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

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:

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

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:

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:

python3 external/tools/sign_tool.py \
  -i exploit/extra/images/fwbl1.img \
  -o exploit/extra/images/fwbl1.img \
  -k external/keys/exynos9830_crecker/crecker_private.pem \
  -H external/keys/exynos9830_crecker/crecker.hmac \
  -s 0x3000 \
  -r 23 \
  -ma 0x9830 \
  -m 0x142 \
  -e 11 \
  -t external/keys/exynos9830_crecker/crecker_stage2_tee_pubkey.bin \
  -re external/keys/exynos9830_crecker/crecker_stage2_ree_pubkey.bin

Short form when sign_tool.py, fwbl1.img, and the crecker_* files are in the current directory:

python3 sign_tool.py -i fwbl1.img -o fwbl1.img -k crecker_private.pem -H crecker.hmac -s 0x3000 -r 23 -ma 0x9830 -m 0x142 -e 11 -t crecker_stage2_tee_pubkey.bin -re crecker_stage2_ree_pubkey.bin

Exploit Modes

Run commands from the repository root unless noted otherwise.

Device Flow Notes

Exynos 9830 Boot Chain

The observed Exynos 9830 boot procedure is:

Exynos 9830 Image Layout

Load Addresses

Boot Source IDs

Raw Boot Source IDs

Boot Source Values

Dump /mem Payload

Note: The mem.bin dump payload can only be used when no working sboot is installed.

1. Send uh.bin over Heimdall to the bootloader:

   root@kitploit:~

   heimdall flash --BOOTLOADER uh.bin
   

2. Run the dump flow:

   root@kitploit:~

   python3 exploit/exploit.py --dump
   

3. Review the generated exynos990.bootrom.bin dump.

Upstream Attribution

Portions of the Python recovery tooling in this repository were adapted from halal-beef/hubble.

That upstream project is published under the GNU GPL v2.0, and this repository keeps a GPL-2.0 license for compatibility. See LICENSE and NOTICE.md.

The Exynos990 custom-key payload under external/payloads/exynos990_boot_custom_key/ is based on the boot-custom-key payload skeleton and control-flow idea from VDavid003/exynos-usbdl, a fork of frederic/exynos-usbdl. It has been substantially rewritten and adapted for the Exynos9830 / Exynos990 GET_CONFIGURATION chain, and is not a verbatim copy of the upstream payload. Because the referenced upstream project is licensed under the GNU GPL v3.0, this payload is kept under GPL-3.0-only; see external/payloads/exynos990_boot_custom_key/LICENSE.

Credits