[ARM Trusted Firmware]: https://github.com/ARM-software/arm-trusted-firmware
+Verified Boot
+-------------
+
+U-Boot supports an image verification method called "Verified Boot".
+This is a brief tutorial to utilize this feature for the UniPhier platform.
+You will find details documents in the doc/uImage.FIT directory.
+
+Here, we take LD20 reference board for example, but it should work for any
+other boards including 32 bit SoCs.
+
+1. Generate key to sign with
+
+ $ mkdir keys
+ $ openssl genpkey -algorithm RSA -out keys/dev.key \
+ -pkeyopt rsa_keygen_bits:2048 -pkeyopt rsa_keygen_pubexp:65537
+ $ openssl req -batch -new -x509 -key keys/dev.key -out keys/dev.crt
+
+Two files "dev.key" and "dev.crt" will be created. The base name is arbitrary,
+but need to match to the "key-name-hint" property described below.
+
+2. Describe FIT source
+
+You need to write an FIT (Flattened Image Tree) source file to describe the
+structure of the image container.
+
+The following is an example for a simple usecase:
+
+---------------------------------------->8----------------------------------------
+/dts-v1/;
+
+/ {
+ description = "Kernel, DTB and Ramdisk for UniPhier LD20 Reference Board";
+ #address-cells = <1>;
+
+ images {
+ kernel@0 {
+ description = "linux";
+ data = /incbin/("PATH/TO/YOUR/LINUX/DIR/arch/arm64/boot/Image.gz");
+ type = "kernel";
+ arch = "arm64";
+ os = "linux";
+ compression = "gzip";
+ load = <0x82080000>;
+ entry = <0x82080000>;
+ hash@0 {
+ algo = "sha256";
+ };
+ };
+
+ fdt@0 {
+ description = "fdt";
+ data = /incbin/("PATH/TO/YOUR/LINUX/DIR/arch/arm64/boot/dts/socionext/uniphier-ld20-ref.dtb");
+ type = "flat_dt";
+ arch = "arm64";
+ compression = "none";
+ hash@0 {
+ algo = "sha256";
+ };
+ };
+
+ ramdisk@0 {
+ description = "ramdisk";
+ data = /incbin/("PATH/TO/YOUR/ROOTFS/DIR/rootfs.cpio");
+ type = "ramdisk";
+ arch = "arm64";
+ os = "linux";
+ compression = "none";
+ hash@0 {
+ algo = "sha256";
+ };
+ };
+ };
+
+ configurations {
+ default = "config@0";
+
+ config@0 {
+ description = "Configuration0";
+ kernel = "kernel@0";
+ fdt = "fdt@0";
+ ramdisk = "ramdisk@0";
+ signature@0 {
+ algo = "sha256,rsa2048";
+ key-name-hint = "dev";
+ sign-images = "kernel", "fdt", "ramdisk";
+ };
+ };
+ };
+};
+---------------------------------------->8----------------------------------------
+
+You need to change the three '/incbin/' lines, depending on the location of
+your kernel image, device tree blob, and init ramdisk. The "load" and "entry"
+properties also need to be adjusted if you want to change the physical placement
+of the kernel.
+
+The "key-name-hint" must specify the key name you have created in the step 1.
+
+The FIT file name is arbitrary. Let's say you saved it into "fit.its".
+
+3. Compile U-Boot with FIT and signature enabled
+
+To use the Verified Boot, you need to enable the following two options:
+ CONFIG_FIT
+ CONFIG_FIT_SIGNATURE
+
+They are disabled by default for UniPhier defconfig files. So, you need to
+tweak the configuration from "make menuconfig" or friends.
+
+ $ make uniphier_v8_defconfig
+ $ make menuconfig
+ [ enable CONFIG_FIT and CONFIG_FIT_SIGNATURE ]
+ $ make CROSS_COMPILE=aarch64-linux-gnu-
+
+4. Build the image tree blob
+
+After building U-Boot, you will see tools/mkimage. With this tool, you can
+create an image tree blob as follows:
+
+ $ tools/mkimage -f fit.its -k keys -K dts/dt.dtb -r -F fitImage
+
+The -k option must specify the key directory you have created in step 1.
+
+A file "fitImage" will be created. This includes kernel, DTB, Init-ramdisk,
+hash data for each of the three, and signature data.
+
+The public key needed for the run-time verification is stored in "dts/dt.dtb".
+
+5. Compile U-Boot again
+
+Since the "dt.dtb" has been updated in step 4, you need to re-compile the
+U-Boot.
+
+ $ make CROSS_COMPILE=aarch64-linux-gnu-
+
+The re-compiled "u-boot.bin" is appended with DTB that contains the public key.
+
+6. Flash the image
+
+Flash the "fitImage" to a storage device (NAND, eMMC, or whatever) on your
+board.
+
+Please note the "u-boot.bin" must be signed, and verified by someone when it is
+loaded. For ARMv8 SoCs, the "someone" is generally ARM Trusted Firmware BL2.
+ARM Trusted Firmware supports an image authentication mechanism called Trusted
+Board Boot (TBB). The verification process must be chained from the moment of
+the system reset. If the Chain of Trust has a breakage somewhere, the verified
+boot process is entirely pointless.
+
+7. Boot verified kernel
+
+Load the fitImage to memory and run the following from the U-Boot command line.
+
+ > bootm <addr>
+
+Here, <addr> is the base address of the fitImage.
+
+If it is successful, you will see messages like follows:
+
+---------------------------------------->8----------------------------------------
+## Loading kernel from FIT Image at 84100000 ...
+ Using 'config@0' configuration
+ Verifying Hash Integrity ... sha256,rsa2048:dev+ OK
+ Trying 'kernel@0' kernel subimage
+ Description: linux
+ Created: 2017-10-20 14:32:29 UTC
+ Type: Kernel Image
+ Compression: gzip compressed
+ Data Start: 0x841000c8
+ Data Size: 6957818 Bytes = 6.6 MiB
+ Architecture: AArch64
+ OS: Linux
+ Load Address: 0x82080000
+ Entry Point: 0x82080000
+ Hash algo: sha256
+ Hash value: 82a37b7f11ae55f4e07aa25bf77e4067cb9dc1014d52d6cd4d588f92eee3aaad
+ Verifying Hash Integrity ... sha256+ OK
+## Loading ramdisk from FIT Image at 84100000 ...
+ Using 'config@0' configuration
+ Trying 'ramdisk@0' ramdisk subimage
+ Description: ramdisk
+ Created: 2017-10-20 14:32:29 UTC
+ Type: RAMDisk Image
+ Compression: uncompressed
+ Data Start: 0x847a5cc0
+ Data Size: 5264365 Bytes = 5 MiB
+ Architecture: AArch64
+ OS: Linux
+ Load Address: unavailable
+ Entry Point: unavailable
+ Hash algo: sha256
+ Hash value: 44980a2874154a2e31ed59222c9f8ea968867637f35c81e4107a984de7014deb
+ Verifying Hash Integrity ... sha256+ OK
+## Loading fdt from FIT Image at 84100000 ...
+ Using 'config@0' configuration
+ Trying 'fdt@0' fdt subimage
+ Description: fdt
+ Created: 2017-10-20 14:32:29 UTC
+ Type: Flat Device Tree
+ Compression: uncompressed
+ Data Start: 0x847a2cb0
+ Data Size: 12111 Bytes = 11.8 KiB
+ Architecture: AArch64
+ Hash algo: sha256
+ Hash value: c517099db537f6d325e6be46b25c871a41331ad5af0283883fd29d40bfc14e1d
+ Verifying Hash Integrity ... sha256+ OK
+ Booting using the fdt blob at 0x847a2cb0
+ Uncompressing Kernel Image ... OK
+ reserving fdt memory region: addr=80000000 size=2000000
+ Loading Device Tree to 000000009fffa000, end 000000009fffff4e ... OK
+
+Starting kernel ...
+---------------------------------------->8----------------------------------------
+
+Please pay attention to the lines that start with "Verifying Hash Integrity".
+
+"Verifying Hash Integrity ... sha256,rsa2048:dev+ OK" means the signature check
+passed.
+
+"Verifying Hash Integrity ... sha256+ OK" (3 times) means the hash check passed
+for kernel, DTB, and Init ramdisk.
+
+If they are not displayed, the Verified Boot is not working.
+
+
UniPhier specific commands
--------------------------
--
Masahiro Yamada <yamada.masahiro@socionext.com>
-Sep. 2017
+Oct. 2017
projects / u-boot.git / commitdiff