Assessment 1, Lab 1

                                                         Title: Introduction to Wireshark

Objective of this workshop:
The basic purpose of this Workshop is to introduce you to Wireshark, a popular protocol analyzer and packet sniffer. By the end of this Workshop, you will be familiar to its environment and will be able to capture packets.

Instructions:
• Read carefully before starting the Workshop.
• These exercises are to be done individually.
• You are supposed to provide the answers to the questions listed at the end of this document and upload the completed report on the moodle.
• Avoid plagiarism by copying from the Internet or from your peers. You may refer to source/ text but you must paraphrase the original work. Your submitted work should be written by yourself. •

1. What is a Protocol Analyzer?

Protocol analyzers capture conversations between two or more systems or devices. A protocol analyzer not only captures the traffic, it also decodes (interprets) the traffic. Decoding allows you to view the conversation in English, as opposed to binary language. A sophisticated protocol analyzer will also provide statistics and trend information on the captured traffic. Protocol analyzers provide information about the traffic flow on your local area network (LAN), from which you can view device specific information.

A protocol analyzer can show runaway traffic (broadcast or multicast storms) and its origin, system errors and retries, and whether a station is sending, trying to send, or only seeming to communicate. You will get information that is otherwise unavaiWorkshople, which results in more efficient troubleshooting and better LAN health.

2. Introduction to Wireshark

Wireshark is a free and open-source packet analyzer, used for network troubleshooting, analysis, software and communications protocol development, and education. The basic tool for observing the messages exchanged between executing protocol entities is called a packet sniffer. As the name suggests, a packet sniffer captures (“sniffs”) messages being sent/received from/by your computer; it will also typically store and/or display the contents of the various protocol fields in these captured messages. A packet sniffer itself is passive. It observes messages being sent and received by applications and protocols running on your computer, but never sends packets itself. Similarly, received packets are never explicitly addressed to the packet sniffer. Instead, a packet sniffer receives a copy of packets that are sent/ received from/by application and protocols executing on your machine.

Figure 1 shows the structure of a packet sniffer. At the right of Figure 1 are the protocols (in this case, Internet protocols) and applications (such as a web browser or ftp client) that normally run on your computer. The packet sniffer, shown within the dashed rectangle in Figure 1 is an addition to the usual software in your computer, and consists of two parts. The packet capture library receives a copy of every link-layer frame that is sent from or received by your computer. The messages exchanged by higher layer protocols such as HTTP, FTP, TCP, UDP, DNS, or IP all are eventually encapsulated in linklayer frames that are transmitted over physical media such as an Ethernet cable. In Figure 1, the assumed physical media is an Ethernet, and so all upper layer protocols are eventually encapsulated within an Ethernet frame. Capturing all link-layer frames thus gives you all messages sent/received from/by all protocols and applications executing in your computer.

The second component of a packet sniffer is the packet analyzer, which displays the contents of all fields within a protocol message. In order to do so, the packet analyzer must “understand” the structure of all messages exchanged by protocols. For example, suppose we are interested in displaying the various fields in messages exchanged by the HTTP protocol in Figure 1. The packet analyzer understands the format of Ethernet frames, and so can identify the IP datagram within an Ethernet frame. It also understands the IP datagram format, so that it can extract the TCP segment within the IP datagram. Finally, it understands the TCP segment structure, so it can extract the HTTP message contained in the TCP segment. Finally, it understands the HTTP protocol and so, for example, knows
that the first bytes of an HTTP message will contain the string “GET,” “POST,” or “HEAD,”.
We will be using the Wireshark packet sniffer [http://www.wireshark.org/] for Workshops in this unit, allowing us to display the contents of messages being sent/ received from/by protocols at different levels of the protocol stack. (Technically speaking, Wireshark is a packet analyzer that uses a packet capture library in your computer). Wireshark is a free network protocol analyzer that runs on Windows, Linux/Unix, and Mac computers. It’s an ideal packet analyzer for our Workshops – it is stable, has a large user-base and well-documented support that includes a user-guide (http://www.wireshark.org/docs/wsug_html_chunked/), man pages
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(http://www.wireshark.org/docs/man-pages/), and a detailed FAQ
(http://www.wireshark.org/faq.html), rich functionality that includes the capability to analyze more than 500 protocols, and a well-designed user interface. It operates in computers using Ethernet, serial (PPP), 802.11 (WiFi) wireless LANs, and many other link-layer technologies.
2.1 Getting Wireshark
In order to run Wireshark, you will need to have access to a computer that supports both Wireshark and the libpcap or WinPCap packet capture library. The libpcap software will be installed for you alongside Wireshark automatically. See http://www.wireshark.org/download.html for a list of supported operating systems and download sites
Download and install the Wireshark software:
• Go to http://www.wireshark.org/download.html and download and install the Wireshark binary for your computer. Wireshark can be installed on both Windows and Linux. See the documentation page of Wireshark for more details.
• Download the Wireshark user guide.
The Wireshark FAQ has a number of helpful hints and interesting tidbits of information, particularly if you have trouble installing or running Wireshark.
2.2 Running Wireshark
When you run the Wireshark program, you will get a startup screen that looks something like the screen below. Different versions of Wireshark will have different startup screens – so don’t panic if yours doesn’t look exactly like the screen below! The Wireshark documentation states “As Wireshark runs on many different platforms with many different window managers, different styles applied and there are different versions of the underlying GUI toolkit used, your screen might look different from the provided screenshots. But as there are no real differences in functionality these screenshots should still be well understandable.” Well said.
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There’s not much that’s very interesting on this screen. But note that under the Capture section, there is a list of so-called interfaces. The Mac computer we’re taking these screenshots from has just one interface – “Wi-Fi en0,” (shaded in blue in Figure 2) which is the interface for Wi-Fi access. All packets to/from this computer will pass through the Wi-Fi interface, so it’s here where we’ll want to capture packets. On a Mac, double click on this interface (or on another computer locate the interface on start-up page through which you are getting Internet connectivity, e.g., mostly likely a WiFi or Ethernet interface, and select that interface).
The Wireshark interface has five major components:
• The command menus are standard pulldown menus located at the top of the Wireshark window (and on a Mac at the top of the screen as well; the screenshot in Figure 3 is from a Mac). Of interest to us now are the File and Capture menus. The File menu allows you to save captured
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packet data or open a file containing previously captured packet data and exit the Wireshark application. The Capture menu allows you to begin packet capture.
• The packet-listing window displays a one-line summary for each packet captured, including the packet number (assigned by Wireshark; note that this is not a packet number contained in any protocol’s header), the time at which the packet was captured, the packet’s source and destination addresses, the protocol type, and protocol-specific information contained in the packet. The packet listing can be sorted according to any of these categories by clicking on a column name. The protocol type field lists the highest-level protocol that sent or received this packet, i.e., the protocol that is the source or ultimate sink for this packet.
• The packet-header details window provides details about the packet selected (highlighted) in the packet-listing window. (To select a packet in the packet-listing window, place the cursor over the packet’s one-line summary in the packet-listing window and click with the left mouse button.). These details include information about the Ethernet frame (assuming the packet was sent/received over an Ethernet interface) and IP datagram that contains this packet. The amount of Ethernet and IP-layer detail displayed can be expanded or minimized by clicking on the plus/minus boxes or right/downward-pointing triangles to the left of the Ethernet frame or IP datagram line in the packet details window. If the packet has been carried over TCP or UDP, TCP or UDP details will also be displayed, which can similarly be expanded or minimized. Finally, details about the highest-level protocol that sent or received this packet are also provided.
• The packet-contents window displays the entire contents of the captured frame, in both ASCII and hexadecimal format.
• Towards the top of the Wireshark graphical user interface, is the packet display filter field, into which a protocol name or other information can be entered in order to filter the information displayed in the packet-listing window (and hence the packet-header and packetcontents windows). In the example below, we’ll use the packet-display filter field to have Wireshark hide (not display) packets except those that correspond to HTTP messages.
Taking Wireshark on a Test Run
The best way to learn about any new piece of software is to try it out! We’ll assume that your computer is connected to the Internet via a wired Ethernet interface or a wireless 802.11 WiFi interface. Do the following:
1. Start up your favorite web browser, which will display your selected homepage.
2. Start up the Wireshark software. You will initially see a window similar to that shown in Figure
2. Wireshark has not yet begun capturing packets.
3. To begin packet capture, select the Capture pull down menu and select Interfaces. This will cause the “Wireshark: Capture Interfaces” window to be displayed (on a PC) or you can choose
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Options on a Mac. You should see a list of interfaces, as shown in Figures 4a (Windows) and 4b (Mac).
Figure 4a: Wireshark Capture interface window, on a Windows computer
Figure 4b: Wireshark Capture interface window, on a Mac computer
4. You’ll see a list of the interfaces on your computer as well as a count of the packets that have been observed on that interface so far. On a Windows machine, click on Start for the interface on which you want to begin packet capture (in the case in Figure 4a, the Gigabit network Connection). On a Windows machine, select the interface and click Start on the bottom of the window). Packet capture will now begin - Wireshark is now capturing all packets being sent/received from/by your computer!
5. Once you begin packet capture, a window similar to that shown in Figure 3 will appear. This window shows the packets being captured. By selecting Capture pulldown menu and selecting Stop, or by click on the red Stop square, you can stop packet capture. But don’t stop packet capture yet. Let’s capture some interesting packets first. To do so, we’ll need to generate some network traffic. Let’s do so using a web browser, which will use the HTTP protocol that we will study in detail in class to download content from a website.
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6. While Wireshark is running, enter the URL:
http://testphp.vulnweb.com/login.php and have that page displayed in your browser. In order to display this page, your browser will contact the HTTP server at http://testphp.vulnweb.com/login.php and exchange HTTP messages with the server in order to download this page. The Ethernet or WiFi frames containing these HTTP messages (as well as all other frames passing through your Ethernet or WiFi adapter) will be captured by Wireshark.
7. After your browser has displayed the http://testphp.vulnweb.com/login.php page, stop Wireshark packet capture by selecting stop in the Wireshark capture window. The main Wireshark window should now look similar to Figure 3. You now have live packet data that contains all protocol messages exchanged between your computer and other network entities! The HTTP message exchanges with the web server should appear somewhere in the listing of packets captured. But there will be many other types of packets displayed as well (see, e.g., the many different protocol types shown in the Protocol column in Figure 3). Even though the only action you took was to download a web page, there were evidently many other protocols running on your computer that are unseen by the user.
8. Type in “http” (without the quotes, and in lower case – all protocol names are in lower case in Wireshark) into the display filter specification window at the top of the main Wireshark window. Then select Apply (to the right of where you entered “http”) or just hit return. This will cause only HTTP message to be displayed in the packet-listing window. Figure 5 below shows a screenshot after the http filter has been applied to the packet capture window shown earlier in Figure 3. Note also that in the Selected packet details window, we’ve chosen to show detailed content for the Hypertext Transfer Protocol application message that was found within the TCP segment, that was inside the IPv4 datagram that was inside the Ethernet II (WiFi) frame. Focusing on content at a specific message, segment, datagram and frame level lets us focus on just what we want to look at (in this case HTTP messages).

9. Find the HTTP GET message that was sent from your computer to the http://testphp.vulnweb.com/login.php. (Look for an HTTP GET message in the “listing of captured packets” portion of the Wireshark window (see Figures 3 and 5) that shows “GET” followed by the shttp://testphp.vulnweb.com/login.php URL that you entered. When you select the HTTP GET message, the Ethernet frame, IP datagram, TCP segment, and HTTP message header information will be displayed in the packet-header window1. By clicking on ‘+’ and ‘-' and right-pointing and down-pointing arrowheads to the left side of the packet details window, minimize the amount of Frame, Ethernet, Internet Protocol, and Transmission Control Protocol information displayed. Maximize the amount information displayed about the HTTP protocol. Your Wireshark display should now look roughly as shown in Figure 5. (Note, in particular, the minimized amount of protocol information for all protocols except HTTP, and the maximized amount of protocol information for HTTP in the packet-header window).
Questions:
1. Is your browser running HTTP version 1.0 or 1.1? (snapshot and text explanations are required)
2. What is the TCP port number used by your machine? What is the TCP port number used by the destination server? (snapshot and text explanations are required)
3. Capture username and password using Wireshark (according to the below instructions): (snapshot and text explanations are required)
Over Hyper Text Transfer Protocol (HTTP)
Your next task is to capture username and password that is entered on a website that uses HTTP. Remember that HTTP does not provide security and usernames and passwords are sent in cleartext (i.e., with no encryption). Follow the steps given below:
a. Start capturing packets with Wireshark and in your browser enter the following URL
http://testphp.vulnweb.com/login.php

1 HTTP GET message that is sent to the http://testphp.vulnweb.com/login.php is contained within a TCP segment, which is contained (encapsulated) in an IP datagram, which is encapsulated in an Ethernet frame.

b. Enter your first name as username and last name as password and then press login.

c. Stop packets capturing by Wireshark and search for HTTP Post method that contains the username and password that is sent by your browser. You have to submit the screenshot of that HTTP message.

Remember that HTTPs is commonly used these days as it provides encryption. More details on this will be provided later in the unit.
                                                         End of Workshop

Important points:

• Labs are in-class activities. Therefore, submitting outside of class and the defined hours is an example of unethical behaviour (academic misconduct). For any late submission, you MUST apply for special consideration before or on the assessment date. ONLY upon getting the approval of the special consideration, a second attempt will be arranged.

• The submitted Doc/PDF file should contain at least 20 words. Otherwise, Turnitin will reject it.

• Only Doc/PDF files are acceptable. Images (screenshots) or other formats will not be marked.

• Do not crop the screenshots.

• Once you submitted a report, please ensure Turnitin has accepted your file. The rejected submissions will not be graded.

• If instructed in the assignment, the screenshots MUST show your name. The answers which do not meet the defined criteria will receive 0 mark, even if the answer is correct