Lab: Infinite money logic flaw
This lab has a logic flaw in its purchasing workflow. To solve the lab, exploit this flaw to buy a "Lightweight l33t leather jacket".
You can log in to your own account using the following credentials:
This solution uses Burp Intruder to automate the process of buying and redeeming gift cards. Users proficient in Python might prefer to use the Turbo Intruder extension instead.
With Burp running, log in and sign up for the newsletter to obtain a coupon code,
SIGNUP30. Notice that you can buy $10 gift cards and redeem them from the "My account" page.
- Add a gift card to your basket and proceed to the checkout. Apply the coupon code to get a 30% discount. Complete the order and copy the gift card code to your clipboard.
- Go to your account page and redeem the gift card. Observe that this entire process has added $3 to your store credit. Now you need to try and automate this process.
Study the proxy history and notice that you redeem your gift card by supplying the code in the
gift-cardparameter of the
- Go to "Project options" > "Sessions". In the "Session handling rules" panel, click "Add". The "Session handling rule editor" dialog opens.
- In the dialog, go to the "Scope" tab. Under "URL Scope", select "Include all URLs".
- Go back to the "Details" tab. Under "Rule actions", click "Add" > "Run a macro". Under "Select macro", click "Add" again to open the Macro Recorder.
Select the following sequence of requests:
Then, click "OK". The Macro Editor opens.
In the list of requests, select
GET /cart/order-confirmation?order-confirmed=true. Click "Configure item". In the dialog that opens, click "Add" to create a custom parameter. Name the parameter
gift-cardand highlight the gift card code at the bottom of the response. Click "OK" twice to go back to the Macro Editor.
POST /gift-cardrequest and click "Configure item" again. In the "Parameter handling" section, use the drop-down menus to specify that the
gift-cardparameter should be derived from the prior response (response 4). Click "OK".
In the Macro Editor, click "Test macro". Look at the response to
GET /cart/order-confirmation?order-confirmation=trueand note the gift card code that was generated. Look at the
POST /gift-cardrequest. Make sure that the
gift-cardparameter matches and confirm that it received a
302response. Keep clicking "OK" until you get back to the main Burp window.
GET /my-accountrequest to Burp Intruder. Use the "Sniper" attack type and clear the default payload positions.
On the "Payloads" tab, select the payload type "Null payloads". Under "Payload options", choose to generate
412payloads. On the "Options" tab, set the thread count to
1. Start the attack.
- When the attack finishes, you will have enough store credit to buy the jacket and solve the lab.