.0.0/0 192.168.0.103 multiport dports 22:23,80,139,445,3306 state NEW
4 0 0 REJECT all -- 0.0.0.0/0 192.168.0.103 reject-with icmp-port-unreachable
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 167 30990 ACCEPT all -- 192.168.0.103 0.0.0.0/0 state ESTABLISHED
2 0 0 ACCEPT udp -- 192.168.0.103 0.0.0.0/0 multiport dports 123,323 state NEW
3 8 688 REJECT all -- 192.168.0.103 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
samba ssh mysql httpd都可以访问，
[root@lamp ~]# smbclient //192.168.0.103/HRDept -U smbuser4
Enter SAMBA\smbuser4's password:
Try "help" to get a list of possible commands.
smb: \>
[root@lamp ~]# mysql -u test -h 192.168.0.103 -ptest
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 14
Server version: 5.5.60-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]>
对于ftp 进行定义规则
[root@lib ~]# systemctl start vsftpd
[root@lib ~]#
装载模块，追踪ftp
[root@lib ~]# modinfo nf_conntrack_ftp
filename: /lib/modules/3.10.0-514.el7.x86_64/kernel/net/netfilter/nf_conntrack_ftp.ko
alias: nfct-helper-ftp
alias: ip_conntrack_ftp
description: ftp connection tracking helper
author: Rusty Russell <rusty@rustcorp.com.au>
license: GPL
rhelversion: 7.3
srcversion: D43BF56A22E3D137BA1227B
depends: nf_conntrack
intree: Y
vermagic: 3.10.0-514.el7.x86_64 SMP mod_unload modversions
signer: CentOS Linux kernel signing key
sig_key: D4:88:63:A7:C1:6F:CC:27:41:23:E6:29:8F:74:F0:57:AF:19:FC:54
sig_hashalgo: sha256
parm: ports:array of ushort
parm: loose:bool
[root@lib ~]# lsmod | grep nf_conntrack_ftp
[root@lib ~]# modprobe nf_conntrack_ftp
[root@lib ~]# lsmod | grep nf_conntrack_ftp
nf_conntrack_ftp 18638 0
nf_conntrack 111302 4 xt_connlimit,xt_conntrack,nf_conntrack_ftp,nf_conntrack_ipv4
[root@lib ~]#
改造开发21 端口和RELATED 状态的入站规则
[root@lib ~]# iptables -R INPUT 3 -d 192.168.0.103 -p tcp -m multiport --dports 21:23,80,139,445,3306 -m state --state NEW -j ACCEPT
[root@lib ~]# iptables -R INPUT 1 -d 192.168.0.103 -m state --state ESTABLISHED,RELATED -j ACCEPT
[root@lib ~]#
[root@lib ~]# iptables -vnL --line-numbers
Chain INPUT (policy ACCEPT 1 packets, 143 bytes)
num pkts bytes target prot opt in out source destination
1 14 1008 ACCEPT all -- 0.0.0.0/0 192.168.0.103 state RELATED,ESTABLISHED
2 0 0 ACCEPT udp -- 0.0.0.0/0 192.168.0.103 udp dpts:137:138 state NEW
3 0 0 ACCEPT tcp -- 0.0.0.0/0 192.168.0.103 multiport dports 21:23,80,139,445,3306 state NEW
4 0 0 REJECT all -- 0.0.0.0/0 192.168.0.103 reject-with icmp-port-unreachable
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 182 34934 ACCEPT all -- 192.168.0.103 0.0.0.0/0 state ESTABLISHED
2 0 0 ACCEPT udp -- 192.168.0.103 0.0.0.0/0 multiport dports 123,323 state NEW
3 8 688 REJECT all -- 192.168.0.103 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
访问ftp成功
[root@lamp ~]# ftp 192.168.0.103
Connected to 192.168.0.103 (192.168.0.103).
220 (vsFTPd 3.0.2)
Name (192.168.0.103:root): tom
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls
227 Entering Passive Mode (192,168,0,103,146,162).
150 Here comes the directory listing.
226 Transfer done (but failed to open directory).
ftp>
[root@lamp ~]# yum install telnet-server --downloadonly --downloaddir=/tmp/
[root@lamp ~]# scp -p /tmp/telnet-server-0.17-64.el7.x86_64.rpm 192.168.0.103:/tmp/
root@192.168.0.103's password:
telnet-server-0.17-64.el7.x86_64.rpm 100% 41KB 40.8KB/s 00:00
[root@lamp ~]#
[root@lib vsftpd]# yum install /tmp/telnet-server-0.17-64.el7.x86_64.rpm
启动telnet 服务
[root@lib vsftpd]# systemctl start telnet.socket
[root@lib vsftpd]# systemctl status telnet.socket
● telnet.socket - Telnet Server Activation Socket
Loaded: loaded (/usr/lib/systemd/system/telnet.socket; disabled; vendor preset: disabled)
Active: active (listening) since Sun 2019-08-04 23:59:04 CST; 5s ago
Docs: man:telnetd(8)
Listen: [::]:23 (Stream)
Accepted: 0; Connected: 0
Aug 04 23:59:04 lib systemd[1]: Listening on Telnet Server Activation Socket.
Aug 04 23:59:04 lib systemd[1]: Starting Telnet Server Activation Socket.
[root@lib vsftpd]#
对telnet加日志规则
[root@lib vsftpd]# iptables -I INPUT 3 -d 192.168.0.103 -p tcp --dport 23 -m state --state NEW -j LOG
[root@lib ~]# iptables -vnL --line-numbers
Chain INPUT (policy ACCEPT 1 packets, 143 bytes)
num pkts bytes target prot opt in out source destination
1 26 2000 ACCEPT all -- 0.0.0.0/0 192.168.0.103 state RELATED,ESTABLISHED
2 0 0 ACCEPT udp -- 0.0.0.0/0 192.168.0.103 udp dpts:137:138 state NEW
3 0 0 LOG tcp -- 0.0.0.0/0 192.168.0.103 tcp dpt:23 state NEW LOG flags 0 level 4
4 0 0 ACCEPT tcp -- 0.0.0.0/0 192.168.0.103 multiport dports 21:23,80,139,445,3306 state NEW
5 0 0 REJECT all -- 0.0.0.0/0 192.168.0.103 reject-with icmp-port-unreachable
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 191 37230 ACCEPT all -- 192.168.0.103 0.0.0.0/0 state ESTABLISHED
2 0 0 ACCEPT udp -- 192.168.0.103 0.0.0.0/0 multiport dports 123,323 state NEW
3 8 688 REJECT all -- 192.168.0.103 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
[root@lamp ~]# telnet 192.168.0.103
Trying 192.168.0.103...
Connected to 192.168.0.103.
Escape character is '^]'.
Kernel 3.10.0-514.el7.x86_64 on an x86_64
lib login: test12
Password:
Last login: Mon Aug 5 00:04:03 from lib
[test12@lib ~]$
[root@lib log]# tail -f messages
Aug 5 00:04:01 lib systemd: Started Session 1106 of user root.
Aug 5 00:04:01 lib systemd: Starting Session 1106 of user root.
Aug 5 00:04:03 lib systemd: Created slice user-1050.slice.
Aug 5 00:04:03 lib systemd: Starting user-1050.slice.
Aug 5 00:04:03 lib systemd-logind: New session 1107 of user test12.
Aug 5 00:04:03 lib systemd: Started Session 1107 of user test12.
Aug 5 00:04:03 lib systemd: Starting Session 1107 of user test12.
Aug 5 00:04:17 lib systemd-logind: Removed session 1107.
Aug 5 00:04:17 lib systemd: Removed slice user-1050.slice.
Aug 5 00:04:17 lib systemd: Stopping user-1050.slice.
Aug 5 00:04:31 lib kernel: IN=ens33 OUT= MAC=00:0c:29:b7:65:02:00:0c:29:20:7b:a8:08:00 SRC=192.168.0.102 DST=192.168.0.103 LEN=60 TOS=0x10 PREC=0x00 TTL=64 ID=43583 DF PROTO=TCP SPT=51302 DPT=23 WINDOW=29200 RES=0x00 SYN URGP=0
Aug 5 00:04:31 lib systemd: Started Telnet Server (192.168.0.102:51302).
Aug 5 00:04:31 lib systemd: Starting Telnet Server (192.168.0.102:51302)...
Aug 5 00:04:36 lib systemd: Created slice user-1050.slice.
Aug 5 00:04:36 lib systemd: Starting user-1050.slice.
Aug 5 00:04:36 lib systemd-logind: New session 1108 of user test12.
Aug 5 00:04:36 lib systemd: Started Session 1108 of user test12.
Aug 5 00:04:36 lib systemd: Starting Session 1108 of user test12.
[root@lib log]# iptables -R INPUT 3 -d 192.168.0.103 -p tcp --dport 23 -m state --state NEW -j LOG --log-prefix "access telnet"
[root@lib log]#
[root@lib ~]# iptables -vnL --line-numbers
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 37 2872 ACCEPT all -- 0.0.0.0/0 192.168.0.103 state RELATED,ESTABLISHED
2 0 0 ACCEPT udp -- 0.0.0.0/0 192.168.0.103 udp dpts:137:138 state NEW
3 0 0 LOG tcp -- 0.0.0.0/0 192.168.0.103 tcp dpt:23 state NEW LOG flags 0 level 4 prefix "access telnet"
4 0 0 ACCEPT tcp -- 0.0.0.0/0 192.168.0.103 multiport dports 21:23,80,139,445,3306 state NEW
5 0 0 REJECT all -- 0.0.0.0/0 192.168.0.103 reject-with icmp-port-unreachable
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 199 39934 ACCEPT all -- 192.168.0.103 0.0.0.0/0 state ESTABLISHED
2 0 0 ACCEPT udp -- 192.168.0.103 0.0.0.0/0 multiport dports 123,323 state NEW
3 8 688 REJECT all -- 192.168.0.103 0.0.0.0/0 reject-with icmp-port-unreachable
[root@lib ~]#
日志有前缀了
[root@lib log]# tail -f messages
Aug 5 00:09:10 lib kernel: access telnetIN=ens33 OUT= MAC=00:0c:29:b7:65:02:58:fb:84:0c:97:07:08:00 SRC=192.168.0.101 DST=192.168.0.103 LEN=52 TOS=0x00 PREC=0x00 TTL=128 ID=14262 DF PROTO=TCP SPT=60250 DPT=23 WINDOW=64240 RES=0x00 SYN URGP=0
Aug 5 00:09:10 lib systemd: Started Telnet Server (192.168.0.101:60250).
Aug 5 00:09:10 lib systemd: Starting Telnet Server (192.168.0.101:60250)...
Aug 5 00:09:13 lib systemd: Created slice user-1050.slice.
Aug 5 00:09:13 lib systemd: Starting user-1050.slice.
Aug 5 00:09:13 lib systemd-logind: New session 1112 of user test12.
Aug 5 00:09:13 lib systemd: Started Session 1112 of user test12.
Aug 5 00:09:13 lib systemd: Starting Session 1112 of user test12.
Aug 5 00:10:01 lib systemd: Started Session 1113 of user root.
Aug 5 00:10:01 lib systemd: Starting Session 1113 of user root.
处理动作（跳转目标）：
-j targetname [per-target-options]
简单target：
ACCEPT， DROP
扩展target：
REJECT
This is used to send back an error packet in response to the matched packet: otherwise it is equivalent to DROP so it is a terminating TARGET, ending rule traversal.
--reject-with type
The type given can be icmp-net-unreachable, icmp-host-unreachable, icmp-port-unreachable, icmp-proto-unreach‐ able, icmp-net-prohibited, icmp-host-prohibited, or icmp-admin-prohibited (*), which return the appropriate ICMP error message
(icmp-port-unreachable is the default).
LOG
Turn on kernel logging of matching packets.
--log-level
--log-prefix
默认日志保存于/var/log/messages
RETURN：
返回调用者；
自定义链做为target：[root@lib ~]# iptables -N in_ping_rules
[root@lib ~]# iptables -A in_ping_rules -d 192.168.0.103 -p icmp --icmp-type 8 -j ACCEPT
[root@lib ~]# iptables -I in_ping_rules -d 192.168.0.103 -s 192.168.0.101 -p icmp -j REJECT
[root@lib ~]# iptables --line-numbers -vnL
Chain INPUT (policy ACCEPT 1 packets, 143 bytes)
num pkts bytes target prot opt in out source destination
1 69 5272 ACCEPT all -- 0.0.0.0/0 192.168.0.103 state RELATED,ESTABLISHED
2 0 0 ACCEPT udp -- 0.0.0.0/0 192.168.0.103 udp dpts:137:138 state NEW
3 0 0 LOG tcp -- 0.0.0.0/0 192.168.0.103 tcp dpt:23 state NEW LOG flags 0 level 4 prefix "access telnet"
4 0 0 ACCEPT tcp -- 0.0.0.0/0 192.168.0.103 multiport dports 21:23,80,139,445,3306 state NEW
5 0 0 REJECT all -- 0.0.0.0/0 192.168.0.103 reject-with icmp-port-unreachable
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 222 45494 ACCEPT all -- 192.168.0.103 0.0.0.0/0 state ESTABLISHED
2 0 0 ACCEPT udp -- 192.168.0.103 0.0.0.0/0 multiport dports 123,323 state NEW
3 96 8256 REJECT all -- 192.168.0.103 0.0.0.0/0 reject-with icmp-port-unreachable
Chain in_ping_rules (0 references) 无效的，需要被调用才行
num pkts bytes target prot opt in out source destination
1 0 0 REJECT icmp -- 192.168.0.101 192.168.0.103 reject-with icmp-port-unreachable
2 0 0 ACCEPT icmp -- 0.0.0.0/0 192.168.0.103 icmptype 8
[root@lib ~]#
[root@lib ~]# iptables -I INPUT 5 -d 192.168.0.103 -p icmp -j in_ping_rules
[root@lib ~]# iptables --line-numbers -vnL
Chain INPUT (policy ACCEPT 1 packets, 143 bytes)
num pkts bytes target prot opt in out source destination
1 84 6368 ACCEPT all -- 0.0.0.0/0 192.168.0.103 state RELATED,ESTABLISHED
2 0 0 ACCEPT udp -- 0.0.0.0/0 192.168.0.103 udp dpts:137:138 state NEW
3 0 0 LOG tcp -- 0.0.0.0/0 192.168.0.103 tcp dpt:23 state NEW LOG flags 0 level 4 prefix "access telnet"
4 0 0 ACCEPT tcp -- 0.0.0.0/0 192.168.0.103 multiport dports 21:23,80,139,445,3306 state NEW
5 0 0 in_ping_rules icmp -- 0.0.0.0/0 192.168.0.103
6 0 0 REJECT all -- 0.0.0.0/0 192.168.0.103 reject-with icmp-port-unreachable
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 232 48662 ACCEPT all -- 192.168.0.103 0.0.0.0/0 state ESTABLISHED 万能的，能进来就能出去
2 0 0 ACCEPT udp -- 192.168.0.103 0.0.0.0/0 multiport dports 123,323 state NEW
3 96 8256 REJECT all -- 192.168.0.103 0.0.0.0/0 reject-with icmp-port-unreachable
Chain in_ping_rules (1 references)
num pkts bytes target prot opt in out source destination
1 0 0 REJECT icmp -- 192.168.0.101 192.168.0.103 reject-with icmp-port-unreachable
2 0 0 ACCEPT icmp -- 0.0.0.0/0 192.168.0.103 icmptype 8
[root@lib ~]#
可以ping通
[root@lamp ~]# ping 192.168.0.103
PING 192.168.0.103 (192.168.0.103) 56(84) bytes of data.
64 bytes from 192.168.0.103: icmp_seq=1 ttl=64 time=0.604 ms
64 bytes from 192.168.0.103: icmp_seq=2 ttl=64 time=0.834 ms
^C
--- 192.168.0.103 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 0.604/0.719/0.834/0.115 ms
[root@lamp ~]#
[root@lib ~]# iptables -X in_ping_rules ，这条规则被调用着，不可删除。
iptables: Too many links.
[root@lib ~]#
保存和载入规则：
保存：iptables-save > /PATH/TO/SOME_RULE_FILE
重载：iptabls-restore < /PATH/FROM/SOME_RULE_FILE
-n, --noflush：不清除原有规则
-t, --test：仅分析生成规则集，但不提交
CentOS 6：
保存规则：
service iptables save
保存规则于/etc/sysconfig/iptables文件，覆盖保存；
重载规则：
service iptables restart
默认重载/etc/sysconfig/iptables文件中的规则
配置文件：/etc/sysconfig/iptables-config
CentOS 7：
(1) 自定义Unit File，进行iptables-restore；
(2) firewalld服务；
(3) 自定义脚本；
规则优化的思路：
使用自定义链管理特定应用的相关规则，模块化管理规则；
(1) 优先放行双方向状态为ESTABLISHED的报文；
(2) 服务于不同类别的功能的规则，匹配到报文可能性更大的放前面；
(3) 服务于同一类别的功能的规则，匹配条件较严格的放在前面；
(4) 设置默认策略：白名单机制
(a) iptables -P，不建议；
(b) 建议在规则的最后定义规则做为默认策略；关闭服务器80 主动往外的链接，即出站不为NEW 状态，只能为ESTABLISHED，防止***
iptables/netfilter：
netfilter： raw 链接追踪，mangle报文修改, nat地址转换, filter
PREROUTING --> INPUT
PREROUTING --> FORWARD --> POSTROUTING
OUTPUT --> POSTROUTING
filter：INPUT，FORWARD，OUTPUT
nat：PREROUTING，INPUT，OUTPUT，POSTROUTING
iptables：
[-t table] COMMAND [chain] rule-specification
-m matchname [per-match-options]
-t targetname [per-target-options]
[options]
匹配 条件：
基本匹配条件：-s, -d, -p, -m, -i, -o
扩展匹配条件：
隐式扩展：
-p tcp: --dport, --sport, --tcp-flags, --syn
-p udp：--dport, --sport
-p imcp: --icmp-type
显式扩展：
multiport：--sports, --dports
iprange：--src-range, --dst-range
time：--timestart, --timestop, --weekdays, --monthdays, --datestart, --datestop
string：--algo {bm|kmp}, --string
connlimit：--connlimit-upto, --connlimit-above
limit：--limit, --limit-burst
state：--state
NEW, ESTABLISHED, RELATED, INVALID, UNTRACKED
target：
-j：
ACCEPT/DROP
REJECT：--reject-with
LOG：--log-level, --log-prefix
自定义链
RETURN
iptables-save/iptables-restoreiptables（3）
iptables/netfilter网络防火墙：
(1) 网关；
(2) filter表的FORWARD链；
要注意的问题：
(1) 请求-响应报文均会经由FORWARD链，要注意规则的方向性；
(2) 如果要启用conntrack机制，建议将双方向的状态为ESTABLISHED的报文直接放行；隐藏内网IP地址，内网IP访问外网服务器时，源IP地址都转换位外网网关的IP地址
NAT: Network Address Translation
请求报文：由管理员定义；
响应报文：由NAT的conntrack机制自动实现；
请求报文：
改源地址：SNAT，MASQUERADE
改目标地址：DNAT
iptables/netfilter：
NAT定义在nat表；
PREROUTING，INPUT，OUTPUT，POSTROUTING
SNAT：POSTROUTING 改源IP
DNAT：PREROUTING 改目标IP
PAT： 改源端口
云端外网IP服务器 ，注意链接追踪数量
target：
SNAT：
This target is only valid in the nat table, in the POSTROUTING and INPUT chains, and user-defined chains which are only called from those chains.
--to-source [ipaddr[-ipaddr]]
DNAT：
This target is only valid in the nat table, in the PREROUTING and OUTPUT chains, and user-defined chains which are only called from those chains.
--to-destination [ipaddr[-ipaddr]][:port[-port]]
MASQUERADE
This target is only valid in the nat table, in the POSTROUTING chain. It should only be used with dynamically assigned IP (dialup) connections: if you have a static IP address, you should use the SNAT target.
SNAT场景中应用于POSTROUTING链上的规则实现源地址转换，但外网地址不固定时，使用此target；
REDIRECT
This target is only valid in the nat table, in the PREROUTING and OUTPUT chains, and user-defined chains which are only called from those chains.
--to-ports port[-port]
layer7
主机A： 192.168.10.2 服务器C: 172.16.0.67主机B路由功能 INC1： 192.168.10.254 INC2： 172.16.0.6 开启IPv4 forware功能
添加路由
#route add -net 192.168.10.0/24 gw 172.16.0.6
添加防火墙规则
#iptables -A FORWARD -j REJECT
请求报文出去
#iptables -I FORWARD -s 192.168.10.0/24 -p tcp --dport 80 -j ACCEPT
响应报文回来
#iptables -I FORWARD -d 192.168.10.0/24 -p tcp --sdport 80 -j ACCEPT
####################
使用状态链接 内网主机可以访问外网任何网络服务，外网不能访问内网
#iptables -D FORWARD 1
#iptables -D FORWARD 1
#iptables -I FORWARD -m state --state ESTABLISHED -j ACCEPT
#iptables -I FORWARD 2 -s 192.169.10.0/24 -m state --state NEW -j ACCEPT
####################
开放内网一个服务给外网访问
#iptables -I FORWARD 3 -d 192.169.10.0/24 -p tcp --dport 80 -m state --state NEW -j ACCEPT
开放多个服务费外网访问
#iptables -R FORWARD -3 -d 192.168.10.2 -p tcp -m multiport --dports 21:23,80,139,445 -m state --state NEW -j ACCEPT
#iptables -I FORWARD 4 -d 192.168.10.2 -p udp --dport 137:138 -m state --state NEW -j ACCEPT
#modprobe nf_conntrack_ftp
[root@lib ~]# lsmod | grep nf_conntrack_ftp
[root@lib ~]#
[root@lib ~]# modprobe nf_conntrack_ftp
[root@lib ~]# lsmod | grep nf_conntrack_ftp nf_conntrack_ftp 18638 0
nf_conntrack 111302 1 nf_conntrack_ftp
[root@lib ~]#
开机会失效，
IPTABLES_MODULES=""
[root@lib ~]#
开放ftp访问
#iptables -I FORWARD 5 -d 192.168.10.2 -p tcp -m state --state RELATED -j ACCEPT
#NAT 功能实现
#iptables -F FORWARD
内网主机访问外网服务，隐藏内网IP，通过构建SNAT实现
#iptables -t nat -A POSTROUTING -s 192.168.10.0/24 -j SNAT --to-source 172.16.0.6
DNAT 实现
外网访问内网服务
#iptables -t nat -F
#iptables -t nat -A PREROUTING -d 172.16.0.6 -p tcp --dport 80 -j DNAT --to-destination 192.168.10.2
PAT 实现 也可以通过DNAT实现
外网访问内网服务80， 实际是访问8080
#iptables -t nat -R PREROUTING 1 -d 172.16.0.6 -p tcp --dport 80 -j DNAT --to-destination 192.168.10.2：8080
#iptables -A FORWARD -s 172.16.0.200 -p tcp --dport 8080 -d 192.168.10.2 -j REJECT
本地端口映射
#iptables -A PREROUTING -t nat -d 192.168.10.2 -p tcp --dport 80 -j REDIRECT --to-ports 8080
tcp_wrapper：
库文件：libwrap.so，tcp包装器；
判断一个服务程序是否能够由tcp_wrapper进行访问控制的方法：
(1) 动态链接至libwrap.so库；
ldd /PATH/TO/PROGRAM
libwrap.so
(2) 静态编译libwrap.so库文件至程序中：
strings /PATH/TO/PGRGRAM
hosts_access
配置文件：/etc/hosts.allow, /etc/hosts.deny
See 'man 5 hosts_options' and 'man 5 hosts_access' for information on rule syntax.
配置文件语法：
daemon_list : client_list[ : option : option ...]
daemon_list：程序文件名称列表
(1) 单个应用程序文件名；
(2) 程序文件名列表，以逗号分隔；
(3) ALL：所有受tcp_wrapper控制的应用程序文件；
client_list：
(1) 单个IP地址或主机名；
(2) 网络地址：n.n.n.n/m.m.m.m，n.n.n.；
(3) 内建的ACL:
ALL：所有客户端主机；
LOCAL：Matches any host whose name does not contain a dot character.
UNKNOWN
KNOWN
PARANOID
OPERATORS：
EXCEPT
list1 EXCEPT list2 EXCEPT list3
sshd: 172.16. EXCEPT 172.16.100. EXCEPT 172.16.100.68
[ : option : option ...]
deny：拒绝，主要用于hosts.allow文件中定义“拒绝”规则；
allow：允许，主要用于hosts.deny文件中定义”允许“规则；
spawn：生成，发起，触发执行用户指定的任意命令，此处通常用于记录日志；
vsftpd: 172.16. : spawn /bin/echo $(date) login attempt from %c to %s >> /var/log/tcp_wrapper.log 免责声明：本站发布的内容（图片、视频和文字）以原创、转载和分享为主，文章观点不代表本网站立场，如果涉及侵权请联系站长邮箱：is@yisu.com进行举报，并提供相关证据，一经查实，将立刻删除涉嫌侵权内容。
