1Building FIP images with support for Trusted Board Boot 2======================================================= 3 4Trusted Board Boot primarily consists of the following two features: 5 6- Image Authentication, described in :ref:`Trusted Board Boot`, and 7- Firmware Update, described in :ref:`Firmware Update (FWU)` 8 9The following steps should be followed to build FIP and (optionally) FWU_FIP 10images with support for these features: 11 12#. Fulfill the dependencies of the ``mbedtls`` cryptographic and image parser 13 modules by checking out a recent version of the `mbed TLS Repository`_. It 14 is important to use a version that is compatible with TF-A and fixes any 15 known security vulnerabilities. See `mbed TLS Security Center`_ for more 16 information. See the :ref:`Prerequisites` document for the appropriate 17 version of mbed TLS to use. 18 19 The ``drivers/auth/mbedtls/mbedtls_*.mk`` files contain the list of mbed TLS 20 source files the modules depend upon. 21 ``include/drivers/auth/mbedtls/mbedtls_config.h`` contains the configuration 22 options required to build the mbed TLS sources. 23 24 Note that the mbed TLS library is licensed under the Apache version 2.0 25 license. Using mbed TLS source code will affect the licensing of TF-A 26 binaries that are built using this library. 27 28#. To build the FIP image, ensure the following command line variables are set 29 while invoking ``make`` to build TF-A: 30 31 - ``MBEDTLS_DIR=<path of the directory containing mbed TLS sources>`` 32 - ``TRUSTED_BOARD_BOOT=1`` 33 - ``GENERATE_COT=1`` 34 35 By default, this will use the Chain of Trust described in the TBBR-client 36 document. To select a different one, use the ``COT`` build option. 37 38 If using a custom build of OpenSSL, set the ``OPENSSL_DIR`` variable 39 accordingly so it points at the OpenSSL installation path, as explained in 40 :ref:`Build Options`. In addition, set the ``LD_LIBRARY_PATH`` variable 41 when running to point at the custom OpenSSL path, so the OpenSSL libraries 42 are loaded from that path instead of the default OS path. Export this 43 variable if necessary. 44 45 In the case of Arm platforms, the location of the ROTPK must also be 46 specified at build time. The following locations are currently supported (see 47 ``ARM_ROTPK_LOCATION`` build option): 48 49 - ``ARM_ROTPK_LOCATION=regs``: the ROTPK hash is obtained from the Trusted 50 root-key storage registers present in the platform. On Juno, these 51 registers are read-only. On FVP Base and Cortex models, the registers 52 are also read-only, but the value can be specified using the command line 53 option ``bp.trusted_key_storage.public_key`` when launching the model. 54 On Juno board, the default value corresponds to an ECDSA-SECP256R1 public 55 key hash, whose private part is not currently available. 56 57 - ``ARM_ROTPK_LOCATION=devel_rsa``: the ROTPK is a hash of the 58 RSA public key corresponding to the private key specified by 59 ``ROT_KEY``. If ``ROT_KEY`` is not specified, the private key is 60 the development key ``plat/arm/board/common/rotpk/arm_rotprivk_rsa.pem``. 61 There are also 3k and 4k RSA development keys in ``plat/arm/board/common/rotpk/``. 62 The hashing algorithm is selected by ``HASH_ALG``; sha256 is used if 63 ``HASH_ALG`` is not specified. 64 65 - ``ARM_ROTPK_LOCATION=devel_ecdsa``: the ROTPK is a hash of the 66 ECDSA public key corresponding to the private key specified by 67 ``ROT_KEY``. If ``ROT_KEY`` is not specified, the private key is 68 the development key ``plat/arm/board/common/rotpk/arm_rotprivk_ecdsa.pem`` by default, 69 a 384 bit key ``plat/arm/board/common/rotpk/arm_rotprivk_ecdsa_secp384r1.pem`` also exists, 70 and can be specified by ``ROT_KEY``. The hashing algorithm is selected by ``HASH_ALG``; 71 sha256 is used if ``HASH_ALG`` is not specified. 72 73 - ``ARM_ROTPK_LOCATION=devel_full_dev_rsa_key``: the ROTPK is an unhashed 74 RSA public key corresponding to the private key specified by ``ROT_KEY``. 75 If ``ROT_KEY`` is not specified, the private key is the development key 76 ``plat/arm/board/common/rotpk/arm_rotprivk_rsa.pem``. There are also 77 3k and 4k RSA development keys in ``plat/arm/board/common/rotpk/``. 78 79 - ``ARM_ROTPK_LOCATION=devel_full_dev_ecdsa_key``: the ROTPK is an unhashed 80 RSA public key corresponding to the private key specified by ``ROT_KEY``. 81 If ``ROT_KEY`` is not specified, the private key is the development key 82 ``plat/arm/board/common/rotpk/arm_rotprivk_ecdsa.pem``, a 384 bit key 83 ``plat/arm/board/common/rotpk/arm_rotprivk_ecdsa_secp384r1.pem`` also exists, 84 and can be specified by ``ROT_KEY``. 85 86 Example of command line using RSA development keys: 87 88 .. code:: shell 89 90 MBEDTLS_DIR=<path of the directory containing mbed TLS sources> \ 91 make PLAT=<platform> TRUSTED_BOARD_BOOT=1 GENERATE_COT=1 \ 92 ARM_ROTPK_LOCATION=devel_rsa \ 93 ROT_KEY=plat/arm/board/common/rotpk/arm_rotprivk_rsa.pem \ 94 BL33=<path-to>/<bl33_image> OPENSSL_DIR=<path-to>/<openssl> \ 95 all fip 96 97 The result of this build will be the bl1.bin and the fip.bin binaries. This 98 FIP will include the certificates corresponding to the selected Chain of 99 Trust. These certificates can also be found in the output build directory. 100 101#. The optional FWU_FIP contains any additional images to be loaded from 102 Non-Volatile storage during the :ref:`Firmware Update (FWU)` process. To build the 103 FWU_FIP, any FWU images required by the platform must be specified on the 104 command line. On Arm development platforms like Juno, these are: 105 106 - NS_BL2U. The AP non-secure Firmware Updater image. 107 - SCP_BL2U. The SCP Firmware Update Configuration image. 108 109 Example of Juno command line for generating both ``fwu`` and ``fwu_fip`` 110 targets using RSA development: 111 112 :: 113 114 MBEDTLS_DIR=<path of the directory containing mbed TLS sources> \ 115 make PLAT=juno TRUSTED_BOARD_BOOT=1 GENERATE_COT=1 \ 116 ARM_ROTPK_LOCATION=devel_rsa \ 117 ROT_KEY=plat/arm/board/common/rotpk/arm_rotprivk_rsa.pem \ 118 BL33=<path-to>/<bl33_image> OPENSSL_DIR=<path-to>/<openssl> \ 119 SCP_BL2=<path-to>/<scp_bl2_image> \ 120 SCP_BL2U=<path-to>/<scp_bl2u_image> \ 121 NS_BL2U=<path-to>/<ns_bl2u_image> \ 122 all fip fwu_fip 123 124 .. note:: 125 The BL2U image will be built by default and added to the FWU_FIP. 126 The user may override this by adding ``BL2U=<path-to>/<bl2u_image>`` 127 to the command line above. 128 129 .. note:: 130 Building and installing the non-secure and SCP FWU images (NS_BL1U, 131 NS_BL2U and SCP_BL2U) is outside the scope of this document. 132 133 The result of this build will be bl1.bin, fip.bin and fwu_fip.bin binaries. 134 Both the FIP and FWU_FIP will include the certificates corresponding to the 135 selected Chain of Trust. These certificates can also be found in the output 136 build directory. 137 138-------------- 139 140*Copyright (c) 2019-2024, Arm Limited. All rights reserved.* 141 142.. _mbed TLS Repository: https://github.com/ARMmbed/mbedtls.git 143.. _mbed TLS Security Center: https://tls.mbed.org/security 144