[U-Boot] nxp: HABv4 secure boot on iMX7 NAND broken

Mon Sep 16 02:54:37 UTC 2019

Hi Igor,

Em qui, 12 de set de 2019 às 10:55, Igor Opaniuk
<igor.opaniuk at gmail.com> escreveu:
>
> Hy Bryan, Breno,
>
> On Tue, Jul 30, 2019 at 5:33 PM Bryan O'Donoghue
> <bryan.odonoghue at linaro.org> wrote:
> >
> >
> >
> > On 30/07/2019 15:26, Igor Opaniuk wrote:
> > > Anyway, let me go through this article one more time,
> > > and I'll get back to you.
> >
> > If I've understood you, you are using the same binary for serial
> > download and flash booting.
> >
> > Won't work unfortunately - there's an extra DCD directive in the
> > recovery image.
> >
> > Here's my recovery CSF
> >
> > deckard at event-horizon:~/Development/mbl-u-boot$ cat uboot-c-s-f-recover.txt
> > # SPDX-License-Identifier:      GPL-2.0
> > [Header]
> > Version = 4.1
> > Security Configuration = Open
> > Hash Algorithm = sha256
> > Engine Configuration = 0
> > Certificate Format = X509
> > Signature Format = CMS
> > Engine = CAAM
> >
> > [Install SRK]
> > File = "SRK_1_2_3_4_table.bin"
> > Source index = 0
> >
> > [Install CSFK]
> > File = "CSF1_1_sha256_2048_65537_v3_usr_crt.pem"
> >
> > [Authenticate CSF]
> >
> > [Install Key]
> > # Key slot index used to authenticate the key to be installed
> > Verification index = 0
> > # Key to install
> > Target index = 2
> > File = "IMG1_1_sha256_2048_65537_v3_usr_crt.pem"
> >
> > [Authenticate Data]
> > Verification index = 2
> > Blocks = HAB_BLOCKS_REPLACE "IMAGE_IMX_HAB_NAME_REPLACE"
> >
> > [Authenticate Data]
> > Verification index = 2
> > Blocks = DCD_BLOCKS_REPLACE "IMAGE_IMX_DCD_NAME_REPLACE"
> >
> > and my eMMC CSF
> >
> > deckard at event-horizon:~/Development/mbl-u-boot$ cat uboot-c-s-f.txt
> > # SPDX-License-Identifier:      GPL-2.0
> > [Header]
> > Version = 4.1
> > Security Configuration = Open
> > Hash Algorithm = sha256
> > Engine Configuration = 0
> > Certificate Format = X509
> > Signature Format = CMS
> > Engine = CAAM
> >
> > [Install SRK]
> > File = "SRK_1_2_3_4_table.bin"
> > Source index = 0
> >
> > [Install CSFK]
> > File = "CSF1_1_sha256_2048_65537_v3_usr_crt.pem"
> >
> > [Authenticate CSF]
> >
> > [Install Key]
> > # Key slot index used to authenticate the key to be installed
> > Verification index = 0
> > # Key to install
> > Target index = 2
> > File = "IMG1_1_sha256_2048_65537_v3_usr_crt.pem"
> >
> > [Authenticate Data]
> > Verification index = 2
> > Blocks = HAB_BLOCKS_REPLACE "IMAGE_IMX_HAB_NAME_REPLACE"
>
> So I've finally got back to this issue.
> I've spent some time digging into links you provided and
>  `Secure Boot on i.MX 50, i.MX 53, i.MX 6 and i.MX 7 Series using HABv4` doc
> from NXP [1]. Some observations/statements I made (correct me if I'm
> wrong) + questions:
>
> 1. Based on information from [1],  if SRK isn't fused and device isn't "closed",
> BootROM HABv4 component actually doesn't care about CSF region at all.
> In case if SRK is fused, but device is still in "open" state, it
> performs verification of
> binary (IVT + Boot Data + DCD Table + U-boot itself), but it continue loading
> U-boot  regardless of the verification results (but in case of invalid signature
> we will  observe HABv4 events by running `hab_status`). Is it correct?
>

HAB will verify the image signature regardless of the SRK Hash fusing
configuration, the SRK Hash is only used to validate the SRK table
which is included in your CSF binary.

In case your SRK Hash isn't programmed HAB won't validate the SRK
table, but you can still see HAB events. You can have more details in
section 4.1.1. SRK HASH and HAB events in open mode of AN4581.

> 2. I tried to boot U-boot on i.MX7D rev1.3 NAND with concatenated CSF binary
> built using the configuration file you provided and without it (no
> fuses are fused) -
> in both cases it doesn't boot.
>

Can you please confirm if your board is booting after enabling
CONFIG_SECURE_BOOT in U-Boot? Can you please point me the U-Boot
target are you trying? You should be able to boot in case your board
still in open mode.

> 3. When `CSF` CMD is removed from imximage.cfg, the image starts booting,
> so obviosly I assumed that something was wrong with IMX image layout
> and how it's
> stored in OCRAM. After analizing IVT table values and input from mkimage for the
> final u-boot-dtb.imx, found out that DCD table is loaded to 0x00910000 (OCRAM):
>
> Image Type:   Freescale IMX Boot Image
> Image Ver:    2 (i.MX53/6/7 compatible)
> Mode:         DCD
> Data Size:    659456 Bytes = 644.00 KiB = 0.63 MiB
> Load Address: 877ff420
> Entry Point:  87800000
> HAB Blocks:   0x877ff400 0x00000000 0x0009cc00
> DCD Blocks:   0x00910000 0x0000002c 0x000001b4
>                        ^^^^^^^^^^^^
>
> In [1] F.1. Signing code downloadable with the manufacturing tool from the
> document about Secure Boot, found the NOTE which says:
>
> "Due to an issue with i.MX7D Rev D, the first 4K of OCRAM is not
> available during boot time, on this case users must set the image start
> address greater or equal to 0x911000. For more details please check
> E11166 in Mask Set Errata for Mask 3N09P."
>
> E11166 description in [2]:
> "e11166: OCRAM: The first 4K of OCRAM (0x910000 - 0x910fff) is not
> available during
> boot time
>
> Description: The first 4K of OCRAM (0x910000 – 0x910fff) is not available
> during boot time which effects plug-ins and custom boot images.Using
> this space may
> cause image corruption during boot time. At time of boot failure, the system may
> enter into serial download mode.
>
> Workaround: Users must set the boot or plugin image start address greater or
> equal to 0x911000 (if the boot image or plug-in is running in OCRAM).
> Alternatively,
> users can use a boot/plugin image load address in the external DDR
> memory instead of
> the internal OCRAM."
>
> Could it be the root cause why I'm facing this issue?
>

When booting from NAND the DCD table is not loaded in OCRAM so that
shouldn't be a problem. The DCD is loaded in OCRAM when booting via
USB OTG using the serial download protocol, you can have more details
in link below:

https://github.com/NXPmicro/mfgtools/wiki/UUU-default-support-protocol-list#habv4-closed-chip-support

> 4. BTW,  is there any publicly available information about analysis of
> BootROM log buffer
> that can be obtained by reading data pointed by Log Buffer Pointer (at
> 0x000001E0)
> on iMX7?
>
> [1] https://www.nxp.com/docs/en/application-note/AN4581.pdf
> [2] https://www.nxp.com/docs/en/errata/IMX7DS_3N09P.pdf
>
>
> Looking forward for your replies/comments.
> Thanks!
>
> --
> Best regards - Freundliche Grüsse - Meilleures salutations
>
> Igor Opaniuk
>
> mailto: igor.opaniuk at gmail.com
> skype: igor.opanyuk
> +380 (93) 836 40 67
> http://ua.linkedin.com/in/iopaniuk
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-- 
Breno Matheus Lima