[nrf noup] bootutil: Add support for nrfxlib_crypto

Add support for subset of functions available in nrfxlib_crypto using
ocrypto SW cryptography:
- ecdsa_p256
- sha256

This allows to bypass layered system of Oberon PSA Crypto drivers and
use SW crypto library calls directly, which can help reducing binary
size.

Changes are intented for Ultralight (nrf54ls05b), which has limited
resources and can benefit from smaller mcuboot binary size.

Ref: ncsdk-37699

Signed-off-by: Adam Szczygieł <adam.szczygiel@nordicsemi.no>

Author: adsz-nordic

boot/bootutil/include/bootutil/crypto/ecdsa.h

@@ -35,8 +35,9 @@
 #if (defined(MCUBOOT_USE_TINYCRYPT) + \
      defined(MCUBOOT_USE_CC310) + \
      defined(MCUBOOT_USE_NRF_EXTERNAL_CRYPTO) + \
-     defined(MCUBOOT_USE_PSA_OR_MBED_TLS)) != 1
-    #error "One crypto backend must be defined: either CC310/TINYCRYPT/MBED_TLS/PSA_CRYPTO"
+     defined(MCUBOOT_USE_PSA_OR_MBED_TLS) + \
+     defined(MCUBOOT_USE_NRF_OBERON)) != 1
+    #error "One crypto backend must be defined: either CC310/TINYCRYPT/MBED_TLS/PSA_CRYPTO/NRF_OBERON"
 #endif
 
 #if defined(MCUBOOT_USE_TINYCRYPT)
@@ -58,8 +59,13 @@
     #define MCUBOOT_ECDSA_NEED_ASN1_SIG
 #endif /* MCUBOOT_USE_MBED_TLS */
 
+#if defined(MCUBOOT_USE_NRF_OBERON)
+  #include <ocrypto_ecdsa_p256.h>
+#endif /* MCUBOOT_USE_NRF_OBERON */
+
 /*TODO: remove this after cypress port mbedtls to abstract crypto api */
-#if defined(MCUBOOT_USE_CC310) || defined(MCUBOOT_USE_MBED_TLS)
+#if defined(MCUBOOT_USE_CC310) || defined(MCUBOOT_USE_MBED_TLS) || \
+  defined(MCUBOOT_USE_NRF_OBERON)
 #define NUM_ECC_BYTES (256 / 8)
 #endif
 
@@ -83,7 +89,8 @@ extern "C" {
 #endif
 
 #if (defined(MCUBOOT_USE_TINYCRYPT) || defined(MCUBOOT_USE_MBED_TLS) || \
-     defined(MCUBOOT_USE_CC310) || defined(MCUBOOT_USE_NRF_EXTERNAL_CRYPTO)) \
+     defined(MCUBOOT_USE_CC310) || defined(MCUBOOT_USE_NRF_EXTERNAL_CRYPTO) || \
+     defined(MCUBOOT_USE_NRF_OBERON)) \
      && !defined(MCUBOOT_USE_PSA_CRYPTO)
 /*
  * Declaring these like this adds NULL termination.
@@ -719,6 +726,66 @@ static inline int bootutil_ecdsa_parse_public_key(bootutil_ecdsa_context *ctx,
 }
 #endif /* MCUBOOT_USE_NRF_EXTERNAL_CRYPTO */
 
+#if defined(MCUBOOT_USE_NRF_OBERON)
+#define UNCOMPRESSED_KEY_PREFIX 0x04
+
+typedef uintptr_t bootutil_ecdsa_context;
+
+static inline void bootutil_ecdsa_init(bootutil_ecdsa_context *ctx)
+{
+  (void)ctx;
+}
+
+static inline void bootutil_ecdsa_drop(bootutil_ecdsa_context *ctx)
+{
+  (void)ctx;
+}
+
+static inline int bootutil_ecdsa_verify(bootutil_ecdsa_context *ctx,
+                                        uint8_t *pk, size_t pk_len,
+                                        uint8_t *hash, size_t hash_len,
+                                        uint8_t *sig, size_t sig_len)
+{
+  if (pk == NULL || hash == NULL || sig == NULL) {
+    return -1;
+  }
+
+  /* API expects particular values:
+   * pk_len -> 64, plus one byte for key type/format (consumed by this function)
+   * hash_len -> 32
+   * sig_len -> 64 but it is encoded in asn1 format which can have variable length
+   * */
+  if (pk_len != 65 || hash_len != 32 || sig_len == 0) {
+    return -1;
+  }
+
+  uint8_t signature[2 * NUM_ECC_BYTES];
+  int rc = bootutil_decode_sig(signature, sig, sig + sig_len);
+  if (rc) {
+    return rc;
+  }
+
+  /* Support only uncompressed keys */
+  if (pk[0] != UNCOMPRESSED_KEY_PREFIX) {
+    return -1;
+  }
+
+  /* Skip the first byte holding key format */
+  pk++;
+
+  return ocrypto_ecdsa_p256_verify_hash(signature, hash, pk);
+}
+
+static inline int bootutil_ecdsa_parse_public_key(bootutil_ecdsa_context *ctx,
+                                                  uint8_t **cp, uint8_t *end)
+{
+  (void)ctx;
+
+  return bootutil_import_key(cp, end);
+}
+
+#endif /* MCUBOOT_USE_NRF_OBERON */
+
 #ifdef __cplusplus
 }
 #endif

boot/bootutil/include/bootutil/crypto/sha.h

@@ -31,8 +31,9 @@
 #if (defined(MCUBOOT_USE_PSA_OR_MBED_TLS) + \
      defined(MCUBOOT_USE_TINYCRYPT) + \
      defined(MCUBOOT_USE_NRF_EXTERNAL_CRYPTO) + \
-     defined(MCUBOOT_USE_CC310)) != 1
-    #error "One crypto backend must be defined: either CC310/MBED_TLS/TINYCRYPT/PSA_CRYPTO"
+     defined(MCUBOOT_USE_CC310) + \
+     defined(MCUBOOT_USE_NRF_OBERON)) != 1
+    #error "One crypto backend must be defined: either CC310/MBED_TLS/TINYCRYPT/PSA_CRYPTO/NRF_OBERON"
 #endif
 
 #if defined(MCUBOOT_SHA512)
@@ -84,6 +85,10 @@
 
 #include <stdint.h>
 
+#if defined(MCUBOOT_USE_NRF_OBERON)
+  #include <ocrypto_sha256.h>
+#endif /* MCUBOOT_USE_NRF_OBERON */
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -302,6 +307,43 @@ static inline int bootutil_sha_finish(bootutil_sha_context *ctx,
 }
 #endif /* MCUBOOT_USE_NRF_EXTERNAL_CRYPTO */
 
+#if defined(MCUBOOT_USE_NRF_OBERON)
+typedef ocrypto_sha256_ctx bootutil_sha_context;
+
+static inline int bootutil_sha_init(bootutil_sha_context *ctx)
+{
+  if (ctx == NULL) {
+    return -1;
+  }
+
+  ocrypto_sha256_init(ctx);
+  return 0;
+}
+
+static inline int bootutil_sha_drop(bootutil_sha_context *ctx)
+{
+  /* NOTE: No corresponding function for ocrypto_sha256 */
+  (void)ctx;
+  return 0;
+}
+
+static inline int bootutil_sha_update(bootutil_sha_context *ctx,
+                                      const void *data,
+                                      uint32_t data_len)
+{
+  ocrypto_sha256_update(ctx, (const uint8_t *)data, (size_t)data_len);
+  return 0;
+}
+
+static inline int bootutil_sha_finish(bootutil_sha_context *ctx,
+                                      uint8_t *output)
+{
+  ocrypto_sha256_final(ctx, output);
+  return 0;
+}
+
+#endif /* MCUBOOT_USE_NRF_OBERON */
+
 #ifdef __cplusplus
 }
 #endif

boot/bootutil/zephyr/CMakeLists.txt

@@ -48,6 +48,11 @@ if(CONFIG_BOOT_USE_TINYCRYPT)
   )
 endif()
 
+if(CONFIG_BOOT_USE_NRF_OBERON)
+  target_include_directories(MCUBOOT_BOOTUTIL INTERFACE ${OBERON_BASE}/include)
+  zephyr_link_libraries(nrfxlib_crypto)
+endif()
+
 if(CONFIG_BOOT_USE_PSA_CRYPTO)
   target_include_directories(MCUBOOT_BOOTUTIL INTERFACE
      ${ZEPHYR_MBEDTLS_MODULE_DIR}/include

boot/zephyr/Kconfig

@@ -54,6 +54,11 @@ config BOOT_USE_CC310
 config BOOT_USE_NRF_CC310_BL
 	bool
 
+config BOOT_USE_NRF_OBERON
+  bool
+  help
+    Use nrf oberon SW crypto.
+
 config NRFXLIB_CRYPTO
 	bool
 
@@ -286,6 +291,10 @@ choice BOOT_ECDSA_IMPLEMENTATION
 	default BOOT_ECDSA_PSA if NRF_SECURITY
 	default BOOT_ECDSA_TINYCRYPT
 
+config BOOT_ECDSA_NRF_OBERON
+  bool "use nrf oberon SW crypto."
+  select BOOT_USE_NRF_OBERON
+
 config BOOT_ECDSA_TINYCRYPT
 	bool "Use tinycrypt"
 	select BOOT_USE_TINYCRYPT

boot/zephyr/include/mcuboot_config/mcuboot_config.h

@@ -51,6 +51,8 @@
 #define MCUBOOT_USE_PSA_CRYPTO
 #elif defined(CONFIG_BOOT_USE_NRF_EXTERNAL_CRYPTO)
 #define MCUBOOT_USE_NRF_EXTERNAL_CRYPTO
+#elif defined(CONFIG_BOOT_USE_NRF_OBERON)
+#define MCUBOOT_USE_NRF_OBERON
 #endif
 
 #ifdef CONFIG_BOOT_IMG_HASH_ALG_SHA512