imx6: Added DEK blob generator command

Freescale's SEC block has built-in Data Encryption
Key(DEK) Blob Protocol which provides a method for
protecting a DEK for non-secure memory storage.
SEC block protects data in a data structure called
a Secret Key Blob, which provides both confidentiality
and integrity protection.
Every time the blob encapsulation is executed,
a AES-256 key is randomly generated to encrypt the DEK.
This key is encrypted with the OTP Secret key
from SoC. The resulting blob consists of the encrypted
AES-256 key, the encrypted DEK, and a 16-bit MAC.

During decapsulation, the reverse process is performed
to get back the original DEK. A caveat to the blob
decapsulation process,  is that the DEK is decrypted
in secure-memory and can only be read by FSL SEC HW.
The DEK is used to decrypt data during encrypted boot.

Commands added
--------------
  dek_blob - encapsulating DEK as a cryptgraphic blob

Commands Syntax
---------------
  dek_blob src dst len

    Encapsulate and create blob of a len-bits DEK at
    address src and store the result at address dst.

Signed-off-by: Raul Cardenas <Ulises.Cardenas@freescale.com>
Signed-off-by: Nitin Garg <nitin.garg@freescale.com>

Signed-off-by: Ulises Cardenas <ulises.cardenas@freescale.com>

Signed-off-by: Ulises Cardenas-B45798 <Ulises.Cardenas@freescale.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/doc/README.mxc_hab b/doc/README.mxc_hab
index 43e64a2..e9340dd 100644
--- a/doc/README.mxc_hab
+++ b/doc/README.mxc_hab
@@ -46,3 +46,51 @@ cat u-boot.imx U-Boot_CSF_pad.bin > u-boot-signed.imx
 
 NOTE: U-Boot_CSF.bin needs to be padded to the value specified in
 the imximage.cfg file.
+
+Setup U-Boot Image for Encrypted Boot
+-------------------------------------
+An authenticated U-Boot image is used as starting point for
+Encrypted Boot. The image is encrypted by Freescale's Code
+Signing Tool (CST). The CST replaces only the image data of
+u-boot.imx with the encrypted data. The Initial Vector Table,
+DCD, and Boot data, remains in plaintext.
+
+The image data is encrypted with a Encryption Key (DEK).
+Therefore, this key is needed to decrypt the data during the
+booting process. The DEK is protected by wrapping it in a Blob,
+which needs to be appended to the U-Boot image and specified in
+the CSF file.
+
+The DEK blob is generated by an authenticated U-Boot image with
+the dek_blob cmd enabled. The image used for DEK blob generation
+needs to have the following configurations enabled:
+
+CONFIG_SECURE_BOOT
+CONFIG_SYS_FSL_SEC_COMPAT    4 /* HAB version */
+CONFIG_FSL_CAAM
+CONFIG_CMD_DEKBLOB
+
+Note: The encrypted boot feature is only supported by HABv4 or
+greater.
+
+The dek_blob command then can be used to generate the DEK blob of
+a DEK previously loaded in memory. The command is used as follows:
+
+dek_blob <DEK address> <Output Address> <Key Size in Bits>
+example: dek_blob 0x10800000 0x10801000 192
+
+The resulting DEK blob then is used to construct the encrypted
+U-Boot image. Note that the blob needs to be transferred back
+to the host.Then the following commands are used to construct
+the final image.
+
+objcopy -I binary -O binary --pad-to 0x2000 --gap-fill=0x00 \
+    U-Boot_CSF.bin U-Boot_CSF_pad.bin
+cat u-boot.imx U-Boot_CSF_pad.bin > u-boot-signed.imx
+objcopy -I binary -O binary --pad-to <blob_dst> --gap-fill=0x00 \
+    u-boot-signed.imx u-boot-signed-pad.bin
+cat u-boot-signed-pad.imx DEK_blob.bin > u-boot-encrypted.imx
+
+    NOTE: u-boot-signed.bin needs to be padded to the value
+    equivalent to the address in which the DEK blob is specified
+    in the CSF.