arm: stm32mp1: Implement ECDSA signature verification

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>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>

diff --git a/arch/arm/mach-stm32mp/Kconfig b/arch/arm/mach-stm32mp/Kconfig
index 8324fa828af1bbea49f18b6a090f589759670d60..5d7eca649a87313e605fa3546f0cb4b93f35bba4 100644 (file)
--- a/arch/arm/mach-stm32mp/Kconfig
+++ b/arch/arm/mach-stm32mp/Kconfig
@@ -179,6 +179,15 @@ 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 879c1961fef00851e7ea2f3d29d1bbb0bb5bdaea..391b47cf13f82d6622240857bb96d8c94aca6081 100644 (file)
--- 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 (file)
index 0000000..a2f63ff
--- /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",
+};