The STM32MP ROM provides several service. One of them is the ability to verify ecdsa256 signatures. Hook the ROM API into the ECDSA uclass.
Signed-off-by: Alexandru Gagniuc mr.nuke.me@gmail.com --- arch/arm/mach-stm32mp/Kconfig | 9 +++ arch/arm/mach-stm32mp/Makefile | 1 + arch/arm/mach-stm32mp/ecdsa_romapi.c | 106 +++++++++++++++++++++++++++ 3 files changed, 116 insertions(+) create mode 100644 arch/arm/mach-stm32mp/ecdsa_romapi.c
diff --git a/arch/arm/mach-stm32mp/Kconfig b/arch/arm/mach-stm32mp/Kconfig index f538d7cb83..f1e00929fd 100644 --- a/arch/arm/mach-stm32mp/Kconfig +++ b/arch/arm/mach-stm32mp/Kconfig @@ -121,6 +121,15 @@ config STM32_ETZPC help Say y to enable STM32 Extended TrustZone Protection
+config STM32_ECDSA_VERIFY + bool "STM32 ECDSA verification via the ROM API" + depends on SPL_ECDSA_VERIFY + default y + help + Say y to enable the uclass driver for ECDSA verification using the + ROM API provided on STM32MP. + The ROM API is only available during SPL for now. + config CMD_STM32PROG bool "command stm32prog for STM32CudeProgrammer" select DFU diff --git a/arch/arm/mach-stm32mp/Makefile b/arch/arm/mach-stm32mp/Makefile index c8aa24d489..c03fedb486 100644 --- a/arch/arm/mach-stm32mp/Makefile +++ b/arch/arm/mach-stm32mp/Makefile @@ -10,6 +10,7 @@ obj-y += bsec.o
ifdef CONFIG_SPL_BUILD obj-y += spl.o +obj-$(CONFIG_STM32_ECDSA_VERIFY) += ecdsa_romapi.o else obj-$(CONFIG_CMD_STM32PROG) += cmd_stm32prog/ obj-$(CONFIG_CMD_STM32KEY) += cmd_stm32key.o diff --git a/arch/arm/mach-stm32mp/ecdsa_romapi.c b/arch/arm/mach-stm32mp/ecdsa_romapi.c new file mode 100644 index 0000000000..7f71d7a341 --- /dev/null +++ b/arch/arm/mach-stm32mp/ecdsa_romapi.c @@ -0,0 +1,106 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * STM32MP ECDSA verification via the ROM API + * + * Implements ECDSA signature verification via the STM32MP ROM. + */ +#include <asm/system.h> +#include <dm/device.h> +#include <linux/types.h> +#include <u-boot/ecdsa.h> +#include <crypto/ecdsa-uclass.h> +#include <linux/libfdt.h> +#include <dm/platdata.h> + +#define ROM_API_SUCCESS 0x77 +#define ROM_API_ECDSA_ALGO_PRIME_256V1 1 +#define ROM_API_ECDSA_ALGO_BRAINPOOL_256 2 + +#define ROM_API_OFFSET_ECDSA_CHECK_KEY 0x5c +#define ROM_API_OFFSET_ECDSA_VERIFY 0x60 + +struct ecdsa_rom_api { + uint32_t (*ecdsa_check_key)(const void *pubkey_in, void *pubkey_out); + uint32_t (*ecdsa_verify_signature)(const void *hash, const void *pubkey, + const void *signature, + uint32_t ecc_algo); +}; + +/* + * Without forcing the ".data" section, this would get saved in ".bss". BSS + * will be cleared soon after, so it's not suitable. + */ +static uintptr_t rom_api_loc __section(".data"); + +/* + * The ROM gives us the API location in r0 when starting. This is only available + * during SPL, as there isn't (yet) a mechanism to pass this on to u-boot. + */ +void save_boot_params(unsigned long r0, unsigned long r1, unsigned long r2, + unsigned long r3) +{ + rom_api_loc = r0; + save_boot_params_ret(); +} + +static void stm32mp_rom_get_ecdsa_functions(struct ecdsa_rom_api *rom) +{ + uintptr_t verify_ptr = rom_api_loc + ROM_API_OFFSET_ECDSA_VERIFY; + uintptr_t check_key_ptr = rom_api_loc + ROM_API_OFFSET_ECDSA_CHECK_KEY; + + rom->ecdsa_verify_signature = *(void **)verify_ptr; + rom->ecdsa_check_key = *(void **)check_key_ptr; +} + +static int ecdsa_key_algo(const char *curve_name) +{ + if (!strcmp(curve_name, "prime256v1")) + return ROM_API_ECDSA_ALGO_PRIME_256V1; + else if (!strcmp(curve_name, "brainpool256")) + return ROM_API_ECDSA_ALGO_BRAINPOOL_256; + else + return -ENOPROTOOPT; +} + +static int romapi_ecdsa_verify(struct udevice *dev, + const struct ecdsa_public_key *pubkey, + const void *hash, size_t hash_len, + const void *signature, size_t sig_len) +{ + struct ecdsa_rom_api rom; + uint8_t raw_key[64]; + uint32_t rom_ret; + int algo; + + /* The ROM API can only handle 256-bit ECDSA keys. */ + if (sig_len != 32 || hash_len != 32 || pubkey->size_bits != 256) + return -EINVAL; + + algo = ecdsa_key_algo(pubkey->curve_name); + if (algo < 0) + return algo; + + /* The ROM API wants the (X, Y) coordinates concatenated. */ + memcpy(raw_key, pubkey->x, 32); + memcpy(raw_key + 32, pubkey->y, 32); + + stm32mp_rom_get_ecdsa_functions(&rom); + rom_ret = rom.ecdsa_verify_signature(hash, raw_key, signature, algo); + + return rom_ret == ROM_API_SUCCESS ? 0 : -EPERM; +} + +static const struct ecdsa_ops rom_api_ops = { + .verify = romapi_ecdsa_verify, +}; + +U_BOOT_DRIVER(stm32mp_rom_api_ecdsa) = { + .name = "stm32mp_rom_api_ecdsa", + .id = UCLASS_ECDSA, + .ops = &rom_api_ops, + .flags = DM_FLAG_PRE_RELOC, +}; + +U_BOOT_DEVICE(stm32mp_rom_api_ecdsa) = { + .name = "stm32mp_rom_api_ecdsa", +};