Return to Exchange when failing to sign in swap mode

src/handle_swap_sign_transaction.c

@@ -80,6 +80,7 @@ void handle_swap_sign_transaction(chain_config_t* config) {
     chainConfig = config;
     reset_app_context();
     G_called_from_swap = true;
+    G_swap_response_ready = false;
     io_seproxyhal_init();
 
     if (N_storage.initialized != 0x01) {

src/main.c

@@ -53,6 +53,7 @@ cx_sha3_t global_sha3;
 uint8_t appState;
 uint16_t apdu_response_code;
 bool G_called_from_swap;
+bool G_swap_response_ready;
 pluginType_t pluginType;
 #ifdef HAVE_STARKWARE
 bool quantumSet;
@@ -78,6 +79,7 @@ void reset_app_context() {
     // PRINTF("!!RESET_APP_CONTEXT\n");
     appState = APP_STATE_IDLE;
     G_called_from_swap = false;
+    G_swap_response_ready = false;
     pluginType = OLD_INTERNAL;
 #ifdef HAVE_STARKWARE
     quantumSet = false;
@@ -456,6 +458,7 @@ void handleApdu(unsigned int *flags, unsigned int *tx) {
             THROW(EXCEPTION_IO_RESET);
         }
         CATCH_OTHER(e) {
+            bool quit_now = G_called_from_swap && G_swap_response_ready;
             switch (e & 0xF000) {
                 case 0x6000:
                     // Wipe the transaction context and report the exception
@@ -476,6 +479,18 @@ void handleApdu(unsigned int *flags, unsigned int *tx) {
             G_io_apdu_buffer[*tx] = sw >> 8;
             G_io_apdu_buffer[*tx + 1] = sw;
             *tx += 2;
+
+            // If we are in swap mode and have validated a TX, we send it and immediately quit
+            if (quit_now) {
+                if (io_exchange(CHANNEL_APDU | IO_RETURN_AFTER_TX, *tx) == 0) {
+                    // In case of success, the apdu is sent immediatly and eth exits
+                    // Reaching this code means we encountered an error
+                    finalize_exchange_sign_transaction(false);
+                } else {
+                    PRINTF("Unrecoverable\n");
+                    os_sched_exit(-1);
+                }
+            }
         }
         FINALLY {
         }

src/shared_context.h

@@ -215,6 +215,7 @@ extern cx_sha3_t global_sha3;
 extern const internalStorage_t N_storage_real;
 
 extern bool G_called_from_swap;
+extern bool G_swap_response_ready;
 
 typedef enum {
     EXTERNAL,     //  External plugin, set by setExternalPlugin.

src_features/signTx/logic_signTx.c

@@ -433,6 +433,15 @@ void finalizeParsing(bool direct) {
         }
     }
 
+    if (G_called_from_swap) {
+        if (G_swap_response_ready) {
+            // Unreachable given current return to exchange mechanism. Safeguard against regression
+            PRINTF("FATAL: safety against double sign triggered\n");
+            os_sched_exit(-1);
+        }
+        G_swap_response_ready = true;
+    }
+
     // User has just validated a swap but ETH received apdus about a non standard plugin / contract
     if (G_called_from_swap && !use_standard_UI) {
         PRINTF("ERR_SILENT_MODE_CHECK_FAILED, G_called_from_swap\n");
@@ -504,6 +513,8 @@ void finalizeParsing(bool direct) {
         // Ensure the values are the same that the ones that have been previously validated
         if (strcmp(strings.common.maxFee, displayBuffer) != 0) {
             PRINTF("ERR_SILENT_MODE_CHECK_FAILED, fees check failed\n");
+            PRINTF("Expected %s\n", strings.common.maxFee);
+            PRINTF("Received %s\n", displayBuffer);
             THROW(ERR_SILENT_MODE_CHECK_FAILED);
         }
     } else {