Difference between revisions of "How to use U-Boot stm32key command"

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Applicable for

STM32MP13x lines, STM32MP15x lines

1 Purpose[edit]

In this article, the stm32key U-Boot command is used to illustrate and experiment the steps to provision the keys in the correct OTP needed to activate secure boot features: authentication and encryption.

It also allows to directly set the device to CLOSED state.

1.1 Prerequisite[edit]

All the required keys have to be generated to provision the OTP.

Warning

Make sure that a device with Secure boot enabled is used: this is mentioned in the chip part number, for STM32MP13 and STM32MP15, otherwise the device will become permanently unusable.

2 stm32key command[edit]

U-Boot in OpenSTLinux embeds a stm32key command that can be called from U-Boot command line interface to manage the keys in OTPs.

 
 stm32key help
 stm32key - Manage key on STM32
 
 Usage:
 stm32key list : list the supported key with description
 stm32key select [<key>] : Select the key identified by <key> or display the key used for read/fuse command
 stm32key read [<addr> | -a ] : Read the curent key at <addr> or current / all (-a) key in OTP
 stm32key fuse [-y] <addr> : Fuse the current key at addr in OTP
 stm32key close [-y] : Close the device, force use of PKH stored in OTP

The optional option -y is used to skip the confirmation message.

The name of the used <key> is

for STM32MP13x lines : PKHTH for authentication and EDMK for encryption

 
 stm32key list
 PKHTH : Hash of the 8 ECC Public Keys Hashes Table (ECDSA is the authentication algorithm)
 	OTP24..32
 EDMK : Encryption/Decryption Master Key"
 	OTP92..95

for STM32MP15x lines : PKH for authentication

 
 stm32key list
 PKH : Hash of the ECC Public Key (ECDSA is the authentication algorithm)
 	OTP24..32

3 Authentication keys provisioning[edit]

The key provisioning is the first step to enable the authentication: burn the keys in OTPs with the key hash output file from STM32 KeyGen.

3.1 Select keys[edit]

Key is selected with the command sm32key select <key>, with <key>=

PKHTH for STM32MP13x lines

 
 sm32key select PKHTH
 PKHTH selected

PKH for STM32MP15x lines

 
 sm32key select PKH
 PKH selected

3.2 Load keys file in DDR[edit]

The keys hash file, output file from STM32 KeyGen, must be available in DDR before proceeding the stm32key command;
this file is loaded at 0xc0000000 in the next examples.

The file publicKeysHash.bin can be loaded from a filesystem partition on a storage device by using the load command. For example, the file publicKeysHash.bin is in the bootfs (partition 7) on SD card (mmc0):

 
 load mmc 0:7 0xc0000000 publicKeysHash.bin
 32 bytes read in 50 ms (0 Bytes/s)

3.3 Verify keys file in DDR[edit]

Once the publicKeysHash.bin file is loaded in DDR, you can verify the content of the file with the command:

 
 stm32key read 0xc0000000

Example for STM32MP13x lines with PKHTH

 stm32key read 0xC0000000
 Read PKHTH at 0xc0000000
 PKHTH OTP 24: [c0000000] 27051956
 PKHTH OTP 25: [c0000004] b56aef2d
 PKHTH OTP 26: [c0000008] 6215263c
 PKHTH OTP 27: [c000000c] 00000439
 PKHTH OTP 28: [c0000010] 00000000
 PKHTH OTP 29: [c0000014] 00000000
 PKHTH OTP 30: [c0000018] 72429173
 PKHTH OTP 31: [c000001c] 05020600

Example for STM32MP15x lines with PKH

 stm32key read 0xC0000000
 Read PKH at 0xc0000000
 PKH OTP 24: [c0000000] 27051956
 PKH OTP 25: [c0000004] b56aef2d
 PKH OTP 26: [c0000008] 6215263c
 PKH OTP 27: [c000000c] 00000439
 PKH OTP 28: [c0000010] 00000000
 PKH OTP 29: [c0000014] 00000000
 PKH OTP 30: [c0000018] 72429173
 PKH OTP 31: [c000001c] 05020600

3.4 Key provisioning[edit]

To write and lock the keys in OTP, you use the command:

 
 stm32key fuse 0xc0000000

Warning

Verify keys before to confirm the operation, it is a irreversible operation !

3.5 Verify keys file in OTP[edit]

After the previous command, the device contains the keys to authenticate images and it can be verified with the command:

 
 stm32key read

Result for STM32MP13x lines with PKHTH

 stm32key read
 PKHTH OTP 24: 27051956 lock : 50000000
 PKHTH OTP 25: b56aef2d lock : 50000000
 PKHTH OTP 26: 6215263c lock : 50000000
 PKHTH OTP 27: 00000439 lock : 50000000
 PKHTH OTP 28: 00000000 lock : 50000000
 PKHTH OTP 29: 00000000 lock : 50000000
 PKHTH OTP 30: 72429173 lock : 50000000
 PKHTH OTP 31: 05020600 lock : 50000000

Result for STM32MP15x lines with PKH

 stm32key read
 PKH OTP 24: 27051956 lock : 50000000
 PKH OTP 25: b56aef2d lock : 50000000
 PKH OTP 26: 6215263c lock : 50000000
 PKH OTP 27: 00000439 lock : 50000000
 PKH OTP 28: 00000000 lock : 50000000
 PKH OTP 29: 00000000 lock : 50000000
 PKH OTP 30: 72429173 lock : 50000000
 PKH OTP 31: 05020600 lock : 50000000

4 Encryption Decryption Master Key provisioning[edit]

The EDMK key provisioning is the first step to enable the image decryption.

It is only available on STM32MP13x lines .

4.1 Select EDMK[edit]

Key is selected with the command sm32key select <key>, with <key>=

EDMK for STM32MP13x lines

 
 stm32key select EDMK
 EDMK selected

4.2 Load EDMK file in DDR[edit]

The keys file must be available in DDR before proceeding the stm32key command;
this file is loaded at 0xc0000000 in the next examples.

The file edmk.bin can be loaded from a filesystem partition on a storage device by using the load command. For example, the file edmk.bin is in the bootfs (partition 7) on SD card (mmc0):

 
 load mmc 0:7 0xc0000000 edmk.bin
 32 bytes read in 50 ms (0 Bytes/s)

4.3 Verify EDMK in DDR[edit]

Then you can verify the content of keys files loaded in DDR with the command: sm32key read <addr>

Result for STM32MP13x lines with EDMK and <addr>=0xc0000000

 
 stm32key read 0xc0000000 
  Read EDMK at 0xc0000000
  EDMK OTP 92: [c0000000] 27051956
  EDMK OTP 93: [c0000004] b56aef2d
  EDMK OTP 94: [c0000008] 6215263c
  EDMK OTP 95: [c000000c] 00000439

4.4 EDMK provisioning[edit]

To write and lock the EDMK in OTP, you use the command with the same address:

 
 stm32key fuse 0xc0000000

Warning

Verify keys before to confirm the operation, it is a irreversible operation !

4.5 Verify EDMK in OTP[edit]

After the previous command, the device contains the keys to decrypt the images and it can be verified with the command:

 
 stm32key read

Result for STM32MP13x lines with EDMK

 stm32key read
 EDMK OTP 92: 00000000 lock : 50000000
 EDMK OTP 93: 00000000 lock : 50000000
 EDMK OTP 94: 00000000 lock : 50000000
 EDMK OTP 95: 00000000 lock : 50000000

Warning the content of the key can't be read, it is masked, but the lock property can be verified to ensure the key as been written.

5 Closing the device[edit]

Once the authentication process is confirmed in ROM code and in TF-A, the device can be closed to ensure that only signed images can be used.

This operation is perform with the U-Boot command:

 
 stm32key close

Warning

This must not be done on STM32MP13 or STM32MP15 part numbers without Secure boot enabled, otherwise the chip will be bricked and could not be used anymore

{{ApplicableFor
|MPUs list=STM32MP13x, STM32MP15x
|MPUs checklist=STM32MP13x, STM32MP15x
}}
__TOC__
== Purpose ==
In this article, the <code>stm32key</code> U-Boot command is used to '''illustrate''' and '''experiment''' the steps to provision the [[How_to_secure_STM32_MPU#STM32MPU_keys|keys]] in the correct OTP needed to activate [[How_to_secure_STM32_MPU#Secure_Boot|secure boot]] features: authentication and encryption.

It also allows to directly set the device to [[How_to_secure_STM32_MPU#Device_life_cycle|'''CLOSED''']] state.

=== Prerequisite ===

All the required [[How_to_secure_STM32_MPU#STM32MPU_keys|keys]] have to be generated to provision the OTP.

{{Warning| Make sure that a device with Secure boot enabled is used: this is mentioned in the chip part number, for [[STM32MP13_microprocessor#Part_number_codification|STM32MP13]] and [[STM32MP15_microprocessor#Part_number_codification|STM32MP15]], otherwise the device will become permanently unusable.}}

== stm32key command ==

U-Boot in OpenSTLinux embeds a <code>stm32key</code> command that can be called from [[U-Boot_overview#U-Boot command line interface (CLI)|U-Boot command line interface]] to manage the keys in OTPs.

  {{U-Boot$}} stm32key help
  stm32key - Manage key on STM32

  Usage:
  stm32key list : list the supported key with description
  stm32key select [{{HighlightParam|<key>}}] : Select the key identified by <key> or display the key used for read/fuse command
  stm32key read [<addr> | -a ] : Read the curent key at <addr> or current / all (-a) key in OTP
  stm32key fuse [-y] <addr> : Fuse the current key at addr in OTP
  stm32key close [-y] : Close the device, force use of PKH stored in OTP

The optional option <code>-y</code> is used to skip the confirmation message.

The name of the used {{HighlightParam|<key>}} is 
* for {{MicroprocessorDevice | device=13}}: {{Highlight|PKHTH}} for authentication and {{Highlight|EDMK}} for encryption
  {{U-Boot$}} stm32key list
  {{Highlight|PKHTH}} : Hash of the 8 ECC Public Keys Hashes Table (ECDSA is the authentication algorithm)
  	OTP24..32
  {{Highlight|EDMK}} : Encryption/Decryption Master Key"
  	OTP92..95
* for {{MicroprocessorDevice | device=15}}: {{Highlight|PKH}} for authentication
  {{U-Boot$}} stm32key list
  {{Highlight|PKH}} : Hash of the ECC Public Key (ECDSA is the authentication algorithm)
  	OTP24..32

==Authentication keys provisioning==

The [[How_to_secure_STM32_MPU#Provisioning|key provisioning]] is the first step to enable the authentication: burn the keys in OTPs with the key hash output file from [[KeyGen_tool|STM32 KeyGen]].

===Select keys===
Key is selected with the command <code>sm32key select {{HighlightParam|<key>}}</code>, with {{HighlightParam|<key>}}=

:* {{Highlight|PKHTH}} for {{MicroprocessorDevice | device=13}}
  {{U-Boot$}} sm32key select {{Highlight|PKHTH}}
  PKHTH selected

:* {{Highlight|PKH}} for {{MicroprocessorDevice | device=15}}
  {{U-Boot$}} sm32key select {{Highlight|PKH}}
  PKH selected

===Load keys file in DDR===

The keys hash file, output file from [[KeyGen_tool|STM32 KeyGen]], must be available in DDR before proceeding the <code>stm32key</code> command;<br/>this file is loaded at {{HighlightParam|0xc0000000}} in the next examples.
<div class="mw-collapsible  mw-collapsed">

The file {{Highlight|publicKeysHash.bin}} can be loaded from a filesystem partition on a storage device by using the <code>load</code> command.
For example, the file {{Highlight|publicKeysHash.bin}} is in the  bootfs (partition {{HighlightParam|7}}) on SD card ({{HighlightParam|mmc0}}):

  {{U-Boot$}} load {{HighlightParam|mmc}} {{HighlightParam|0}}:{{HighlightParam|7}} {{HighlightParam|0xc0000000}} {{Highlight|publicKeysHash.bin}}
  32 bytes read in 50 ms (0 Bytes/s)</div></div>


===Verify keys file in DDR===

Once the {{Highlight|publicKeysHash.bin}} file is loaded in DDR, you can verify the content of the file with the command:

  {{U-Boot$}} stm32key read {{HighlightParam|0xc0000000}} 

Example for {{MicroprocessorDevice | device=13}} with {{Highlight|PKHTH}}
 {{U-Boot$}} stm32key read 0xC0000000
  Read PKHTH at 0xc0000000
  PKHTH OTP 24: [c0000000] 27051956
  PKHTH OTP 25: [c0000004] b56aef2d
  PKHTH OTP 26: [c0000008] 6215263c
  PKHTH OTP 27: [c000000c] 00000439
  PKHTH OTP 28: [c0000010] 00000000
  PKHTH OTP 29: [c0000014] 00000000
  PKHTH OTP 30: [c0000018] 72429173
  PKHTH OTP 31: [c000001c] 05020600

Example for {{MicroprocessorDevice | device=15}} with {{Highlight|PKH}}

 {{U-Boot$}} stm32key read 0xC0000000
  Read PKH at 0xc0000000
  PKH OTP 24: [c0000000] 27051956
  PKH OTP 25: [c0000004] b56aef2d
  PKH OTP 26: [c0000008] 6215263c
  PKH OTP 27: [c000000c] 00000439
  PKH OTP 28: [c0000010] 00000000
  PKH OTP 29: [c0000014] 00000000
  PKH OTP 30: [c0000018] 72429173
  PKH OTP 31: [c000001c] 05020600

===Key provisioning===

To write and lock the keys in OTP, you use the command:

  {{U-Boot$}} stm32key fuse {{HighlightParam|0xc0000000}} 

{{Warning| Verify keys before to confirm the operation, it is a irreversible operation !}}

===Verify keys file in OTP===

After the previous command, the device contains the keys to authenticate images and it can be verified with the command:

  {{U-Boot$}} stm32key read

Result for {{MicroprocessorDevice | device=13}} with {{Highlight|PKHTH}}

 {{U-Boot$}} stm32key read
  PKHTH OTP 24: 27051956 lock : 50000000
  PKHTH OTP 25: b56aef2d lock : 50000000
  PKHTH OTP 26: 6215263c lock : 50000000
  PKHTH OTP 27: 00000439 lock : 50000000
  PKHTH OTP 28: 00000000 lock : 50000000
  PKHTH OTP 29: 00000000 lock : 50000000
  PKHTH OTP 30: 72429173 lock : 50000000
  PKHTH OTP 31: 05020600 lock : 50000000

Result for {{MicroprocessorDevice | device=15}} with {{Highlight|PKH}}

 {{U-Boot$}} stm32key read
  PKH OTP 24: 27051956 lock : 50000000
  PKH OTP 25: b56aef2d lock : 50000000
  PKH OTP 26: 6215263c lock : 50000000
  PKH OTP 27: 00000439 lock : 50000000
  PKH OTP 28: 00000000 lock : 50000000
  PKH OTP 29: 00000000 lock : 50000000
  PKH OTP 30: 72429173 lock : 50000000
  PKH OTP 31: 05020600 lock : 50000000

==Encryption Decryption Master Key provisioning==

The [[How_to_secure_STM32_MPU#Provisioning|EDMK key provisioning]] is the first step to enable the image decryption.

It is only available on {{MicroprocessorDevice | device=13}}.

===Select EDMK===
Key is selected with the command <code>sm32key select {{HighlightParam|<key>}}</code>, with {{HighlightParam|<key>}}=

:* {{Highlight|EDMK}} for {{MicroprocessorDevice | device=13}}
  {{U-Boot$}} stm32key select {{Highlight|EDMK}}
  EDMK selected

===Load EDMK file in DDR===

The keys file must be available in DDR before proceeding the <code>stm32key</code> command;<br/>this file is loaded at {{HighlightParam|0xc0000000}} in the next examples.
<div class="mw-collapsible  mw-collapsed">

The file {{Highlight|edmk.bin}} can be loaded from a filesystem partition on a storage device by using the <code>load</code> command.
For example, the file {{Highlight|edmk.bin}} is in the bootfs (partition {{HighlightParam|7}}) on SD card ({{HighlightParam|mmc0}}):

  {{U-Boot$}} load {{HighlightParam|mmc}} {{HighlightParam|0}}:{{HighlightParam|7}} {{HighlightParam|0xc0000000}} {{Highlight|edmk.bin}}
  32 bytes read in 50 ms (0 Bytes/s)</div></div>


===Verify EDMK in DDR===

Then you can verify the content of keys files loaded in DDR with the command: <code>sm32key read {{HighlightParam|<addr>}}</code>


Result for {{MicroprocessorDevice | device=13}} with {{Highlight|EDMK}} and <addr>=0xc0000000
  {{U-Boot$}} stm32key read {{HighlightParam|0xc0000000}} 
   Read EDMK at 0xc0000000
   EDMK OTP 92: [c0000000] 27051956
   EDMK OTP 93: [c0000004] b56aef2d
   EDMK OTP 94: [c0000008] 6215263c
   EDMK OTP 95: [c000000c] 00000439

===EDMK provisioning===

To write and lock the EDMK in OTP, you use the command with the same address:

  {{U-Boot$}} stm32key fuse {{HighlightParam|0xc0000000}}

{{Warning| Verify keys before to confirm the operation, it is a irreversible operation !}}

===Verify EDMK in OTP===

After the previous command, the device contains the keys to decrypt the images and it can be verified with the command:

  {{U-Boot$}} stm32key read

Result for {{MicroprocessorDevice | device=13}} with {{Highlight|EDMK}}
 {{U-Boot$}} stm32key read
  EDMK OTP 92: 00000000 lock : {{HighlightParam|50000000}}
  EDMK OTP 93: 00000000 lock : {{HighlightParam|50000000}}
  EDMK OTP 94: 00000000 lock : {{HighlightParam|50000000}}
  EDMK OTP 95: 00000000 lock : {{HighlightParam|50000000}}

Warning the content of the key can't be read, it is masked, but the lock property can be verified to ensure the key as been written.

==Closing the device==

Once the authentication process is confirmed in [[How_to_secure_STM32_MPU#ROM_code_secure_boot_validation|ROM code]] and in TF-A, the device can be [[How_to_secure_STM32_MPU#Device_life_cycle|closed]] to ensure that {{Highlight|only signed images}} can be used.

[[How_to_secure_STM32_MPU#Close_the_device|This operation]] is perform with the U-Boot command:

  {{U-Boot$}} stm32key close

{{Warning| This must not be done on [[STM32MP13_microprocessor#Security_and_Cortex-A7_frequency|STM32MP13]] or [[STM32MP15_microprocessor#Security_and_Cortex-A7_frequency|STM32MP15]] part numbers without '''Secure boot enabled''', otherwise the chip will be bricked and could not be used anymore}}
<noinclude>

[[Category:How to populate boards]]
[[Category:U-Boot|U-Boot - 9]]{{PublicationRequestId | No TLMS yet | 2022-08-29 | TLMS to be entered by NSA}}</noinclude>

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Difference between revisions of "How to use U-Boot stm32key command"

Contents

1 Purpose[edit]

1.1 Prerequisite[edit]

2 stm32key command[edit]

3 Authentication keys provisioning[edit]

3.1 Select keys[edit]

3.2 Load keys file in DDR[edit]

3.3 Verify keys file in DDR[edit]

3.4 Key provisioning[edit]

3.5 Verify keys file in OTP[edit]

4 Encryption Decryption Master Key provisioning[edit]

4.1 Select EDMK[edit]

4.2 Load EDMK file in DDR[edit]

4.3 Verify EDMK in DDR[edit]

4.4 EDMK provisioning[edit]

4.5 Verify EDMK in OTP[edit]

5 Closing the device[edit]

Manage page

Toolbox

QR code

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