IP camouflage and port forwarding

Firewall supports two types of network address translation

• IP address masquerade

  • It can share multiple addresses in LAN and access to the Internet with a single public address
  • IP address camouflage only supports IPv4, not IPv6
  • Address masquerading is enabled in the default external area
• Forward port
  • Also known as destination address translation or port mapping
  • Through port forwarding, the specified IP address and port traffic will be forwarded to different ports on the same computer, or to ports on different computers

Address camouflage configuration

• Add address camouflage function to specified area

firewall-cmd [--permanent] [--zone= zone] --add-masquerade [--timeout seconds]
 //--timeout=seconds: automatically delete the function after a period of time

• Remove address masquerading for the specified area

firewall-cmd [--permanent] [--zone= zone] --remove-masquerade

• Query whether the address camouflage function is enabled in the specified area

firewall-cmd [--permanent] [--zone=zone] --query-masquerade

Port forwarding configuration

• List port forwarding configuration

firewall-cmd [--permanent] [--zone=zone] --list-forward-ports

• Add port forwarding rule

firewall-cmd [--permanent] [--zone=zone] --add-forward-port=port=portid[-portid]:proto=protocol[:toport-portid[-portid]][:toaddr-address[/mask]][--timeout=seconds]

• Delete port forwarding rule

firewall-cmd [--permanent] [--zone=zone] --remove-forward-port=port=portid[-portid]:proto=protocol[:toport=portid[-portid]][:toaddr=address[/mask]]

• Query port forwarding rules

firewall-cmd [--permanent] [--zone=zone] --query-forward-port-port-portid[-portid]:proto=protocol[:toport-portid[-portid]][:toaddr=address[/mask]]

Firewall direct rules

Direct interface

• Allow administrator manually written iptables, ip6tables, and ebtables rules to be inserted into the firewall managed zone
• Through the -- direct option in the firewall CMD command
• In addition to showing how to insert, match direct rules first

Custom rule chain

• Firewalld automatically creates a custom rule chain for areas configured with rules
  • IN zone name deny: store the deny statement, which takes precedence over the rule of "IN zone domain name" allow "
  • IN area name allow: store allow statement

Allow inbound traffic for TCP/9000 port

irewall-cmd --direct --add-rule ipv4 filter IN work_ allow 0 -p tcp --dport 9000 j ACCEPT

• In work "allow: match the rule chain of work area
• 0: stands for the rule with the highest priority, placed at the top of the rule
• You can add -- permanent option to indicate permanent configuration

Query all direct rules

firewall-cmd --direct --get-all-rules
ipv4 filter IN_ work _allow 0 -p tcp --dport 9000 -j ACCEPT

• You can add -- permanent option to view permanent configuration

Firewall rich language rules

Rich language

• Expressive configuration language, no need to understand iptables syntax
• Used to express basic allow / deny rules, configuration records (for syslog and audited), port forwarding, spoofing, and rate limiting

rule [family="<rule family>"]
  [ source address="<address>" [invert "True"] ]
  [ destination address="<address>" [invert="True"] ]
  [ <element> ]
  [ log [prefix="<prefix text>"] [level="<log level>"] [limit value="rate/duration"] ]
  [ audit ]
  [ acceptlrejectldrop ]

Understanding rich language rule commands

• Common options for dealing with rich language rules in firewall CMD

Rich language rule display is configured

• firewall-cmd --list-all
• firewall-cmd --list-all-zones
• --list-rich-rules

Rich language rules specific grammar

• source,destination, element, service, port, protocol,icmp-block,masquerade, forward-port, log, audit,acceptlreject|drop

Reject all traffic from 192.168.8.101

firewall-cmd --permanent --zone=work --add-rich-rule='rule family=ipv4 source address=192.168.8.101/32 reject'

• When the a ddress option uses source or destination, you must use family= ipv4 | ipv6

Accept TCP traffic of 192.168.1.0/24 subnet port range 8000-9000

firewall-cmd --permanent --one=work --add-rich-rule='rule family=ipv4 source address=192.168.1.0/24 port port=8000-9000 protocol=tcp accept'

Discard all icmp packets

firewall-cmd --permanent --add-rich-rule='rule protocol value=icmp drop'

Accept http traffic from 192.168.8.1 and log

firewall-cmd --add-rich-rule='rule family=ipv4 source address=192.168.8.1/32 service name="http" log level=notice prefix= "NEW HTTP"limit value "3/s" accept'

• Visit http at 192.168.8.1 and observe / var/log/messages

Apr 16 17:09:55 Server kernel: NEW HTTP IN=ens33 OUT=
MAC=00:0c:29:69:01:c4:00:50:56:c0:00:08:08:00 SRC=192.168.8.1 DST=192.168.8.131
LEN=52 TOS=0xOO PREC=0x00 TTL =64 ID=20582 DF PROTO=TCP SPT=65289 DPT=80
WINDOW=8192 RES=0x00 SYN URGP=0
Apr 16 17:09:55 Server kernel: NEW HTTP IN=ens33 OUT=
MAC=00:0c:29:69:01:c4:00:50:56:c0:00:08:08:00 SRC=192.168.8.1 DST=192.168.8.131
LEN=52 TOS=0x0O PREC=0x0O TTL =64 ID=20590 DF PROTO=TCP SPT=65291 DPT=80
WINDOW=8192 RES=0x00 SYN URGP=0
Apr 16 17:09:55 Server kernel: NEW HTTP IN=ens33 OUT=
MAC=00:0c:29:69:01:c4:00:50:56:c0:00:08:08:00 SRC=192.168.8.1 DST=192.168.8.131
LEN=52 TOS=0x0O PREC=0x0O TTL =64 ID=20602 DF PROTO=TCP SPT=65292 DPT=80
WINDOW=8192 RES=0x00 SYN URGP=0