fix(legacy): Stricter Bitcoin transaction checks.

[no changelog]

legacy/firmware/signing.c

@@ -1370,7 +1370,12 @@ static void tx_info_finish(TxInfo *tx_info) {
 
 static bool signing_add_input(TxInputType *txinput) {
   // hash all input data to check it later (relevant for fee computation)
-  tx_input_check_hash(&hasher_check, txinput);
+  if (!tx_input_check_hash(&hasher_check, txinput)) {
+    fsm_sendFailure(FailureType_Failure_ProcessError,
+                    _("Failed to hash input"));
+    signing_abort();
+    return false;
+  }
 
   if (!fsm_checkCoinPath(coin, txinput->script_type, txinput->address_n_count,
                          txinput->address_n, txinput->has_multisig, true)) {
@@ -1634,8 +1639,13 @@ static bool signing_add_orig_input(TxInputType *orig_input) {
     return false;
   }
 
-  // The first original input that has address_n set and a signature gets chosen
-  // as the verification input. Set script_sig for legacy digest computation.
+  // The first original non-multisig input that has address_n set and a
+  // signature gets chosen as the verification input. Set script_sig for legacy
+  // digest computation.
+  // NOTE: Supporting replacement transactions where all internal inputs are
+  // multisig would require checking the signatures of all of the original
+  // internal inputs or not allowing unverified external inputs in transactions
+  // where multisig inputs are present.
   if (!have_orig_verif_input && orig_input->address_n_count != 0 &&
       !orig_input->has_multisig &&
       ((orig_input->has_script_sig && orig_input->script_sig.size != 0) ||
@@ -2736,7 +2746,12 @@ void signing_txack(TransactionType *tx) {
       if (idx1 == 0) {
         hasher_Reset(&hasher_check);
       }
-      tx_input_check_hash(&hasher_check, tx->inputs);
+      if (!tx_input_check_hash(&hasher_check, tx->inputs)) {
+        fsm_sendFailure(FailureType_Failure_ProcessError,
+                        _("Failed to hash input"));
+        signing_abort();
+        return;
+      }
 
       memcpy(&input, tx->inputs, sizeof(TxInputType));
 
@@ -2943,7 +2958,12 @@ void signing_txack(TransactionType *tx) {
         hasher_Reset(&hasher_check);
       }
       // check inputs are the same as those in phase 1
-      tx_input_check_hash(&hasher_check, tx->inputs);
+      if (!tx_input_check_hash(&hasher_check, tx->inputs)) {
+        fsm_sendFailure(FailureType_Failure_ProcessError,
+                        _("Failed to hash input"));
+        signing_abort();
+        return;
+      }
       if (idx2 == idx1) {
         if (!tx_info_check_input(&info, &tx->inputs[0]) ||
             !derive_node(&tx->inputs[0]) ||

legacy/firmware/transaction.c

@@ -556,22 +556,37 @@ uint32_t serialize_script_multisig(const CoinInfo *coin,
 }
 
 // tx methods
-void tx_input_check_hash(Hasher *hasher, const TxInputType *input) {
-  hasher_Update(hasher, input->prev_hash.bytes, sizeof(input->prev_hash.bytes));
-  hasher_Update(hasher, (const uint8_t *)&input->prev_index,
-                sizeof(input->prev_index));
-  hasher_Update(hasher, (const uint8_t *)&input->script_type,
-                sizeof(input->script_type));
+bool tx_input_check_hash(Hasher *hasher, const TxInputType *input) {
   hasher_Update(hasher, (const uint8_t *)&input->address_n_count,
                 sizeof(input->address_n_count));
   for (int i = 0; i < input->address_n_count; ++i)
     hasher_Update(hasher, (const uint8_t *)&input->address_n[i],
                   sizeof(input->address_n[0]));
+  hasher_Update(hasher, input->prev_hash.bytes, sizeof(input->prev_hash.bytes));
+  hasher_Update(hasher, (const uint8_t *)&input->prev_index,
+                sizeof(input->prev_index));
+  tx_script_hash(hasher, input->script_sig.size, input->script_sig.bytes);
   hasher_Update(hasher, (const uint8_t *)&input->sequence,
                 sizeof(input->sequence));
+  hasher_Update(hasher, (const uint8_t *)&input->script_type,
+                sizeof(input->script_type));
+  uint8_t multisig_fp[32] = {0};
+  if (input->has_multisig) {
+    if (cryptoMultisigFingerprint(&input->multisig, multisig_fp) == 0) {
+      // Invalid multisig parameters.
+      return false;
+    }
+  }
+  hasher_Update(hasher, multisig_fp, sizeof(multisig_fp));
   hasher_Update(hasher, (const uint8_t *)&input->amount, sizeof(input->amount));
+  tx_script_hash(hasher, input->witness.size, input->witness.bytes);
+  hasher_Update(hasher, (const uint8_t *)&input->has_orig_hash,
+                sizeof(input->has_orig_hash));
+  hasher_Update(hasher, input->orig_hash.bytes, sizeof(input->orig_hash.bytes));
+  hasher_Update(hasher, (const uint8_t *)&input->orig_index,
+                sizeof(input->orig_index));
   tx_script_hash(hasher, input->script_pubkey.size, input->script_pubkey.bytes);
-  return;
+  return true;
 }
 
 uint32_t tx_prevout_hash(Hasher *hasher, const TxInputType *input) {

legacy/firmware/transaction.h

@@ -79,7 +79,7 @@ int compile_output(const CoinInfo *coin, AmountUnit amount_unit,
 int fill_input_script_pubkey(const CoinInfo *coin, const HDNode *root,
                              TxInputType *in);
 
-void tx_input_check_hash(Hasher *hasher, const TxInputType *input);
+bool tx_input_check_hash(Hasher *hasher, const TxInputType *input);
 uint32_t tx_prevout_hash(Hasher *hasher, const TxInputType *input);
 uint32_t tx_amount_hash(Hasher *hasher, const TxInputType *input);
 uint32_t tx_script_hash(Hasher *hasher, uint32_t size, const uint8_t *data);