* HABv4 with SPL and u-boot-dtb.img on i.MX6
@ 2024-02-20 9:50 Benjamin Lemouzy
2024-02-20 16:29 ` Sean Anderson
0 siblings, 1 reply; 3+ messages in thread
From: Benjamin Lemouzy @ 2024-02-20 9:50 UTC (permalink / raw)
To: u-boot
Hello,
I'm trying to make secure boot work on i.MX6 SABRE with SPL and u-boot-dtb.img files and I'm not sure how to do it.
I'm using the U-Boot vanilla master branch (2024.04-rc2) with the following configuration:
# Remove some stuff to not exceed file size limit
$ cat <<EOF >> configs/mx6sabresd_defconfig
CONFIG_BOOTMETH_EFILOADER=n
CONFIG_CMD_NET=n
CONFIG_NET=n
EOF
# Enable secure boot
$ cat <<EOF >> configs/mx6sabresd_defconfig
CONFIG_IMX_HAB=y
CONFIG_SPL_LOAD_FIT_ADDRESS=0x18000000
EOF
$ make ARCH=arm O=build mx6sabresd_defconfig
$ make ARCH=arm O=build
I have no issue to generate a working SPL-signed file following doc/imx/habv4/guides/mx6_mx7_spl_secure_boot.txt instructions.
doc/imx/habv4/guides/mx6_mx7_spl_secure_boot.txt only gives instructions to sign u-boot-ivt.img but this file doesn't contain device trees listed in CONFIG_OF_LIST as u-boot-dtb.img does and I need them.
NXP AN4581 lists 2 possible formats to sign additional images:
- Image format:
------- +-----------------------------+ <-- *load_address
^ | |
| | |
| | Image data |
Signed | | |
Data | | |
| +-----------------------------+
| | Padding Next Boundary |
| +-----------------------------+ <-- *ivt
v | Image Vector Table |
------- +-----------------------------+ <-- *csf
| |
| Command Sequence File (CSF) |
| |
+-----------------------------+
| Padding (optional) |
+-----------------------------+
- FIT image format:
------- +-----------------------------+ -------
^ | | ^
| | | |
| | FDT FIT | |
| | | |
Signed data | | | |
| +-----------------------------+ |
| | Padding Next Boundary | |
| +-----------------------------+ |
v | Image Vector Table | |
------- +-----------------------------+ | FIT image
| | |
| Command Sequence File (CSF) | |
| | |
+-----------------------------+ |
| Padding (optional) | |
------- +-----------------------------+ |
^ | | |
Signed data | | U-Boot | |
v | | v
------- +-----------------------------+ -------
And as u-boot-dtb.img is a FIT image, I probably have to use the FIT image format, right?
I manually craft the signed FIT image using doc/imx/habv4/csf_examples/mx8m/csf.sh as reference and everything looks fine:
U-Boot SPL 2024.04-rc2-00025-g9e00b6993f-dirty (Feb 19 2024 - 13:17:31 +0100)
>>SPL: board_init_r()
spl_init
Trying to boot from MMC1
fit read offset 11400, size=12800, dst=18000000, count=12800
spl_load_simple_fit_fix_load: ivt: 18001000 offset: 1000 size: 3060
spl_load_simple_fit_fix_load: ivt self: 18001000
hab fuse not enabled
Authenticate image from DDR location 0x18000000...
ivt_offset = 0x1000, ivt addr = 0x18001000
ivt entry = 0x18000000, dcd = 0x00000000, csf = 0x18001020
Dumping IVT
.. @............
........ .......
Dumping CSF Header
..PC...........P
................
.......<........
...............8
Calling authenticate_image in ROM
ivt_offset = 0x1000
start = 0x18000000
bytes = 0x3060
firmware: 'firmware-1'
External data: dst=17800000, offset=3060, size=86138
Image OS is U-Boot
fdt: 'fdt-1'
Can't get 'load' property from FIT 0x18000000, node: offset 464, name fdt-1 (FDT_ERR_NOTFOUND)
External data: dst=17886140, offset=89198, size=ac00
Can't get 'entry' property from FIT 0x18000000, node: offset 464, name fdt-1 (FDT_ERR_NOTFOUND)
loadables: 'firmware-1'
no string for index 1
Jumping to U-Boot...
SPL malloc() used 0x0 bytes (0 KB)
image entry point: 0x
U-Boot 2024.04-rc2-00025-g9e00b6993f-dirty (Feb 19 2024 - 13:17:31 +0100)
CPU: Freescale i.MX6Q rev1.2 996 MHz (running at 792 MHz)
CPU: Automotive temperature grade (-40C to 125C) at 35C
Reset cause: POR
Model: Freescale i.MX6 Quad SABRE Smart Device Board
DRAM: 1 GiB
Core: 94 devices, 23 uclasses, devicetree: separate
WDT: Started watchdog@20c0000 with servicing every 1000ms (128s timeout)
MMC: FSL_SDHC: 4, FSL_SDHC: 1, FSL_SDHC: 3
Loading Environment from MMC... *** Warning - bad CRC, using default environment
No panel detected: default to Hannstar-XGA
Display: Hannstar-XGA (1024x768)
In: serial
Out: serial
Err: serial
SEC0: RNG instantiated
Hit any key to stop autoboot: 0
=> hab_status
Secure boot disabled
HAB Configuration: 0xf0, HAB State: 0x66
No HAB Events Found!
But as only the FDT part of the FIT image is checked through HAB, U-Boot and DTB are only protected by FIT image hashes, right?
Using fdtdump shows that crc32 is used as hash algorithm for FIT image which is a super weak one.
I tried to pass another algo (sha256) using mkimage -o option but that doesn't work.
./tools/mkimage -f auto -A arm -T firmware -C none -O u-boot -a 0x17800000 -e 0x17800000 -p 0x0 -n "U-Boot 2024.04-rc2-00025-g9e00b6993f-dirty for mx6sabresd board" -E -b arch/arm/dts/imx6q-sabresd.dtb -b arch/arm/dts/imx6qp-sabresd.dtb -b arch/arm/dts/imx6dl-sabresd.dtb -d u-boot-nodtb.bin -o sha256 u-boot-dtb.img
Is there any way to change U-Boot FIT image hash?
I also try to use image format and force the HAB to verify the whole u-boot-dtb.img file by patching the FIT image size:
image_size=$(stat -tc %s u-boot-dtb.img)
printf "00000004: %08x" "$image_size" | xxd -r - u-boot-dtb.img
SPL starts, authentication looks fine but the boot fails.
Is there any chance to make it work or is it insane to try to use this format?
Regards,
Benjamin
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: HABv4 with SPL and u-boot-dtb.img on i.MX6
2024-02-20 9:50 HABv4 with SPL and u-boot-dtb.img on i.MX6 Benjamin Lemouzy
@ 2024-02-20 16:29 ` Sean Anderson
2024-02-22 8:05 ` Benjamin Lemouzy
0 siblings, 1 reply; 3+ messages in thread
From: Sean Anderson @ 2024-02-20 16:29 UTC (permalink / raw)
To: Benjamin Lemouzy, u-boot
On 2/20/24 04:50, Benjamin Lemouzy wrote:
> Hello,
>
> I'm trying to make secure boot work on i.MX6 SABRE with SPL and u-boot-dtb.img files and I'm not sure how to do it.
>
> I'm using the U-Boot vanilla master branch (2024.04-rc2) with the following configuration:
>
> # Remove some stuff to not exceed file size limit
> $ cat <<EOF >> configs/mx6sabresd_defconfig
> CONFIG_BOOTMETH_EFILOADER=n
> CONFIG_CMD_NET=n
> CONFIG_NET=n
> EOF
>
> # Enable secure boot
> $ cat <<EOF >> configs/mx6sabresd_defconfig
> CONFIG_IMX_HAB=y
> CONFIG_SPL_LOAD_FIT_ADDRESS=0x18000000
> EOF
>
> $ make ARCH=arm O=build mx6sabresd_defconfig
>
> $ make ARCH=arm O=build
>
> I have no issue to generate a working SPL-signed file following doc/imx/habv4/guides/mx6_mx7_spl_secure_boot.txt instructions.
>
> doc/imx/habv4/guides/mx6_mx7_spl_secure_boot.txt only gives instructions to sign u-boot-ivt.img but this file doesn't contain device trees listed in CONFIG_OF_LIST as u-boot-dtb.img does and I need them.
>
>
>
> NXP AN4581 lists 2 possible formats to sign additional images:
>
> - Image format:
>
> ------- +-----------------------------+ <-- *load_address
> ^ | |
> | | |
> | | Image data |
> Signed | | |
> Data | | |
> | +-----------------------------+
> | | Padding Next Boundary |
> | +-----------------------------+ <-- *ivt
> v | Image Vector Table |
> ------- +-----------------------------+ <-- *csf
> | |
> | Command Sequence File (CSF) |
> | |
> +-----------------------------+
> | Padding (optional) |
> +-----------------------------+
>
> - FIT image format:
>
> ------- +-----------------------------+ -------
> ^ | | ^
> | | | |
> | | FDT FIT | |
> | | | |
> Signed data | | | |
> | +-----------------------------+ |
> | | Padding Next Boundary | |
> | +-----------------------------+ |
> v | Image Vector Table | |
> ------- +-----------------------------+ | FIT image
> | | |
> | Command Sequence File (CSF) | |
> | | |
> +-----------------------------+ |
> | Padding (optional) | |
> ------- +-----------------------------+ |
> ^ | | |
> Signed data | | U-Boot | |
> v | | v
> ------- +-----------------------------+ -------
>
> And as u-boot-dtb.img is a FIT image, I probably have to use the FIT image format, right?
>
>
>
> I manually craft the signed FIT image using doc/imx/habv4/csf_examples/mx8m/csf.sh as reference and everything looks fine:
>
> U-Boot SPL 2024.04-rc2-00025-g9e00b6993f-dirty (Feb 19 2024 - 13:17:31 +0100)
> >>SPL: board_init_r()
> spl_init
> Trying to boot from MMC1
> fit read offset 11400, size=12800, dst=18000000, count=12800
> spl_load_simple_fit_fix_load: ivt: 18001000 offset: 1000 size: 3060
> spl_load_simple_fit_fix_load: ivt self: 18001000
> hab fuse not enabled
>
> Authenticate image from DDR location 0x18000000...
>
> ivt_offset = 0x1000, ivt addr = 0x18001000
> ivt entry = 0x18000000, dcd = 0x00000000, csf = 0x18001020
> Dumping IVT
> .. @............
> ........ .......
> Dumping CSF Header
> ..PC...........P
> ................
> .......<........
> ...............8
>
> Calling authenticate_image in ROM
> ivt_offset = 0x1000
> start = 0x18000000
> bytes = 0x3060
> firmware: 'firmware-1'
> External data: dst=17800000, offset=3060, size=86138
> Image OS is U-Boot
> fdt: 'fdt-1'
> Can't get 'load' property from FIT 0x18000000, node: offset 464, name fdt-1 (FDT_ERR_NOTFOUND)
> External data: dst=17886140, offset=89198, size=ac00
> Can't get 'entry' property from FIT 0x18000000, node: offset 464, name fdt-1 (FDT_ERR_NOTFOUND)
> loadables: 'firmware-1'
> no string for index 1
> Jumping to U-Boot...
> SPL malloc() used 0x0 bytes (0 KB)
> image entry point: 0x
>
>
> U-Boot 2024.04-rc2-00025-g9e00b6993f-dirty (Feb 19 2024 - 13:17:31 +0100)
>
> CPU: Freescale i.MX6Q rev1.2 996 MHz (running at 792 MHz)
> CPU: Automotive temperature grade (-40C to 125C) at 35C
> Reset cause: POR
> Model: Freescale i.MX6 Quad SABRE Smart Device Board
> DRAM: 1 GiB
> Core: 94 devices, 23 uclasses, devicetree: separate
> WDT: Started watchdog@20c0000 with servicing every 1000ms (128s timeout)
> MMC: FSL_SDHC: 4, FSL_SDHC: 1, FSL_SDHC: 3
> Loading Environment from MMC... *** Warning - bad CRC, using default environment
>
> No panel detected: default to Hannstar-XGA
> Display: Hannstar-XGA (1024x768)
> In: serial
> Out: serial
> Err: serial
> SEC0: RNG instantiated
> Hit any key to stop autoboot: 0
> => hab_status
>
> Secure boot disabled
>
> HAB Configuration: 0xf0, HAB State: 0x66
> No HAB Events Found!
>
> But as only the FDT part of the FIT image is checked through HAB, U-Boot and DTB are only protected by FIT image hashes, right?
>
> Using fdtdump shows that crc32 is used as hash algorithm for FIT image which is a super weak one.
> I tried to pass another algo (sha256) using mkimage -o option but that doesn't work.
>
> ./tools/mkimage -f auto -A arm -T firmware -C none -O u-boot -a 0x17800000 -e 0x17800000 -p 0x0 -n "U-Boot 2024.04-rc2-00025-g9e00b6993f-dirty for mx6sabresd board" -E -b arch/arm/dts/imx6q-sabresd.dtb -b arch/arm/dts/imx6qp-sabresd.dtb -b arch/arm/dts/imx6dl-sabresd.dtb -d u-boot-nodtb.bin -o sha256 u-boot-dtb.img
>
> Is there any way to change U-Boot FIT image hash?
I believe these options are only used for signed FIT images (e.g. for
verified boot [1]). Since you are using an external signing process,
they have no effect. I suggest creating your FIT manually (e.g. -f
u-boot.its instead of -f auto). You should be able to specify the hashes
manually that way.
> I also try to use image format and force the HAB to verify the whole u-boot-dtb.img file by patching the FIT image size:
>
> image_size=$(stat -tc %s u-boot-dtb.img)
> printf "00000004: %08x" "$image_size" | xxd -r - u-boot-dtb.img
>
> SPL starts, authentication looks fine but the boot fails.
> Is there any chance to make it work or is it insane to try to use this format?
I have always just used verified boot for U-Boot and the kernel, and
only used vendor-specific stuff for SPL.
--Sean
[1] https://docs.u-boot.org/en/latest/usage/fit/verified-boot.html
[2] https://docs.u-boot.org/en/latest/usage/fit/source_file_format.html
[Embedded World 2024, SECO SpA]<https://www.messe-ticket.de/Nuernberg/embeddedworld2024/Register/ew24517689>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: HABv4 with SPL and u-boot-dtb.img on i.MX6
2024-02-20 16:29 ` Sean Anderson
@ 2024-02-22 8:05 ` Benjamin Lemouzy
0 siblings, 0 replies; 3+ messages in thread
From: Benjamin Lemouzy @ 2024-02-22 8:05 UTC (permalink / raw)
To: Sean Anderson; +Cc: u-boot
On Tue, 20 Feb 2024 11:29:53 -0500
Sean Anderson <sean.anderson@seco.com> wrote:
> On 2/20/24 04:50, Benjamin Lemouzy wrote:
> > Using fdtdump shows that crc32 is used as hash algorithm for FIT image which is a super weak one.
> > I tried to pass another algo (sha256) using mkimage -o option but that doesn't work.
> >
> > ./tools/mkimage -f auto -A arm -T firmware -C none -O u-boot -a 0x17800000 -e 0x17800000 -p 0x0 -n "U-Boot 2024.04-rc2-00025-g9e00b6993f-dirty for mx6sabresd board" -E -b arch/arm/dts/imx6q-sabresd.dtb -b arch/arm/dts/imx6qp-sabresd.dtb -b arch/arm/dts/imx6dl-sabresd.dtb -d u-boot-nodtb.bin -o sha256 u-boot-dtb.img
> >
> > Is there any way to change U-Boot FIT image hash?
>
> I believe these options are only used for signed FIT images (e.g. for
> verified boot [1]). Since you are using an external signing process,
> they have no effect. I suggest creating your FIT manually (e.g. -f
> u-boot.its instead of -f auto). You should be able to specify the hashes
> manually that way.
Using "fdtdump -s u-boot-dtb.img" output as reference to create a u-boot.its file, I now have a u-boot.itb file with sha256 hashes.
> > I also try to use image format and force the HAB to verify the whole u-boot-dtb.img file by patching the FIT image size:
> >
> > image_size=$(stat -tc %s u-boot-dtb.img)
> > printf "00000004: %08x" "$image_size" | xxd -r - u-boot-dtb.img
> >
> > SPL starts, authentication looks fine but the boot fails.
> > Is there any chance to make it work or is it insane to try to use this format?
>
> I have always just used verified boot for U-Boot and the kernel, and
> only used vendor-specific stuff for SPL.
That indeed a good idea but CONFIG_SPL_FIT_SIGNATURE and CONFIG_SPL_DM (as dependency) take a lot of space and SPL overflows i.MX6 OCRAM.
I finally succeed to make U-Boot check with HAB work using the new u-boot.itb image with the following signature format:
------- +-----------------------------+ <-- *load_address
^ | |
| | |
| | Image data |
Signed | | |
Data | | |
| +-----------------------------+
| | Padding Next Boundary |
| +-----------------------------+ <-- *ivt
v | Image Vector Table |
------- +-----------------------------+ <-- *csf
| |
| Command Sequence File (CSF) |
| |
+-----------------------------+
| Padding (optional) |
+-----------------------------+
I don't really understand what u-boot-dtb.img file is but it doesn't work with U-Boot CONFIG_IMX_HAB.
Thanks for help!
Benjamin
^ permalink raw reply [flat|nested] 3+ messages in thread
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2024-02-20 9:50 HABv4 with SPL and u-boot-dtb.img on i.MX6 Benjamin Lemouzy
2024-02-20 16:29 ` Sean Anderson
2024-02-22 8:05 ` Benjamin Lemouzy
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