mstflint: Secure Firmware Update

A “Secure firmware update” is the ability of a device to verify digital signatures of new firmware binaries, in order to assure that only officially approved versions can be installed from the host, the network[1] or a Board Management Controller (BMC).

The firmware of devices with “secure firmware up date” functionality (secure FW), restricts access to specific commands and registers that can be used to modify the firmware binary image on the flash, as well as commands that can jeopardize security in general. Most notably, the commands and registers for random flash access are disabled.

Secure FW verifies new binaries before activating them, compared to legacy devices where this task is done by the update tool using direct flash access commands. In addition to signature verification, secure FW also checks that the binary is designated to the same device model, that the new firmware is also secured, and that the new FW version is not included in a forbidden versions blacklist. The firmware rejects binaries that do not match the verification criteria.

Secure FW utilizes the same ‘fail safe’ upgrade procedures, so events like power failure during update should not leave the device in an unstable state. The table below lists the impact of secure FW update on mstflint tools.

The following sections describe how Secure FW updates are performed.

Signing Binary Image Files

For firmware Secure purposes, you may sign the image file using the sign command. If you do not provide the sign command with a private key and UUID, the command will only compute SHA256 digest and add it to the image signature section. The sign command supports RSA keys with lengths of 2048 and 4096 bits.

• If you provide a private key with the length of 2048 bits, the command will compute SHA256 digest and encrypt it with the private key and add the result with the provided UUID to the appropriate image signature section.

• If you provide a private key with the length of 4096 bits, the command will compute SHA512 digest and encrypt it with the provided key and add the result with the provided UUID to the appropriate image signature.

You can sign with two keys in the same command by providing keys with lengths of 2048 and 4096 bits. The flags to be used for the first private key and uuid are “--private_key“ and “--key_uuid”, and for the second private and uuid use “--private_key2” and “–key_uuid2”.

The motivation for signing with two keys is to allow a firmware update from both firmwares, the one that supports only 2048bit keys and the one that supports 4096bit keys.

Examples:

            

            
# mstflint -i /tmp/image.bin sign --private_key privatekey.pem --key_uuid "e0129552-13ba-11e7-a990-0cc47a6d39d2"
        

            

            
# mstflint -i /tmp/image.bin sign --private_key privatekey_2048.pem --key_uuid "e0129552-13ba-11e7-a990-0cc47a6d39d2" --private_key2 privatekey_4096.pem --key_uuid2 "a0b43568-17cb-16e9-a990-0ff47a6d39e4"
        

To override the public keys section in a given binary image file, use set_public_key.

            

            
# mstflint -i /tmp/image.bin set_public_keys public_key.bin
        

To override the forbidden versions section in a given binary image file, use set_forbidden_versions.

            

            
# mstflint -i /tmp/image.bin set_forbidden_versions forbidden_versions.bin
        

When Secure Firmware is enabled, the mstflint output slightly changes due to the differences in the underlying NIC accessing methods. Some functionalities may be restricted according to the device security level.
mstflint query under secure mode:

            

            
# mstflint -d 41:00.0 q
Image type:      FS3
FW Version:      12.19.2278
FW Release Date: 7.6.2017
Description:     UID                GuidsNumber
Base GUID:       7cfe90030029205e   4
Base MAC:        00007cfe9029205e   4
Image VSD:
Device VSD:
PSID:            MT_2190110032
Security Attributes: secure-fw, dev
        

In secure firmware, a firmware update will be successful if an image is signed with a valid key that is recognized by the running firmware on the chip. for more information, please refer to Signing Binary Image Files.If the security type permits legacy flash access commands, the --no_fw_ctrl flag can be used to command the mstflint to work in the non firmware controlled mode. This means that all the non-secure functionality will be supported using this flag, and the burn flow will work without requiring a signed image.Example:

            

            
# mstflint -d 41:00.0 --no_fw_ctrl q
Image type:      FS3
FW Version:      12.19.2096
FW Release Date: 26.3.2017
Description:     UID                 GuidsNumber
Base GUID:       248a07030094050c    4
Base MAC:        0000248a0794050c    4
Image VSD:
Device VSD:
PSID:            MT_2170110021
        

The following procedure is intended to be implemented by customers who want to use their keys to sign a secured firmware.

1. Set the public keys in a given firmware image:
   

   1. Generate a binary file that contains 8 public keys.
      You can use mstconfig command xml2bin to generate the file:

      1. To generate 2048 bits public keys:

         1. Run: mstconfig gen_tlvs_file output.txt.

         2. Open the output.txt.

         3. Go to the line starting with "file_public_key" and change the 0 to 1.

         4. Save the file and exit.

         5. Run: mstconfig gen_xml_template output.txt output.xml

         6. Open the output.xml.

         7. Duplicate the xml node "file_public_key" so the file has 8 copies, for each node fill it as follows:
            • cs_token_en = 0
            • fw_en = 1
            • mlnx_nvconf_en = 1
            • vendor_nvconf_en = 1
            • auth_type: 0x3 for 2048 bits keys and 0x4 for 4096 bits keys.
            Example for public_key_exp, keypair_uuid, key:

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            <public_key_exp>4083403379</public_key_exp>
            <keypair_uuid>5A7A2B2A87DB7416</keypair_uuid>
              <key> f8000003000000000000000000010001c459afea005911e797dc000000000000b8168ba624e5cac81d491f48c6a3b8f1a816cb7dea789d770893b0fb5abeb67f7a8d19ad8d4203dd8b85b3faaaf96187b116eb1c5d3f3517c3ce8b4422395f2e43ccb286d4bc4474c8385e857349f35be3094f25ccbd71c209c6531f0d8bcaacdbbf14af58809e8937e4db424b3d0c48e0cae7b89f53f797b9e24335900448466b0e5182e3a94c31e18487f8fe367862c8a70e8c7007d2400760461bbb36470a26d6db13d2e63d137d67cd449c0788c307ce2dbc3f580ec7207cdb856472520ee956912cfaf77e6e793f620d6e362fa13da036003f85ae8dbb22d4b314ceb64c
              </key>
                    

            Warning

            You can have spaces between the bytes: f8 00 00 03, or you can have multiple lines.
            The order of the bytes is the same as the output of openssl file, Therefore, you can take the key as is from the openssl file.

         8. Save and Exit.

         9. Run: mstconfig xml2bin output.xml output.bin.

      2. To generate 4096 bits public keys, please follow the same steps as above, but use "file_public_key_4096" instead of "file_public_key".
         For further information, see mstconfig xml2bin Command.

   2. Set the key's binary file in the firmware image using the mstflint set_public_keys command.
      For further information, see Setting a “Public Keys” Section in a Binary Image File.

2. If there is need to modify the definition for the forbidden_versions in a given firmware image then:

   1. Generate a binary file that contains the forbidden versions.
      You can use the mstconfig command xml2bin to generate it according to the steps described in Step a above (Generate a binary file that contains 8 public keys).
      An example for forbidden versions xml node:

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      <nv_forbidden_versions>
      <creation_time_day>18</creation_time_day>
      <creation_time_month>6</creation_time_month>
      <creation_time_year>7e2</creation_time_year>
      <creation_time_second>d</creation_time_second>
      <creation_time_minute>19</creation_time_minute>
      <creation_time_hour>12</creation_time_hour>
      <min_allowed_fw_version>0</min_allowed_fw_version>
      <forbidden_fw_version index="0">53:1f:0d06</forbidden_fw_version>
      <forbidden_fw_version index="1..31">0</forbidden_fw_version>
      </nv_forbidden_versions>
              

   2. Set the key's binary file in the firmware image using the mstflint set_forbidden_versions command.
      For further information, see Setting a "Forbidden Versions" Section in a Binary Image File.

3. Sign the firmware image with a private key.

   Warning

   Please notice that signing the image must be after setting the public keys, and the forbidden versions. For further information, see Secure Firmware Update.

   1. Run the mstflint sign command.

      Warning

      To sign with a 2048 bits private key only, make sure that the firmware image does not contain a 4096 bits key signature.
      Run the mstflint set_public_keys command with a 4096 bits keys section filled with zeros and then sign with a 2048 bits private key.
      For further information, see Signing Binary Image Files.

      Warning

      To sign with 4096 bits private key only, run the mstflint set_public_keys command with a 2048 bits keys section filled with zeros and then sign with the a 4096 bits private key.
      For further information, see Signing Binary Image Files.