Keyshuffling Attack for Persistent Early Code Execution in the Nintendo 3DS Secure Bootchain
This work addresses a security vulnerability in the Nintendo 3DS's secure bootchain, enabling persistent exploitation for attackers, but it is incremental as it builds on known ECB mode weaknesses.
The researchers tackled the problem of gaining persistent early code execution on the Nintendo 3DS by exploiting a block shuffling vulnerability in the ECB cipher mode to rearrange keys in the encrypted keystore, resulting in the ability to reliably execute a payload that extracts hardware secrets and sets up a persistent exploit.
We demonstrate an attack on the secure bootchain of the Nintendo 3DS in order to gain early code execution. The attack utilizes the block shuffling vulnerability of the ECB cipher mode to rearrange keys in the Nintendo 3DS's encrypted keystore. Because the shuffled keys will deterministically decrypt the encrypted firmware binary to incorrect plaintext data and execute it, and because the device's memory contents are kept between hard reboots, it is possible to reliably reach a branching instruction to a payload in memory. This payload, due to its execution by a privileged processor and its early execution, is able to extract the hash of hardware secrets necessary to decrypt the device's encrypted keystore and set up a persistent exploit of the system.