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fix(security): Formatting cleanup to Secure Boot page
Changes the indentation to 3 spaces, adds :file: and :code: directive to appropriate places, and wrap long lines to 80 characters. While here, also update the name "U-Boot" to have a consistent case everywhere, and update ATF to TF-A. Signed-off-by: T Pratham <t-pratham@ti.com>
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‎source/linux/Foundational_Components_Secure_Boot.rst‎

Lines changed: 125 additions & 98 deletions
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@@ -15,7 +15,7 @@ pass authentication for Public Boot ROM to continue boot. It is then the respons
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each next stage is itself authenticated. One weak link and all lower trust levels could be compromised.
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.. Note::
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Example: Forgetting to disable u-boot console or environment loading means a non-secured linux can be loaded. The U-Boot console (or command
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Example: Forgetting to disable U-Boot console or environment loading means a non-secured linux can be loaded. The U-Boot console (or command
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line interface (CLI)) and environment are powerful features that make it great for creating a customized boot process. However,
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leaving either or them enabled in a production system allows non-secured software to be loaded and the Chain-of-Trust to be broken.
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@@ -24,7 +24,7 @@ The following is an example list where Chain-of-Trust should be maintained.
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- Remove U-Boot uEnv.txt loading support.
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- Disable environment loading (the default built-in environment must be compiled to be the one you want).
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- Environment must not fallback to other boot modes.
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- Place firewalls in board-config to match the location of loaded artifacts (ATF/OP-TEE).
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- Place firewalls in board-config to match the location of loaded artifacts (TF-A/OP-TEE).
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- Update debug sections of initial image cert.
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- Enable DM-verity/DM-crypt.
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- Set root password or disable root account.
@@ -55,11 +55,12 @@ The following is an example list where Chain-of-Trust should be maintained.
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.. Image:: /images/K3_KF.png
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:scale: 70%
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Secure boot has layers. Some layers are trusted more than others. Secure ROM has the highest trust and Runtime Execution
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Environment (REE) non-trustzone user-space applications have the least. If a
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lower trust entity must load a higher trust code, an even higher trust entity
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must verify it and not allow access by the lower trust entity after that
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point. Some such trust inversions are as follows:
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Secure boot has layers. Some layers are trusted more than others. Secure ROM
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has the highest trust and Runtime Execution Environment (REE) non-trustzone
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user-space applications have the least. If a lower trust entity must load a
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higher trust code, an even higher trust entity must verify it and not allow
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access by the lower trust entity after that point. Some such trust inversions
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are as follows:
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.. ifconfig:: CONFIG_part_variant in ('AM62LX')
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@@ -73,7 +74,8 @@ point. Some such trust inversions are as follows:
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- R5 Public Boot ROM loading TIFS
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- Linux loading Trusted applications (TA)
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These are called out in the sequence as shown in the following image and their method of ensuring trust is explained.
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These are called out in the sequence as shown in the following image and
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their method of ensuring trust is explained.
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Secure Boot Flow
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--------------------
@@ -128,7 +130,8 @@ Secure Boot Flow
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location is device dependent. More details can be found in the device
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"Technical Reference Manual".
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The contents of this first stage image are authenticated and decrypted by the Secure ROM. Contents include:
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The contents of this first stage image are authenticated and decrypted by
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the Secure ROM. Contents include:
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* `Texas Instruments Foundational Security (TIFS)` firmware: After authentication/decryption, TIFS firmware replaces the Secure ROM as the authenticator entity executing on the M4 core in the 2nd phase of the boot.
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* BL-1: The pre-bootloader executed on the A53 core, initializes the console and DDR for the 2nd phase of the boot.
@@ -212,84 +215,98 @@ Secure Boot Flow
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.. rubric:: U-Boot
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The boot flow continues as it does on a non-secure device, until loading the next FIT image named `fitImage`. This FIT image includes the Linux kernel, DTB, and
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other required boot artifacts. U-boot verifies the signed images on boot independently, without using TIFS. U-boot extracts each component from the FIT image and verifies its signature. Once u-boot verifies all components, it starts Linux. For more information, see: `U-Boot FIT Signature Documentation <https://docs.u-boot.org/en/latest/usage/fit/signature.html>`__
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The boot flow continues as it does on a non-secure device, until loading the
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next FIT image named :file:`fitImage`. This FIT image includes the Linux
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kernel, DTB, and other required boot artifacts. U-Boot verifies the signed
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images on boot independently, without using TIFS. U-Boot extracts each
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component from the FIT image and verifies its signature. Once U-Boot verifies
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all components, it starts Linux. For more information, see:
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`U-Boot FIT Signature Documentation <https://docs.u-boot.org/en/latest/usage/fit/signature.html>`__
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U-boot's output will be similar to this:
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U-Boot's output will be similar to this:
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.. code-block:: console
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U-Boot 2021.01-g2de57d278b (May 16 2022 - 14:28:40 +0000)
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SoC: AM64X SR1.0
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Model: Texas Instruments AM642 EVM
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Board: AM64-GPEVM rev A
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DRAM: 2 GiB
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NAND: 0 MiB
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MMC: mmc@fa10000: 0, mmc@fa00000: 1
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Loading Environment from FAT... *** Warning - bad CRC, using default environment
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In: serial@2800000
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Out: serial@2800000
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Err: serial@2800000
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Net: eth0: ethernet@8000000port@1
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Hit any key to stop autoboot: 0
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switch to partitions #0, OK
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mmc1 is current device
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SD/MMC found on device 1
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Failed to load 'boot.scr'
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1011 bytes read in 2 ms (493.2 KiB/s)
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Loaded env from uEnv.txt
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Importing environment from mmc1 ...
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Running uenvcmd ...
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7862647 bytes read in 328 ms (22.9 MiB/s)
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## Loading kernel from FIT Image at 90000000 ...
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Using 'k3-am642-evm.dtb' configuration
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Trying 'kernel@1' kernel subimage
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Description: Linux kernel
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Type: Kernel Image
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Compression: gzip compressed
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Data Start: 0x900000f8
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Data Size: 7743643 Bytes = 7.4 MiB
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Architecture: AArch64
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OS: Linux
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Load Address: 0x80080000
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Entry Point: 0x80080000
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Verifying Hash Integrity ... OK
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## Loading fdt from FIT Image at 90000000 ...
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Using 'k3-am642-evm.dtb' configuration
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Trying 'k3-am642-evm.dtb' fdt subimage
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Description: Flattened Device Tree blob
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Type: Flat Device Tree
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Compression: uncompressed
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Data Start: 0x90762a54
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Data Size: 56436 Bytes = 55.1 KiB
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Architecture: AArch64
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Load Address: 0x83000000
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Verifying Hash Integrity ... OK
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Loading fdt from 0x90762a54 to 0x83000000
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Booting using the fdt blob at 0x83000000
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Uncompressing Kernel Image
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Loading Device Tree to 000000008ffef000, end 000000008ffff602 ... OK
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U-Boot 2021.01-g2de57d278b (May 16 2022 - 14:28:40 +0000)
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SoC: AM64X SR1.0
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Model: Texas Instruments AM642 EVM
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Board: AM64-GPEVM rev A
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DRAM: 2 GiB
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NAND: 0 MiB
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MMC: mmc@fa10000: 0, mmc@fa00000: 1
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Loading Environment from FAT... *** Warning - bad CRC, using default environment
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In: serial@2800000
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Out: serial@2800000
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Err: serial@2800000
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Net: eth0: ethernet@8000000port@1
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Hit any key to stop autoboot: 0
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switch to partitions #0, OK
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mmc1 is current device
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SD/MMC found on device 1
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Failed to load 'boot.scr'
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1011 bytes read in 2 ms (493.2 KiB/s)
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Loaded env from uEnv.txt
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Importing environment from mmc1 ...
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Running uenvcmd ...
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7862647 bytes read in 328 ms (22.9 MiB/s)
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## Loading kernel from FIT Image at 90000000 ...
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Using 'k3-am642-evm.dtb' configuration
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Trying 'kernel@1' kernel subimage
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Description: Linux kernel
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Type: Kernel Image
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Compression: gzip compressed
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Data Start: 0x900000f8
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Data Size: 7743643 Bytes = 7.4 MiB
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Architecture: AArch64
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OS: Linux
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Load Address: 0x80080000
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Entry Point: 0x80080000
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Verifying Hash Integrity ... OK
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## Loading fdt from FIT Image at 90000000 ...
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Using 'k3-am642-evm.dtb' configuration
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Trying 'k3-am642-evm.dtb' fdt subimage
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Description: Flattened Device Tree blob
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Type: Flat Device Tree
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Compression: uncompressed
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Data Start: 0x90762a54
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Data Size: 56436 Bytes = 55.1 KiB
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Architecture: AArch64
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Load Address: 0x83000000
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Verifying Hash Integrity ... OK
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Loading fdt from 0x90762a54 to 0x83000000
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Booting using the fdt blob at 0x83000000
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Uncompressing Kernel Image
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Loading Device Tree to 000000008ffef000, end 000000008ffff602 ... OK
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.. rubric:: Linux
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If initramfs is included, we can trust our initial modules and tasks, but we cannot trust anything beyond this as the root file-system may have been
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modified. To allow trusted use of files outside of our initramfs we use dm-verity. With this we can authenticate a block device as we read from it. As
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any changes to this block-device will cause the authentication to fail, we cannot put any user-modifiable configurations or user installed programs
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here. Only important, read-only, files should be placed on this partition, such as static kernel and operating system files and configurations. All
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other files must be placed in a non-verifiable read-write user partition.
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If initramfs is included, we can trust our initial modules and tasks, but we
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cannot trust anything beyond this as the root file-system may have been
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modified. To allow trusted use of files outside of our initramfs we use
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dm-verity. With this we can authenticate a block device as we read from it. As
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any changes to this block-device will cause the authentication to fail, we
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cannot put any user-modifiable configurations or user installed programs here.
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Only important, read-only, files should be placed on this partition, such as
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static kernel and operating system files and configurations. All other files
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must be placed in a non-verifiable read-write user partition.
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HS Boot Flow Tools
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-------------------
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U-boot:
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U-Boot:
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.. ifconfig:: CONFIG_part_variant not in ('AM62LX')
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The ti-u-boot source is a project used to create tiboot3.bin, tispl.bin, and u-boot.img. To create tiboot3.bin for K3 family devices, u-boot builds R5 SPL and
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binman packages it in a `tiboot3.bin` image. To build A53 SPL, binman takes TF-A (bl31.bin), OPTEE (bl32.bin), A53 SPL, and A53 DTBs and packages
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them in a `tispl.bin` image. U-Boot can then use the openssl library to sign each component as specified in k3-<soc>-binman.dtsi.
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The ti-u-boot source is a project used to create :file:`tiboot3.bin`,
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:file:`tispl.bin`, and :file:`u-boot.img`. To create :file:`tiboot3.bin`
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for K3 family devices, U-Boot builds R5 SPL and binman packages it in a
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:file:`tiboot3.bin` image. To build A53 SPL, binman takes TF-A
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(:file:`bl31.bin`), OPTEE (:file:`bl32.bin`), A53 SPL, and A53 DTBs and
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packages them in a :file:`tispl.bin` image. U-Boot can then use the
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openssl library to sign each component as specified in
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:file:`k3-<soc>-binman.dtsi`.
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.. code-block:: console
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@@ -320,47 +337,57 @@ U-boot:
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Linux:
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The ti-linux source is a TI project used to build Linux kernel, DTB, and other boot artifacts. Some of these components could be included in a verifiable image
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`fitImage`. For HS devices, only the fitImage will be allowed to boot once `fitImage` has been authenticated.
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The ti-linux source is a TI project used to build Linux kernel, DTB, and
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other boot artifacts. Some of these components could be included in a
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verifiable image :file:`fitImage`. For HS devices, only the fitImage will be
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allowed to boot once :file:`fitImage` has been authenticated.
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.. code-block:: console
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.. code-block:: console
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$ git clone https://git.ti.com/git/ti-linux-kernel/ti-linux-kernel.git
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$ git clone https://git.ti.com/git/ti-linux-kernel/ti-linux-kernel.git
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Example use:
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$ make ARCH=arm64 CROSS_COMPILE=aarch64-none-linux-gnu- defconfig ti_arm64_prune.config
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$ make ARCH=arm64 CROSS_COMPILE=aarch64-none-linux-gnu- menuconfig
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$ make ARCH=arm64 CROSS_COMPILE=aarch64-none-linux-gnu-
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$ #Example use:
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$ make ARCH=arm64 CROSS_COMPILE=aarch64-none-linux-gnu- defconfig ti_arm64_prune.config
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$ make ARCH=arm64 CROSS_COMPILE=aarch64-none-linux-gnu- menuconfig
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$ make ARCH=arm64 CROSS_COMPILE=aarch64-none-linux-gnu-
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ATF:
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TF-A:
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The ATF source (now called TF-A) is used to build `bl31.bin` that gets packaged into `tispl.bin`. For HS devices, this binary needs to be signed.
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The TF-A source (formerly called ATF) is used to build :file:`bl31.bin` that
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gets packaged into :file:`tispl.bin`. For HS devices, this binary needs to
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be signed.
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.. code-block:: console
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.. code-block:: console
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$ git clone https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git
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$ git clone https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git
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Example use:
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$ make ARCH=aarch64 CROSS_COMPILE=aarch64-none-linux-gnu- PLAT=k3 TARGET_BOARD=lite SPD=opteed
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$ # Example use:
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$ make ARCH=aarch64 CROSS_COMPILE=aarch64-none-linux-gnu- PLAT=k3 TARGET_BOARD=lite SPD=opteed
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OPTEE:
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The OPTEE source is used to build `bl32.bin/tee-pager_v2.bin` that gets packaged into `tispl.bin`. For HS devices, this binary needs to be signed.
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The OPTEE source is used to build :file:`bl32.bin/tee-pager_v2.bin` that
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gets packaged into :file:`tispl.bin`. For HS devices, this binary needs to
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be signed.
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.. code-block:: console
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.. code-block:: console
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$ git clone https://github.com/OP-TEE/optee_os.git
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$ git clone https://github.com/OP-TEE/optee_os.git
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Example use:
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$ make CROSS_COMPILE64=aarch64-linux-gnu- PLATFORM=k3-<soc> CFG_ARM64_core=y
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$ # Example use:
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$ make CROSS_COMPILE64=aarch64-linux-gnu- PLATFORM=k3-<soc> CFG_ARM64_core=y
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Ti-linux-firmware:
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The ti-linux-firmware is a TI repository where all firmware releases are stored. Firmwares for a device family can also be found in the pre-built SDK
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under :file:`<path-to-tisdk>/board-support/prebuilt-images/<evm>`. Binman expects to find the device firmware with the following appended to u-boot build command:
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BINMAN_INDIRS=<path-to-tisdk>/board-support/prebuilt-images, and expects to find a ti-sysfw directory in this path.
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The ti-linux-firmware is a TI repository where all firmware releases are
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stored. Firmwares for a device family can also be found in the pre-built SDK
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under :file:`<path-to-tisdk>/board-support/prebuilt-images/<evm>`. Binman
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expects to find the device firmware with the following appended to U-Boot
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build command:
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:code:`BINMAN_INDIRS=<path-to-tisdk>/board-support/prebuilt-images`, and
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expects to find a ti-sysfw directory in this path.
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.. code-block:: console
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.. code-block:: console
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$ <https://git.ti.com/git/processor-firmware/ti-linux-firmware.git
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Branch: ti-linux-firmware.
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$ git clone https://git.ti.com/git/processor-firmware/ti-linux-firmware.git
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Branch: ti-linux-firmware.

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