Some Nespresso Pro machines in Europe could be hacked to provide free unlimited coffee. The hack is possible because Nespresso machines use a smart card payment system that uses insecure technology , MIFARE Classic smart cards . The vulnerability was discovered by security researcher Polle Vanhoof. Specifically, the researcher found a way to hack older Nespresso machine smart cards to obtain almost unlimited free drinks.
MIFARE Classic smart card technology has been known to be insecure since 2008, when security researchers from Radboud University Nijmegen reverse engineered the chip and published their findings. The researchers showed how to “clone” and manipulate the contents of a MIFARE Classic chip.
As Security Affairs reports, chipmaker NXP Semiconductor attempted to stop the research from being published, but its request was denied. NXP Semiconductor then recommended that customers use Mifare Plus cards that use AES-128.
Vanhoof's arsenal included an NFC card reader/writer, the nfc-mfclassic – MIFARE classic command line tool, and a version of the mfoc MIFARE Classic offline cracker. The researchers also wrote a Python script that was used to crack the weak encryption.
The researcher managed to “crack” the keys and dump them on the “smart” cards. In addition, the researcher stated the following: “First, we attempt to “crack” any non-default keys present on the Nespresso card. This can be easily done using the mfoc tool. We execute the following command: mfoc -P 500 -O nespresso.dmp”.
"We see in the output below that the card uses default keys for most sectors except the last 4. The tool takes a few minutes to 'crack' the remaining 4 keys." The researcher was then able to manually grab the keys found in the data dump.
In the second part of the hack, the expert tried to find the field related to money when buying coffee. To do this, he made different purchases with different amounts of money. The researcher noted the following:
“We work with the assumption that the value of the card is stored on the card itself and not on a central server. This is a much simpler and more cost-effective design, requiring less hardware and software to implement, making it a potential option for those developing such a system without being aware of the security weakness of MIFARE Classic. We charge our card with some value.”
Once he identified the bytes on the card that were changing during the coffee purchase, Vanhoof demonstrated that by changing them, he was able to “manipulate” the amount of money to pay for the coffee. He wrote a value of €167,772.15 to the card using the nfc-mfclassic tool.
The researcher also provided potential mitigations to secure the payment process on Nespresso machines and prevent a potential hack:
- Hardware upgrade: Upgrade smart cards for future products and use more secure alternatives.
- Software mitigation: Upgrade machines to store the value of money on a backend server and not on the card itself, using only the cards as “Personal ID”.
