mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-21 02:33:07 +00:00
586a1bf5b2
Convert Android documentation from regular txt format to Sphinx (RST).
Also add Android index.rst file and reference it in root index.rst, so
that Android documentation is visible.
Test:
$ make htmldocs
$ xdg-open doc/output/index.html
Signed-off-by: Sam Protsenko <joe.skb7@gmail.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
133 lines
4.3 KiB
ReStructuredText
133 lines
4.3 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
|
|
|
|
Android Verified Boot 2.0
|
|
=========================
|
|
|
|
This file contains information about the current support of Android Verified
|
|
Boot 2.0 in U-Boot.
|
|
|
|
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 [1]_.
|
|
|
|
AVB using OP-TEE (optional)
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
If AVB is configured to use OP-TEE (see `Enable on your board`_) rollback
|
|
indexes and device lock state are stored in RPMB. The RPMB partition is managed
|
|
by OP-TEE (see [2]_ for details) which is a secure OS leveraging ARM
|
|
TrustZone.
|
|
|
|
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>
|
|
|
|
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
|
|
|
|
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; \
|
|
|
|
If partitions you want to verify are slotted (have A/B suffixes), then current
|
|
slot suffix should be passed to ``avb verify`` sub-command, e.g.::
|
|
|
|
=> avb verify _a
|
|
|
|
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
|
|
|
|
References
|
|
----------
|
|
|
|
.. [1] https://android.googlesource.com/platform/external/avb/+/master/README.md
|
|
.. [2] https://www.op-tee.org/
|