add more details to btc tx description

app/bitcoin/bitcoin.h

@@ -49,6 +49,7 @@ typedef struct {
   psbt_txin_t inputs[BTC_MAX_INPUTS];
   psbt_txout_t outputs[BTC_MAX_OUTPUTS];
   psbt_input_data_t input_data[BTC_MAX_INPUTS];
+  bool output_is_change[BTC_MAX_OUTPUTS];
   size_t input_count;
   size_t output_count;
 

app/core/core_btc.c

@@ -533,6 +533,17 @@ static app_err_t core_btc_validate(btc_tx_ctx_t* tx_ctx) {
     }
   }
 
+  for (int i = 0; i < tx_ctx->output_count; i++) {
+    for (int j = 0; j < tx_ctx->input_count; j++) {
+      if (tx_ctx->input_data[j].can_sign &&
+          (tx_ctx->input_data[j].script_pubkey_len == tx_ctx->outputs[i].script_len) &&
+          !memcmp(tx_ctx->input_data[j].script_pubkey, tx_ctx->outputs[i].script, tx_ctx->outputs[i].script_len)) {
+        tx_ctx->output_is_change[i] = true;
+        break;
+      }
+    }
+  }
+
   return can_sign_something ? ERR_OK : ERR_MISMATCH;
 }
 

app/ui/dialog.c

@@ -287,11 +287,11 @@ static void dialog_indexed_string(char* dst, const char* label, size_t index) {
 // TODO: move this to more general function to recognize data and display correct data accordingly
 static i18n_str_id_t dialog_recognize_data(const txContent_t* tx) {
   if (tx->dataLength == 0) {
-    return TX_DATA_NONE;
+    return TX_NO;
   } else if (tx->value.length == 0 && tx->dataLength == ETH_ERC20_TRANSFER_LEN && !memcmp(tx->data, ETH_ERC20_SIGNATURE, ETH_ERC20_SIGNATURE_LEN)) {
     return TX_DATA_ERC20;
   } else {
-    return TX_DATA_PRESENT;
+    return TX_YES;
   }
 }
 
@@ -375,6 +375,8 @@ void dialog_confirm_btc_summary(const btc_tx_ctx_t* tx) {
   uint64_t signed_amount = 0;
   uint64_t total_output = 0;
 
+  bool has_sighash_none = false;
+
   for (int i = 0; i < tx->input_count; i++) {
     uint64_t t;
     memcpy(&t, tx->input_data[i].amount, sizeof(uint64_t));
@@ -382,24 +384,57 @@ void dialog_confirm_btc_summary(const btc_tx_ctx_t* tx) {
     if (tx->input_data[i].can_sign) {
       signed_amount += t;
     }
+
+    if ((tx->input_data[i].sighash_flag & SIGHASH_MASK) == SIGHASH_NONE) {
+      has_sighash_none = true;
     }
+  }
+
+  uint64_t change = 0;
+  int dest_idx = -1;
 
   for (int i = 0; i < tx->output_count; i++) {
     uint64_t t;
     memcpy(&t, tx->outputs[i].amount, sizeof(uint64_t));
     total_output += t;
+    if (tx->output_is_change[i]) {
+      change += t;
+    } else {
+      if (dest_idx == -1) {
+        dest_idx = i;
+      } else {
+        dest_idx = -2;
+      }
+    }
   }
 
-  // TODO: fix labels, add basic informations on destination address
+  dialog_btc_amount(&ctx, TX_AMOUNT, total_input);
 
-  if (total_input == signed_amount) {
+  if (total_input != signed_amount) {
-    dialog_btc_amount(&ctx, TX_AMOUNT, total_input);
-  } else {
-    dialog_btc_amount(&ctx, TX_AMOUNT, total_input);
     dialog_btc_amount(&ctx, TX_SIGNED_AMOUNT, signed_amount);
   }
 
+  if (change) {
+    dialog_btc_amount(&ctx, TX_CHANGE, change);
+  }
+
   dialog_btc_amount(&ctx, TX_FEE, total_input - total_output);
+
+
+  if (has_sighash_none) {
+    ctx.x = TH_DATA_LEFT_MARGIN;
+    screen_draw_text(&ctx, MESSAGE_MAX_X, MESSAGE_MAX_Y, (const uint8_t*) LSTR(TX_SIGHASH_WARNING), strlen(LSTR(TX_SIGHASH_WARNING)), false, false);
+  } else {
+    char buf[BIGNUM_STRING_LEN];
+    dialog_label(&ctx, LSTR(TX_ADDRESS));
+
+    if (dest_idx >= 0) {
+      script_output_to_address(tx->outputs[dest_idx].script, tx->outputs[dest_idx].script_len, buf);
+      dialog_data(&ctx, buf);
+    } else {
+      dialog_data(&ctx, LSTR(TX_MULTIPLE_RECIPIENT));
+    }
+  }
 }
 
 static inline void dialog_btc_sign_scheme_format(char* buf, uint32_t flag) {
@@ -457,7 +492,7 @@ void dialog_confirm_btc_inouts(const btc_tx_ctx_t* tx, size_t page) {
     dialog_inline_data(&ctx, buf);
 
     dialog_label(&ctx, LSTR(TX_SIGNED));
-    dialog_inline_data(&ctx, tx->input_data[i].can_sign ? LSTR(TX_DATA_PRESENT) : LSTR(TX_DATA_NONE));
+    dialog_inline_data(&ctx, tx->input_data[i].can_sign ? LSTR(TX_YES) : LSTR(TX_NO));
 
     i++;
     displayed++;
@@ -477,6 +512,9 @@ void dialog_confirm_btc_inouts(const btc_tx_ctx_t* tx, size_t page) {
     memcpy(&t, tx->outputs[i].amount, sizeof(uint64_t));
     dialog_btc_amount(&ctx, TX_AMOUNT, t);
 
+    dialog_label(&ctx, LSTR(TX_CHANGE));
+    dialog_inline_data(&ctx, tx->output_is_change[i] ? LSTR(TX_YES) : LSTR(TX_NO));
+
     i++;
     displayed++;
   }

app/ui/english.c

@@ -46,6 +46,8 @@ const char *const i18n_english_strings[] = {
     "To",
     "Amount",
     "Signed amount",
+    "Multiple recipients",
+    "WARNING: recipients could change! Do not sign unless you absolutely know what you are doing.",
     "Fee",
     "Signer",
     "Data",
@@ -60,6 +62,7 @@ const char *const i18n_english_strings[] = {
     "NONE",
     "SINGLE",
     "ANYONECANPAY",
+    "Change",
 
     // MSG Confirmation
     "Sign message",

app/ui/i18n.h

@@ -52,12 +52,14 @@ typedef enum {
   TX_ADDRESS,
   TX_AMOUNT,
   TX_SIGNED_AMOUNT,
+  TX_MULTIPLE_RECIPIENT,
+  TX_SIGHASH_WARNING,
   TX_FEE,
   TX_SIGNER,
   TX_DATA,
-  TX_DATA_NONE,
+  TX_NO,
   TX_DATA_ERC20,
-  TX_DATA_PRESENT,
+  TX_YES,
   TX_INPUT,
   TX_OUTPUT,
   TX_SIGNED,
@@ -66,6 +68,7 @@ typedef enum {
   TX_SIGN_NONE,
   TX_SIGN_SINGLE,
   TX_SIGN_ANYONECANPAY,
+  TX_CHANGE,
 
   // MSG Confirmation
   MSG_CONFIRM_TITLE,