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File Uploading

In this subtopic, participants are tasked with identifying and exploiting weak or poorly implemented file type restrictions in the upload functionality of a vulnerable web application. The challenge focuses on testing how easily attackers can manipulate the system by bypassing checks that rely on file extensions, MIME types, or even file content.

Task 1 The Files of the Forbidden Library

Scenario:-

You’ve gained access to the secret, hidden part of the Forbidden Library's server. The library stores rare and ancient books in digital format. To gain access to the knowledge inside, you must bypass the server’s sophisticated file upload system. This system is designed to filter and check every file that is uploaded, but the admins have made a small mistake in its configuration. The uploaded files, though seemingly harmless, hold the key to unlocking the library’s forbidden archives.

Answer The Questions

Question 1: The Overlooked Validation

You’ve found an upload form that accepts .jpg files, but you notice that the system checks for file extensions without validating the actual content of the file.

Question 2: The Bypassed Filters

The file upload system has an extensive filter list that blocks certain keywords in the filenames. However, you find that the filter doesn’t check for encoded characters.

Question 3: The Path of Escape

After uploading an innocuous .jpg file, you discover it’s stored in a folder where it shouldn’t be. The file should have been placed in a restricted subfolder.

Question 4: The Hidden Code

You manage to upload a .php file despite the system only allowing images. When you try to execute the file, the server returns an error saying "Permission Denied." The file seems harmless.

Question 5: The Blind Spot

The server accepts .png files, but it only verifies if the file is a valid image header. When you upload a .png with PHP code inside the metadata, the file seems fine, but it doesn’t display as an image.

Question 6: The Execution Trap

You’ve uploaded a file, but it’s stored in a public directory. The system seems to allow certain script executions, but you can’t directly access the file.

Question 7: The Dangerous Preview

You find an uploaded file on the server. When you attempt to view it, you get a 404 error. However, you notice that there’s a URL parameter related to the file you uploaded.

Question 8: The Uploading Bot

You notice that there is a bot responsible for filtering uploaded files. However, the bot seems to miss one specific condition for validation. It checks the file extension, but not the contents of multipart files.

File Uploading

Task 1 The Files of the Forbidden Library

Admin Panel