AM6421: Customized certificate can not be programmed by OTP KeyWriter

Hello,

What is the OpenSSL version you are using? Can you share the command as well used to generate the certificate?

Thanks!

Hi Prashant,

thanks for your attention.

My OpenSSL version is: 3.2.4

Due to the company's signature requirements, our development team cannot directly obtain the signature private key. We can only provide the fields to be signed to the company for signature and embed them into the final x509 certificate.

Here's the command:

./gen_keywr_cert.sh -t tifek/ti_fek_public.pem --msv 0xC0FFE -a keys_devel/aes256.key --smpk-def --smek keys_devel/aes256.key --keycnt 1 --keyrev 1

and changes made into 'gen_keywr_cert.sh':

'aes256.key.hash.sigraw' is the signed aes256.key.hash.

'keys_devel/ARK_AM64_ROT.pubkey' is the public key.

This command will generate a x509 certificate, but it's signed with default SMPK key. So, afterward, we'll extract the TBS field, and signed by our company, and replace corresponding signature field. 

Thanks for the clarification, Jenny! I will get back to you by today EOD.

Hi Prashant,

thanks for your attention, I though I've root cuase the issue. There's difference between 'keys_devel/ARK_AM64_ROT.pubkey' and publicKey required by 'gen_keywr_cert.sh'.

Specifically, there's an extra 'rsaEncryptionDes' entry need to be added.

With this change, OTP KeyWriter can succeed to program the OPT. I'll try to secure boot sbl today.

Jenny Zhou said:

With this change, OTP KeyWriter can succeed to program the OPT. I'll try to secure boot sbl today.

That is good. Let me know if you need any help with the secure boot.

Hi Prashant,

I did need your help for secure boot sbl.

I tried to modify the 'publicKey' and 'tbs's signature' within SBL's x509, but I failed to boot the device. 

Here's the output of 'parse_uart_boot_socid.py', which I suppose OPT has been program successfully, since 'Sec Cust MPK Hash' matches my customer hash.

$ python parse_uart_boot_socid.py socid.txt
-----------------------
SoC ID Header Info:
-----------------------
NumBlocks : 2
-----------------------
SoC ID Public ROM Info:
-----------------------
SubBlockId : 1
SubBlockSize : 26
DeviceName : am64x
DeviceType : HSSE
DMSC ROM Version : [0, 2, 0, 0]
R5 ROM Version : [0, 2, 0, 0]
-----------------------
SoC ID Secure ROM Info:
-----------------------
Sec SubBlockId : 2
Sec SubBlockSize : 166
Sec Prime : 0
Sec Key Revision : 1
Sec Key Count : 1
Sec TI MPK Hash : b018658ad99dc903c8c9bfb27b12751099920a042ad1dfea7b7ba57369f15546de285edde6a7b39a8bdc40a27b237f8fb1e57f245e80b929c1e28b024aa2ecc6
Sec Cust MPK Hash : d248d61ff31637daa7e8053e83ea3a868c39319783620af7b0dd74c8ef5c97d2e0df51c12b0654a56dfca1a565b1601492f16c759527800293e59a722c67aee3
Sec Unique ID : 13f8f762ee412cd0d0c741127b1bf893c841afe076755aee1b6c5bf40040374c

I replace the public key by "dd if=./ARK_AM64_ROT.pubkey of=sbl_qspi.Debug.hs.tiimage bs=1 seek=376 count=550 conv=notrunc"

and after signed the extracted TBS area, I replace the TBS signature by "dd if=sbl_tbs_certificate.bin.hash.sigraw of=sbl_qspi.Debug.hs.tiimage bs=1 seek=1588 count=512 conv=notrunc"

I uploaded the essential files including, would you please help to review if there's anything wrong?

sbl_qspi.Debug.hs.tiimage.before_customized -- sbl built by TI-Dummy MPK

sbl_qspi.Debug.hs.tiimage  ----------------------------sbl modified by me

temp_cert739 ----------------------------------------------x509 certificate config

ARK_AM64_ROT.pubkey-------------------------------my public key

Is there a way to know why RBL can not boot SBL?

Debug_for_sbl_secure_boot.zip

If you are only manipulating the certificate then the sizes should not differ.

❯ /usr/bin/ls -l sbl_qspi.Debug.hs.tiimage*
-rw-r--r-- 1 p-shivhare p-shivhare 388552 Apr 25 17:46 sbl_qspi.Debug.hs.tiimage
-rw-r--r-- 1 p-shivhare p-shivhare 383208 Apr 25 17:43 sbl_qspi.Debug.hs.tiimage.bk

The size difference seems to be because of an extra certificate appended at the very last of your own key signed SBL.

❯ binwalk sbl_qspi.Debug.hs.tiimage

DECIMAL       HEXADECIMAL     DESCRIPTION
--------------------------------------------------------------------------------
0             0x0             Certificate in DER format (x509 v3), header length: 4, sequence length: 2012
383208        0x5D8E8         Certificate in DER format (x509 v3), header length: 4, sequence length: 1680

❯ binwalk sbl_qspi.Debug.hs.tiimage.bk

DECIMAL       HEXADECIMAL     DESCRIPTION
--------------------------------------------------------------------------------
0             0x0             Certificate in DER format (x509 v3), header length: 4, sequence length: 2012

Can you please remove this extra certificate and try booting?

Also, instead of directly manipulating the certificate bytes, you should create the OpenSSL config file and sign it.