Raspberry Pi 4 - secure boot

This directory contains the latest stable versions of the bootloader EEPROM and recovery.bin files that support secure-boot.

Steps for enabling secure boot:

Optional. Specify the private key file in an environment variable.

Alternatively, specify the path when invoking the helper scripts.

export KEY_FILE="${HOME}/private.pem"

Optional. Customize the EEPROM config.

Custom with the desired bootloader settings. See: Bootloader configuration

Setting SIGNED_BOOT=1 instructs the bootloader to only load the OS from boot.img and to verify it against the signature in boot.sig. If secure-boot is enabled in OTP then the bootloader then SIGNED_BOOT is implicitly set to 1 and this cannot be disabled.

Generate the signed bootloader image

cd secure-boot-recovery
../tools/update-pieeprom.sh -k "${KEY_FILE}"

pieeprom.bin can then be flashed to the bootloader EEPROM via rpiboot.

Program secure-boot mode

Secure boot is implemented by programming the hash of the customer public key into the SoC OTP memory.

Once set:-

* The bootloader will only load OS images signed with the customer private key. * The EEPROM configuration file must be signed with the customer private key. * It is not possible to downgrade to an old version of the bootloader that doesn't support secure boot.

WARNING: This operation cannot be undone and the key hash cannot be changed.

To enable this edit the config.txt file in this directory and set program_pubkey=1

Disabling VideoCore JTAG

VideoCore JTAG may be permanently disabled by setting program_jtag_lock=1 in config.txt. This option has no effect unless secure-boot has been enabled.

See default secure-boot-recovery config.txt file.

Program the EEPROM image using rpiboot

* Power off CM4 * Set nRPIBOOT jumper and remove EEPROM WP protection * If possible connect a UART to the CM4 and capture the output for debug * Power ON CM4

cd secure-boot-recovery
mkdir -p metadata
../rpiboot -d . -j metadata

Example UART output

148.84 Verify BOOT EEPROM
148.85 Reading EEPROM: 524288 bytes 0xc0b60000
148.35 645ms
149.89 BOOT-EEPROM: UPDATED
149.08 secure_boot_provision program_pubkey 1
149.09 bootconf.sig
149.09 hash: b503f8ad7f8aea93a272a5ba5248cc5222d0c55af28a4345d0a496bdba9d16bf
149.10 rsa2048: 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
149.14 RSA verify
149.81 rsa-verify pass (0x0)
149.18 Public key hash 8251a63a2edee9d8f710d63e9da5d639064929ce15a2238986a189ac6fcd3cee
149.19 OTP-WR: boot-mode 000048b0
149.19 OTP-WR: boot-mode 000048b0
149.19 OTP-WR: flags 00000081
149.19 Write OTP key
149.22 OTP updated for key 8251a63a2edee9d8f710d63e9da5d639064929ce15a2238986a189ac6fcd3cee
149.23 Revoke development key

Metadata

Metadata output is enabled by default to stdout. Optional argument can be used to specify writing a JSON file to the given directory. This can be useful for debug or for storing in a provisioning database.

If secure-boot is enabled then the CUSTOMER_KEY_HASH field will be non-zero.

Example metadata file contents written to metadata/SERIAL_NUMBER.json:

{
        "MAC_ADDR": "d8:3a:dd:05:ee:78",
        "EEPROM_UPDATE": "success",
        "EEPROM_HASH": "dfc8ef2c77b8152a5cfa008c2296246413fd580fdc26dfacd431e348571a2137",
        "SECURE_BOOT_PROVISION": "success",
        "CUSTOMER_KEY_HASH": "8251a63a2edee9d8f710d63e9da5d639064929ce15a2238986a189ac6fcd3cee",
        "BOOT_ROM": "0000c8b0",
        "BOARD_ATTR": "00000000",
        "USER_BOARDREV": "c03141",
        "JTAG_LOCKED": "0",
        "ADVANCED_BOOT": "0000e8e8"
}