Manufacturing Firmware

Testplan

Testpoints

Stage Name Tests Description
V3 manuf_cp_unlock_raw

Verify transition from RAW to TEST_UNLOCKED lc_state.

  • Pre-load OTP with RAW lc_state.
  • Bring device out of reset selecting the Life Cycle (LC) TAP interface using strap pins.

Perfom the following steps via LC TAP interface:

  • Switch to external clock via TRANSITION_CTRL.EXT_CLOCK_EN.
  • Provide RAW_UNLOCK.
  • Poll for lc_ctrl STATUS register for TRANSITION_SUCCESSFUL. Check for errors or timeout.
  • Perform reset by toggling the POR pin.
  • Verify the lc_state is TEST_UNLOCKED0.

The manufacturing environment is required to support test reruns whenever possible:

  • Verify that the RAW_UNLOCK process can be re-tried after failed or interrupted attempts.
V3 manuf_scrap

Verify transition from any state to SCRAP lc_state.

Manufacturing tests should be able to move the device from any lc_state into SCRAP state.

For each manufacturing lc_state s:

  • Pre-load OTP with s lc_state image.
  • Bring device out of reset selecting the Life Cycle (LC) TAP interface using strap pins.
  • Request transition to SCRAP state via LC TAP interface.
  • Perform reset by togglig the POR pin.
  • Check we are in SCRAP state via LC TAP interface.

The manufacturing environment is required to support test reruns whenever possible:

  • Verify that the transition to SCRAP mode can be re-tried after failed or interrupted attempts.
V3 manuf_cp_yield_test

Verify that it is possible to switch TAP interfaces while injecting external clock.

Verify that it is possible to access TAP interfaces while injecting an external clock. This test case is valid only in test life cycle states.

  • Pre-load OTP with TEST_UNLOCKED lc_state in pre-silicon environments. Advance to state in silicon.
  • Enable external clock injection.
  • Connect to CPU JTAG and perform register read/writes to memory/registers.
  • Switch to LC TAP by manipulating the strap pins.
  • Verify that read/writes to lc_ctrl work as expected.
V3 manuf_cp_ast_test_execution

Verify that the tester is able to load/exec test sequences into/from SRAM.

An expected pattern during manufacturing involves loading small program sequences into SRAM, and use them to run higher level operations such as configuring OTP values in the OTP hardware partition.

  • Pre-load OTP with TEST_UNLOCKED lc_state in pre-silicon environments. Advance to state in silicon.
  • Select CPU JTAG via strap pins.
  • Load program into SRAM to execute OTP word write sequences.
  • Trigger OTP writes to HW partition (e.g. device ID).
  • Perform reset by toggling POR pin.
  • Select CPU JTAG via strap pins.
  • Verify that OTP write was successful.
V3 manuf_cp_device_info_flash_wr

Verify that the tester is able to write to flash info pages.

During early manufacturing stages, the tester writes information for later use into flash info pages.

  • Pre-load OTP with TEST_UNLOCKED lc_state in pre-silicon environments. Advance to state in silicon.
  • Select CPU JTAG via strap pins.
  • Load program into SRAM to execute flash write sequences.
  • Write 32B to the isolated flash info partition. Verify unable to read back.

In silicon, a separate test program must perform the following additional operations. In pre-silicon, they can be part of the same program.

  • Switch to LC TAP at runtime.
  • Request transition to DEV or PROD state (test both cases).
  • Perform reset by toggling POR pin.
  • Verify isolated flash info partition expected data.
V3 manuf_cp_test_lock

Verify provisioning and use of unlock tokens.

In transit devices will need to be switched into TEST_LOCKED states to disable debug access and code execution. This test verifies that a TEST_UNLOCKED token can be provisioned as part of this process.

  • Pre-load OTP with TEST_UNLOCKED lc_state in pre-silicon environments. Advance to state in silicon.
  • Select CPU JTAG via strap pins.
  • Program TEST_UNLOCK_TOKEN in OTP transition via JTAG.
  • Select LC TAP via strap pins (at runtime).
  • Request transition into TEST_LOCKED state.
  • Perform reset by toggling POR pin.
  • Select LC TAP via strap pins.
  • Verify lc state.

Implement the following steps in a way in which it could be executed at a later time in silicon targets:

  • Load OTP state generted by previous steps.
  • Select LC TAP via strap pins.
  • Request transition to TEST_UNLCOKED by providing the TEST_UNLOCK_TOKEN provisioned in previous steps.
  • Perform reset by toggling POR pin.
  • Select LC TAP via strap pins.
  • Verify lc_state.

Repeat the same flow for the number of supported TEST_LOCK/UNLOCKED states.

V3 manuf_ft_exit_token

Verify provisioning and use of test exit token.

The test exit token is used to move the device from test mode into DEV, PROD or PROD_END state. This test also incorporates enabling of ROM execution before triggering the lc_state change.

  • Pre-load OTP with TEST_UNLOCKED lc_state in pre-silicon environments. Advance to state in silicon.
  • Select CPU JTAG via strap pins.
  • Program TEST_EXIT_TOKEN in OTP transition via JTAG.
  • Reset device by toggling POR pin.
  • Select CPU JTAG via strap pins.
  • Program CREATOR_SW_CFG_ROM_EXEC_EN in OTP via JTAG.
  • Select LC TAP via strap pins (at runtime).
  • Request transition into {pick one: DEV, PROD, PROD_END} state providing TEST_EXIT_TOKEN.
  • Perform reset by toggling POR pin.
  • Select LC TAP via strap pins.
  • Verify lc state.

After this test most of the following manuf_ft_* test cases can be loaded into flash via boostrap in silicon.

V3 manuf_ft_sku_individualization

Configure device fuses.

This includes configuration for most countermeasures and hardware options. It does not include configuration of the device identity and RMA token, which is done in the personalization step.

The test steps are expected to be executed from flash. In silicon, the program is loaded using the ROM bootstrap protocol. It is recommended to use the same approach on the FPGA, and enable it as a configuration option in DV.

  • Pre-load OTP with {pick one: DEV, PROD, PROD_END} lc_state in pre-silicon environments. Advance to state in silicon.
  • Load test program into flash and start execution.
  • Check device lc_state. Return error to the host if device in invalid state.
  • Configure the following OTP fuses to enable access to entropy:
    • EN_CSRNG_SW_APP_READ
    • EN_ENTROPY_SRC_FW_READ
    • EN_ENTROPY_SRC_FW_OVER
  • Configure remaining HW_CFG OTP fields:
    • DEVICE_ID
    • MANUF_STATE
  • Lock HW_CFG OPT partition.
  • Configure CREATOR_SW_CFG OTP words according to device SKU configuration.
  • Configure OWNER_SW_CFG OTP words according to device SKU configuration.
  • Perform reset trigered by software.
  • Initialize entropy_src in FIPS mode. Check health status after setting appropriate health test parameters. Configure SW csrng instance to generate enough data to configure the following OTP fields:
    • FLASH_ADDR_KEY_SEED
    • FLASH_DATA_KEY_SEED
    • SRAM_DATA_KEY_SEED
  • Lock SECRET1 partition.
  • Perform reset triggered by software.
  • Load test program again into flash and start execution.
  • Send response to host with test result serialized in JSON format.
  • Check status response on the host side.

Note: Tests are easier to integrate with Automated Test Equipment (ATE) if all device-host interfaces are unidirectional. This influences the type of physical interface selection (e.g. SPI versus UART). Make sure the interface design takes this constraint into consideration.

V3 manuf_ft_provision_rma_token_and_personalization

Provision RMA unlock token.

Provisioning of RMA_UNLOCK_TOKEN

The RMA_UNLOCK_TOKEN is used to take a device from a production ls_state (i.e. DEV, PROD) in to RMA state. RMA entry is conditional to flash erase, and it also triggers a diversification change in the key manager to ensure that user assets are not exposed to the manufacturer.

Since RMA enables debug interfaces in the chip, it is important to maintain the confidentiality of the RMA_UNLOCK_TOKEN. For this reason, asymmetric encryption is used to export the token.

The manufactuer is expected to maintain the RMA_UNLOCK_TOKEN decryption key in an offline HSM.

Personalization

The device is configured with a unique set of secrets, which once provisioned, are hidden from software. These secrets are use to as the root of the key derivation function in the key manager.

Test steps

Prep steps

  • Pre-load the OTP state with an image of an individualized device. See manuf_ft_sku_individualization for more details.
  • Check expected ls_state and OTP locked partitions (SECRET1, HW_CFG).
  • Initialize entropy source in FIPS mode. Check health status after setting appropriate health test parameters.

Device secrets

  • Instantiate the SW CSRNG, and configure it to generate data.
  • Configure the following OTP entries with data extracted from the CSRNG:
    • CREATOR_ROOT_KEY_SHARE0
    • CREATOR_ROOT_KEY_SHARE1
  • Configure the flash info secret partition with data extracted from the CSRNG.
  • Lock SECRET2 OTP partition.
  • Perform reset triggered by software.

RMA provisioning

  • Instantiate the SW CSRNG, and configure it to generate data.
  • Configure RMA_TOKEN in the OTP partition with data extracted from the CSRNG.
  • Encrypt RMA_TOKEN with asymmetric algorithm (e.g RSA-3072). The encrypted blob will be sent to the host in the result status.
  • Uninstantiate the sw CSRNG.

Device Identity

The OWNER_SW_CFG_ROM_KEYMGR_ROM_EXT_MEAS_EN OTP must be configured so that the attestation measurement can be provided in the manifest of the test program. This way the provisioning program is able to generate the key manager derivation matching the production ROM_EXT configuration.

TODO: Left details vague on purpose until we get the attestation flow reviewed.

  • Advance the keymgr to CREATOR_ROOT_KEY state.
  • Derive CREATOR attestation key pair.
  • Calculate SHA2 hash of the public key with the device secret provisionined in the manuf_cp_device_info_flash_wr test. The device secret is known by the provisioning appliance.
  • Disable the key manager.
  • Configure OWNER_SW_CFG_ROM_KEYMGR_ROM_EXT_MEAS_EN OTP to switch to attestation mode associated with the device SKU.

Result status

  • Send response to host with test result serialized in JSON format. The result must include the encrypted RMA_UNLOCK_TOKEN, the DEVICE_ID, the public attestation key and its hash.
V3 manuf_ft_load_transport_image

Load transport stack into flash.

Ensure the ROM is able to bootstrap the transport image. The transport image supports functionality such as full device attestation, and ownership transfer, which are required to enable device integration into a system.

  • Pre-load the OTP with an image of a personalized device. See manuf_ft_provision_rma_token_and_personalization for more details.
  • Bootstrap transport image.
  • Reset device by toggling POR pin.
  • Check device firmware version.
V3 manuf_ft_load_certificates

Load endorsed certificates.

Load device certificate endorsing the creator public key. The certificate is signed by the silicon creator.

TODO: This assumes the ROM_EXT supports a mechanism to update the certificate. TODO: Should the transport image contain silicon creator pubilc keys to be able to verify the certificate before install?

  • Pre-load the OTP with an image of a personalized device. See manuf_ft_provision_rma_token_and_personalization for more details.
  • The device flash should be loaded with the transprot image. See manuf_ft_load_transport_image for details.
  • The host sends a command to the device including the device certificate.
  • The device verifies that the certificate corresponds to its device key.
  • The certificate is then stored into a flash page (info versus regular flash TBD).
  • Send response to the host with test result.
V3 manuf_ft_eom

End of manufacturing.

This test requires the device to have completed the manuf_ft_load_certificates test.

  • The host sends a command to the device to trigger the end of manufacturing.
  • Final OTP configuration options are set.
  • Manufacturing functionality supported by the ROM_EXT and transport image will be disabled after reset.
  • Trigger software reset.
  • The host sends a command to ensure device is in post-manufacturing state.
V3 manuf_rma_entry

Verifies RMA entry.

In silicon, the entire process is executed in a secure environment in adherence to certification requirements.

  • Initialize device to reflect eom state. See manuf_ft_eom for more details.
  • Select LC TAP via strap pins.
  • Read DEVICE_ID via LC TAP interface.
  • Powerdown the device.

The Silicon Creator is expected to lookup the RMA_UNLOCK_TOKEN in a manufacturing database using the DEVICE_ID and decrypt it at an offline location. The token cannot leave the secure environment in unencrypted form at any time, implying that there is a way for the secure environment to handle the decryption operation.

  • Select LC TAP via strap pins.
  • Power on the device.

The following steps are performed via the LC TAP interface:

  • Read DEVICE_ID. Confirm expected response.
  • Load RMA_UNLOCK_TOKEN and request transition to RMA state.
  • Poll for status completion.
  • Reset device by toggling POR pin.

RMA entry will trigger a rotation of scrambling keys. It is recommended to either connect to the CPU JTAG to continue debug, or bootstrap the device with new a firmware image. Otherwise the ROM will fail to boot.