[Audit] Fix EIP712 part

Author: cedelavergne-ledger

src_features/signMessageEIP712/ui_logic.c

@@ -1227,8 +1227,8 @@ void ui_712_set_trusted_name_requirements(uint8_t type_count,
  *
  */
 void ui_712_push_pairs(void) {
-    uint16_t nbPairs = 0;
-    uint16_t pair = 0;
+    uint8_t nbPairs = 0;
+    uint8_t pair = 0;
     s_ui_712_pair *tmp = NULL;
 
     // Initialize the pairs list

src_features/signMessageEIP712_common/common_712.c

@@ -67,6 +67,9 @@ static char *format_hash(const uint8_t *hash, char *buffer, size_t buffer_size,
 }
 
 void eip712_format_hash(uint8_t index) {
+    if ((g_pairs == NULL) || (g_pairsList == NULL) || (index >= g_pairsList->nbPairs)) {
+        return;
+    }
     g_pairs[index].item = "Domain hash";
     g_pairs[index].value = format_hash(tmpCtx.messageSigningContext712.domainHash,
                                        strings.tmp.tmp,

src_nbgl/ui_sign_712.c

@@ -28,7 +28,9 @@ static void ui_712_start_review(nbgl_operationType_t operationType,
     // Initialize the finish title string
     finish_len += strlen(tx_check_str);
     finish_len += strlen(title_suffix);
-    ui_buffers_init(0, 0, finish_len);
+    if (!ui_buffers_init(0, 0, finish_len)) {
+        return;
+    }
     snprintf(g_finishMsg, finish_len, "%s%s", tx_check_str, title_suffix);
 #ifdef HAVE_TRANSACTION_CHECKS
     set_tx_simulation_warning();