Shafrira Goldwasser

Challenge Description

Challenge Attachment

1MB

webapp.zip

archive

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so this application gives you options and for each one it brings the biography related to it from the database

SQL Injection

to find an attack vector we will look at the source code

so we have an sql injection since the user input is not parametrized and sanitized but even if we manage to pull the whole database we won't find the flag in it

Command Injection

we have another attack vector which is command injection since the sql command is executed within a subprocess so what we have to is try to find a way to inject other commands besides sqlite3 command

doing it directly without visualizing the query generated is going to be very hard so what we will be doing is running the app locally and print the query and the result to help us construct the payload

using burp repeater we will be manipulating the user input to find a working payload

so the payload we will generate is simple we will try to escape the first command which is

sqlite3 database.db "SELECT biography FROM cyberheroines WHERE name='userInput' "

to do that we have to get out of the double quote add the injected command and then the remaining garbage should be commented

payload

AdaLovelace'";ls;#

now let's go back to the original web server and try to use this and find the flag

listing the current directory doesn't contain the flag file

let's check the current working directory using pwd command

let's see what are the files in the root / directory

let's read its content using cat command

Flag

chctf{CH4ng3d_h0w_w3_th1Nk_of_pr00f$}