Eric Lee / smarc-uboot

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Commit 03865f7279b6f66625ecad83bf8364989e5da4c1

Authored by Breno Lima
Committed by Ye Li
1 parent 77e37901c6
Exists in smarc_8mq_lf_v2020.04 and in 4 other branches pitx_8mp_lf_v2020.04, smarc-8m-android-11.0.0_2.0.0, smarc-8mp-android-11.0.0_2.0.0, smarc_8mp_lf_v2020.04

MLK-20270-1 doc: imx: habv4: Add Secure Boot documentation for i.MX8M and i.MX8MM devices 

Add HABv4 documentation for i.MX8M and i.MX8MM targets covering the
following topics:

- How to sign an securely boot an flash.bin image.
- How to extend the root of trust for additional boot images.
- Add 2 CSF examples.

Reviewed-by: Utkarsh Gupta <utkarsh.gupta@nxp.com>
Signed-off-by: Breno Lima <breno.lima@nxp.com>
(cherry picked from commit cc63be298a3e5f44e417f4098c124715917d09e1)
(cherry picked from commit ca9c6f091095d3bf09cac42c3eb4493490ac8912)

Showing 3 changed files with 611 additions and 0 deletions Side-by-side Diff

doc/imx/habv4/csf_examples/mx8m_mx8mm/csf_fit.txt
Diff comments   View file @ 03865f7
  1 +[Header]
  2 + Version = 4.3
  3 + Hash Algorithm = sha256
  4 + Engine = CAAM
  5 + Engine Configuration = 0
  6 + Certificate Format = X509
  7 + Signature Format = CMS
  8 +
  9 +[Install SRK]
  10 + # Index of the key location in the SRK table to be installed
  11 + File = "../crts/SRK_1_2_3_4_table.bin"
  12 + Source index = 0
  13 +
  14 +[Install CSFK]
  15 + # Key used to authenticate the CSF data
  16 + File = "../crts/CSF1_1_sha256_2048_65537_v3_usr_crt.pem"
  17 +
  18 +[Authenticate CSF]
  19 +
  20 +[Install Key]
  21 + # Key slot index used to authenticate the key to be installed
  22 + Verification index = 0
  23 + # Target key slot in HAB key store where key will be installed
  24 + Target index = 2
  25 + # Key to install
  26 + File = "../crts/IMG1_1_sha256_2048_65537_v3_usr_crt.pem"
  27 +
  28 +[Authenticate Data]
  29 + # Key slot index used to authenticate the image data
  30 + Verification index = 2
  31 + # Authenticate Start Address, Offset, Length and file
  32 + Blocks = 0x401fcdc0 0x057c00 0x01020 "flash.bin", \
  33 + 0x40200000 0x05AC00 0x9AAC8 "flash.bin", \
  34 + 0x00910000 0x0F56C8 0x09139 "flash.bin", \
  35 + 0xFE000000 0x0FE804 0x4D268 "flash.bin", \
  36 + 0x4029AAC8 0x14BA6C 0x06DCF "flash.bin"
doc/imx/habv4/csf_examples/mx8m_mx8mm/csf_spl.txt
Diff comments   View file @ 03865f7
  1 +[Header]
  2 + Version = 4.3
  3 + Hash Algorithm = sha256
  4 + Engine = CAAM
  5 + Engine Configuration = 0
  6 + Certificate Format = X509
  7 + Signature Format = CMS
  8 +
  9 +[Install SRK]
  10 + # Index of the key location in the SRK table to be installed
  11 + File = "../crts/SRK_1_2_3_4_table.bin"
  12 + Source index = 0
  13 +
  14 +[Install CSFK]
  15 + # Key used to authenticate the CSF data
  16 + File = "../crts/CSF1_1_sha256_2048_65537_v3_usr_crt.pem"
  17 +
  18 +[Authenticate CSF]
  19 +
  20 +[Unlock]
  21 + # Leave Job Ring and DECO master ID registers Unlocked
  22 + Engine = CAAM
  23 + Features = MID
  24 +
  25 +[Install Key]
  26 + # Key slot index used to authenticate the key to be installed
  27 + Verification index = 0
  28 + # Target key slot in HAB key store where key will be installed
  29 + Target index = 2
  30 + # Key to install
  31 + File = "../crts/IMG1_1_sha256_2048_65537_v3_usr_crt.pem"
  32 +
  33 +[Authenticate Data]
  34 + # Key slot index used to authenticate the image data
  35 + Verification index = 2
  36 + # Authenticate Start Address, Offset, Length and file
  37 + Blocks = 0x7e0fc0 0x1a000 0x2a600 "flash.bin"
doc/imx/habv4/guides/mx8m_mx8mm_secure_boot.txt
Diff comments   View file @ 03865f7
  1 + +=======================================================+
  2 + + i.MX8M, i.MX8MM Secure Boot guide using HABv4 +
  3 + +=======================================================+
  4 +
  5 +1. HABv4 secure boot process
  6 +-----------------------------
  7 +
  8 +This document describes a step-by-step procedure on how to sign and securely
  9 +boot a bootloader image on i.MX8M and i.MX8MM devices. It is assumed that
  10 +the reader is familiar with basic HAB concepts and with the PKI tree generation.
  11 +
  12 +Details about HAB can be found in the application note AN4581[1] and in the
  13 +introduction_habv4.txt document.
  14 +
  15 +1.1 Understanding the i.MX8M and i.MX8MM flash.bin image layout
  16 +----------------------------------------------------------------
  17 +
  18 +Due to the new the architecture, multiple firmwares and softwares are required
  19 +to boot i.MX8M and i.MX8MM devices. In order to store all the images in a
  20 +single binary the FIT (Flattened Image Tree) image structure is used.
  21 +
  22 +The final image is generated by the imx-mkimage project, the tool combines all
  23 +the input images in a FIT structure, generating a flash.bin image with an
  24 +appropriate IVT set.
  25 +
  26 +For a secure boot process users should ensure all images included in flash.bin
  27 +file are covered by a digital signature.
  28 +
  29 +- The diagram below illustrate a signed flash.bin image layout:
  30 +
  31 + +-----------------------------+
  32 + | |
  33 + | *Signed HDMI/DP FW |
  34 + | |
  35 + +-----------------------------+
  36 + | Padding |
  37 + ------- +-----------------------------+ --------
  38 + ^ | IVT - SPL | ^
  39 + Signed | +-----------------------------+ |
  40 + Data | | u-boot-spl.bin | |
  41 + | | + | | SPL
  42 + v | DDR FW | | Image
  43 + ------- +-----------------------------+ |
  44 + | CSF - SPL + DDR FW | v
  45 + +-----------------------------+ --------
  46 + | Padding |
  47 + ------- +-----------------------------+ --------
  48 + Signed ^ | FDT - FIT | ^
  49 + Data | +-----------------------------+ |
  50 + v | IVT - FIT | |
  51 + ------- +-----------------------------+ |
  52 + | CSF - FIT | |
  53 + ------- +-----------------------------+ |
  54 + ^ | u-boot-nodtb.bin | | FIT
  55 + | | + | | Image
  56 + | | u-boot.bin | |
  57 + Signed | +-----------------------------+ |
  58 + Data | | OP-TEE (Optional) | |
  59 + | +-----------------------------+ |
  60 + | | bl31.bin (ATF) | |
  61 + | +-----------------------------+ |
  62 + v | u-boot.dtb | v
  63 + ------- +-----------------------------+ --------
  64 + * Only supported on i.MX8M series
  65 +
  66 +The boot flow on i.MX8M and i.MX8MM devices are slightly different when compared
  67 +with i.MX6 and i.MX7 series, the diagram below illustrate the boot sequence
  68 +overview:
  69 +
  70 +- i.MX8M and i.MX8MM devices boot flow:
  71 +
  72 + Secure World Non-Secure World
  73 + |
  74 + |
  75 + +------------+ +------------+ |
  76 + | SPL | | i.MX 8M/MM | |
  77 + | + | ---> | ROM | |
  78 + | DDR FW | | + HAB | |
  79 + +------------+ +------------+ |
  80 + | |
  81 + v |
  82 + +------------+ |
  83 + | *Signed | |
  84 + | HDMI/DP FW | |
  85 + +------------+ |
  86 + | |
  87 + v |
  88 + +------------+ +------------+ |
  89 + | FIT Image: | | SPL | |
  90 + | ATF + TEE | ---> | + | |
  91 + | + U-Boot | | DDR FW | | +-----------+
  92 + +------------+ +------------+ | | Linux |
  93 + | | +-----------+
  94 + v | ^
  95 + +------------+ | | +-------+
  96 + | ARM | | +-----------+ | Linux |
  97 + | Trusted | ----+---> | U-Boot | <--- | + |
  98 + | Firmware | | +-----------+ | DTB |
  99 + +------------+ | +-------+
  100 + | |
  101 + v |
  102 + +----------+ |
  103 + | **OP-TEE | |
  104 + +----------+ |
  105 + * Only supported on i.MX8M series
  106 + ** Optional
  107 +
  108 +On i.MX8M devices the HDMI firmware or DisplayPort firmware are the first image
  109 +to boot on the device. These firmwares are signed and distributed by NXP, and
  110 +are always authenticated regardless of security configuration. In case not
  111 +required by the application the HDMI or DisplayPort controllers can be disabled
  112 +by eFuses and the firmwares are not required anymore.
  113 +
  114 +The next images are not signed by NXP and users should follow the signing
  115 +procedure as described in this document.
  116 +
  117 +The Second Program Loader (SPL) and DDR firmware are loaded and authenticated
  118 +by the ROM code, these images are executed in the internal RAM and responsible
  119 +for initializing essential features such as DDR, UART, PMIC and clock
  120 +enablement.
  121 +
  122 +Once the DDR is available, the SPL code loads all the images included in the
  123 +FIT structure to their specific execution addresses, the HAB APIs are called
  124 +to extend the root of trust, authenticating the U-Boot, ARM trusted firmware
  125 +(ATF) and OP-TEE (If included).
  126 +
  127 +The root of trust can be extended again at U-Boot level to authenticate Kernel
  128 +and M4 images.
  129 +
  130 +1.2 Enabling the secure boot support in U-Boot
  131 +-----------------------------------------------
  132 +
  133 +The first step is to generate an U-Boot image supporting the HAB features,
  134 +similar to i.MX6 and i.MX7 series the U-Boot provides extra functions for
  135 +HAB, such as the HAB status logs retrievement through the hab_status command
  136 +and support to extend the root of trust.
  137 +
  138 +The support is enabled by adding the CONFIG_SECURE_BOOT to the build
  139 +configuration:
  140 +
  141 +- Defconfig:
  142 +
  143 + CONFIG_SECURE_BOOT=y
  144 +
  145 +- Kconfig:
  146 +
  147 + ARM architecture -> Support i.MX HAB features
  148 +
  149 +1.3 Preparing the fit image
  150 +----------------------------
  151 +
  152 +The imx-mkimage project is used to combines all the images in a single
  153 +flash.bin binary, the following files are required:
  154 +
  155 +- U-Boot:
  156 + u-boot.bin
  157 + u-boot-nodtb.bin
  158 + u-boot-spl.bin
  159 + U-Boot DTB file (e.g. fsl-imx8mq-evk.dtb)
  160 +
  161 +- ATF image:
  162 + bl31.bin
  163 +
  164 +- DDR firmware:
  165 + lpddr4_pmu_train_1d_dmem.bin
  166 + lpddr4_pmu_train_1d_imem.bin
  167 + lpddr4_pmu_train_2d_dmem.bin
  168 + lpddr4_pmu_train_2d_imem.bin
  169 +
  170 +- HDMI firmware (Only in i.MX8M):
  171 + signed_hdmi_imx8m.bin
  172 +
  173 +- DisplayPort firmware (Only in i.MX8M):
  174 + signed_dp_imx8m.bin
  175 +
  176 +- OP-TEE (Optional):
  177 + tee.bin
  178 +
  179 +The procedure to build ATF and download the firmwares are out of the scope
  180 +of this document, please refer to the Linux BSP Release Notes and AN12212[2]
  181 +for further details.
  182 +
  183 +Copy all files to iMX8M directory and run the following command according to
  184 +the target device, on this example we are building a HDMI target and also
  185 +including the OP-TEE binary:
  186 +
  187 +- Assembly flash.bin binary:
  188 +
  189 + $ make SOC=<SoC Name> flash_hdmi_spl_uboot
  190 +
  191 +The mkimage log can be used to calculate the authenticate image command
  192 +parameters and CSF offsets:
  193 +
  194 +- imx-mkimage build log:
  195 +
  196 + Loader IMAGE:
  197 + header_image_off 0x1a000
  198 + dcd_off 0x0
  199 + image_off 0x1a040
  200 + csf_off 0x44600
  201 + spl hab block: 0x7e0fd0 0x1a000 0x2e600
  202 +
  203 + Second Loader IMAGE:
  204 + sld_header_off 0x57c00
  205 + sld_csf_off 0x58c20
  206 + sld hab block: 0x401fcdc0 0x57c00 0x1020
  207 +
  208 +Additional HAB information is provided by running the following command:
  209 +
  210 +- Printing HAB FIT information:
  211 +
  212 + $ make SOC=<SoC Name> print_fit_hab
  213 +
  214 + TEE_LOAD_ADDR=0xfe000000 ATF_LOAD_ADDR=0x00910000 ./print_fit_hab.sh \
  215 + 0x60000 fsl-imx8mq-evk.dtb
  216 + 0x40200000 0x5AC00 0x9AAC8
  217 + 0x910000 0xF56C8 0x9139
  218 + 0xFE000000 0xFE804 0x4D268
  219 + 0x4029AAC8 0x14BA6C 0x6DCF
  220 +
  221 +1.4 Creating the CSF description file
  222 +--------------------------------------
  223 +
  224 +The CSF contains all the commands that the ROM executes during the secure
  225 +boot. These commands instruct the HAB code on which memory areas of the image
  226 +to authenticate, which keys to install, use and etc.
  227 +
  228 +CSF examples are available under doc/imx/hab/habv4/csf_examples/ directory.
  229 +
  230 +As explained in sections above the SPL is first authenticated by the ROM code
  231 +and the root of trust is extended to the FIT image, hence two CSF files are
  232 +necessary to completely sign an flash.bin image.
  233 +
  234 +The build log provided by imx-mkimage can be used to define the "Authenticate
  235 +Data" parameter in CSF.
  236 +
  237 +- SPL "Authenticate Data" addresses in flash.bin build log:
  238 +
  239 + spl hab block: 0x7e0fd0 0x1a000 0x2e600
  240 +
  241 +- "Authenticate Data" command in csf_spl.txt file:
  242 +
  243 + Blocks = 0x7e0fd0 0x1a000 0x2e600 "flash.bin"
  244 +
  245 +- FIT image "Authenticate Data" addresses in flash.bin build log:
  246 +
  247 + sld hab block: 0x401fcdc0 0x57c00 0x1020
  248 +
  249 +- FIT image "Authenticate Data" addresses in print_fit_hab build log:
  250 +
  251 + 0x40200000 0x5AC00 0x9AAC8
  252 + 0x910000 0xF56C8 0x9139
  253 + 0xFE000000 0xFE804 0x4D268
  254 + 0x4029AAC8 0x14BA6C 0x6DCF
  255 +
  256 +- "Authenticate Data" command in csf_fit.txt file:
  257 +
  258 + Blocks = 0x401fcdc0 0x057c00 0x01020 "flash.bin", \
  259 + 0x40200000 0x05AC00 0x9AAC8 "flash.bin", \
  260 + 0x00910000 0x0F56C8 0x09139 "flash.bin", \
  261 + 0xFE000000 0x0FE804 0x4D268 "flash.bin", \
  262 + 0x4029AAC8 0x14BA6C 0x06DCF "flash.bin"
  263 +
  264 +1.4.1 Avoiding Kernel crash in closed devices
  265 +----------------------------------------------
  266 +
  267 +For devices prior to HAB v4.4.0, the HAB code locks the Job Ring and DECO
  268 +master ID registers in closed configuration. In case the user specific
  269 +application requires any changes in CAAM MID registers it's necessary to
  270 +add the "Unlock CAAM MID" command in CSF file.
  271 +
  272 +The current NXP BSP implementation expects the CAAM registers to be unlocked
  273 +when configuring CAAM to operate in non-secure TrustZone world.
  274 +
  275 +The Unlock command is already included by default in the signed HDMI and
  276 +DisplayPort firmwares, on i.MX8MM devices or in case the HDMI or DisplayPort
  277 +controllers are disabled, users must ensure this command is included in SPL CSF.
  278 +
  279 +- Add Unlock MID command in csf_spl.txt:
  280 +
  281 + [Unlock]
  282 + Engine = CAAM
  283 + Features = MID
  284 +
  285 +1.5 Signing the flash.bin binary
  286 +---------------------------------
  287 +
  288 +The CST tool is used for singing the flash.bin image and generating the CSF
  289 +binary. Users should input the CSF description file created in the step above
  290 +and receive a CSF binary, which contains the CSF commands, SRK table,
  291 +signatures and certificates.
  292 +
  293 +- Create SPL CSF binary file:
  294 +
  295 + $ ./cst -i csf_spl.txt -o csf_spl.bin
  296 +
  297 +- Create FIT CSF binary file:
  298 +
  299 + $ ./cst -i csf_fit.txt -o csf_fit.bin
  300 +
  301 +1.6 Assembling the CSF in flash.bin binary
  302 +-------------------------------------------
  303 +
  304 +The CSF binaries generated in the step above have to be inserted into the
  305 +flash.bin image.
  306 +
  307 +The CSF offsets can be obtained from the flash.bin build log:
  308 +
  309 +- SPL CSF offset:
  310 +
  311 + csf_off 0x44600
  312 +
  313 +- FIT CSF offset:
  314 +
  315 + sld_csf_off 0x58c20
  316 +
  317 +The signed flash.bin image can be then assembled:
  318 +
  319 +- Create a flash.bin copy:
  320 +
  321 + $ cp flash.bin signed_flash.bin
  322 +
  323 +- Insert csf_spl.bin in signed_flash.bin at 0x44600 offset:
  324 +
  325 + $ dd if=csf_spl.bin of=signed_flash.bin seek=$((0x44600)) bs=1 conv=notrunc
  326 +
  327 +- Insert csf_fit.bin in signed_flash.bin at 0x58c20 offset:
  328 +
  329 + $ dd if=csf_fit.bin of=signed_flash.bin seek=$((0x58c20)) bs=1 conv=notrunc
  330 +
  331 +- Flash signed flash.bin image:
  332 +
  333 + $ sudo dd if=signed_flash.bin of=/dev/sd<x> bs=1K seek=33 && sync
  334 +
  335 +1.7 Programming SRK Hash
  336 +-------------------------
  337 +
  338 +As explained in AN4581[1] and in introduction_habv4.txt document the SRK Hash
  339 +fuse values are generated by the srktool and should be programmed in the
  340 +SoC SRK_HASH[255:0] fuses.
  341 +
  342 +Be careful when programming these values, as this data is the basis for the
  343 +root of trust. An error in SRK Hash results in a part that does not boot.
  344 +
  345 +The U-Boot fuse tool can be used for programming eFuses on i.MX SoCs.
  346 +
  347 +- Dump SRK Hash fuses values in host machine:
  348 +
  349 + $ hexdump -e '/4 "0x"' -e '/4 "%X""\n"' SRK_1_2_3_4_fuse.bin
  350 + 0x20593752
  351 + 0x6ACE6962
  352 + 0x26E0D06C
  353 + 0xFC600661
  354 + 0x1240E88F
  355 + 0x1209F144
  356 + 0x831C8117
  357 + 0x1190FD4D
  358 +
  359 +- Program SRK_HASH[255:0] fuses on i.MX8MQ and i.MX8MM devices:
  360 +
  361 + => fuse prog 6 0 0x20593752
  362 + => fuse prog 6 1 0x6ACE6962
  363 + => fuse prog 6 2 0x26E0D06C
  364 + => fuse prog 6 3 0xFC600661
  365 + => fuse prog 7 0 0x1240E88F
  366 + => fuse prog 7 1 0x1209F144
  367 + => fuse prog 7 2 0x831C8117
  368 + => fuse prog 7 3 0x1190FD4D
  369 +
  370 +
  371 +1.8 Verifying HAB events
  372 +-------------------------
  373 +
  374 +The next step is to verify that the signatures included in flash.bin image is
  375 +successfully processed without errors. HAB generates events when processing
  376 +the commands if it encounters issues.
  377 +
  378 +The hab_status U-Boot command call the hab_report_event() and hab_status()
  379 +HAB API functions to verify the processor security configuration and status.
  380 +This command displays any events that were generated during the process.
  381 +
  382 +Prior to closing the device users should ensure no HAB events were found, as
  383 +the example below:
  384 +
  385 +- Verify HAB events:
  386 +
  387 + => hab_status
  388 +
  389 + Secure boot disabled
  390 +
  391 + HAB Configuration: 0xf0, HAB State: 0x66
  392 +
  393 +1.9 Closing the device
  394 +-----------------------
  395 +
  396 +After the device successfully boots a signed image without generating any HAB
  397 +events, it is safe to close the device. This is the last step in the HAB
  398 +process, and is achieved by programming the SEC_CONFIG[1] fuse bit.
  399 +
  400 +Once the fuse is programmed, the chip does not load an image that has not been
  401 +signed using the correct PKI tree.
  402 +
  403 +- Program SEC_CONFIG[1] fuse on i.MX8MQ and i.MX8MM devices:
  404 +
  405 + => fuse prog 1 3 0x2000000
  406 +
  407 +1.10 Completely secure the device
  408 +----------------------------------
  409 +
  410 +Additional fuses can be programmed for completely secure the device, more
  411 +details about these fuses and their possible impact can be found at AN4581[1].
  412 +
  413 +- Program SRK_LOCK:
  414 +
  415 + => fuse prog 0 0 0x200
  416 +
  417 +- Program DIR_BT_DIS:
  418 +
  419 + => fuse prog 1 3 0x8000000
  420 +
  421 +- Program SJC_DISABLE:
  422 +
  423 + => fuse prog 1 3 0x200000
  424 +
  425 +- JTAG_SMODE:
  426 +
  427 + => fuse prog 1 3 0xC00000
  428 +
  429 +2. Authenticating additional boot images
  430 +-----------------------------------------
  431 +
  432 +The High Assurance Boot (HAB) code located in the on-chip ROM provides an
  433 +Application Programming Interface (API) making it possible to call back
  434 +into the HAB code for authenticating additional boot images.
  435 +
  436 +The U-Boot is running in non-secure TrustZone world and to make use of this
  437 +feature it's necessary to use a SIP call to the ATF, this is already
  438 +implemented in hab.c code and it's transparent to the user.
  439 +
  440 +The process of signing an additional image is similar as in i.MX6 and i.MX7
  441 +series devices, the steps below are using the Linux Kernel image as example.
  442 +
  443 +The diagram below illustrate the Image layout:
  444 +
  445 + ------- +-----------------------------+ <-- *load_address
  446 + ^ | |
  447 + | | |
  448 + | | |
  449 + | | |
  450 + | | Image |
  451 + Signed | | |
  452 + Data | | |
  453 + | | |
  454 + | +-----------------------------+
  455 + | | Padding to Image size |
  456 + | | in header |
  457 + | +-----------------------------+ <-- *ivt
  458 + v | Image Vector Table |
  459 + ------- +-----------------------------+ <-- *csf
  460 + | |
  461 + | Command Sequence File (CSF) |
  462 + | |
  463 + +-----------------------------+
  464 + | Padding (optional) |
  465 + +-----------------------------+
  466 +
  467 +2.1 Padding the image
  468 +----------------------
  469 +
  470 +The Image must be padded to the size specified in the Image header, this can be
  471 +achieved by using the od command.
  472 +
  473 +- Read Image size:
  474 +
  475 + $ od -x -j 0x10 -N 0x4 --endian=little Image
  476 + 0000020 5000 0145
  477 + 0000024
  478 +
  479 +The tool objcopy can be used for padding the image.
  480 +
  481 +- Pad the Image:
  482 +
  483 + $ objcopy -I binary -O binary --pad-to 0x1455000 --gap-fill=0x00 \
  484 + Image Image_pad.bin
  485 +
  486 +2.2 Generating Image Vector Table
  487 +----------------------------------
  488 +
  489 +The HAB code requires an Image Vector Table (IVT) for determining the image
  490 +length and the CSF location. Since Image does not include an IVT this has
  491 +to be manually created and appended to the end of the padded Image, the
  492 +script genIVT.pl in script_examples directory can be used as reference.
  493 +
  494 +- Generate IVT:
  495 +
  496 + $ genIVT.pl
  497 +
  498 +Note: The load Address may change depending on the device.
  499 +
  500 +- Append the ivt.bin at the end of the padded Image:
  501 +
  502 + $ cat Image_pad.bin ivt.bin > Image_pad_ivt.bin
  503 +
  504 +2.3 Signing the image
  505 +----------------------
  506 +
  507 +A CSF file has to be created to sign the image. HAB does not allow to change
  508 +the SRK once the first image is authenticated, so the same SRK key used in
  509 +the initial image must be used when extending the root of trust.
  510 +
  511 +CSF examples are available in ../csf_examples/additional_images/ directory.
  512 +
  513 +- Create CSF binary file:
  514 +
  515 + $ ./cst --i csf_additional_images.txt --o csf_Image.bin
  516 +
  517 +- Attach the CSF binary to the end of the image:
  518 +
  519 + $ cat Image_pad_ivt.bin csf_Image.bin > Image_signed.bin
  520 +
  521 +2.4 Verifying HAB events
  522 +-------------------------
  523 +
  524 +The U-Boot includes the hab_auth_img command which can be used for
  525 +authenticating and troubleshooting the signed image, the Image must be
  526 +loaded at the load address specified in the IVT.
  527 +
  528 +- Authenticate additional image:
  529 +
  530 + => hab_auth_img <Load Address> <Image Size> <IVT Offset>
  531 +
  532 +If no HAB events were found the Image is successfully signed.
  533 +
  534 +References:
  535 +[1] AN4581: "Secure Boot on i.MX 50, i.MX 53, i.MX 6 and i.MX 7 Series using
  536 + HABv4" - Rev 2.
  537 +[2] AN12212: "Software Solutions for Migration Guide from Aarch32 to
  538 +Aarch64" - Rev 0.