topic Encrypted u-boot with SPL for iMX6UL in i.MX Processors

Encrypted u-boot with SPL for iMX6UL

julienpanis — Wed, 01 Aug 2018 10:31:11 GMT

Hello,

I have some problems for encrypting u-boot with SPL, on iMX6UL.

SIGNING :

I have signed u-boot with SPL for iMX6UL, and it works ("No HAB events found" message). I used those 4 files :

//============================

// 1) SPL.log

//============================

Image Type:   Freescale IMX Boot Image
Image Ver:    2 (i.MX53/6/7 compatible)
Mode:         DCD
Data Size:    53248 Bytes = 52.00 KiB = 0.05 MiB
Load Address: 00908420
Entry Point: 00909000
HAB Blocks:   00908400 00000000 0000ac00
DCD Blocks:   00910000 0000002c 00000004

//============================

// 2) SPL.csf

//============================

[Header]
Version = 4.1
Hash Algorithm = sha256
Engine = ANY
Engine Configuration = 0
Certificate Format = X509
Signature Format = CMS

[Install SRK]
File = "../../crts/SRK_1_2_3_4_table.bin"
Source index = 0 # Index of the key location in the SRK table to be installed

[Install CSFK]
# Key used to authenticate the CSF data
File = "../../crts/CSF1_1_sha256_4096_65537_v3_usr_crt.pem"

[Authenticate CSF]

[Install Key]
# Key slot index used to authenticate the key to be installed
Verification index = 0
# Target key slot in HAB key store where key will be installed
Target index = 2
# Key to install
File = "../../crts/IMG1_1_sha256_4096_65537_v3_usr_crt.pem"

[Authenticate Data]
# Key slot index used to authenticate the image data
Verification index = 2
# Address Offset Length Data File Path
Blocks = 0x00908400 0x00000000 0x0000ac00 "SPL"

[Unlock]
Engine = CAAM
Features = RNG

//============================

// 3) u-boot-ivt.img.log

//============================

Image Name:   U-Boot 2017.03-27251-g01c382a fo
Created:      Fri Jul 27 16:12:28 2018
Image Type:   ARM U-Boot Firmware with HABv4 IVT (uncompressed)
Data Size:    364480 Bytes = 355.94 KiB = 0.35 MiB
Load Address: 86000000
Entry Point: 00000000
HAB Blocks:   0x85ffffc0   0x0000   0x00057020

//============================

// 4) u-boot-ivt.img.csf

//============================

[Header]
Version = 4.1
Hash Algorithm = sha256
Engine = ANY
Engine Configuration = 0
Certificate Format = X509
Signature Format = CMS

[Install SRK]
File = "../../crts/SRK_1_2_3_4_table.bin"
Source index = 0 # Index of the key location in the SRK table to be installed

[Install CSFK]
# Key used to authenticate the CSF data
File = "../../crts/CSF1_1_sha256_4096_65537_v3_usr_crt.pem"

[Authenticate CSF]

[Authenticate Data]
# Key slot index used to authenticate the image data
Verification index = 2
# Address Offset Length Data File Path
Blocks = 0x85ffffc0 0x0000 0x00057020 "u-boot-ivt.img"

ENCRYPTION :

Then, I tried to modify u-boot CSF file because I also want to encrypt u-boot. Based on the questions already asked on NXP forum and on others websites, I have tried many things for 2 days but it does NOT work. Here is what I did (in bold : added/modified parts - in red : address/length that are probably wrong) :

//============================

// 4) u-boot-ivt.img.csf

//============================

[Header]
Version = 4.1
Hash Algorithm = sha256
Engine = CAAM
Engine Configuration = 0
Certificate Format = X509
Signature Format = CMS

[Install SRK]
File = "../../crts/SRK_1_2_3_4_table.bin"
Source index = 0 # Index of the key location in the SRK table to be installed

[Install CSFK]
# Key used to authenticate the CSF data
File = "../../crts/CSF1_1_sha256_4096_65537_v3_usr_crt.pem"

[Authenticate CSF]

[Unlock]
Engine = CAAM
Features = RNG

[Authenticate Data]
# Key slot index used to authenticate the image data
Verification index = 2
# Address Offset Length Data File Path
Blocks = 0x85ffffc0 0x0000 0x00000030 "u-boot-ivt.img"

Explanation : 0x30 = 0x2c + 0x4 (see "SPL.log" file)

#Encrypt the boot image and create a DEK
[Install Secret Key]
Verification Index = 0
Target Index = 0
Key = "dek.bin"
Key Length = 128
Blob Address = 0x86058f98

Explanation :

0x86058f98 = 0x86000000 [load address] - 0x40 [header size] + 0x57020 [uboot size] + 0x2000 [csf size] - 0x48 [blob size]

#Provide DEK blob location to decrypt
[Decrypt Data]
Verification Index = 0
Mac Bytes = 16
Blocks = 0x86000000 0x00000040 0x00056fe0 "u-boot-ivt.img"

Explanation :

0x86000000 is load address (see "u-boot-ivt.img.log" file)...which is not the same as entry point address (problem ?)

0x40 = 0x86000000 - 0x85ffffc0

0x56fe0 = 0x57020 - 0x40

This was followed by the following u-boot commands...

=> load mmc 0 0x80800000 dek.bin

=> dcache off

=> icache off

=> dek_blob 0x80800000 0x86058f98 128

=> fatwrite mmc 0 0x86058f98 dek_blob.bin 0x48

...and by the following host commands :

$ objcopy -I binary -O binary --pad-to=0x1fb8 --gap-fill=0x00 u-boot-ivt.img_csf.bin u-boot-ivt.img_csf.bin

$ cat u-boot-ivt.img u-boot-ivt.img_csf.bin dek_blob.bin > u-boot-ivt.img_signed_encrypted

Explanation : 0x1fb8 [padding] + 0x48 [blob size] = 0x2000 because DEK blob is supposed to be included in CSF region (which size is 0x2000)

REFERENCES :

High Assurance Boot (HAB) for dummies - Boundary Devices

Encrypted boot loader on SabreSD i.MX6q board | NXP Community

Encrypted U-boot Example

Encrypted boot loader on SabreSD i.MX6q board

u-boot/README.mxc_hab at master · theopolis/u-boot · GitHub

https://community.nxp.com/message/845992?commentID=845992#comment-845992

Signed and encrypted boot in i.MX6UL

Multi-stage Secure Boot in iMX6 through SPL & u-boot.img

QUESTIONS (to make u-boot encryption work) :

1) What value should I use for :

- authenticated data length (instead of 0x30, if it is wrong) ?

- decrypted data start address (instead of 0x86000000, if it is wrong) ?

- offset for decryption (instead of 0x40, if it is wrong) ?

- decrypted data length (instead of 0x56fe0, if it is wrong) ?

2) Is there anything else to modify in u-boot CSF file ?

3) Is there anything to modify in SPL CSF file ?

4) Is there anything else that I am missing ?

Any help will be appreciated... :-)

Julien

Re: Encrypted u-boot with SPL for iMX6UL

julienpanis — Thu, 02 Aug 2018 14:49:10 GMT

Here is the last version of what I did (which still does NOT work)...

Please find the memory layout picture to make things clear...

If somebody has any idea to help me... :smileyhappy:

//============================

// 1) SPL.csf

//============================

[Header]
Version = 4.1
Hash Algorithm = sha256
Engine = CAAM
Engine Configuration = 0
Certificate Format = X509
Signature Format = CMS

[Install SRK]
File = "../../crts/SRK_1_2_3_4_table.bin"
Source index = 0   # Index of the key location in the SRK table to be installed

[Install CSFK]
# Key used to authenticate the CSF data
File = "../../crts/CSF1_1_sha256_4096_65537_v3_usr_crt.pem"

[Authenticate CSF]

[Install Key]
# Key slot index used to authenticate the key to be installed
Verification index = 0
# Target key slot in HAB key store where key will be installed
Target index = 2
# Key to install
File = "../../crts/IMG1_1_sha256_4096_65537_v3_usr_crt.pem"

[Unlock]
Engine = CAAM
Features = RNG

[Authenticate Data]
# Key slot index used to authenticate the header
Verification index = 2
#        Address      Offset     Length       Data File Path
Blocks = 0x00908400   0x00000000   0x00000c00   "SPL"

#Encrypt the SPL image and create a DEK
[Install Secret Key]
Verification Index = 0
Target Index = 0
Key = "dek.bin"
Key Length = 128
Blob Address = 0x00914fb8

#Provide DEK blob location to decrypt
[Decrypt Data]
Verification Index = 0
Mac Bytes = 16
Blocks = 0x00909000 0x00000c00 0x0000a000 "SPL"

//============================

// 2) u-boot-ivt.csf

//============================

[Header]
Version = 4.1
Hash Algorithm = sha256
Engine = CAAM
Engine Configuration = 0
Certificate Format = X509
Signature Format = CMS

[Install SRK]
File = "../../crts/SRK_1_2_3_4_table.bin"
Source index = 0   # Index of the key location in the SRK table to be installed

[Install CSFK]
# Key used to authenticate the CSF data
File = "../../crts/CSF1_1_sha256_4096_65537_v3_usr_crt.pem"

[Authenticate CSF]

[Install Key]
# Key slot index used to authenticate the key to be installed
Verification index = 0
# Target key slot in HAB key store where key will be installed
Target index = 2
# Key to install
File = "../../crts/IMG1_1_sha256_4096_65537_v3_usr_crt.pem"

[Unlock]
Engine = CAAM
Features = RNG

[Authenticate Data]
# Key slot index used to authenticate the IVT
Verification index = 2
#        Address      Offset     Length       Data File Path
Blocks = 0x86056fc0   0x00057000   0x00000020   "u-boot-ivt.img"

#Encrypt the boot image and create a DEK
[Install Secret Key]
Verification Index = 0
Target Index = 0
Key = "dek.bin"
Key Length = 128
Blob Address = 0x86058f98

#Provide DEK blob location to decrypt
[Decrypt Data]
Verification Index = 0
Mac Bytes = 16
Blocks = 0x86000000 0x00000040 0x00056fc0 "u-boot-ivt.img"

STEPS :

1-2) ... [cst tool used to generate files, included a signed zImage]

3) Copy DEK onto SD card :

sudo cp dek_SPL.bin /media/julien/BOOT-VARSOM/dek_SPL.bin

sudo cp dek_u-boot-ivt.img.bin /media/julien/BOOT-VARSOM/dek_u-boot-ivt.img.bin

4) Power on the board from eMMC, and press any key to enter into u-boot prompt :

4.1) Load DEK binary from SD card

=> load mmc 0 0x909000 dek_SPL.bin

=> load mmc 0 0x86000000 dek_u-boot-ivt.img.bin

4.2) Disable cache memory

=> icache off

=> dcache off

4.3) Create DEK blob

=> dek_blob 0x909000 0x914fb8 128

=> dek_blob 0x86000000 0x86058f98 128

4.4) Copy DEK blob binary onto SD card

=> fatwrite mmc 0 0x914fb8 dek_blob_SPL.bin 0x48

=> fatwrite mmc 0 0x86058f98 dek_blob_u-boot-ivt.img.bin 0x48

5) Back on host, copy DEK blob from SD card :

sudo cp /media/julien/BOOT-VARSOM/dek_blob_SPL.bin ./dek_blob_SPL.bin

sudo cp /media/julien/BOOT-VARSOM/dek_blob_u-boot-ivt.img.bin ./dek_blob_u-boot-ivt.img.bin

6) Pad CSF :

objcopy -I binary -O binary --pad-to=0x1fb8 --gap-fill=0x00 SPL_csf.bin SPL_csf.bin

objcopy -I binary -O binary --pad-to=0x1fb8 --gap-fill=0x00 u-boot-ivt.img_csf.bin u-boot-ivt.img_csf.bin

7) Concatenate [Image + CSF + DEK blob] to generate [Image_signed_encrypted] :

cat SPL SPL_csf.bin dek_blob_SPL.bin > SPL_signed_encrypted

cat u-boot-ivt.img u-boot-ivt.img_csf.bin dek_blob_u-boot-ivt.img.bin > u-boot-ivt.img_signed_encrypted

8) Copy images onto SD card :

sudo cp zImage-ivt_signed /media/julien/rootfs/opt/images/Debian/zImage

sudo cp SPL_signed_encrypted /media/julien/rootfs/opt/images/Debian/SPL.mmc

sudo cp u-boot-ivt.img_signed_encrypted /media/julien/rootfs/opt/images/Debian/u-boot.img.mmc

9) Power on the board from SD card, and flash images onto eMMC

Thank you.

Julien

Re: Encrypted u-boot with SPL for iMX6UL

Yuri — Fri, 17 Aug 2018 07:51:22 GMT

Hello,

If You use the CST 3.0 - please try the previous release CST 2.3

Have a great day,

Yuri

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