Re: [PATCH v4 14/14] qemu: arm64: Add documentation for capsule update

On 30.12.20 14:57, Sughosh Ganu wrote:

Add documentation highlighting the steps for using the uefi capsule update feature for updating the u-boot firmware image.

Signed-off-by: Sughosh Ganu sughosh.ganu@linaro.org

Changes since V3: None

doc/board/emulation/index.rst | 1 + doc/board/emulation/qemu_capsule_update.rst | 210 ++++++++++++++++++++ 2 files changed, 211 insertions(+) create mode 100644 doc/board/emulation/qemu_capsule_update.rst

diff --git a/doc/board/emulation/index.rst b/doc/board/emulation/index.rst index 1adefee155..a09ead1c35 100644 --- a/doc/board/emulation/index.rst +++ b/doc/board/emulation/index.rst @@ -10,3 +10,4 @@ Emulation qemu-mips qemu-riscv qemu-x86

• qemu_capsule_update

diff --git a/doc/board/emulation/qemu_capsule_update.rst b/doc/board/emulation/qemu_capsule_update.rst new file mode 100644 index 0000000000..9fec75f8f1 --- /dev/null +++ b/doc/board/emulation/qemu_capsule_update.rst @@ -0,0 +1,210 @@ +.. SPDX-License-Identifier: GPL-2.0+ +.. Copyright (C) 2020, Linaro Limited

+Enabling UEFI Capsule Update feature +------------------------------------

+Support has been added for the UEFI capsule update feature which +enables updating the U-Boot image using the UEFI firmware management +protocol (fmp). The capsules are not passed to the firmware through +the UpdateCapsule runtime service. Instead, capsule-on-disk +functionality is used for fetching the capsule from the EFI System +Partition (ESP) by placing the capsule file under the +\EFI\UpdateCapsule directory.

+Currently, support has been added on the QEMU ARM64 virt platform for +updating the U-Boot binary as a raw image when the platform is booted +in non-secure mode, i.e. with CONFIG_TFABOOT disabled. For this +configuration, the QEMU platform needs to be booted with +'secure=off'. The U-Boot binary placed on the first bank of the NOR +flash at offset 0x0. The U-Boot environment is placed on the second +NOR flash bank at offset 0x4000000.

+The capsule update feature is enabled with the following configuration +settings::

• CONFIG_MTD=y
• CONFIG_FLASH_CFI_MTD=y
• CONFIG_CMD_MTDPARTS=y
• CONFIG_CMD_DFU=y
• CONFIG_DFU_MTD=y
• CONFIG_PCI_INIT_R=y
• CONFIG_EFI_CAPSULE_ON_DISK=y
• CONFIG_EFI_CAPSULE_FIRMWARE_MANAGEMENT=y
• CONFIG_EFI_CAPSULE_FIRMWARE=y
• CONFIG_EFI_CAPSULE_FIRMWARE_RAW=y
• CONFIG_EFI_CAPSULE_FMP_HEADER=y

+In addition, the following config needs to be disabled(QEMU ARM specific)::

• CONFIG_TFABOOT

+The capsule file can be generated by using the GenerateCapsule.py +script in EDKII::

• $ ./BaseTools/BinWrappers/PosixLike/GenerateCapsule -e -o \
• <capsule_file_name> --fw-version <val> --lsv <val> --guid \
• e2bb9c06-70e9-4b14-97a3-5a7913176e3f --verbose --update-image-index \
• <val> --verbose <u-boot.bin>

+The above is a wrapper script(GenerateCapsule) which eventually calls +the actual GenerateCapsule.py script.

+As per the UEFI specification, the capsule file needs to be placed on +the EFI System Partition, under the \EFI\UpdateCapsule directory. The +EFI System Partition can be a virtio-blk-device.

+Before initiating the firmware update, the efi variables BootNext, +BootXXXX and OsIndications need to be set. The BootXXXX variable needs +to be pointing to the EFI System Partition which contains the capsule +file. The BootNext, BootXXXX and OsIndications variables can be set +using the following commands::

• => efidebug boot add 0 Boot0000 virtio 0:1 <capsule_file_name>
• => efidebug boot next 0
• => setenv -e -nv -bs -rt -v OsIndications =0x04
• => saveenv

+Finally, the capsule update can be initiated with the following +command::

• => efidebug capsule disk-update

+The updated U-Boot image will be booted on subsequent boot.

+Enabling Capsule Authentication +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+The UEFI specification defines a way of authenticating the capsule to +be updated by verifying the capsule signature. The capsule signature +is computed and prepended to the capsule payload at the time of +capsule generation. This signature is then verified by using the +public key stored as part of the X509 certificate. This certificate is +in the form of an efi signature list (esl) file, which is embedded as +part of the platform's device tree blob using the mkeficapsule +utility.

+On the QEMU virt platforms, the device-tree is generated on the fly +based on the devices configured. This device tree is then passed on to +the various software components booting on the platform, including +U-Boot. Therefore, on the QEMU virt platform, the signatute is +embedded on an overlay. This overlay is then applied at runtime to the +base platform device-tree. Steps needed for embedding the esl file in +the overlay are highlighted below.

+The capsule authentication feature can be enabled through the +following config, in addition to the configs listed above for capsule +update::

• CONFIG_EFI_CAPSULE_AUTHENTICATE=y

+The public and private keys used for the signing process are generated +and used by the steps highlighted below::

• 1. Install utility commands on your host

•   * OPENSSL
  

•   * efitools
  

• 2. Create signing keys and certificate files on your host

•    $ openssl req -x509 -sha256 -newkey rsa:2048 -subj /CN=CRT/ \
  

•        -keyout CRT.key -out CRT.crt -nodes -days 365
  

•    $ cert-to-efi-sig-list CRT.crt CRT.esl
  

•    $ openssl x509 -in CRT.crt -out CRT.cer -outform DER
  

•    $ openssl x509 -inform DER -in CRT.cer -outform PEM -out CRT.pub.pem
  

•    $ openssl pkcs12 -export -out CRT.pfx -inkey CRT.key -in CRT.crt
  

•    $ openssl pkcs12 -in CRT.pfx -nodes -out CRT.pem
  

+The capsule file can be generated by using the GenerateCapsule.py +script in EDKII::

• $ ./BaseTools/BinWrappers/PosixLike/GenerateCapsule -e -o \

•  <capsule_file_name> --monotonic-count <val> --fw-version \
  

•  <val> --lsv <val> --guid \
  

•  e2bb9c06-70e9-4b14-97a3-5a7913176e3f --verbose \
  

•  --update-image-index <val> --signer-private-cert \
  

•  /path/to/CRT.pem --trusted-public-cert \
  

•  /path/to/CRT.pub.pem --other-public-cert /path/to/CRT.pub.pem \
  

•  <u-boot.bin>
  

+Place the capsule generated in the above step on the EFI System +Partition under the EFI/UpdateCapsule directory

+For embedding the public key certificate, the following steps need to +be followed::

• 1. Generate a skeleton overlay dts file, with a single fragment

•   node and an empty __overlay__ node
  

•   A typical skeleton overlay file will look like this
  

•   /dts-v1/;
  

•   /plugin/;
  

•   / {
  

•           fragment@0 {
  

•                   target-path = "/";
  

•                   __overlay__ {
  

•                   };
  

•           };
  

•   };
  

• 2. Convert the dts to a corresponding dtb with the following

Shouldn't this be dtbo?

•   command
  

•    ./scripts/dtc/dtc -@ -I dts -O dtb -o <ov_dtb_file_name> \
  

•    <dts_file>
  

• 3. Run the dtb file generated above through the mkeficapsule tool

•   in U-Boot
  

•    ./tools/mkeficapsule -O <pub_key.esl> -D <ov_dtb>
  

+Running the above command results in the creation of a 'signature' +node in the dtb, under which the public key is stored as a +'capsule-key' property. The '-O' option is to be used since the +public key certificate(esl) file is being embedded in an overlay.

+The dtb file embedded with the certificate is now to be placed on an +EFI System Partition. This would then be loaded and "merged" with the +base platform flattened device-tree(dtb) at runtime.

+Build U-Boot with the following steps(QEMU ARM64)::

• $ make qemu_arm64_defconfig
• $ make menuconfig

•    Disable CONFIG_TFABOOT
  

•    Enable CONFIG_EFI_CAPSULE_AUTHENTICATE
  

•    Enable all configs needed for capsule update(listed above)
  

• $ make all

+Boot the platform and perform the following steps on the U-Boot +command line::

• 1. Enable capsule authentication by setting the following env

•   variable
  

•    => setenv capsule_authentication_enabled 1
  

•    => saveenv
  

• 2. Load the overlay dtb to memory and merge it with the base fdt

•    => fatload virtio 0:1 <$fdtovaddr> EFI/<ov_dtb_file>
  

•    => fdt addr $fdtcontroladdr
  

•    => fdt resize <size_of_ov_dtb_file>
  

•    => fdt apply <$fdtovaddr>
  

Having the public key on the disk means that any public key can be placed here and we get zero security.

We need to build the public key into U-Boot.

Could you, please, investigate how we can adjust the build process accordingly.

Best regards

Heinrich

• 3. Set the following environment and UEFI boot variables

•    => setenv -e -nv -bs -rt -v OsIndications =0x04
  

•    => efidebug boot add 0 Boot0000 virtio 0:1 <capsule_file_name>
  

•    => efidebug boot next 0
  

•    => saveenv
  

• 4. Finally, the capsule update can be initiated with the following

•   command
  

•    => efidebug capsule disk-update
  

+On subsequent reboot, the platform should boot the updated U-Boot binary.