GeekWind

今回はiptablesの設定である。

セキュリティの強化ってことで、まずはiptablesがインストールされているかをチェック。

# yum list | grep iptables
iptables.x86_64                            1.3.5-5.3.el5_4.1           installed
iptables-ipv6.x86_64                       1.3.5-5.3.el5_4.1           installed
iptables-devel.i386                        1.3.5-5.3.el5_4.1           base
iptables-devel.x86_64                      1.3.5-5.3.el5_4.1           base

# rpm -qa | grep iptables
iptables-ipv6-1.3.5-5.3.el5_4.1
iptables-1.3.5-5.3.el5_4.1

インストールされているので、今度はiptbelsの設定を確認。

# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

iptablesを編集する。
もちろん、root で設定を行っていく。

# su -
Password:
# vi /etc/sysconfig/iptables
*filter
:INPUT   ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT  ACCEPT [0:0]
:RH-Firewall-1-INPUT - [0:0]

-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp --icmp-type any -j ACCEPT
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp --dport 5353 -d 224.0.0.251 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# SSH, HTTP, FTP1, FTP2, HTTPS, MySQL  
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport XXXXX -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 80    -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 20    -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 21    -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 443 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport YYYY  -j ACCEPT

-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited

COMMIT

iptablesの編集が済んだところで、起動。

# /etc/rc.d/init.d/iptables start
Flushing firewall rules:                                   [  OK  ]
Setting chains to policy ACCEPT: filter                    [  OK  ]
Unloading iptables modules:                                [  OK  ]
Applying iptables firewall rules:                          [  OK  ]

起動後、自動起動するようにchkconfigで設定。自動起動のiptablesサービスがどう設定されている確認。

# chkconfig iptables on
#
# chkconfig --list iptables
iptables        0:off   1:off   2:on    3:on    4:on    5:on    6:off

設定がどのように反映されている確認。よくよく考えると、ftpを使う気がないので20,21ポートは閉じてもいいかも、と思ったりしている。

# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination
RH-Firewall-1-INPUT  all  --  anywhere             anywhere

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination
RH-Firewall-1-INPUT  all  --  anywhere             anywhere

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Chain RH-Firewall-1-INPUT (2 references)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere
ACCEPT     icmp --  anywhere             anywhere            icmp any
ACCEPT     esp  --  anywhere             anywhere
ACCEPT     ah   --  anywhere             anywhere
ACCEPT     udp  --  anywhere             224.0.0.251         udp dpt:mdns
ACCEPT     udp  --  anywhere             anywhere            udp dpt:ipp
ACCEPT     tcp  --  anywhere             anywhere            tcp dpt:ipp
ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTABLISHED
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:XXXXX
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:http
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:ftp-data
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:ftp
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:https
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:mysql
REJECT     all  --  anywhere             anywhere            reject-with icmp-host-prohibited

これでひとまずのセキュリティ強化は終了。