SM-G985F / Exynos9830 Bootrom exploit

[!CAUTION] The current key bundle and generated files are fusing-capable. Once a device has been fused, the eFuse change is irreversible and the device must continue to use boot images and key material that match the fused key. Using these files or flows is at your own risk because of the fusing behavior; all consequences remain the responsibility of the user running them. Verify the eFuse file, private keys, signed FWBL1, LK / sboot.bin images, and target device before running any fusing flow.

Contents

• Repository Layout
• Requirements
• Image Preparation
• Payload Build
• Signed SBoot Image Generation
• Exploit Modes
• Exynos 9830 Boot Chain
• Exynos 9830 Image Layout
• Load Addresses
• Boot Source IDs
• Dump /mem Payload
• Upstream Attribution
• Credits

Repository Layout

Path	Purpose
bootLoaderFiles/	Bootloader binaries, split bootloader parts, original images, decrypted images, and dump artifacts.
bootromNotes/	Boot ROM notes, flowcharts, and USB context offsets.
exploit/	Python tooling, exploit runner, split/merge scripts, payload build helper, and SoC data.
exploit/extra/images/	Working bootloader images consumed by the exploit flows.
exploit/extra/payloads/	Built payload binaries copied from external/payloads/.
external/	Payload sources, build Makefile, decompiled notes, shared key material, and helper tools.
external/keys/exynos9830_crecker/	Shared Exynos9830 / Exynos990 custom-key bundle used by the signed-loader flow.
exynos990reverseEng/	Exynos 990 reverse engineering project files.

Requirements

Linux Toolchain

sudo apt-get update
sudo apt-get install -y gcc-aarch64-linux-gnu binutils-aarch64-linux-gnu

macOS Toolchain

brew tap messense/macos-cross-toolchains
brew install aarch64-unknown-linux-gnu

Python Dependencies

python3 -m pip install -r requirements.txt

requirements.txt includes coloredlogs, cryptography, hexdump, libusb, pyusb, and pycryptodome.

Windows USB Driver

On Windows, the BootROM USB device 04e8:1234 must use a WinUSB/libusb-compatible driver before PyUSB can open it. See exploit/windows/README.md.

The repository includes a WinUSB driver package at exploit/windows/Exynos_USB_Device.inf, with its matching catalog and certificate import file in the same directory.

Image Preparation

Split sboot.bin

python3 exploit/split.py bootLoaderFiles/originalSboot_K/sboot.bin -o exploit/extra/images

The split script writes image parts and a split_manifest.json file into the output directory.

Patch LK Custom Key

The LK image must use the ROM secure boot key 2 command IDs for the custom-key flow:

Key 1 command	Value	Key 2 command	Value
CMD_W_ROM_SEC_BOOT_KEY1	0x001	CMD_W_ROM_SEC_BOOT_KEY2	0x016
CMD_W_USE_ROM_SEC_BOOT_KEY1	0x002	CMD_W_USE_ROM_SEC_BOOT_KEY2	0x017
CMD_C_ROM_SEC_BOOT_KEY1	0x100	CMD_C_ROM_SEC_BOOT_KEY2	0x114
CMD_R_USE_ROM_SEC_BOOT_KEY1	0x101	CMD_R_USE_ROM_SEC_BOOT_KEY2	0x115

When applying the LK patch TSV inside the Ghidra project, the helper was called through Ghidra headless like this:

GHIDRA=/path/to/ghidra_12.0.4_PUBLIC
REPO=$(pwd)
"$GHIDRA/support/analyzeHeadless" "$REPO/exynos990reverseEng" exynos990 \
  -process lk.bin \
  -noanalysis \
  -scriptPath "$REPO/external/ghidra" \
  -postScript ApplyLkPatches.java "$REPO/external/ghidra/lk_985_selected_patches.tsv"

Embed the 32-byte eFuse key into lk.bin at offset 0x205008, replacing the stock key:

dd if=external/keys/exynos9830_crecker/crecker.efuse of=exploit/extra/images/lk.bin bs=1 seek=$((0x205008)) count=32 conv=notrunc
xxd -g1 -s $((0x205008)) -l 32 exploit/extra/images/lk.bin

Merge Split Parts

python3 exploit/merge.py exploit/extra/images Exynos9830

The merge script writes sboot.bin in the current working directory.

Payload Build

Build the payload projects under external/payloads/ and copy the resulting binaries into exploit/extra/payloads/:

./exploit/build_payloads.sh

Payload	Output path	Purpose
mem.bin	exploit/extra/payloads/mem.bin	Boot ROM memory dump payload.
loader.bin	exploit/extra/payloads/loader.bin	UFS path payload used by --ufs.
Exynos990_boot_custom_key.bin	exploit/extra/payloads/Exynos990_boot_custom_key.bin	Custom-key signed-loader payload used by --signed.

The UFS loader and custom-key payload embed a 32-byte efuse file at build time. By default the Makefile reads external/keys/exynos9830_crecker/crecker.efuse; override this with CUSTOM_KEY_EFUSE=/path/to/crecker.efuse when needed.

Signed SBoot Image Generation

The preflight step run by exploit/exploit.py re-signs the SBoot image set in exploit/extra/images/ in place before each signed run. No separate signed output is kept. The signing step uses the intentionally tracked shared key bundle under external/keys/exynos9830_crecker/.

Equivalent repo-root command for the complete image set:

python3 external/tools/sign_sboot_images.py \
  --images-dir exploit/extra/images \
  --keys-dir external/keys/exynos9830_crecker

This signs:

Image	Key material used	Rollback revision
fwbl1.img	BL1 private key + Stage2 TEE/REE pubkeys	23
epbl.img	Stage2 TEE private key	23
bl2.img	Stage2 REE private key	23
lk.bin	Stage2 REE private key	23
el3_mon.img	Stage2 TEE private key	23
ldfw.img	Stage2 TEE private key, inner + outer	23
tzsw.img	Stage2 TEE private key, inner + outer	23

The batch signer passes decimal 23 for every image and does not reuse an older rollback value already present in an existing footer.

epbl.img is re-encrypted first when needed, then signed over the final bytes. ldfw.img and tzsw.img still need the external AVB flow if their AVB content is meant to be refreshed.

The FWBL1-only command is: