Technical Paper: Programming eMMC on Qualcomm MSM8953 via Firehose Protocol using DDR.mbn

1. Introduction

Qualcomm’s Firehose (also known as Sahara / Streaming Download) is a proprietary protocol used to load and execute a Programmer (MBN) into the device’s DDR (Dynamic Random-Access Memory). Once loaded, the programmer enables low-level access to internal storage (eMMC) for read, write, erase, and partition management.

: A popular open-source command-line tool for advanced users.

• 8953 → Qualcomm Snapdragon 625 / 626 / 635 (MSM8953 platform).
• emmc → Targets eMMC storage (not UFS).
• ddr → Suggests this version loads into DDR (SDRAM) for running the Firehose protocol.
• .mbn → Qualcomm MBN bootloader/programmer image format.

6. Detection and Mitigation

6.1 Detecting Firehose Activity

• USB vendor ID 0x05C6 (Qualcomm), product ID 0x9008 (EDL).
• Host logs show bulk transfers of large blocks (e.g., libusb calls).
• dmesg output: "qcserial ttyUSB0: Qualcomm USB modem converter detected".

One evening, as Rachel was reviewing the firehose file's code, she noticed a peculiar sequence of hexadecimal values. She called Mike over to take a look, and together, they realized that the file contained a previously unknown parameter that was specific to the EMMC chip's DDR (double data rate) configuration.

Unbricking: Reviving "dead" devices, including smartphones and even automotive hardware like Carlinkit T-Box units.

1. Introduction

1.1 Background

• Firehose: A streaming protocol over USB (or UART) that allows a host PC to send SCSI-like commands to a device in Emergency Download (EDL) mode (9008).
• .mbn file: A Qualcomm MBN bootloader image, often containing ELF segments or raw code/data for the device’s Hexagon DSP or ARM core.
• MSM8953: A mid-range SoC found in devices like Xiaomi Redmi Note 4/5, Moto G5S, and many others.