![]() One solution could simply be to de-solder the flash chip and try again, but that requires additional tools (like a heat gun or de-soldering iron), which you may not already have. If you recall in part one of the series, an issue users may occasionally encounter when trying to dump an SPI flash chip is providing too much power to the device through the VCC connection, thereby subsequently forcing the flash chip to be in use by the SoC (system on a chip) and preventing us from dumping the firmware. So, you may be wondering – if we can already dump the firmware of a device through its flash chip, why would we need to access it or dump its firmware through UART instead? By accessing a device’s UART interface you will generally get presented a bash terminal of sorts to access the firmware which may allow you to traverse the filesystem and execute arbitrary commands, view web files, find 0 days in binaries, find scheduled tasks, backdoors, and understand generally how the device works. With the proper cabling and baud rate, the two devices can now communicate successfully. Once the UART communication begins, bits are read at a specific frequency called the “baud rate”, which can differ between devices by up to approximately 10% before the timing of bits becomes corrupted. The receiver and transmitter, marked RX and TX respectively, need to connect to a second respective UART device’s TX and RX in order to establish communications. UART works by communicating through two wires (a transmitter wire and a receiver wire) to talk to the microcontroller or system on a chip (basically the brains of the device) directly. UART is used for asynchronous serial communications to send and receive data from devices for purposes such as updating firmware manually, debugging tests, or interfacing with the underlying system (kind of like opening a new terminal in Ubuntu). What is UART?īefore we get into breaking a device and accessing it through its UART interface, let’s first discuss what UART is and how it’s used. ![]() We will discuss what UART is, why we would want to access a device through UART, and finally, how to identify and access an arbitrary UART interface on any device. In this post, we will review the process of accessing and dumping the firmware of a device through an alternative serial interface called UART(Universal Asynchronous Receiver-Transmitter). ![]() In the first part of my hardware hacking series, we discussed dumping firmware through the SPI flash chip. ![]()
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