mirror of
https://github.com/smaeul/u-boot.git
synced 2025-11-03 21:48:15 +00:00
6663e07478
With CONFIG_OPTEE_TA_AVB use the trusted application AVB provided by OP-TEE to manage rollback indexes and device-lock status. Reviewed-by: Simon Glass <sjg@chromium.org> Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
112 lines
3.9 KiB
Plaintext
112 lines
3.9 KiB
Plaintext
Android Verified Boot 2.0
|
|
|
|
This file contains information about the current support of Android Verified
|
|
Boot 2.0 in U-boot
|
|
|
|
1. OVERVIEW
|
|
---------------------------------
|
|
Verified Boot establishes a chain of trust from the bootloader to system images
|
|
* Provides integrity checking for:
|
|
- Android Boot image: Linux kernel + ramdisk. RAW hashing of the whole
|
|
partition is done and the hash is compared with the one stored in
|
|
the VBMeta image
|
|
- system/vendor partitions: verifying root hash of dm-verity hashtrees.
|
|
* Provides capabilities for rollback protection.
|
|
|
|
Integrity of the bootloader (U-boot BLOB and environment) is out of scope.
|
|
|
|
For additional details check:
|
|
https://android.googlesource.com/platform/external/avb/+/master/README.md
|
|
|
|
1.1. AVB using OP-TEE (optional)
|
|
---------------------------------
|
|
If AVB is configured to use OP-TEE (see 4. below) rollback indexes and
|
|
device lock state are stored in RPMB. The RPMB partition is managed by
|
|
OP-TEE (https://www.op-tee.org/) which is a secure OS leveraging ARM
|
|
TrustZone.
|
|
|
|
|
|
2. AVB 2.0 U-BOOT SHELL COMMANDS
|
|
-----------------------------------
|
|
Provides CLI interface to invoke AVB 2.0 verification + misc. commands for
|
|
different testing purposes:
|
|
|
|
avb init <dev> - initialize avb 2.0 for <dev>
|
|
avb verify - run verification process using hash data from vbmeta structure
|
|
avb read_rb <num> - read rollback index at location <num>
|
|
avb write_rb <num> <rb> - write rollback index <rb> to <num>
|
|
avb is_unlocked - returns unlock status of the device
|
|
avb get_uuid <partname> - read and print uuid of partition <partname>
|
|
avb read_part <partname> <offset> <num> <addr> - read <num> bytes from
|
|
partition <partname> to buffer <addr>
|
|
avb write_part <partname> <offset> <num> <addr> - write <num> bytes to
|
|
<partname> by <offset> using data from <addr>
|
|
|
|
|
|
3. PARTITIONS TAMPERING (EXAMPLE)
|
|
-----------------------------------
|
|
Boot or system/vendor (dm-verity metadata section) is tampered:
|
|
=> avb init 1
|
|
=> avb verify
|
|
avb_slot_verify.c:175: ERROR: boot: Hash of data does not match digest in
|
|
descriptor.
|
|
Slot verification result: ERROR_IO
|
|
|
|
Vbmeta partition is tampered:
|
|
=> avb init 1
|
|
=> avb verify
|
|
avb_vbmeta_image.c:206: ERROR: Hash does not match!
|
|
avb_slot_verify.c:388: ERROR: vbmeta: Error verifying vbmeta image:
|
|
HASH_MISMATCH
|
|
Slot verification result: ERROR_IO
|
|
|
|
|
|
4. ENABLE ON YOUR BOARD
|
|
-----------------------------------
|
|
The following options must be enabled:
|
|
CONFIG_LIBAVB=y
|
|
CONFIG_AVB_VERIFY=y
|
|
CONFIG_CMD_AVB=y
|
|
|
|
In addtion optionally if storing rollback indexes in RPMB with help of
|
|
OP-TEE:
|
|
CONFIG_TEE=y
|
|
CONFIG_OPTEE=y
|
|
CONFIG_OPTEE_TA_AVB=y
|
|
CONFIG_SUPPORT_EMMC_RPMB=y
|
|
|
|
Then add `avb verify` invocation to your android boot sequence of commands,
|
|
e.g.:
|
|
|
|
=> avb_verify=avb init $mmcdev; avb verify;
|
|
=> if run avb_verify; then \
|
|
echo AVB verification OK. Continue boot; \
|
|
set bootargs $bootargs $avb_bootargs; \
|
|
else \
|
|
echo AVB verification failed; \
|
|
exit; \
|
|
fi; \
|
|
|
|
=> emmc_android_boot= \
|
|
echo Trying to boot Android from eMMC ...; \
|
|
... \
|
|
run avb_verify; \
|
|
mmc read ${fdtaddr} ${fdt_start} ${fdt_size}; \
|
|
mmc read ${loadaddr} ${boot_start} ${boot_size}; \
|
|
bootm $loadaddr $loadaddr $fdtaddr; \
|
|
|
|
|
|
To switch on automatic generation of vbmeta partition in AOSP build, add these
|
|
lines to device configuration mk file:
|
|
|
|
BOARD_AVB_ENABLE := true
|
|
BOARD_AVB_ALGORITHM := SHA512_RSA4096
|
|
BOARD_BOOTIMAGE_PARTITION_SIZE := <boot partition size>
|
|
|
|
After flashing U-boot don't forget to update environment and write new
|
|
partition table:
|
|
=> env default -f -a
|
|
=> setenv partitions $partitions_android
|
|
=> env save
|
|
=> gpt write mmc 1 $partitions_android
|