From: Markus Valentin mv@denx.de
Introduce functions that check the integrity of u-boot by utilising the hashes stored in the oem-data block.
The verification functions get called in fsp_init()
Signed-off-by: Markus Valentin mv@denx.de --- arch/x86/cpu/baytrail/Makefile | 1 + arch/x86/cpu/baytrail/secure_boot.c | 117 +++++++++++++++++++++ .../include/asm/arch-baytrail/fsp/fsp_configs.h | 3 + arch/x86/lib/fsp/fsp_support.c | 15 +++ 4 files changed, 136 insertions(+) create mode 100644 arch/x86/cpu/baytrail/secure_boot.c
diff --git a/arch/x86/cpu/baytrail/Makefile b/arch/x86/cpu/baytrail/Makefile index a0216f3..dbf9a82 100644 --- a/arch/x86/cpu/baytrail/Makefile +++ b/arch/x86/cpu/baytrail/Makefile @@ -8,4 +8,5 @@ obj-y += cpu.o obj-y += early_uart.o obj-y += fsp_configs.o obj-y += valleyview.o +obj-$(CONFIG_BAYTRAIL_SECURE_BOOT) += secure_boot.o obj-$(CONFIG_GENERATE_ACPI_TABLE) += acpi.o diff --git a/arch/x86/cpu/baytrail/secure_boot.c b/arch/x86/cpu/baytrail/secure_boot.c new file mode 100644 index 0000000..37c83db --- /dev/null +++ b/arch/x86/cpu/baytrail/secure_boot.c @@ -0,0 +1,117 @@ +/* + * Copyright (C) 2017 Markus Valentin mv@denx.de + * + * SPDX-License-Identifier: GPL-2.0+ + */ + +#include <common.h> + +#define SB_MANIFEST_BASE 0xFFFE0000 +#define SB_MANIFEST_SIZE 0x400 +#define SB_MANIFEST_OEM_DATA_OFFSET 0x58 +#define SB_MANIFEST_OEM_HASH_OFFSET (SB_MANIFEST_OEM_DATA_OFFSET + 4) +#define SB_MANIFEST_OEM_HASH_BASE (SB_MANIFEST_BASE +\ + SB_MANIFEST_OEM_HASH_OFFSET) +#define SB_MANIFEST_END (SB_MANIFEST_BASE + SB_MANIFEST_SIZE) + +#define PUB_KEY_MODULUS_SIZE 0x100 +#define U_BOOT_STAGE_SIZE 0xDD360 +#define U_BOOT_OFFSET 0x2CA0 + +#define U_BOOT_STAGE_START (CONFIG_SYS_TEXT_BASE + U_BOOT_OFFSET) +#define U_BOOT_STAGE_END (U_BOOT_STAGE_START + U_BOOT_STAGE_SIZE) + +#define SHA256_U_BOOT_STAGE_ID 0 +#define SHA256_FSP_STAGE2_ID 1 +#define SHA256_FIT_PUB_KEY_ID 2 + +#define FIT_KEY_NAME "dev" + +/** + * This function compares a hash which gets retrieved from the oem data block + * with the runtime calculated hash of start_address+size. If they match, + * this function returns true. If not, it returns false. + * + * @param hash_id offset of oem-data block for hash to compare + * @param start_address address where the hash calculation should start + * @param size length of the region for hash calculation + * @return true on success, false on error + */ +static bool verify_oem_sha256(unsigned int hash_id, + void *start_address, + size_t size) +{ + uint8_t value[SHA256_SUM_LEN]; + int value_len; + + /* calculate address of hash to compare in the oemdata block*/ + void *hash_to_verify = (void *)SB_MANIFEST_OEM_HASH_BASE + + (SHA256_SUM_LEN * hash_id); +#ifdef DEBUG + unsigned int i = 0; + uint8_t oem_value[SHA256_SUM_LEN]; + + memcpy(oem_value, hash_to_verify, SHA256_SUM_LEN); + printf("SB: Hash to verify:\t"); + for (i = 0; i < SHA256_SUM_LEN; i++) + printf("%X", oem_value[i]); + printf("\n"); +#endif + + /* caluclate the hash of the binary */ + calculate_hash(start_address, size, "sha256", (unsigned char *)value, + &value_len); + +#ifdef DEBUG + printf("SB: calculated hash:\t"); + for (i = 0; i < SHA256_SUM_LEN; i++) + printf("%X", value[i]); + printf("\n"); +#endif + /* compare the two hash values */ + if (memcmp(hash_to_verify, value, SHA256_SUM_LEN)) + return false; + return true; +} + +/** + * This function verifies the integrity for u-boot, its devicetree and the ucode + * appended or inserted to the devicetree. + * + * @return true on success, false on error + */ +bool verify_u_boot_bin(void) +{ + return verify_oem_sha256(SHA256_U_BOOT_STAGE_ID, + (void *)U_BOOT_STAGE_START, + U_BOOT_STAGE_SIZE); +} + +/** + * This function verifies the integrity for the modulus of the public key which + * is stored in the u-boot devicetree for fit image verification. It tries to + * find the "rsa,modulus" property in the dtb and then verifies it with the + * checksum stored in the oem-data block + * + * @return true on success, false on error + */ +bool verify_public_key(void) +{ + void *fit_public_key_modulus; + + int offset = fdt_node_offset_by_prop_value(gd->fdt_blob, -1, + "key-name-hint", + FIT_KEY_NAME, + 4); + + fit_public_key_modulus = (void *)fdt_getprop(gd->fdt_blob, offset, + "rsa,modulus", NULL); + if (!fit_public_key_modulus) { + debug("SB: Could not fetch public key from U-Boot Devicetree\n"); + return false; + } + + return verify_oem_sha256(SHA256_FIT_PUB_KEY_ID, + fit_public_key_modulus, + PUB_KEY_MODULUS_SIZE); +} diff --git a/arch/x86/include/asm/arch-baytrail/fsp/fsp_configs.h b/arch/x86/include/asm/arch-baytrail/fsp/fsp_configs.h index e539890..b5dd5a4 100644 --- a/arch/x86/include/asm/arch-baytrail/fsp/fsp_configs.h +++ b/arch/x86/include/asm/arch-baytrail/fsp/fsp_configs.h @@ -16,4 +16,7 @@ struct fspinit_rtbuf { struct common_buf common; /* FSP common runtime data structure */ };
+bool verify_u_boot_bin(void); +bool verify_public_key(void); + #endif /* __FSP_CONFIGS_H__ */ diff --git a/arch/x86/lib/fsp/fsp_support.c b/arch/x86/lib/fsp/fsp_support.c index 3a537d0..5669700 100644 --- a/arch/x86/lib/fsp/fsp_support.c +++ b/arch/x86/lib/fsp/fsp_support.c @@ -149,6 +149,21 @@ void fsp_init(u32 stack_top, u32 boot_mode, void *nvs_buf) */ printf("FSP: Secure Boot %sabled\n", fsp_vpd->enable_secure_boot == 1 ? "en" : "dis"); + if (!verify_u_boot_bin()) { + /* if our u-boot binary checksum isn't equal to + * our expected checksum we need to stop booting + */ + puts("SB: Failed to verify u-boot and dtb\n"); + hang(); + } + + /* + * verification of the public key happens with verification of + * the devicetree binary (thats where its stored), this check is + * not necessary, but nice to see its integer + */ + if (!verify_public_key()) + puts("SB: Failed to verify public key for fit-image\n"); #endif /* Copy default data from Flash */ memcpy(fsp_upd, (void *)(fsp_hdr->img_base + fsp_vpd->upd_offset),