PSA implementation of ed25519 image verification and x25519 random key encryption/decryption

boot/boot_serial/src/boot_serial_encryption.c

@@ -36,11 +36,7 @@ boot_image_validate_encrypted(const struct flash_area *fa_p,
     memset(&boot_data, 0, sizeof(struct boot_loader_state));
     image_index = BOOT_CURR_IMG(state);
     if(IS_ENCRYPTED(hdr)) {
-        rc = boot_enc_load(BOOT_CURR_ENC(state), image_index, hdr, fa_p, bs);
-        if (rc < 0) {
-            FIH_RET(fih_rc);
-        }
-        rc = flash_area_id_to_multi_image_slot(image_index, flash_area_get_id(fa_p));
+        rc = boot_enc_load(BOOT_CURR_ENC(state), 1, hdr, fa_p, bs);
         if (rc < 0) {
             FIH_RET(fih_rc);
         }
@@ -129,10 +125,11 @@ decrypt_region_inplace(struct boot_loader_state *state,
     size_t blk_off;
     uint16_t idx;
     uint32_t blk_sz;
-    uint8_t image_index;
-
+    int slot = flash_area_id_to_multi_image_slot(BOOT_CURR_IMG(state),
+                                                 flash_area_get_id(fap));
     uint8_t buf[sz] __attribute__((aligned));
     assert(sz <= sizeof buf);
+    assert(slot >= 0);
 
     bytes_copied = 0;
     while (bytes_copied < sz) {
@@ -147,7 +144,6 @@ decrypt_region_inplace(struct boot_loader_state *state,
             return BOOT_EFLASH;
         }
 
-        image_index = BOOT_CURR_IMG(state);
         if (IS_ENCRYPTED(hdr)) {
             blk_sz = chunk_sz;
             idx = 0;
@@ -175,7 +171,7 @@ decrypt_region_inplace(struct boot_loader_state *state,
                     blk_sz = tlv_off - (off + bytes_copied);
                 }
             }
-            boot_encrypt(BOOT_CURR_ENC(state), image_index, fap,
+            boot_enc_decrypt(BOOT_CURR_ENC(state), slot,
                     (off + bytes_copied + idx) - hdr->ih_hdr_size, blk_sz,
                     blk_off, &buf[idx]);
         }
@@ -222,7 +218,6 @@ decrypt_image_inplace(const struct flash_area *fa_p,
     size_t sect_size;
     size_t sect_count;
     size_t sect;
-    uint8_t image_index;
     struct flash_sector sector;
 
     memset(&boot_data, 0, sizeof(struct boot_loader_state));
@@ -232,8 +227,6 @@ decrypt_image_inplace(const struct flash_area *fa_p,
     rc = flash_area_get_sector(fa_p, boot_status_off(fa_p), &sector);
 
 
-    image_index = BOOT_CURR_IMG(state);
-
     if(IS_ENCRYPTED(hdr)) {
 #if 0 //Skip this step?, the image will just not boot if it's not decrypted properly
         static uint8_t tmpbuf[BOOT_TMPBUF_SZ];
@@ -245,7 +238,7 @@ decrypt_image_inplace(const struct flash_area *fa_p,
 #endif
         memset(&boot_data, 0, sizeof(struct boot_loader_state));
         /* Load the encryption keys into cache */
-        rc = boot_enc_load(BOOT_CURR_ENC(state), image_index, hdr, fa_p, bs);
+        rc = boot_enc_load(BOOT_CURR_ENC(state), 0, hdr, fa_p, bs);
         if (rc < 0) {
             FIH_RET(fih_rc);
         }

boot/bootutil/include/bootutil/crypto/aes_ctr.h

@@ -15,8 +15,8 @@
 #include "mcuboot_config/mcuboot_config.h"
 
 #if (defined(MCUBOOT_USE_MBED_TLS) + \
-     defined(MCUBOOT_USE_TINYCRYPT)) != 1
-    #error "One crypto backend must be defined: either MBED_TLS or TINYCRYPT"
+     defined(MCUBOOT_USE_TINYCRYPT) + defined(MCUBOOT_USE_PSA_CRYPTO)) != 1
+    #error "One crypto backend must be defined: either MBED_TLS or TINYCRYPT or PSA"
 #endif
 
 #if defined(MCUBOOT_USE_MBED_TLS)
@@ -38,12 +38,46 @@
     #define BOOTUTIL_CRYPTO_AES_CTR_BLOCK_SIZE TC_AES_BLOCK_SIZE
 #endif /* MCUBOOT_USE_TINYCRYPT */
 
+
+#if defined(MCUBOOT_USE_PSA_CRYPTO)
+    #include <psa/crypto.h>
+    #include "bootutil/enc_key_public.h"
+    #define BOOTUTIL_CRYPTO_AES_CTR_KEY_SIZE BOOT_ENC_KEY_SIZE
+    #define BOOTUTIL_CRYPTO_AES_CTR_BLOCK_SIZE (16)
+#endif
+
 #include <stdint.h>
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if defined(MCUBOOT_USE_PSA_CRYPTO)
+typedef struct {
+	/* Fixme: This should not be, here, psa_key_id should be passed */
+	uint8_t key[BOOT_ENC_KEY_SIZE];
+} bootutil_aes_ctr_context;
+
+void bootutil_aes_ctr_init(bootutil_aes_ctr_context *ctx);
+
+static inline void bootutil_aes_ctr_drop(bootutil_aes_ctr_context *ctx)
+{
+    memset(ctx, 0, sizeof(ctx));
+}
+
+static inline int bootutil_aes_ctr_set_key(bootutil_aes_ctr_context *ctx, const uint8_t *k)
+{
+    memcpy(ctx->key, k, sizeof(ctx->key));
+
+    return 0;
+}
+
+int bootutil_aes_ctr_encrypt(bootutil_aes_ctr_context *ctx, uint8_t *counter,
+        const uint8_t *m, uint32_t mlen, size_t blk_off, uint8_t *c);
+int bootutil_aes_ctr_decrypt(bootutil_aes_ctr_context *ctx, uint8_t *counter,
+        const uint8_t *c, uint32_t clen, size_t blk_off, uint8_t *m);
+#endif
+
 #if defined(MCUBOOT_USE_MBED_TLS)
 typedef mbedtls_aes_context bootutil_aes_ctr_context;
 static inline void bootutil_aes_ctr_init(bootutil_aes_ctr_context *ctx)

boot/bootutil/include/bootutil/crypto/common.h

@@ -17,4 +17,13 @@
 #define MBEDTLS_CONTEXT_MEMBER(X) X
 #endif
 
+/* Newer versions of Mbed TLS have removed the private accessor requirement for
+ * the ASN1 fields.
+ */
+#if (MBEDTLS_VERSION_NUMBER >= 0x03000000) && (MBEDTLS_VERSION_NUMBER < 0x03010000)
+#define ASN1_CONTEXT_MEMBER(X) MBEDTLS_PRIVATE(X)
+#else
+#define ASN1_CONTEXT_MEMBER(X) X
+#endif
+
 #endif /* __BOOTUTIL_CRYPTO_COMMON_H__ */

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

@@ -109,13 +109,13 @@ static int bootutil_import_key(uint8_t **cp, uint8_t *end)
         return -2;
     }
     /* id-ecPublicKey (RFC5480) */
-    if (alg.MBEDTLS_CONTEXT_MEMBER(len) != sizeof(ec_pubkey_oid) - 1 ||
-        memcmp(alg.MBEDTLS_CONTEXT_MEMBER(p), ec_pubkey_oid, sizeof(ec_pubkey_oid) - 1)) {
+    if (alg.ASN1_CONTEXT_MEMBER(len) != sizeof(ec_pubkey_oid) - 1 ||
+        memcmp(alg.ASN1_CONTEXT_MEMBER(p), ec_pubkey_oid, sizeof(ec_pubkey_oid) - 1)) {
         return -3;
     }
     /* namedCurve (RFC5480) */
-    if (param.MBEDTLS_CONTEXT_MEMBER(len) != sizeof(ec_secp256r1_oid) - 1 ||
-        memcmp(param.MBEDTLS_CONTEXT_MEMBER(p), ec_secp256r1_oid, sizeof(ec_secp256r1_oid) - 1)) {
+    if (param.ASN1_CONTEXT_MEMBER(len) != sizeof(ec_secp256r1_oid) - 1 ||
+        memcmp(param.ASN1_CONTEXT_MEMBER(p), ec_secp256r1_oid, sizeof(ec_secp256r1_oid) - 1)) {
         return -4;
     }
     /* ECPoint (RFC5480) */
@@ -521,12 +521,12 @@ static int bootutil_parse_eckey(bootutil_ecdsa_context *ctx, uint8_t **p, uint8_
     if (mbedtls_asn1_get_alg(p, end, &alg, &param)) {
         return -2;
     }
-    if (alg.MBEDTLS_CONTEXT_MEMBER(len) != sizeof(ec_pubkey_oid) - 1 ||
-      memcmp(alg.MBEDTLS_CONTEXT_MEMBER(p), ec_pubkey_oid, sizeof(ec_pubkey_oid) - 1)) {
+    if (alg.ASN1_CONTEXT_MEMBER(len) != sizeof(ec_pubkey_oid) - 1 ||
+      memcmp(alg.ASN1_CONTEXT_MEMBER(p), ec_pubkey_oid, sizeof(ec_pubkey_oid) - 1)) {
         return -3;
     }
-    if (param.MBEDTLS_CONTEXT_MEMBER(len) != sizeof(ec_secp256r1_oid) - 1||
-      memcmp(param.MBEDTLS_CONTEXT_MEMBER(p), ec_secp256r1_oid, sizeof(ec_secp256r1_oid) - 1)) {
+    if (param.ASN1_CONTEXT_MEMBER(len) != sizeof(ec_secp256r1_oid) - 1||
+      memcmp(param.ASN1_CONTEXT_MEMBER(p), ec_secp256r1_oid, sizeof(ec_secp256r1_oid) - 1)) {
         return -4;
     }
 

boot/bootutil/include/bootutil/enc_key.h

@@ -48,19 +48,21 @@ struct enc_key_data {
 extern const struct bootutil_key bootutil_enc_key;
 struct boot_status;
 
+/* Decrypt random, symmetric encryption key */
+int boot_decrypt_key(const uint8_t *buf, uint8_t *enckey);
+
 int boot_enc_init(struct enc_key_data *enc_state, uint8_t slot);
 int boot_enc_drop(struct enc_key_data *enc_state, uint8_t slot);
 int boot_enc_set_key(struct enc_key_data *enc_state, uint8_t slot,
         const struct boot_status *bs);
-int boot_enc_load(struct enc_key_data *enc_state, int image_index,
+int boot_enc_load(struct enc_key_data *enc_state, int slot,
         const struct image_header *hdr, const struct flash_area *fap,
         struct boot_status *bs);
-int boot_enc_decrypt(const uint8_t *buf, uint8_t *enckey);
-bool boot_enc_valid(struct enc_key_data *enc_state, int image_index,
-        const struct flash_area *fap);
-void boot_encrypt(struct enc_key_data *enc_state, int image_index,
-        const struct flash_area *fap, uint32_t off, uint32_t sz,
-        uint32_t blk_off, uint8_t *buf);
+bool boot_enc_valid(struct enc_key_data *enc_state, int slot);
+void boot_enc_encrypt(struct enc_key_data *enc_state, int slot,
+        uint32_t off, uint32_t sz, uint32_t blk_off, uint8_t *buf);
+void boot_enc_decrypt(struct enc_key_data *enc_state, int slot,
+        uint32_t off, uint32_t sz, uint32_t blk_off, uint8_t *buf);
 void boot_enc_zeroize(struct enc_key_data *enc_state);
 
 #ifdef __cplusplus

boot/bootutil/src/bootutil_misc.c

@@ -283,7 +283,7 @@ boot_read_enc_key(const struct flash_area *fap, uint8_t slot, struct boot_status
         }
         /* Only try to decrypt non-erased TLV metadata */
         if (i != BOOT_ENC_TLV_ALIGN_SIZE) {
-            rc = boot_enc_decrypt(bs->enctlv[slot], bs->enckey[slot]);
+            rc = boot_decrypt_key(bs->enctlv[slot], bs->enckey[slot]);
         }
     }
 #else

boot/bootutil/src/ed25519_psa.c

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2020 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+#include <assert.h>
+#include <string.h>
+#include <stdint.h>
+
+#include <mcuboot_config/mcuboot_config.h>
+#include "bootutil/bootutil_log.h"
+
+#include <psa/crypto.h>
+#include <psa/crypto_types.h>
+
+BOOT_LOG_MODULE_DECLARE(ed25519_psa);
+
+#define SHA512_DIGEST_LENGTH    64
+#define EDDSA_KEY_LENGTH        32
+#define EDDSA_SIGNAGURE_LENGTH  64
+
+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])
+{
+    /* Set to any error */
+    psa_status_t status = PSA_ERROR_BAD_STATE;
+    psa_key_attributes_t key_attr = PSA_KEY_ATTRIBUTES_INIT;
+    psa_key_id_t kid;
+    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\n", status);
+        return 0;
+    }
+
+    status = PSA_ERROR_BAD_STATE;
+
+    psa_set_key_type(&key_attr,
+                     PSA_KEY_TYPE_ECC_PUBLIC_KEY(PSA_ECC_FAMILY_TWISTED_EDWARDS));
+    psa_set_key_usage_flags(&key_attr, PSA_KEY_USAGE_VERIFY_MESSAGE);
+    psa_set_key_algorithm(&key_attr, PSA_ALG_PURE_EDDSA);
+
+    status = psa_import_key(&key_attr, public_key, EDDSA_KEY_LENGTH, &kid);
+    if (status != PSA_SUCCESS) {
+        BOOT_LOG_ERR("ED25519 key import failed %d", status);
+        return 0;
+    }
+
+    status = psa_verify_message(kid, PSA_ALG_PURE_EDDSA, message, message_len,
+                                signature, EDDSA_SIGNAGURE_LENGTH);
+    if (status != PSA_SUCCESS) {
+        BOOT_LOG_ERR("ED25519 signature verification failed %d", status);
+        ret = 0;
+        /* Pass through to destroy key */
+    } else {
+	ret = 1;
+        /* Pass through to destroy key */
+    }
+
+    status = psa_destroy_key(kid);
+
+    if (status != PSA_SUCCESS) {
+        /* Just for logging */
+        BOOT_LOG_WRN("Failed to destroy key %d", status);
+    }
+
+    return ret;
+}