MTK secure boot.pdf-资料库

1.Basic Feature Why is Software Secure Boot? Device requirements of Widevine level 3 security for DRM contents’ protection. (https://en.wikipedia.org/wiki/Digital_rights_management) – Device manufacturers must provide a Boot Loader that loads signed system images only. For devices that allow users to load a custom operating system or gain root privileges on the device by unlocking the Boot Loader, device manufacturers must support the following: • Device manufacturers must provide a Boot Loader that allows a Widevine key-box to be written only when the Boot Loader is in a locked state. • Device manufacturers must ensure that the Widevine key-box is not readable when the Boot Loader is unlocked. • The Widevine key-box must be stored in a region of memory that is erased or is inaccessible when the device Boot Loader is in an unlocked state. What is Software Secure Boot? Secure Boot is responsible for validating the legality of bootloader binaries when SOC is started. The Bootloader binary is started by the Rom Code of SOC, so the authentication of the Bootloader needs to be implemented by Rom Code. Where is the public key used by the Bootloader authentication? The answer is that in the efuse unit of SOC, the factory needs to use the tools provided by SOC manufacturers to burn the public key to SOC (no change can be made after a burn) in the production phase of the product. ▪ Feature Description: – Software-based protection – Format and first loaders upgrade are not allowed – Locked state protection (configurable) • Only authorized software images are booted – Unlocked state protection (configurable)

• Non-authorized software images are booted • Key-box should be cleaned Policy and Limitations 1) SECRO image is always needed to be signed and verified. 2) Format and first loaders’ upgrade are not allowed once locked SECRO are downloaded. 3) BROM command is permanently disabled once the pre-loader is downloaded to target. 4) DA needs to be verified by pre-loader in pre-loader download mode. 5) Once unlock flow is not done, the following operations are not allowed. – Format operation is forbidden – Image download operation except for SECRO – BL download is forbidden – Secure boot check for signed images 2.MTK Secure Boot 2.1 Normal Download Procedure(not used with effuse) 1. Boot ROM is activated when the device is powered on 2. BROM check preloader signature 3. BROM load preloader in ISRAM 4. Pre-loader executes in ISRAM and SYNC with FLASHTOOL , if RSA check passed,FLASHTOOL Via USB copy Pre- DA to ISRAM 5. FLASHTOOL Via USB copy DA binary to DRAM 6. DA SYNC with FLASHTOOL copy Pre-Loader to storage 7. DA download the U-BOOT(lk) to storage(check image signature) 8. DA download the Linux Kernel to storage(check image signature) 9. DA download other images to storage(check image signature)

2.2 Emergency Download Procedure(used with effuse) Overall Download Procedure 1. Boot ROM is activated when the device is powered on 2. Boot ROM initializes software stack, communication ports, and bootable storages 3. Boot ROM handshakes with flash tool via USB when emergency DL key is pressed 4. FLASHTOOL Via UART/USB copy Pre-DA to ISRAM(effuse signature check) 5. FLASHTOOL Via UART/USB copy DA binary to DRAM 6. DA SYNC with FLASHTOOL copy Pre-Loader to storage 7. DA download the U-BOOT(lk) to storage(check image signature) 8. DA download the Linux Kernel to storage(check image signature) 9. DA download other images to storage(check image signature) 2.3 Boot up Procedure Emergency Download Procedure 1. Boot ROM is activated when the device is powered on. 2. Boot ROM initializes software stack, communication ports, and bootable storages 3. Boot ROM loads the pre-loader from storage to L2 Share Sram since DRAM is not initialized yet 4. Boot ROM jumps to pre-loader and executes 5. Pre-loader initializes DRAM and loads U-Boot to DRAM 6. Pre-loader jumps to U-Boot/LK and executes then U-Boot/LK does some initializations, such as display. 7. U-Boot/LK loads the boot image, including the Linux kernel and the ramdisk, from storage to DRAM 8. U-Boot/LK jumps to Linux kernel and executes

2.3.1 Boot up verify http://source.android.com/devices/tech/security/verifiedboot/verified-boot.html Overall Boot up Procedure lk/secro verify(preloader) ./bootable/bootloader/preloader/platform/mt6735/src/security/sec_boot.c boot/recovery verify(lk) /vendor/mediatek/proprietary/bootable/bootloader/lk/platform/mt6735/load_image.c

logo 分区目前校验有问题 2.4 SecroImage config With secure boot mechanism, the images which are downloaded to target will be checked for its signature for validity at each boot time. If the check is failed, then the boot will be halted. This can make sure the images on flash are correct and signed by customer key. For the device which has already downloaded with a locked SECRO, the behaviors are listed below 3.Related Changes 3.1 Secure boot verify images(image RSA2048 public key) bootable/bootloader/preloader/custom/joyasz8735b_3tb_n/inc/cust_sec_ctrl.h bootable/bootloader/lk/target/joyasz8735b_3tb_n/inc/oemkey.h custom/joyasz8735b_3tb_n/security/image_auth/VERIFIED_BOOT_IMG_AUTH_KEY.ini 3.2 Sign images for secure boot(image RSA2048 private key) custom/joyasz8735b_3tb_n/security/image_auth/VERIFIED_BOOT_IMG_AUTH_KEY.ini bootable/bootloader/preloader/custom/joyasz8735b_3tb_n/security/chip_config/s/key/CHIP_TEST_KEY.ini(SBC) 3.3 Tool Verify Image(image RSA1024 private key) bootable/bootloader/preloader/custom/joyasz8735b_3tb_n/security/image_auth/IMG_AUTH_KEY.ini(difference between N and M)

custom/joyasz8735b_3tb_n/security/image_auth/IMG_AUTH_KEY.ini 3.4 Preloader verify DA_PL(DA RSA2048 public key) bootable/bootloader/preloader/custom/joyasz8735b_3tb_n/inc/cust_sec_ctrl.h 3.5 Sign DA DA_Kit\build\tools\SignDA_SV5.ini(RSA2048) Customization_Kit_buildspec\custom\security\usbdl4enduser_dummy\VERIFIED_BOOT_IMG_AUTH_KEY.ini(RSA2048) Customization_Kit_buildspec\custom\security\usbdl4enduser_dummy\dummy_k2.bin(RSA1024) 3.6 Secro Image config custom/common/secro/SECRO_GMP.ini All the download and boot check permission is controlled and configured by SECRO image. • vendor/mediatek/proprietary/custom/common/secro/SECRO_GMP.ini FACTORY_MODE_EN: factory mode is enabled/disabled (1: enable, 0:disable) SW_SECURE_BOOT_EN: SECRO setting is enabled/disabled (1: enable, 0:disable) DEFAULT_STATE: When device state (stored in SECCFG) is default state and SECRO setting is enabled, this field determines which policy is applied DL_1ST_LOADER_LOCK:When device state is locked,check if can download pl(1:forbid,2:enable) DL_2ND_LOADER_LOCK:When device state is locked,check if can download lk(1:forbid,2:enable) 3.7 execution 3.7.1 generate keys openssl genrsa -out sbc_key.pem 2048(sbc check key brom->preloader) openssl genrsa -out verified_key.pem 2048(verified image key preloader -> lk,logo,boot,system...) openssl genrsa -out img_key.pem 1024(image auth key) 3.7.2 secureboot_autoconfig cp secureboot_autoconfig -rf vendor/mediatek/proprietary/scripts/ cp three keys into vendor/mediatek/proprietary/scripts/secureboot_autoconfig/keyfiles/ modify configuration.xml which below the folder:

python tool.py add our private image to sign 3.7.3 build sign image source build/envsetup.sh lunch make clean&&make -j16 ./vendor/mediatek/proprietary/scripts/sign-image/sign_image.sh

cp MT6737M_Android_scatter.txt preloader_joyasz8735b_3tb_n.bin signed_bin/ 3.7.4 sign DA copy dummy_k2.bin and VERIFIED_BOOT_IMG_AUTH_KEY.ini into custom\security\usbdl4enduser_dummy run the sig.bat first,then run package.bat

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MTK secure boot.pdf

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