HTTP in Detail

TryHackMe Walkthroughs ⋅ Guided ⋅ HTTP in Detail

Task 1: What is HTTP(S)?

HyperText Transfer Protocol (HTTP) is a protocol, or set of rules, used to communicate with web servers and transmit webpage data. HTTPS, the S standing for secure, is the encrypted version of HTTP.

What does HTTP stand for?

HyperText Transfer Protocol

The HyperText Transfer Protocol is used to send and receive webpage data.

What does the S in HTTPS stand for?

Secure

HTTPS is the secure and encrypted version of HTTP.

On the mock webpage on the right there is an issue, once you've found it, click on it. What is the challenge flag?

THM{INVALID_HTTP_CERT}

Notice the lock with the red slash on the left of the URL. This means that your connection is insecure.

Task 2: Requests And Responses

A uniform resource locator (URL) is an instruction on how to access a resource on the Internet. Consider the url http://user:password@tryhackme.com:80/view-room?id=1#task3.

http: This is the scheme, which instructs what protocol to use for accessing the resource
user:password: This is the user, which is needed if logging is necessary to access the resource
tryhackme.com: This is the host, also known as the domain name or IP address of the resource
80: This is the port to connect to
view-room: This is the path, also known as the file name or location of the resource
?id=1: This is the query string, which includes extra bits of information that can be sent to the requested path
#task3: This is the fragment, which is a reference to a location on the actual page that is only viewable to the client

HTTP uses a series of requests and responses to transmit data.

Consider this request:

GET / HTTP/1.1
Host: tryhackme.com
User-Agent: Mozilla/5.0 Firefox/87.0
Referer: https://tryhackme.com/

Line 1 says that we are making a GET request using HTTP/1.1 to the home page with /. Lines 2-4 are optional. Host indicates that we want tryhackme.com. User-agent indicates that we are using Firefox version 87 Browser, and referer indicates that we came from tryhackme.com. HTTP requests end with a blank line, meaning the request has finished.

Consider this response:

HTTP/1.1 200 OK
Server: nginx/1.15.8
Date: Fri, 09 Apr 2021 13:34:03 GMT
Content-Type: text/html
Content-Length: 98

<html>
<head>
    <title>TryHackMe</title>
</head>
<body>
    Welcome To TryHackMe.com
</body>
</html>

Line 1 indicates that the protocol used was HTTP 1.1 and that the request was successfully completed. Lines 2-5 indicate information about the server software, server date and time, the content type, and the length of the content. Following these lines is a blank line signalling the end of the HTTP response and the content sent by the server.

What HTTP protocol is being used in the above example?

HTTP/1.1

The HTTP protocol being used can be found on the first line of the request or response.

What response header tells the browser how much data to expect?

Content-Length

This header specifies the length of the content included in the response.

Task 3: HTTP Methods

We can express our intended action when making an HTTP request using different methods.

GET: Used for getting information from a web server
POST: Used for submitting data to a web server, potentially creating new records
PUT: Used for submitting data to a web server to update information
DELETE: Used for deleting information from a web server

What method would be used to create a new user account?

POST

POST is used when we want to create a new record, such as a new user account.

What method would be used to update your email address?

PUT

PUT is used for updating information.

What method would be used to remove a picture you've uploaded to your account?

DELETE

DELETE is used for removing information.

What method would be used to view a news article?

GET

GET is used for receiving information, which can then be viewed.

Task 4: HTTP Status Codes

When an HTTP server responds, the first line contains a status code informing the client of the outcome of their request.

Status codes can be broken down into 5 different ranges:

100-199: These codes inform the client that the first part of their request was accepted and that they should send the rest of their request
200-299: These codes inform the client that their request was successful
300-399: These codes redirect the client's request to another resource
400-499: These codes indicate there was a client-side error with the request
500-599: These codes indicate that there was a server-side error with the request

Common HTTP status codes include, 200-OK, 400-Bad Request, 403-Forbidden, 404-Page Not Found, and 500-Internal Service Error.

What response code might you receive if you've created a new user or blog post article?

201

201 is the Created response code.

What response code might you receive if you've tried to access a page that doesn't exist?

404

404 is the Page Not Found response code.

What response code might you receive if the web server cannot access its database and the application crashes?

503

503 is the Service Unavailable response code.

What response code might you receive if you try to edit your profile without logging in first?

401

401 is the Not Authorized response code.

Task 5: Headers

Headers can be used to send additional information when making a HTTP request.

Common request headers include:

Host: Specifies which website on the server is wanted
User-Agent: Specifies the client browser and version number
Content-Length: Specifies the length of the content sent to the server
Accept-Encoding: Specifies what data compression methods the browser supports
Cookie: Specifies a piece of data remembered by the browser and used by the server to remember client information

Common response headers include:

Set-Cookie: Specifies a piece of data sent by the server that the browser will remember for later requests
Cache-Control: Specifies how long to store the content of the response in the browser's cache
Content-Type: Specifies what type of content is being returned so that the browser can properly process the data
Content-Encoding: Specifies what method was used to compress the data

What header tells the web server what browser is being used?

User-Agent

User-Agent specifies browser and version number.

What header tells the browser what type of data is being returned?

Content-Type

Content-Type, as per its name, specifies the type of content returned by the web server.

What header tells the web server which website is being requested?

Host

Host is used to specify which website on a web server is wanted. This header is especially important if a web server hosts multiple websites.

Task 6: Cookies

HTTP is a stateless protocol; this means that it does not keep track of previous requests. Thus, a server remembers a client by sending a cookie, a small piece of data that is stored by the browser, with the Set-Cookie header. Whenever the client queries the server in the future, the cookie is sent along with the request using the Cookie header. Cookies allows a server to keep track of clients.

Which header is used to save cookies to your computer?

Set-Cookie

Set-Cookie is a header included in HTTP responses that includes a cookie for the browser to save.

Task 7: Making Requests

Open the site associated with the task to answer the following questions.

Make a GET request to /room

THM{YOU'RE_IN_THE_ROOM}

Change the request type to GET and type room into the search bar. Then, press go.

Make a GET request to /blog and using the gear icon set the id parameter to 1 in the URL field

THM{YOU_FOUND_THE_BLOG}

Change the request type to GET and type blog into the search bar. Set the id parameter to 1 and press go.

Make a DELETE request to /user/1

THM{USER_IS_DELETED}

Change the request type to DELETE and type user/1 into the search bar.

Make a PUT request to /user/2 with the username parameter set to admin

THM{USER_HAS_UPDATED}

Change the request type to PUT and type user/2 into the search bar. Set the username parameter to admin and press go.

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