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Diffstat (limited to 'doc/imx/habv4/secure_boot.txt')
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diff --git a/doc/imx/habv4/secure_boot.txt b/doc/imx/habv4/secure_boot.txt new file mode 100644 index 00000000000..ae68dc8040d --- /dev/null +++ b/doc/imx/habv4/secure_boot.txt @@ -0,0 +1,100 @@ +1. High Assurance Boot (HAB) for i.MX CPUs +------------------------------------------ + +To enable the authenticated or encrypted boot mode of U-Boot, it is +required to set the proper configuration for the target board. This +is done by adding the following configuration in the defconfig file: + +CONFIG_SECURE_BOOT=y + +In addition, the U-Boot image to be programmed into the +boot media needs to be properly constructed, i.e. it must contain a +proper Command Sequence File (CSF). + +The CSF itself is generated by the i.MX High Assurance Boot Reference +Code Signing Tool. +https://www.nxp.com/webapp/sps/download/license.jsp?colCode=IMX_CST_TOOL + +More information about the CSF and HAB can be found in the AN4581. +https://www.nxp.com/docs/en/application-note/AN4581.pdf + +We don't want to explain how to create a PKI tree or SRK table as +this is well explained in the Application Note. + +2. Secure Boot on non-SPL targets +--------------------------------- + +On non-SPL targets a singe U-Boot binary is generated, mkimage will +output additional information about "HAB Blocks" which can be used +in the CST to authenticate the U-Boot image (entries in the CSF file). + +Image Type: Freescale IMX Boot Image +Image Ver: 2 (i.MX53/6 compatible) +Data Size: 327680 Bytes = 320.00 kB = 0.31 MB +Load Address: 177ff420 +Entry Point: 17800000 +HAB Blocks: 0x177ff400 0x00000000 0x0004dc00 + ^^^^^^^^^^ ^^^^^^^^^^ ^^^^^^^^^^ + | | | + | | ----- (1) + | | + | ---------------- (2) + | + --------------------------- (3) + +(1) Size of area in file u-boot-dtb.imx to sign + This area should include the IVT, the Boot Data the DCD + and U-Boot itself. +(2) Start of area in u-boot-dtb.imx to sign +(3) Start of area in RAM to authenticate + +CONFIG_SECURE_BOOT currently enables only an additional command +'hab_status' in U-Boot to retrieve the HAB status and events. This +can be useful while developing and testing HAB. + +Commands to generate a signed U-Boot using i.MX HAB CST tool: +# Compile CSF and create signature +cst --o csf-u-boot.bin --i command_sequence_uboot.csf +# Append compiled CSF to Binary +cat u-boot-dtb.imx csf-u-boot.bin > u-boot-signed.imx + +3. Secure Boot on SPL targets +----------------------------- + +This version of U-Boot is able to build a signable version of the SPL +as well as a signable version of the U-Boot image. The signature can +be verified through High Assurance Boot (HAB). + +After building, you need to create a command sequence file and use +i.MX HAB Code Signing Tool to sign both binaries. After creation, +the mkimage tool outputs the required information about the HAB Blocks +parameter for the CSF. During the build, the information is preserved +in log files named as the binaries. (SPL.log and u-boot-ivt.log). + +Example Output of the SPL (imximage) creation: + Image Type: Freescale IMX Boot Image + Image Ver: 2 (i.MX53/6/7 compatible) + Mode: DCD + Data Size: 61440 Bytes = 60.00 kB = 0.06 MB + Load Address: 00907420 + Entry Point: 00908000 + HAB Blocks: 0x00907400 0x00000000 0x0000cc00 + +Example Output of the u-boot-ivt.img (firmware_ivt) creation: + Image Name: U-Boot 2016.11-rc1-31589-g2a4411 + Created: Sat Nov 5 21:53:28 2016 + Image Type: ARM U-Boot Firmware with HABv4 IVT (uncompressed) + Data Size: 352192 Bytes = 343.94 kB = 0.34 MB + Load Address: 17800000 + Entry Point: 00000000 + HAB Blocks: 0x177fffc0 0x0000 0x00054020 + +# Compile CSF and create signature +cst --o csf-u-boot.bin --i command_sequence_uboot.csf +cst --o csf-SPL.bin --i command_sequence_spl.csf +# Append compiled CSF to Binary +cat SPL csf-SPL.bin > SPL-signed +cat u-boot-ivt.img csf-u-boot.bin > u-boot-signed.img + +These two signed binaries can be used on an i.MX in closed +configuration when the according SRK Table Hash has been flashed. |