Protocols and Servers

February 29, 2024

Task 1: Introduction

Task 2: Telnet

Task 3: Hypertext Transfer Protocol (HTTP)

First you have to enter the telnet command, so you can connect to the web server.

telnet 10.10.116.245 80

Then after you are connected to the IP address and its port.

We have to input some commands to retrieve the html page

GET /index.html HTTP/1.1

The finally we will provide some value like host: telnet and hit the Enter/Return key twice. Now we got the html page that we desire

telnet 10.10.116.245 80

# Then after we are connected to telnet
GET /flag.thm

Here's the answer for the question about the flag

Task 4: File Transfer Protocol (FTP)

First we will have to connect to the IP address through File Transfer Protocol and we will provide credentials since it does not accept anonymous login.

• user - frank

• pass - D2xc9CgD

ftp 10.10.116.245

Additional information about this task!!!!!!!!!!!

We can try to connect using the telnet protocol using this command. But ofcourse, we will input some credentials to the telnet server so that we can logged in as a user.

telnet 10.10.116.245 21

USER frank
PASS D2xc9CgD

The first command that we can use is STAT command. We can see some additional information about the system type of the target.

We did try some default command of telnet protocol

• PASV - "Passive Mode" This mode is referred to as PASV mode because the server tells the client the port to which it should connect for data transfer.

• TYPE A - The command TYPE A switches the file transfer mode to ASCII.

• TYPE I - switches to file transfer mode to binary.

However, we cannot transfer a file using a simple client such as Telnet because FTP creates a separate connection for file transfer.

Task 5: Simple Mail Transfer Protocol (SMTP)

The figure shows the following five steps that an email needs to go through to reach the recipient’s inbox:

1. A Mail User Agent (MUA), or simply an email client, has an email message to be sent. The MUA connects to a Mail Submission Agent (MSA) to send its message.

2. The MSA receives the message, checks for any errors before transferring it to the Mail Transfer Agent (MTA) server, commonly hosted on the same server.

3. The MTA will send the email message to the MTA of the recipient. The MTA can also function as a Mail Submission Agent (MSA).

4. A typical setup would have the MTA server also functioning as a Mail Delivery Agent (MDA).

5. The recipient will collect its email from the MDA using their email client.

If the above steps sound confusing, consider the following analogy:

1. You (MUA) want to send postal mail.

2. The post office employee (MSA) checks the postal mail for any issues before your local post office (MTA) accepts it.

3. The local post office checks the mail destination and sends it to the post office (MTA) in the correct country.

4. The post office (MTA) delivers the mail to the recipient mailbox (MDA).

5. The recipient (MUA) regularly checks the mailbox for new mail. They notice the new mail, and they take it.

telnet 10.10.63.138 25

Task 6: Post Office Protocol 3 (POP3)

We have to connect to the default port of Post Office Protocol 3 (POP3) and use the STAT command. But first we have to login for authentication. Use the credentials below for us to get the STAT information.

telnet 10.10.63.138 110
USER frank
PASS D2xc9CgD

As we use the LIST command we will able to see the list of new messages on the server and by using the RETR 1 we can read the first message in the list. However, we failed to retrieve the messages because there's none.

Task 7: Internet Message Access Protocol (IMAP)

It is clear that IMAP sends the login credentials in cleartext, as we can see in the command LOGIN frank D2xc9CgD. Anyone watching the network traffic would be able to know Frank’s username and password.

Task 8: Summary