HP BIOS Hacking
BIOS Hacking
Using the Bus Pirate I have been successful in recovering several HP ProBook laptops that have BIOS Administrator passwords set. Below is a rough outline of the process.
- Gain physical access to the BIOS chip and identify the manufacturer and model number of the IC. Mine was a 25L6406E, YMMV.
- Obtain a datasheet for your particular IC and determine the pinout for all the necessary pins required for flashing.
- Connections
- The table below shows how a typical SPI flash chip (sitting in the center of the table) needs to be connected (NB: not all flash chips feature all of the pins below, but in general you should always connect all input pins of ICs to some defined potential (usually GND or VCC), ideally with a pull-up/down resistor in between).
| Description | Bus Pirate | Dir. | Flash chip | Dir. | Bus Pirate | Description | |||
|---|---|---|---|---|---|---|---|---|---|
| (not) Chip Select | CS | → | 1 | /CS | VCC | 8 | ← | +3.3v | Supply |
| Master In, Slave Out | MISO | ← | 2 | DO (IO1) | /HOLD (IO3) | 7 | ← | +3.3v | (not) hold (see datasheets) |
| (not) Write Protect | +3.3v | → | 3 | /WP (IO2) | CLK | 6 | ← | CLK | The SPI clock |
| Ground | GND | → | 4 | GND | DI (IO0) | 5 | ← | MOSI | Master Out, Slave In |
- Most SPI flash chips require a 3.3V supply voltage, but there exist some models that use e.g. 1.8V. Make sure the device in question is compatible before connecting any wires. NB: Some rather rare SPI flash chips (e.g. Atmel AT45DB series) have a completely different layout, please beware.
- I have found that you do not need to connect the Vcc lines on any of the pins indicated if you let the laptop power brick provide the proper regulated voltage. If you use a genuine HP power supply and do not have the battery connected, it may detect the absence of the battery and turn off. Also, if you use an aftermarket supply with poor regulation, you may experience poor consistency in your reads and SHOULD NOT flash your BIOS over SPI if this is the case. If you cannot get consistent reads.... DO NOT WRITE!! You have been warned My suggestion is to make sure you can get, at a minimum, THREE full binary reads that have the same checksum. If you cannot do this, you may have to resort to supplying the proper Vcc to the chip externally with proper regulation. DO SO AT YOUR OWN RISK.
- Reading
$ flashrom -p buspirate_spi:dev=/dev/ttyUSB0,spispeed=1M -r flash.bin
- you will have to define your BusPirate device /dev/whatEVER
- you must also define your output fine (eg. flash.bin). This will become important in the next step.
I hope to start a small library of BIOS binaries for the models I have recovered and the procedure used to recover a locked system.
HP ProBook & EliteBook
Sources
- General info about pinouts and flashrom
- Official flashrom Bus Pirate wiki
- flashrom man page(I guess no women allowed)