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Laboratory 4: Configuring a Firewall
INFA 620
Laboratory 4: Configuring a Firewall
In this exercise you will be working with firewalld (see https://www.linode.com/docs/security/firewalls/introduction-to-firewalld-on-centos), a front-end to controlling Iptables. Iptables is a flexible firewall utility built for Linux operating systems (see https://www.howtogeek.com/177621/the-beginners-guide-to-iptables-the-linux-firewall/). It is too low level, however, and, as such, hard to use and configure the rules for filtering traffic. firewalld provides higher-level command line and graphical interfaces over Iptables to ease the pain of configuring the firewall features provided by Linux. For this lab exercise, we will only be using only the high-level command line interface. firewalld provides a dynamically managed firewall with support for network/firewall “zones” to assign a level of trust to a network and its associated connections, interfaces or sources. It has support for IPv4 and IPv6. There is a separation of the runtime and permanent configuration options.
For this lab exercise, we will be using two machines, one machine will behave like an Enterprise and the other machine will behave like machines outside an enterprise. We will these machines as External, external to the enterprise. The firewall, as part of the enterprise will control traffic both coming into the enterprise and going out of the enterprise (to External).
NIXENT01 (Enterprise) is a CentOS 7 machine. CentOS is a Linux distribution that attempts to provide a free, enterprise-class, community-supported computing platform. Firewalld will be running on this host.
NIXEXT01 (External) is Kali Linux. Kali Linux is a Debian-based Linux distribution aimed at advanced Penetration Testing and Security Auditing. Kali contains several hundred tools which are geared towards various information security tasks, such as Penetration Testing, Security research, Computer Forensics and Reverse Engineering. You have already used this machine for Lab2 and Lab 3 in analyzing packets using Wireshark. (Wireshark is available as part of Kali distribution.)
Although there are only two machines, we are going to pretend that the Enterprise has three machines (three IP addresses) and each machine has certain services running on those machines, as follows:
NIXENT01 (Enterprise)
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Service |
Associated IP Address |
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domain, telnet |
192.168.10.10 |
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http, https |
192.168.10.20 |
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ftp, imap2, imaps, pop3, pop3s, urd |
192.168.10.30 |
Similarly, we are going to emulate three machines on the External machine with three IP addresses, each running only certain services as follows:
NIXEXT01 (External)
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Service |
Associated IP Address |
|
domain, telnet |
192.168.10.210 |
|
http, https |
192.168.10.220 |
|
ftp, imap, imaps, pop3, pop3s, urd |
192.168.10.230 |
The instructions to use the remote UMUC machine in the DaaS environment is provided in the Accessing Remote DaaS Lab under Course Content. Allocating the Lab Machines.
- Once Lab Broker is available, open the “UMUC Labs” link on the desktop.
- Look for “INFA 620” and select “Nodes.”
- Select “Allocate Lab” *this should take no more than 1 minute.*
*Please Note* Allocated lab resources expire in 7 days. If a lab expires, work done within the lab machine.
Connecting to the Lab Machines
- Within the Lab Broker interface, view the current allocated nodes for INFA 620
- Use the “Connect” button to initiate a connection to each of the two machines:
- When prompted, enter the course credentials:
- Username: StudentFirst
- Password: Cyb3rl@b
- Proceed with the connection. You will need to re-enter the above credentials.
Network Traffic Simulation Script
The Network traffic Simulation script allows users to test pathways to lab resource machines by using the terminal to initiate test packets. The script takes 2 input variables (IP address and service) and uses this information to initiate a test. The script is implemented using bash shell. The script accepts a target IP (-t) and any service name (-s) available in /etc/services
To run the script:
- Open Terminal window.
- Enter command “sudo /usr/local/sbin/traffic_test -t (target IP) -s (service)”
- Target IP and Service are taken from the Enterprise and External Tables above
- Http example: “sudo /usr/local/sbin/traffic_test -t 192.168.10.20 -s http”
- Input the Password for the StudentFirst User: Cyb3rl@b
- The script will then run a 5 packet test and display the results.
The firewall is initially is set up to Deny by Default. So, no traffic will be admitted in either direction until we explicitly change the firewall rules.
Filtering Incoming Traffic
We will show by one example how to configure the http traffic coming into 192.168.10.20. Before we do that, let us verify, no http is coming in:
Initial State Test (You are generating traffic from External to reach Enterprise.)
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EXAMPLE: Incoming traffic to Enterprise on http port not allowed |
|
StudentFirst@infa620-nixext01:~$ sudo /usr/local/sbin/traffic_test -t 192.168.10.20 -s http [sudo] password for StudentFirst: HPING 192.168.10.20 (daaslab 192.168.10.20): S set, 40 headers + 0 data bytes
--- 192.168.10.20 hping statistic --- 5 packets transmitted, 0 packets received, 100% packet loss round-trip min/avg/max = 0.0/0.0/0.0 ms StudentFirst@infa620-nixext01:~$ |
Let us add an incoming traffic rule to the firewall to allow http traffic to 192.168.10.20
|
Adding inbound rules to daaslab zone |
|
|
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[StudentFirst@infa620-nixent01 ~]$ sudo firewall-cmd --zone=daaslab --add-rich-rule='rule family="ipv4" destination address="192.168.10.20/32" port protocol="tcp" port="80" accept’ [StudentFirst@infa620-nixent01 ~]$ password for StudentFirst: Success
You can verify whether a rule was added as follows: [StudentFirst@infa620-nixent01 ~]$ sudo firewall-cmd --zone=daaslab --list-rich-rules rule family="ipv4" destination address="192.168.10.20/32" port port="80" protocol="tcp" accept [StudentFirst@infa620-nixent01 ~]$ |
Test the effect of the new rule added:
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EXAMPLE: Incoming traffic to Enterprise on http port is now allowed |
|
StudentFirst@infa620-nixext01:~$ sudo /usr/local/sbin/traffic_test -t 192.168.10.20 -s http [sudo] password for StudentFirst: HPING 192.168.10.20 (daaslab 192.168.10.20): S set, 40 headers + 0 data bytes len=44 ip=192.168.10.20 ttl=64 DF id=0 sport=80 flags=SA seq=0 win=29200 rtt=3.9 ms len=44 ip=192.168.10.20 ttl=64 DF id=0 sport=80 flags=SA seq=1 win=29200 rtt=3.8 ms len=44 ip=192.168.10.20 ttl=64 DF id=0 sport=80 flags=SA seq=2 win=29200 rtt=3.7 ms len=44 ip=192.168.10.20 ttl=64 DF id=0 sport=80 flags=SA seq=3 win=29200 rtt=3.6 ms len=44 ip=192.168.10.20 ttl=64 DF id=0 sport=80 flags=SA seq=4 win=29200 rtt=3.5 ms
--- 192.168.10.20 hping statistic --- 5 packets transmitted, 5 packets received, 0% packet loss round-trip min/avg/max = 3.5/3.7/3.9 ms StudentFirst@infa620-nixext01:~$ |
As you can see, the inbound http traffic to 192.168.10.20 has been enabled.
On your own now, configure rules to allow the following nine services (45 Points):
https to 192.168.10.20
domain and telnet to 192.168.10.1 0
ftp, imap2, imaps, pop3, pop3s, and urd to 192.168.10.30
Domain is often known as DNS (Domain Name Service). You should be able to google port numbers for various services.
Before you configure, first make sure, using the test script given, these traffic types are not allowed to the respective hosts. After configuring them, make sure they are allowed to the respective hosts. Also, verify that the rules were added using sudo firewall-cmd --zone=daaslab --list-rich-rules. There should be one rule for each service added. If you have done correctly, this is what will be listed:
rule family="ipv4" destination address="192.168.10.20/32" port port="80" protocol="tcp" accept
rule family="ipv4" destination address="192.168.10.20/32" port port="443" protocol="tcp" accept
rule family="ipv4" destination address="192.168.10.10/32" port port="23" protocol="tcp" accept
rule family="ipv4" destination address="192.168.10.10/32" port port="53" protocol="tcp" accept
rule family="ipv4" destination address="192.168.10.30/32" port port="20" protocol="tcp" accept
rule family="ipv4" destination address="192.168.10.30/32" port port="21" protocol="tcp" accept
rule family="ipv4" destination address="192.168.10.30/32" port port="143" protocol="tcp" accept
rule family="ipv4" destination address="192.168.10.30/32" port port="993" protocol="tcp" accept
rule family="ipv4" destination address="192.168.10.30/32" port port="110" protocol="tcp" accept
rule family="ipv4" destination address="192.168.10.30/32" port port="995" protocol="tcp" accept
rule family="ipv4" destination address="192.168.10.30/32" port port="465" protocol="tcp" accept
Outgoing Traffic
Initial State Test
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Outgoing traffic to External on http port not allowed (You are generating traffic from Enterprise to reach External.) |
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[StudentFirst@infa620-nixent01 ~]$ sudo /usr/local/sbin/traffic_test -t 192.168.10.220 -s http [sudo] password for StudentFirst: HPING 192.168.10.220 (daaslab 192.168.10.220): S set, 40 headers + 0 data bytes [send_ip] sendto: Operation not permitted [StudentFirst@infa620-nixent01 ~]$ |
Adding an outgoing traffic rules to the firewall
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Adding outbound rules |
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Via the Terminal |
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[StudentFirst@infa620-nixent01 ~]$ sudo firewall-cmd --direct --add-rule ipv4 filter OUTPUT 1 -p tcp -m tcp --dport 80 -j ACCEPT success [StudentFirst@infa620-nixent01 ~]$ |
Outbound Rules Test
|
Outgoing traffic to External on http port allowed |
|
[StudentFirst@infa620-nixent01 ~]$ sudo /usr/local/sbin/traffic_test -t 192.168.10.220 -s http [sudo] password for StudentFirst: HPING 192.168.10.220 (daaslab 192.168.10.220): S set, 40 headers + 0 data bytes len=44 ip=192.168.10.220 ttl=64 DF id=0 sport=80 flags=SA seq=0 win=29200 rtt=1.9 ms len=44 ip=192.168.10.220 ttl=64 DF id=0 sport=80 flags=SA seq=1 win=29200 rtt=2.0 ms len=44 ip=192.168.10.220 ttl=64 DF id=0 sport=80 flags=SA seq=2 win=29200 rtt=3.8 ms len=44 ip=192.168.10.220 ttl=64 DF id=0 sport=80 flags=SA seq=3 win=29200 rtt=2.0 ms len=44 ip=192.168.10.220 ttl=64 DF id=0 sport=80 flags=SA seq=4 win=29200 rtt=2.0 ms
--- 192.168.10.220 hping statistic --- 5 packets transmitted, 5 packets received, 0% packet loss round-trip min/avg/max = 1.9/2.3/3.8 ms [StudentFirst@infa620-nixent01 ~]$ |
On your own now, configure rules to allow the following nine services (45 Points):
https to 192.168.10.220
domain and telnet to 192.168.10.210
ftp, imap2, imaps, pop3, pop3s and urd to 192.168.10.230
Before you configure, first make sure using the test script these traffic types are not allowed to the respective hosts. After configuring them, make sure they are allowed to the respective hosts.
Miscellaneous Tasks
Making Rules Persistent (Not needed for this lab exercise)
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Making rules persistent |
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[StudentFirst@infa620-nixent01 ~]$ sudo firewall-cmd --runtime-to-permanent success [StudentFirst@infa620-nixent01 ~]$ |
You can view the Iptables to see what rules you have added. In the example below, the table entries that are highlighted are the ones we have just added.
Viewing the IP Tables
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Viewing iptables rules (Just an example output) |
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Chain INPUT (policy ACCEPT) target prot opt source destination ACCEPT udp -- anywhere anywhere multiport dports rfe 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_daaslab all -- anywhere anywhere FWDI_trusted all -- anywhere anywhere FWDI_trusted all -- anywhere anywhere
Chain FORWARD_IN_ZONES_SOURCE (1 references) target prot opt source destination
Chain FORWARD_OUT_ZONES (1 references) target prot opt source destination FWDO_daaslab all -- anywhere anywhere FWDO_trusted all -- anywhere anywhere FWDO_trusted all -- anywhere anywhere
Chain FORWARD_OUT_ZONES_SOURCE (1 references) target prot opt source destination
Chain FORWARD_direct (1 references) target prot opt source destination
Chain FWDI_daaslab (1 references) target prot opt source destination FWDI_daaslab_log all -- anywhere anywhere FWDI_daaslab_deny all -- anywhere anywhere FWDI_daaslab_allow all -- anywhere anywhere DROP all -- anywhere anywhere
Chain FWDI_daaslab_allow (1 references) target prot opt source destination
Chain FWDI_daaslab_deny (1 references) target prot opt source destination
Chain FWDI_daaslab_log (1 references) target prot opt source destination
Chain FWDI_trusted (2 references) target prot opt source destination FWDI_trusted_log all -- anywhere anywhere FWDI_trusted_deny all -- anywhere anywhere FWDI_trusted_allow all -- anywhere anywhere ACCEPT all -- anywhere anywhere
Chain FWDI_trusted_allow (1 references) target prot opt source destination
Chain FWDI_trusted_deny (1 references) target prot opt source destination
Chain FWDI_trusted_log (1 references) target prot opt source destination
Chain FWDO_daaslab (1 references) target prot opt source destination FWDO_daaslab_log all -- anywhere anywhere FWDO_daaslab_deny all -- anywhere anywhere FWDO_daaslab_allow all -- anywhere anywhere DROP all -- anywhere anywhere
Chain FWDO_daaslab_allow (1 references) target prot opt source destination
Chain FWDO_daaslab_deny (1 references) target prot opt source destination
Chain FWDO_daaslab_log (1 references) target prot opt source destination
Chain FWDO_trusted (2 references) target prot opt source destination FWDO_trusted_log all -- anywhere anywhere FWDO_trusted_deny all -- anywhere anywhere FWDO_trusted_allow all -- anywhere anywhere ACCEPT all -- anywhere anywhere
Chain FWDO_trusted_allow (1 references) target prot opt source destination
Chain FWDO_trusted_deny (1 references) target prot opt source destination
Chain FWDO_trusted_log (1 references) target prot opt source destination
Chain INPUT_ZONES (1 references) target prot opt source destination IN_daaslab all -- anywhere anywhere IN_trusted all -- anywhere anywhere IN_trusted all -- anywhere anywhere
Chain INPUT_ZONES_SOURCE (1 references) target prot opt source destination
Chain INPUT_direct (1 references) target prot opt source destination
Chain IN_daaslab (1 references) target prot opt source destination IN_daaslab_log all -- anywhere anywhere IN_daaslab_deny all -- anywhere anywhere IN_daaslab_allow all -- anywhere anywhere DROP all -- anywhere anywhere
Chain IN_daaslab_allow (1 references) target prot opt source destination ACCEPT tcp -- anywhere ip-192-168-10-20.ec2.internal tcp dpt:http ctstate NEW ACCEPT tcp -- anywhere ip-192-168-10-20.ec2.internal tcp dpt:https ctstate NEW ACCEPT tcp -- anywhere ip-192-168-10-10.ec2.internal tcp dpt:telnet ctstate NEW ACCEPT tcp -- anywhere ip-192-168-10-10.ec2.internal tcp dpt:domain ctstate NEW ACCEPT tcp -- anywhere ip-192-168-10-30.ec2.internal tcp dpt:ftp-data ctstate NEW ACCEPT tcp -- anywhere ip-192-168-10-30.ec2.internal tcp dpt:ftp ctstate NEW ACCEPT tcp -- anywhere ip-192-168-10-30.ec2.internal tcp dpt:imap ctstate NEW ACCEPT tcp -- anywhere ip-192-168-10-30.ec2.internal tcp dpt:imaps ctstate NEW ACCEPT tcp -- anywhere ip-192-168-10-30.ec2.internal tcp dpt:pop3 ctstate NEW ACCEPT tcp -- anywhere ip-192-168-10-30.ec2.internal tcp dpt:pop3s ctstate NEW ACCEPT tcp -- anywhere ip-192-168-10-30.ec2.internal tcp dpt:urd ctstate NEW
Chain IN_daaslab_deny (1 references) target prot opt source destination
Chain IN_daaslab_log (1 references) target prot opt source destination
Chain IN_trusted (2 references) target prot opt source destination IN_trusted_log all -- anywhere anywhere IN_trusted_deny all -- anywhere anywhere IN_trusted_allow all -- anywhere anywhere ACCEPT all -- anywhere anywhere
Chain IN_trusted_allow (1 references) target prot opt source destination
Chain IN_trusted_deny (1 references) target prot opt source destination
Chain IN_trusted_log (1 references) target prot opt source destination
Chain OUTPUT_direct (1 references) target prot opt source destination ACCEPT all -- anywhere anywhere ctstate RELATED,ESTABLISHED ACCEPT tcp -- anywhere anywhere tcp dpt:http ACCEPT tcp -- anywhere anywhere tcp dpt:https ACCEPT tcp -- anywhere anywhere tcp dpt:telnet ACCEPT tcp -- anywhere anywhere tcp dpt:domain ACCEPT tcp -- anywhere anywhere tcp dpt:ftp-data ACCEPT tcp -- anywhere anywhere tcp dpt:imap ACCEPT tcp -- anywhere anywhere tcp dpt:pop3 ACCEPT tcp -- anywhere anywhere tcp dpt:pop3s ACCEPT tcp -- anywhere anywhere tcp dpt:urd ACCEPT tcp -- anywhere anywhere tcp dpt:ftp ACCEPT tcp -- anywhere anywhere tcp dpt:imaps REJECT all -- anywhere anywhere reject-with icmp-host-prohibited [StudentFirst@infa620-nixent01 ~]$ |
Export the IP Tables, as illustrated below (for submission)
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Exporting iptables rules |
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[StudentFirst@infa620-nixent01 ~]$ sudo iptables-save > ~/Desktop/iptables_rules-May17-17.txt [sudo] password for StudentFirst: [StudentFirst@infa620-nixent01 ~]$ |
Transfer this file, iptables_rules-May17-17.txt, first to the workspsace Desktop. From there, you can email the file using the Chrome browser to yourself and then submit it to the Lab 4 folder in the classroom.
(10 Points) Also, provide a short summary of your experience of using DaaS for this Lab (Difficulties you have encountered, what worked, what did not work, etc.)
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16 Nov 2017
Due Date: 16 Nov 2017
Answers (2)
INFA 620 Laboratory 4: Configuring a Firewall
INFA 620 Laboratory 4: Configuring a Firewall
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