CURL to Access a Page – FAQ

What is the -b option used for in curl?

The -b option in curl refers to a file, list of cookies to be passed with the current request. This enables you to pass cookies of authentication in your request as you imitate the session of a logged in user.

How about capturing cookies with curl?

To capture cookies using curl, one can use the -c parameter and specify the filename that one wants to use to store the cookies. For example, curl -c cookies. txt https://example. The cookies from the login response will be captured at com/login and will then be saved in a file called cookies. txt.

How does the -b and -c options in curl work?

While the former is used to forward the request with cookies read from a file, the latter is used to save the cookies received from the server into a file.

What is the correct syntax of a POST request using curl?

In a curl command, you can use the -X POST option in order to send a POST request, as well as include data into the request body. For example, curl -X POST -d “username=your_username&password=your_password” https://examplecom/login will make an HTTP request with the ‘POST’ method to the login URL with the required username and password.

Is curl can be used to test web application security vulnerabilities?

Yes, curl can be used to test for web application security flaws including authentication vulnerabilities, session handling weaknesses, and access control flaws. By emulating various user scenarios and analyzing the replies, one can determine the possible susceptibilities in the application to security threats.

In this article, I have illustrated how you can utilize curl, a versatile command-line tool, to mimic the login process and access confidential web pages. I have also shown you how to perform the necessary steps to send POST requests using the correct credentials, no doubt, how to deal with authorization cookies and enable you to send GET requests and access your chosen secured web pages. Now that you’ve followed this guide, you have learned how to apply curl to browse through authenticated web apps. With that done, your web application security analysis and testing could be more productive.

Step 1: Inspect the login process.

To successfully log in, you need to simulate the login process by sending a POST request with the correct username and password, and then properly handle the authentication cookies that are returned in the response.

For example, we will use the Bugzilla Login page and we will enter our username and password. Open the developer mode by pressing F12. Head toward the network section.

As you can see in the above image, Under Headers there is Content-Type and Cookie Name and Cookie value.

Step 2: Open the Terminal and paste the below code and edit it as per your details.

curl -X POST -d “username=your_username&password=your_password” \

-H “Content-Type: application/x-www-form-urlencoded” \

-b “cookie_name=cookie_value” \

https://example.com/login

“Upon successful login, the website responds with authentication tokens, such as cookies or session IDs, which verify our logged-in state. We can then utilize curl’s -c option to capture these cookies and store them in a file, allowing us to reuse them in subsequent requests to access restricted areas.”

Step 3: Capture the Cookies by entering the below command. Dont forget to edit it as per your details.

curl -X POST -d “username=your_username&password=your_password” \

-H “Content-Type: application/x-www-form-urlencoded” \

-c cookies.txt \

https://example.com/login

This will save the cookies in the cookies.txt file, which looks like this.

Step 4: Having obtained the required authentication cookies

We’ll proceed to access the logged-in page. To do this, we’ll issue a GET request to the desired protected page, ensuring that we include the previously captured authentication cookies in the request.

Enter the following command.

curl -b cookies.txt https://example.com/logged-in-page

The output of this curl command will give you the HTML content of the logged-in page.