Implement the crypto_algo .verify() function for ecdsa256. Because it backends on UCLASS_ECDSA, this change is focused on parsing the keys from devicetree and passing this information to the specific UCLASS driver.

Signed-off-by: Alexandru Gagniuc mr.nuke.me@gmail.com Reviewed-by: Simon Glass sjg@chromium.org --- lib/Kconfig | 1 + lib/Makefile | 1 + lib/ecdsa/Kconfig | 23 +++++++ lib/ecdsa/Makefile | 1 + lib/ecdsa/ecdsa-verify.c | 134 +++++++++++++++++++++++++++++++++++++++ 5 files changed, 160 insertions(+) create mode 100644 lib/ecdsa/Kconfig create mode 100644 lib/ecdsa/Makefile create mode 100644 lib/ecdsa/ecdsa-verify.c

diff --git a/lib/Kconfig b/lib/Kconfig index fdcf7ea405..014a2f7f77 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -303,6 +303,7 @@ config AES supported by the algorithm but only a 128-bit key is supported at present.

+source lib/ecdsa/Kconfig source lib/rsa/Kconfig source lib/crypto/Kconfig source lib/crypt/Kconfig diff --git a/lib/Makefile b/lib/Makefile index 07c2ccd7cf..8ba745faa0 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -60,6 +60,7 @@ endif

obj-$(CONFIG_$(SPL_)ACPIGEN) += acpi/ obj-$(CONFIG_$(SPL_)MD5) += md5.o +obj-$(CONFIG_ECDSA) += ecdsa/ obj-$(CONFIG_$(SPL_)RSA) += rsa/ obj-$(CONFIG_HASH) += hash-checksum.o obj-$(CONFIG_SHA1) += sha1.o diff --git a/lib/ecdsa/Kconfig b/lib/ecdsa/Kconfig new file mode 100644 index 0000000000..a95c4ff581 --- /dev/null +++ b/lib/ecdsa/Kconfig @@ -0,0 +1,23 @@ +config ECDSA + bool "Enable ECDSA support" + depends on DM + help + This enables the ECDSA (elliptic curve signature) algorithm for FIT + image verification in U-Boot. The ECDSA algorithm is implemented + using the driver model, so CONFIG_DM is required by this library. + See doc/uImage.FIT/signature.txt for more details. + ECDSA is enabled for mkimage regardless of this option. + +if ECDSA + +config ECDSA_VERIFY + bool "Enable ECDSA verification support in U-Boot." + help + Allow ECDSA signatures to be recognized and verified in U-Boot. + +config SPL_ECDSA_VERIFY + bool "Enable ECDSA verification support in SPL" + help + Allow ECDSA signatures to be recognized and verified in SPL. + +endif diff --git a/lib/ecdsa/Makefile b/lib/ecdsa/Makefile new file mode 100644 index 0000000000..771d6d3135 --- /dev/null +++ b/lib/ecdsa/Makefile @@ -0,0 +1 @@ +obj-$(CONFIG_$(SPL_)ECDSA_VERIFY) += ecdsa-verify.o diff --git a/lib/ecdsa/ecdsa-verify.c b/lib/ecdsa/ecdsa-verify.c new file mode 100644 index 0000000000..0601700c4f --- /dev/null +++ b/lib/ecdsa/ecdsa-verify.c @@ -0,0 +1,134 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * ECDSA signature verification for u-boot + * + * This implements the firmware-side wrapper for ECDSA verification. It bridges + * the struct crypto_algo API to the ECDSA uclass implementations. + * + * Copyright (c) 2020, Alexandru Gagniuc mr.nuke.me@gmail.com + */ + +#include <crypto/ecdsa-uclass.h> +#include <dm/uclass.h> +#include <u-boot/ecdsa.h> + +/* + * Derive size of an ECDSA key from the curve name + * + * While it's possible to extract the key size by using string manipulation, + * use a list of known curves for the time being. + */ +static int ecdsa_key_size(const char *curve_name) +{ + if (!strcmp(curve_name, "prime256v1")) + return 256; + else + return 0; +} + +static int fdt_get_key(struct ecdsa_public_key *key, const void *fdt, int node) +{ + int x_len, y_len; + + key->curve_name = fdt_getprop(fdt, node, "ecdsa,curve", NULL); + key->size_bits = ecdsa_key_size(key->curve_name); + if (key->size_bits == 0) { + debug("Unknown ECDSA curve '%s'", key->curve_name); + return -EINVAL; + } + + key->x = fdt_getprop(fdt, node, "ecdsa,x-point", &x_len); + key->y = fdt_getprop(fdt, node, "ecdsa,y-point", &y_len); + + if (!key->x || !key->y) + return -EINVAL; + + if (x_len != (key->size_bits / 8) || y_len != (key->size_bits / 8)) { + printf("%s: node=%d, curve@%p x@%p+%i y@%p+%i\n", __func__, + node, key->curve_name, key->x, x_len, key->y, y_len); + return -EINVAL; + } + + return 0; +} + +static int ecdsa_verify_hash(struct udevice *dev, + const struct image_sign_info *info, + const void *hash, const void *sig, uint sig_len) +{ + const struct ecdsa_ops *ops = device_get_ops(dev); + const struct checksum_algo *algo = info->checksum; + struct ecdsa_public_key key; + int sig_node, key_node, ret; + + if (!ops || !ops->verify) + return -ENODEV; + + if (info->required_keynode > 0) { + ret = fdt_get_key(&key, info->fdt_blob, info->required_keynode); + if (ret < 0) + return ret; + + return ops->verify(dev, &key, hash, algo->checksum_len, + sig, sig_len); + } + + sig_node = fdt_subnode_offset(info->fdt_blob, 0, FIT_SIG_NODENAME); + if (sig_node < 0) + return -ENOENT; + + /* Try all possible keys under the "/signature" node */ + fdt_for_each_subnode(key_node, info->fdt_blob, sig_node) { + ret = fdt_get_key(&key, info->fdt_blob, key_node); + if (ret < 0) + continue; + + ret = ops->verify(dev, &key, hash, algo->checksum_len, + sig, sig_len); + + /* On success, don't worry about remaining keys */ + if (!ret) + return 0; + } + + return -EPERM; +} + +int ecdsa_verify(struct image_sign_info *info, + const struct image_region region[], int region_count, + uint8_t *sig, uint sig_len) +{ + const struct checksum_algo *algo = info->checksum; + uint8_t hash[algo->checksum_len]; + struct udevice *dev; + int ret; + + ret = uclass_first_device_err(UCLASS_ECDSA, &dev); + if (ret) { + debug("ECDSA: Could not find ECDSA implementation: %d\n", ret); + return ret; + } + + ret = algo->calculate(algo->name, region, region_count, hash); + if (ret < 0) + return -EINVAL; + + return ecdsa_verify_hash(dev, info, hash, sig, sig_len); +} + +U_BOOT_CRYPTO_ALGO(ecdsa) = { + .name = "ecdsa256", + .key_len = ECDSA256_BYTES, + .verify = ecdsa_verify, +}; + +/* + * uclass definition for ECDSA API + * + * We don't implement any wrappers around ecdsa_ops->verify() because it's + * trivial to call ops->verify(). + */ +UCLASS_DRIVER(ecdsa) = { + .id = UCLASS_ECDSA, + .name = "ecdsa_verifier", +};

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 | 102 +++++++++++++++++++++++++++ 3 files changed, 112 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 ace07fd70f..4c1eeef165 100644 --- a/arch/arm/mach-stm32mp/Kconfig +++ b/arch/arm/mach-stm32mp/Kconfig @@ -172,6 +172,15 @@ 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_STM32KEY bool "command stm32key to fuse public key hash" default n diff --git a/arch/arm/mach-stm32mp/Makefile b/arch/arm/mach-stm32mp/Makefile index 879c1961fe..391b47cf13 100644 --- a/arch/arm/mach-stm32mp/Makefile +++ b/arch/arm/mach-stm32mp/Makefile @@ -11,6 +11,7 @@ obj-y += bsec.o ifdef CONFIG_SPL_BUILD obj-y += spl.o obj-y += tzc400.o +obj-$(CONFIG_STM32_ECDSA_VERIFY) += ecdsa_romapi.o else obj-y += cmd_stm32prog/ obj-$(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..a2f63ff879 --- /dev/null +++ b/arch/arm/mach-stm32mp/ecdsa_romapi.c @@ -0,0 +1,102 @@ +// 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_VERIFY 0x60 + +struct ecdsa_rom_api { + 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; + + rom->ecdsa_verify_signature = *(void **)verify_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 != 64 || 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_DRVINFO(stm32mp_rom_api_ecdsa) = { + .name = "stm32mp_rom_api_ecdsa", +};

This test verifies that ECDSA_UCLASS is implemented, and that ecdsa_verify() works as expected. The definition of "expected" is "does not find a device, and returns -ENODEV".

The lack of a hardware-independent ECDSA implementation prevents us from having one in the sandbox, for now.

Signed-off-by: Alexandru Gagniuc mr.nuke.me@gmail.com Reviewed-by: Simon Glass sjg@chromium.org --- configs/sandbox_defconfig | 2 ++ test/dm/Makefile | 1 + test/dm/ecdsa.c | 38 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 41 insertions(+) create mode 100644 test/dm/ecdsa.c

diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig index bcd82f76ff..8bb981d6f5 100644 --- a/configs/sandbox_defconfig +++ b/configs/sandbox_defconfig @@ -299,3 +299,5 @@ CONFIG_TEST_FDTDEC=y CONFIG_UNIT_TEST=y CONFIG_UT_TIME=y CONFIG_UT_DM=y +CONFIG_ECDSA=y +CONFIG_ECDSA_VERIFY=y diff --git a/test/dm/Makefile b/test/dm/Makefile index d5c42e7643..516f69d61c 100644 --- a/test/dm/Makefile +++ b/test/dm/Makefile @@ -36,6 +36,7 @@ obj-$(CONFIG_DEVRES) += devres.o obj-$(CONFIG_DMA) += dma.o obj-$(CONFIG_VIDEO_MIPI_DSI) += dsi_host.o obj-$(CONFIG_DM_DSA) += dsa.o +obj-$(CONFIG_ECDSA_VERIFY) += ecdsa.o obj-$(CONFIG_DM_ETH) += eth.o ifneq ($(CONFIG_EFI_PARTITION),) obj-$(CONFIG_FASTBOOT_FLASH_MMC) += fastboot.o diff --git a/test/dm/ecdsa.c b/test/dm/ecdsa.c new file mode 100644 index 0000000000..da535c98b5 --- /dev/null +++ b/test/dm/ecdsa.c @@ -0,0 +1,38 @@ +// SPDX-License-Identifier: GPL-2.0-or-later + +#include <crypto/ecdsa-uclass.h> +#include <dm.h> +#include <dm/test.h> +#include <test/ut.h> +#include <u-boot/ecdsa.h> + +/* + * Basic test of the ECDSA uclass and ecdsa_verify() + * + * ECDSA implementations in u-boot are hardware-dependent. Until we have a + * software implementation that can be compiled into the sandbox, all we can + * test is the uclass support. + * + * The uclass_get() test is redundant since ecdsa_verify() would also fail. We + * run both functions in order to isolate the cause more clearly. i.e. is + * ecdsa_verify() failing because the UCLASS is absent/broken? + */ +static int dm_test_ecdsa_verify(struct unit_test_state *uts) +{ + struct uclass *ucp; + + struct checksum_algo algo = { + .checksum_len = 256, + }; + + struct image_sign_info info = { + .checksum = &algo, + }; + + ut_assertok(uclass_get(UCLASS_ECDSA, &ucp)); + ut_assertnonnull(ucp); + ut_asserteq(-ENODEV, ecdsa_verify(&info, NULL, 0, NULL, 0)); + + return 0; +} +DM_TEST(dm_test_ecdsa_verify, UT_TESTF_SCAN_PDATA | UT_TESTF_SCAN_FDT);