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

[Heinrich Schuchardt]

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 at 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 at 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.
>