[nrf noup] bootutil: Add support for KMU stored ED25519 signature key

The commit adds verification of image using keys stored in KMU. Signed-off-by: Dominik Ermel <[email protected]> (cherry picked from commit 1dbca8f)
nrfconnect · Oct 24, 2024 · 40543f1 · 40543f1
1 parent d5aa215
commit 40543f1
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Showing 5 changed files with 102 additions and 6 deletions.
diff --git a/boot/bootutil/src/ed25519_psa.c b/boot/bootutil/src/ed25519_psa.c
@@ -12,13 +12,28 @@
 
 #include <psa/crypto.h>
 #include <psa/crypto_types.h>
+#if defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
+#include <cracen_psa_kmu.h>
+#endif
 
 BOOT_LOG_MODULE_DECLARE(ed25519_psa);
 
 #define SHA512_DIGEST_LENGTH    64
 #define EDDSA_KEY_LENGTH        32
 #define EDDSA_SIGNAGURE_LENGTH  64
 
+#if defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
+/* List of KMU stored key ids available for MCUboot */
+#define MAKE_PSA_KMU_KEY_ID(id) PSA_KEY_HANDLE_FROM_CRACEN_KMU_SLOT(CRACEN_KMU_KEY_USAGE_SCHEME_RAW, id)
+static psa_key_id_t kmu_key_ids[3] =  {
+    MAKE_PSA_KMU_KEY_ID(226),
+    MAKE_PSA_KMU_KEY_ID(228),
+    MAKE_PSA_KMU_KEY_ID(230)
+};
+#define KMU_KEY_COUNT (sizeof(kmu_key_ids)/sizeof(kmu_key_ids[0]))
+#endif
+
+#if !defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
 int ED25519_verify(const uint8_t *message, size_t message_len,
                           const uint8_t signature[EDDSA_SIGNAGURE_LENGTH],
                           const uint8_t public_key[EDDSA_KEY_LENGTH])
@@ -69,3 +84,39 @@ int ED25519_verify(const uint8_t *message, size_t message_len,
 
     return ret;
 }
+#else
+int ED25519_verify(const uint8_t *message, size_t message_len,
+                          const uint8_t signature[EDDSA_SIGNAGURE_LENGTH],
+                          const uint8_t public_key[EDDSA_KEY_LENGTH])
+{
+    ARG_UNUSED(public_key);
+    /* Set to any error */
+    psa_status_t status = PSA_ERROR_BAD_STATE;
+    int ret = 0;        /* Fail by default */
+
+    /* Initialize PSA Crypto */
+    status = psa_crypto_init();
+    if (status != PSA_SUCCESS) {
+        BOOT_LOG_ERR("PSA crypto init failed %d", status);
+        return 0;
+    }
+
+    status = PSA_ERROR_BAD_STATE;
+
+    for (int i = 0; i < KMU_KEY_COUNT; ++i) {
+        psa_key_id_t kid = kmu_key_ids[i];
+
+        status = psa_verify_message(kid, PSA_ALG_PURE_EDDSA, message,
+                                    message_len, signature,
+                                    EDDSA_SIGNAGURE_LENGTH);
+        if (status == PSA_SUCCESS) {
+            ret = 1;
+            break;
+        }
+
+        BOOT_LOG_ERR("ED25519 signature verification failed %d", status);
+    }
+
+    return ret;
+}
+#endif
diff --git a/boot/bootutil/src/image_ed25519.c b/boot/bootutil/src/image_ed25519.c
@@ -25,14 +25,16 @@
 #include "bootutil/crypto/sha.h"
 
 #define EDDSA_SIGNATURE_LENGTH 64
-
-static const uint8_t ed25519_pubkey_oid[] = MBEDTLS_OID_ISO_IDENTIFIED_ORG "\x65\x70";
 #define NUM_ED25519_BYTES 32
 
 extern int ED25519_verify(const uint8_t *message, size_t message_len,
                           const uint8_t signature[EDDSA_SIGNATURE_LENGTH],
                           const uint8_t public_key[NUM_ED25519_BYTES]);
 
+#if !defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
+
+static const uint8_t ed25519_pubkey_oid[] = MBEDTLS_OID_ISO_IDENTIFIED_ORG "\x65\x70";
+
 /*
  * Parse the public key used for signing.
  */
@@ -71,21 +73,25 @@ bootutil_import_key(uint8_t **cp, uint8_t *end)
 
     return 0;
 }
+#endif
 
 fih_ret
 bootutil_verify_sig(uint8_t *hash, uint32_t hlen, uint8_t *sig, size_t slen,
   uint8_t key_id)
 {
     int rc;
     FIH_DECLARE(fih_rc, FIH_FAILURE);
-    uint8_t *pubkey;
+    uint8_t *pubkey = NULL;
+#if !defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
     uint8_t *end;
+#endif
 
     if (hlen != IMAGE_HASH_SIZE || slen != EDDSA_SIGNATURE_LENGTH) {
         FIH_SET(fih_rc, FIH_FAILURE);
         goto out;
     }
 
+#if !defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
     pubkey = (uint8_t *)bootutil_keys[key_id].key;
     end = pubkey + *bootutil_keys[key_id].len;
 
@@ -94,6 +100,7 @@ bootutil_verify_sig(uint8_t *hash, uint32_t hlen, uint8_t *sig, size_t slen,
         FIH_SET(fih_rc, FIH_FAILURE);
         goto out;
     }
+#endif
 
     rc = ED25519_verify(hash, IMAGE_HASH_SIZE, sig, pubkey);
 
@@ -115,14 +122,17 @@ bootutil_verify_img(const uint8_t *img, uint32_t size,
 {
     int rc;
     FIH_DECLARE(fih_rc, FIH_FAILURE);
-    uint8_t *pubkey;
+    uint8_t *pubkey = NULL;
+#if !defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
     uint8_t *end;
+#endif
 
     if (slen != EDDSA_SIGNATURE_LENGTH) {
         FIH_SET(fih_rc, FIH_FAILURE);
         goto out;
     }
 
+#if !defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
     pubkey = (uint8_t *)bootutil_keys[key_id].key;
     end = pubkey + *bootutil_keys[key_id].len;
 
@@ -131,6 +141,7 @@ bootutil_verify_img(const uint8_t *img, uint32_t size,
         FIH_SET(fih_rc, FIH_FAILURE);
         goto out;
     }
+#endif
 
     rc = ED25519_verify(img, size, sig, pubkey);
 

diff --git a/boot/bootutil/src/image_validate.c b/boot/bootutil/src/image_validate.c
@@ -245,6 +245,7 @@ bootutil_img_hash(struct enc_key_data *enc_state, int image_index,
 #   define KEY_BUF_SIZE         (SIG_BUF_SIZE + 24)
 #endif /* !MCUBOOT_HW_KEY */
 
+#if !defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
 #if !defined(MCUBOOT_HW_KEY)
 static int
 bootutil_find_key(uint8_t *keyhash, uint8_t keyhash_len)
@@ -310,6 +311,7 @@ bootutil_find_key(uint8_t image_index, uint8_t *key, uint16_t key_len)
 }
 #endif /* !MCUBOOT_HW_KEY */
 #endif /* !MCUBOOT_BUILTIN_KEY */
+#endif /* !defined(CONFIG_BOOT_SIGNATURE_USING_KMU) */
 #endif /* EXPECTED_SIG_TLV */
 
 /**
@@ -626,6 +628,7 @@ bootutil_img_validate(struct enc_key_data *enc_state, int image_index,
             break;
         }
 #endif /* defined(EXPECTED_HASH_TLV) && !defined(MCUBOOT_SIGN_PURE) */
+#if !defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
 #ifdef EXPECTED_KEY_TLV
         case EXPECTED_KEY_TLV:
         {
@@ -656,14 +659,17 @@ bootutil_img_validate(struct enc_key_data *enc_state, int image_index,
             break;
         }
 #endif /* EXPECTED_KEY_TLV */
+#endif /* !defined(CONFIG_BOOT_SIGNATURE_USING_KMU) */
 #ifdef EXPECTED_SIG_TLV
         case EXPECTED_SIG_TLV:
         {
+#if !defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
             /* Ignore this signature if it is out of bounds. */
             if (key_id < 0 || key_id >= bootutil_key_cnt) {
                 key_id = -1;
                 continue;
             }
+#endif /* !defined(CONFIG_BOOT_SIGNATURE_USING_KMU) */
             if (!EXPECTED_SIG_LEN(len) || len > sizeof(buf)) {
                 rc = -1;
                 goto out;

diff --git a/boot/zephyr/CMakeLists.txt b/boot/zephyr/CMakeLists.txt
@@ -313,7 +313,7 @@ if(CONFIG_MCUBOOT_SERIAL)
   endif()
 endif()
 
-if(NOT CONFIG_BOOT_SIGNATURE_KEY_FILE STREQUAL "")
+if(NOT CONFIG_BOOT_SIGNATURE_USING_KMU OR NOT CONFIG_BOOT_SIGNATURE_KEY_FILE STREQUAL "")
   # CONF_FILE points to the KConfig configuration files of the bootloader.
   foreach (filepath ${CONF_FILE})
     file(READ ${filepath} temp_text)

diff --git a/boot/zephyr/Kconfig b/boot/zephyr/Kconfig
@@ -194,6 +194,7 @@ endchoice # BOOT_IMG_HASH_ALG
 
 config BOOT_SIGNATURE_TYPE_PURE_ALLOW
 	bool
+	depends on NRF_SECURITY
 	help
 	  Hidden option set by configurations that allow Pure variant,
 	  for example ed25519. The pure variant means that image
@@ -293,6 +294,7 @@ config BOOT_ED25519_MBEDTLS
 
 config BOOT_ED25519_PSA
 	bool "Use PSA crypto"
+	depends on NRF_SECURITY
 	select BOOT_USE_PSA_CRYPTO
 	select BOOT_ED25519_PSA_DEPENDENCIES
 	select BOOT_X25519_PSA_DEPENDENCIES if BOOT_ENCRYPT_IMAGE
@@ -302,6 +304,22 @@ endif
 
 endchoice
 
+config BOOT_SIGNATURE_USING_KMU
+	bool "Use KMU stored keys for signature verification"
+	depends on NRF_SECURITY
+	depends on CRACEN_LIB_KMU
+	select PSA_WANT_ALG_GCM
+	select PSA_WANT_KEY_TYPE_AES
+	select PSA_WANT_AES_KEY_SIZE_256
+	select PSA_WANT_ALG_SP800_108_COUNTER_CMAC
+	select PSA_WANT_ALG_CMAC
+	select PSA_WANT_ALG_ECB_NO_PADDING
+	help
+	  MCUboot will use keys provisioned to the device key management unit for signature
+	  verification instead of compiling in key data from a file.
+
+if !BOOT_SIGNATURE_USING_KMU
+
 config BOOT_SIGNATURE_KEY_FILE
 	string "PEM key file"
 	default "root-ec-p256.pem" if BOOT_SIGNATURE_TYPE_ECDSA_P256
@@ -319,6 +337,8 @@ config BOOT_SIGNATURE_KEY_FILE
 	  with the public key information will be written in a format expected by
 	  MCUboot.
 
+endif
+
 config MCUBOOT_CLEANUP_ARM_CORE
 	bool "Perform core cleanup before chain-load the application"
 	depends on CPU_CORTEX_M
@@ -335,10 +355,18 @@ config MCUBOOT_CLEANUP_ARM_CORE
 	  start-up code which can cause a module fault and potentially make the
 	  module irrecoverable.
 
+# Disable MBEDTLS from being selected if NRF_SECURITY is enabled, and use default NRF_SECURITY
+# configuration file for MBEDTLS
+config MBEDTLS
+	depends on !NRF_SECURITY
+
+config NRF_SECURITY
+	select MBEDTLS_PROMPTLESS
+
 if MBEDTLS
 
 config MBEDTLS_CFG_FILE
-	default "mcuboot-mbedtls-cfg.h"
+	default "mcuboot-mbedtls-cfg.h" if !NRF_SECURITY
 
 endif