Re: [U-Boot] [PATCH v2 3/3] sunxi: README.sunxi64: Document verified-boot for a64

Hi,

On Fri, Nov 10, 2017 at 10:21:10PM +0530, Jagan Teki wrote:

Add verified-boot documentation for sunxi a64 platform.

Signed-off-by: Jagan Teki jagan@amarulasolutions.com

Changes for v2:

• New patch

board/sunxi/README.sunxi64 | 177 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 177 insertions(+)

diff --git a/board/sunxi/README.sunxi64 b/board/sunxi/README.sunxi64 index c492f74..5a2fe69 100644 --- a/board/sunxi/README.sunxi64 +++ b/board/sunxi/README.sunxi64 @@ -160,6 +160,183 @@ Then write this image to a microSD card, replacing /dev/sdx with the right device file (see above): $ dd if=firmware.img of=/dev/sdx bs=8k seek=1

+Verified Boot +=============

+U-Boot supports an image verification method called "Verified Boot". +This is a brief tutorial to utilize this feature for the Sunxi A64 platform. +You will find details documents in the doc/uImage.FIT directory.

+Here, we take Orangepi Win board for example, but it should work for any +other boards including 32 bit SoCs.

It should be in another file then I guess?

+1. Generate RSA key to sign

• $ 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. FIT Input

+---------------------------------------->8---------------------------------------- +/dts-v1/; +/ {

• description = "FIT image with single Linux kernel, FDT blob";
• #address-cells = <1>;
• images {

• kernel@0 {
  

• 	description = "ARM64 Linux kernel";
  

• 	data = /incbin/("/path/to/linux/dir/arch/arm64/boot/Image.gz");
  

• 	type = "kernel";
  

• 	arch = "arm64";
  

• 	os = "linux";
  

• 	compression = "gzip";
  

• 	load = <0x50080000>;
  

• 	entry = <0x50080000>;
  

• 	hash@1 {
  

• 		algo = "sha256";
  

• 	};
  

• };
  

• fdt@0 {
  

• 	description = "Orangepi Win/Win+ Devicetree blob";
  

• 	data = /incbin/("/path/to/linux/dir/arch/arm64/boot/dts/allwinner/sun50i-a64-orangepi-win.dtb");
  

• 	type = "flat_dt";
  

• 	arch = "arm64";
  

• 	compression = "none";
  

• 	hash@1 {
  

• 		algo = "sha256";
  

• 	};
  

• };
  

• };
• configurations {

• default = "conf@0";
  

• conf@0 {
  

• 	description = "Boot Linux kernel, FDT blob";
  

• 	kernel = "kernel@0";
  

• 	fdt = "fdt@0";
  

• 	signature@0 {
  

• 		algo = "sha256,rsa2048";
  

• 		key-name-hint = "dev";
  

• 		sign-images = "kernel", "fdt";
  

• 	};
  

• };
  

• };

+}; +---------------------------------------->8----------------------------------------

+You need to change the two '/incbin/' lines, depending on the location of +your kernel image and devicetree blob. 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
• $ make orangepi_win_defconfig
• $ make CROSS_COMPILE=aarch64-linux-gnu-

+4. FIT Output

+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, +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 Verified U-Boot

+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 (SD, NAND, eMMC, or whatever) on your +board.

+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---------------------------------------- +=> setenv bootargs console=ttyS0,115200 earlyprintk root=/dev/mmcblk0p1 rootwait +=> ext4load mmc 0:1 $kernel_addr_r /boot/fitImage +16321738 bytes read in 1049 ms (14.8 MiB/s) +=> bootm $kernel_addr_r +## Loading kernel from FIT Image at 40080000 ...

• Using 'conf@0' configuration
• Verifying Hash Integrity ... OK
• Trying 'kernel@0' kernel subimage

• Description:  ARM64 Linux kernel
  

• Type:         Kernel Image
  

• Compression:  gzip compressed
  

• Data Start:   0x400800e4
  

• Data Size:    6884659 Bytes = 6.6 MiB
  

• Architecture: AArch64
  

• OS:           Linux
  

• Load Address: 0x50080000
  

• Entry Point:  0x50080000
  

• Hash algo:    sha256
  

• Hash value:   6808fe51ea3c15f31c4510d2701d4707b56d20213c9da05bce79fb53bf108f1a
  

• Verifying Hash Integrity ... sha256+ OK

+## Loading fdt from FIT Image at 40080000 ...

• Using 'conf@0' configuration
• Trying 'fdt@0' fdt subimage

• Description:  Orangepi Win/Win+ Devicetree blob
  

• Type:         Flat Device Tree
  

• Compression:  uncompressed
  

• Data Start:   0x40710f24
  

• Data Size:    9032 Bytes = 8.8 KiB
  

• Architecture: AArch64
  

• Hash algo:    sha256
  

• Hash value:   ca3d874cd10466633ff133cc0156828d48c8efb96987fa45f885761d22a25dc1
  

• Verifying Hash Integrity ... sha256+ OK
• Booting using the fdt blob at 0x40710f24
• Uncompressing Kernel Image ... OK
• Loading Device Tree to 0000000049ffa000, end 0000000049fff347 ... 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" (2 times) means the hash check passed +for kernel and DTB.

+If they are not displayed, the Verified Boot is not working.

One thing that we should make *really* clear is that it will sign only the kernel and device trees, but it's far from sufficient to implement a full fledged secure boot, and you shouldn't consider your device protected. At least the signature of the SPL and the U-Boot binary are missing to implement something that would have a chance to qualify.

Maxime