Image
Image selection
The boot process shall be uninterruptible and shall irrevocably boot the image as specified in the boot environment.
In U-Boot set the "bootdelay" environment variable and/or define
CONFIG_BOOTDELAY to -2.
| Domain | Variable / Config name |
Value |
|---|---|---|
| Boot-Image-Selection-1 | CONFIG_BOOTDELAY |
-2 |
| Boot-Image-Selection-2 | bootdelay | -2 |
Image authenticity
It shall not be possible to boot from an unverified image. The secure boot feature in U-Boot shall be enabled. The secure boot feature is available from U-Boot 2013.07 version. To enable the secure boot feature, enable the following features:
CONFIG_FIT: Enables support for Flat Image Tree (FIT) uImage format.
CONFIG_FIT_SIGNATURE: Enables signature verification of FIT images.
CONFIG_RSA: Enables RSA algorithm used for FIT image verification.
CONFIG_OF_CONTROL: Enables Flattened Device Tree (FDT) configuration.
CONFIG_OF_SEPARATE: Enables separate build of u-Boot from the device tree.
CONFIG_DEFAULT_DEVICE_TREE: Specifies the default Device Tree used for the run-time configuration of U-Boot.
Generate the U-Boot image with public keys to validate and load the image. It shall use RSA2048 and SHA256 for authentication.
| Domain | Config name |
State |
|---|---|---|
| Boot-Image-Authenticity-1 | CONFIG_FIT |
Enable |
| Boot-Image-Authenticity-2 | CONFIG_FIT_SIGNATURE |
Enable |
| Boot-Image-Authenticity-3 | CONFIG_RSA |
Enable |
| Boot-Image-Authenticity-4 | CONFIG_OF_CONTROL |
Enable |
| Boot-Image-Authenticity-5 | CONFIG_OF_SEPARATE |
Enable |
| Boot-Image-Authenticity-6 | CONFIG_DEFAULT_DEVICE_TREE |
Enable |