Level 23 - Level 24

Username: natas24
Password: 0xzF30T9Av8lgXhW7slhFCIsVKAPyl2r
URL:      http://natas24.natas.labs.overthewire.org

Overview

This time we got an input field and also a link to the source code.

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Source Code Anlysis

The application looks out for a URL parameter passwd and if it exists, it compares with the the <censored> string using PHP strcmp function, and if it satisfies the condition, it will show the credentials for the next level.

In the above PHP code block, the comparison is done using the strcmp function. This function is not array-aware, and it is designed for comparing two strings. When you pass an array to strcmp, it will treat the array as a string, resulting in unexpected behavior.

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Getting the Password

The problem here is that strcmp is expecting a string, but the value of "passwd" is an array (passwd[]= ''). When strcmp encounters an array, it treats it as a string, and the result might not be as expected. In this case, result will be 0 because the array is cast to a string, resulting in an empty string (''), and strcmp compares it with the other string ('<censored>'), which satisfies the condition and shows the credentials for the next level.