Secure Boot

Secure Boot in this section is "UEFI Secure Boot". It's different from soc's secboot.

Enable SecureBoot

Compile uefi with -s 1.

Replace Certs

Aloha uefi uses our own certs by default. It's private and will not be shared with anyone so it's secure enough. However, if you want your uefi to run executable binaries signed by yourself, this section may help.

Generate Key Pairs

This script can help you generate certs. Replace the Path, Name, and E-mail in the script with your own before running.

• SBCertGen.ps1
• SBCertGen.sh

After generating, you can find the key pairs under the Certs folder.

Replace Keys in uefi

Clone our uefi source and this repo:

git clone https://github.com/project-aloha/mu_aloha_platforms --depth=1
git clone https://github.com/microsoft/secureboot_objects/ --depth=1

Replace WOAMSMNILE-KEK.der and WOAMSMNILE-PK.der located at:

Platforms/AndromedaPkg/Include/Resources/SecureBoot/keystore/

then edit keystore/keystore.toml at the same folder to reference them.

TIP

The RootPK and KEK generated by the script end with .cer and are already in X509 DER format. Just rename the suffix to .der.

Generate secure objects

Install python dependencies and run the build script in secure boot objects:

# Create venv and install dependencies
cd secureboot_objects
python3 -m venv .venv
source .venv/bin/activate
pip install -r pip-requirements.txt

# Generate EFI Signature Lists
cd ../mu_aloha_platforms/Platforms/AndromedaPkg/Include/Resources/SecureBoot

python3 ../../../../../../secureboot_objects/scripts/secure_boot_default_keys.py \
  --keystore keystore/keystore.toml \
  -o Artifacts

Output BIN files are generated under Artifacts/Aarch64/keystore/Firmware. Ignore bins under Artifacts/Aarch64/keystore/Imaging/, they are not used here.

Convert BIN to DSC PCDs

Run the following script under mu_aloha_platforms/Platforms/AndromedaPkg/Include/Resources/SecureBoot/. It uses MU_BASECORE (checked out as a submodule of mu_aloha_platforms) to locate BinToPcd.py, and generates SecureBootKeys.dsc.inc in the current folder.

TIP

MU_BASECORE is a submodule. You must run build_uefi.py -i for at least 1 time or clone uefi repo with --recursive before using script below.

SCRIPTS=../../../../../MU_BASECORE/BaseTools/Scripts
BIN_DIR=Artifacts/Aarch64/keystore/Firmware/
OUT=/tmp

python3 $SCRIPTS/BinToPcd.py -i $BIN_DIR/DefaultPk.bin    -o $OUT/pk.inc   -p gMsCorePkgTokenSpaceGuid.PcdDefaultPk
python3 $SCRIPTS/BinToPcd.py -i $BIN_DIR/DefaultDb.bin    -o $OUT/db.inc   -p gMsCorePkgTokenSpaceGuid.PcdDefaultDb
python3 $SCRIPTS/BinToPcd.py -i $BIN_DIR/Default3PDb.bin  -o $OUT/3pdb.inc -p gMsCorePkgTokenSpaceGuid.PcdDefault3PDb
python3 $SCRIPTS/BinToPcd.py -i $BIN_DIR/DefaultDbx.bin   -o $OUT/dbx.inc  -p gMsCorePkgTokenSpaceGuid.PcdDefaultDbx
python3 $SCRIPTS/BinToPcd.py -i $BIN_DIR/DefaultKek.bin   -o $OUT/kek.inc  -p gMsCorePkgTokenSpaceGuid.PcdDefaultKek

# Merge all fragments into SecureBootKeys.dsc.inc.
echo "[PcdsFixedAtBuild.common]" > SecureBootKeys.dsc.inc
for f in $OUT/pk.inc $OUT/db.inc $OUT/3pdb.inc $OUT/dbx.inc $OUT/kek.inc; do
  echo "" >> SecureBootKeys.dsc.inc
  cat "$f" >> SecureBootKeys.dsc.inc
done

Then, you should check this file and compare with:

Platforms/AndromedaPkg/SecureBootKeys.dsc.inc

If it looks fine, replace the file under AndromedaPkg.

By the way, the file format should look like:

[PcdsFixedAtBuild.common]

  # The PK
  gMsCorePkgTokenSpaceGuid.PcdDefaultPk|{ 0x.., ... }

  # The DB
  gMsCorePkgTokenSpaceGuid.PcdDefaultDb|{ 0x.., ... }

  # The Third Party DB
  gMsCorePkgTokenSpaceGuid.PcdDefault3PDb|{ 0x.., ... }

  # The DBX
  gMsCorePkgTokenSpaceGuid.PcdDefaultDbx|{ 0x.., ... }

  # The KEK
  gMsCorePkgTokenSpaceGuid.PcdDefaultKek|{ 0x.., ... }

Rebuild & Test

Rebuild uefi with the -s 1 parameter and boot it on your device. Your device will reject running unsigned bootaa64.efi in this case.

Important Constraints

• PK: Only one certificate is supported. If multiple certs are present, UEFI enrollment will fail with Invalid Parameter.
• KEK: Multiple certificates allowed (Microsoft KEKs + your own KEK + other KEKs).
• DB: Multiple certificates allowed. This is what verifies signed EFI binaries at runtime.
• DBX: Revocation list of SHA256 hashes. Sourced from Microsoft's dbx_info_msft_latest.json.
• SignatureOwner GUID: Each cert entry needs a unique GUID. Do not reuse Microsoft's GUID (77fa9abd-...) for your own certs. Generate a new UUID per cert family.

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References

• Secure Boot on Surface Duo devices with mu_andromeda_platforms