Cleanup the AES CTR IV.

Author: dgarske

include/encrypt.h

@@ -65,7 +65,7 @@ int aes_init(void);
 void aes_set_iv(uint8_t *nonce, uint32_t address);
 #endif /* ENCRYPT_WITH_CHACHA */
 
-/* Internal read/write functions (not exported in the libwolfboot API) */
+/* external flash encryption read/write functions */
 int ext_flash_encrypt_write(uintptr_t address, const uint8_t *data, int len);
 int ext_flash_decrypt_read(uintptr_t address, uint8_t *data, int len);
 

src/libwolfboot.c

@@ -1600,13 +1600,14 @@ int aes_init(void)
         /* register AES crypto callback */
         wc_CryptoCb_RegisterDevice(devId, wc_tsip_AesCipher, NULL);
 
-        /* AES_ENCRYPTION is used for both directions in CTR */
-        /* unwrapped key never leaves TSIP and is referenced by tsip_keyIdx */
+        /* AES_ENCRYPTION is used for both directions in CTR
+         * IV is set later with "wc_AesSetIV" */
         wc_AesSetKeyDirect(&aes_enc, enc_key->encrypted_user_key,
-            ENCRYPT_KEY_SIZE, enc_key->initial_vector, AES_ENCRYPTION);
+            ENCRYPT_KEY_SIZE, NULL, AES_ENCRYPTION);
         wc_AesSetKeyDirect(&aes_dec, enc_key->encrypted_user_key,
-            ENCRYPT_KEY_SIZE, enc_key->initial_vector, AES_ENCRYPTION);
+            ENCRYPT_KEY_SIZE, NULL, AES_ENCRYPTION);
 
+        /* set IV nonce use in aes_set_iv */
         XMEMCPY(encrypt_iv_nonce, enc_key->initial_vector, ENCRYPT_NONCE_SIZE);
         encrypt_initialized = 1;
     }
@@ -1619,7 +1620,6 @@ int aes_init(void)
         ENCRYPT_TMP_SECRET_OFFSET);
 #endif
     uint8_t ff[ENCRYPT_KEY_SIZE];
-    uint8_t iv_buf[ENCRYPT_NONCE_SIZE];
     uint8_t* stored_nonce;
 
 #ifdef NVM_FLASH_WRITEONCE
@@ -1641,11 +1641,13 @@ int aes_init(void)
     if (XMEMCMP(key, ff, ENCRYPT_KEY_SIZE) == 0)
         return -1;
 
+    /* AES_ENCRYPTION is used for both directions in CTR
+     * IV is set later with "wc_AesSetIV" */
+    wc_AesSetKeyDirect(&aes_enc, key, ENCRYPT_KEY_SIZE, NULL, AES_ENCRYPTION);
+    wc_AesSetKeyDirect(&aes_dec, key, ENCRYPT_KEY_SIZE, NULL, AES_ENCRYPTION);
+
+    /* set IV nonce use in aes_set_iv */
     XMEMCPY(encrypt_iv_nonce, stored_nonce, ENCRYPT_NONCE_SIZE);
-    XMEMCPY(iv_buf, stored_nonce, ENCRYPT_NONCE_SIZE);
-    /* AES_ENCRYPTION is used for both directions in CTR */
-    wc_AesSetKeyDirect(&aes_enc, key, ENCRYPT_KEY_SIZE, iv_buf, AES_ENCRYPTION);
-    wc_AesSetKeyDirect(&aes_dec, key, ENCRYPT_KEY_SIZE, iv_buf, AES_ENCRYPTION);
     encrypt_initialized = 1;
 #endif
     return 0;