This code enables measured boot and verified boot support. Verified boot is available in coreboot, but based on ChromeOS. This vendorcode security solution is intended to be used for system without ChromeOS support.
This solution allows implementing verified boot support for systems that do not contain a TPM.
The API functions of
3rdparty/vboot/firmware are used.
Measured boot support requires a TPM2 device.
The items specified in
*_verify_list will be measured.
mb_log_list should only contain items that are not contained in one of the verify_lists
below (except for the
The list can contain the following items:
oemmanifest.bin should be added to the list when Verified boot is enabled.
Verified boot support will use the OEM manifest to verify the items.
The verification process is controlled using the following verify lists:
bootblock_verify_list(will not be measured, verified in bootblock)
romstage_verify_list(verified in early romstage)
postcar_verify_list(verified in just before postcar loading)
ramstage_verify_list(verified in just before ramstage loading)
payload_verify_list(verified in just before payload loading)
oprom_verify_list(verified before option rom execution)
A verify_list entry contains a
related_items member. This can point to an additional
which will be verified before the specified item is verified. As an example the
grub entry in
payload_verify_list can point to the
grub_additional_list that contains the items used by
the grub payload and the
seabios entry in
payload_verify_list can point to the
seabios_additional_list that contains the items used by the seabios payload. By doing this the
entries that are verified (and measured) depend on the payload selected at runtime.
Creating private and public keys¶
Create private key in RSA2048 format:
openssl genrsa -F4 -out <private_key_file> 2048
Create public key using private key:
futility --vb1 create <private_key_file> <public_key_file_without_extension>
The public key will be included into coreboot and used for verified boot only.
To enable measured boot support:
- Enabled VENDORCODE_ELTAN_MBOOT
mb_log_listtable with list of items to measure
To enable verified boot support:
- Enable VENDORCODE_ELTAN_VBOOT
- Create the verify lists
- VENDORCODE_ELTAN_VBOOT_KEY_FILE must point to location of the public key file created with
Creating signed binary¶
During build of coreboot binary an empty
oemmanifest.bin is added to the binary.
This binary must be replaced by a correct (signed) binary when VENDORCODE_ELTAN_VBOOT is enabled
oemmanifest.bin file contains the SHA-256 (or SHA-512) hashes of all the different parts
contained in verify_lists.
When VENDORCODE_ELTAN_VBOOT_SIGNED_MANIFEST is enabled the manifest should be signed and the signature should appended to the manifest.
Please make sure the public key is in the RO part of the coreboot image. The
should be in the RW part of the coreboot image.
oemmanifest.bin file contains the hashes of different binaries parts of the binary e.g.:
bootblock, romstage, postcar, ramstage, fsp etc.
The total number of items must match
For every part the SHA (SHA-256) must be calculated. First extract the binary from the coreboot
cbfstool <coreboot_file_name> extract -n <cbfs_name> -f <item_binary_file_name>
openssl dgst -sha256 -binary -out <hash_file_name> <item_binary_file_name>
Replace -sha256 with -sha512 when
VENDORCODE_ELTAN_VBOOT_USE_SHA512 is enabled.
All the hashes must be combined to a hash binary. The hashes need to be placed in the same order as
defined by the
The oemmanifest needs to be signed when
VENDORCODE_ELTAN_VBOOT_SIGNED_MANIFEST is enabled.
This can be done with the following command:
openssl dgst -sign <private_key_file_name> -sha256 -out <signature_binary> <hash_binary>
The signed manifest can be created by adding the signature to the manifest:
cat <hash_binary> <signature_binary> >hash_table.bin
oemmanifest.bin file must be replaced in the coreboot binary by the generated
To replace the binary: Remove using:
cbfstool <coreboot_file_name> remove -n oemmanifest.bin
Then add the new image using:
cbfstool coreboot.bin add -f <hash_table_file_name> -n oemmanifest.bin -t raw \
You can enable verbose console output in menuconfig.