wallet: respect frozen key images in multisig wallets

Before this change, if a multisig peer asked you to sign a transaction with a frozen enote, the wallet will do it without any error or warning. This change makes it
so that wallets will refuse to sign multisig transactions with frozen enotes.

Disclaimer: This PR was generously funded by @LocalMonero.

src/wallet/wallet2.cpp

@@ -1732,6 +1732,36 @@ bool wallet2::frozen(size_t idx) const
   return td.m_frozen;
 }
 //----------------------------------------------------------------------------------------------------
+bool wallet2::frozen(const multisig_tx_set& txs) const
+{
+  // Each call to frozen(const key_image&) is O(N), so if we didn't use batching like we did here,
+  // this op would be O(M * N) instead of O(M + N). N = # wallet transfers, M = # key images in set.
+  // Step 1. Collect all key images from all pending txs into set
+  std::unordered_set<crypto::key_image> kis_to_sign;
+  for (const auto& ptx : txs.m_ptx)
+  {
+    const tools::wallet2::tx_construction_data& cd = ptx.construction_data;
+    CHECK_AND_ASSERT_THROW_MES(cd.sources.size() == ptx.tx.vin.size(), "mismatched multisg tx set source sizes");
+    for (size_t src_idx = 0; src_idx < cd.sources.size(); ++src_idx)
+    {
+      // Check that the key images are consistent between tx vin and construction data
+      const crypto::key_image multisig_ki = rct::rct2ki(cd.sources[src_idx].multisig_kLRki.ki);
+      CHECK_AND_ASSERT_THROW_MES(ptx.tx.vin[src_idx].type() == typeid(cryptonote::txin_to_key), "multisig tx cannot be miner");
+      const crypto::key_image vin_ki = boost::get<cryptonote::txin_to_key>(ptx.tx.vin[src_idx]).k_image;
+      CHECK_AND_ASSERT_THROW_MES(multisig_ki == vin_ki, "Mismatched key image b/t vin and construction data");
+
+      // Add key image to set
+      kis_to_sign.insert(multisig_ki);
+    }
+  }
+  // Step 2. Scan all transfers for frozen key images
+  for (const auto& td : m_transfers)
+    if (td.m_frozen && kis_to_sign.count(td.m_key_image))
+      return true;
+
+  return false;
+}
+//----------------------------------------------------------------------------------------------------
 void wallet2::freeze(const crypto::key_image &ki)
 {
   freeze(get_transfer_details(ki));
@@ -1752,8 +1782,13 @@ size_t wallet2::get_transfer_details(const crypto::key_image &ki) const
   for (size_t idx = 0; idx < m_transfers.size(); ++idx)
   {
     const transfer_details &td = m_transfers[idx];
-    if (td.m_key_image_known && td.m_key_image == ki)
-      return idx;
+    if (td.m_key_image == ki)
+    {
+      if (td.m_key_image_known)
+        return idx;
+      else if (td.m_key_image_partial)
+        CHECK_AND_ASSERT_THROW_MES(false, "Transfer detail lookups are not allowed for multisig partial key images");
+    }
   }
   CHECK_AND_ASSERT_THROW_MES(false, "Key image not found");
 }
@@ -7377,6 +7412,8 @@ bool wallet2::sign_multisig_tx(multisig_tx_set &exported_txs, std::vector<crypto
       error::wallet_internal_error, "Transaction was signed by too many signers");
   THROW_WALLET_EXCEPTION_IF(exported_txs.m_signers.size() == m_multisig_threshold,
       error::wallet_internal_error, "Transaction is already fully signed");
+  THROW_WALLET_EXCEPTION_IF(frozen(exported_txs),
+    error::wallet_internal_error, "Will not sign multisig tx containing frozen outputs")
 
   txids.clear();
 

src/wallet/wallet2.h

@@ -1592,6 +1592,7 @@ private:
     void thaw(const crypto::key_image &ki);
     bool frozen(const crypto::key_image &ki) const;
     bool frozen(const transfer_details &td) const;
+    bool frozen(const multisig_tx_set& txs) const; // does partially signed txset contain frozen enotes?
 
     bool save_to_file(const std::string& path_to_file, const std::string& binary, bool is_printable = false) const;
     static bool load_from_file(const std::string& path_to_file, std::string& target_str, size_t max_size = 1000000000);

tests/functional_tests/multisig.py

@@ -77,6 +77,9 @@ class MultisigTest():
         txid = self.transfer([1, 2])
         self.import_multisig_info([0, 1, 2, 3], 6)
         self.check_transaction(txid)
+        txid = self.try_transfer_frozen([2, 3])
+        self.import_multisig_info([0, 1, 2, 3], 7)
+        self.check_transaction(txid)
 
     def reset(self):
         print('Resetting blockchain')
@@ -316,6 +319,104 @@ class MultisigTest():
         daemon.generateblocks('42ey1afDFnn4886T7196doS9GPMzexD9gXpsZJDwVjeRVdFCSoHnv7KPbBeGpzJBzHRCAs9UxqeoyFQMYbqSWYTfJJQAWDm', 1)
         return txid
 
+    def try_transfer_frozen(self, signers):
+        assert len(signers) >= 2
+
+        daemon = Daemon()
+
+        print("Creating multisig transaction from wallet " + str(signers[0]))
+
+        dst = {'address': '42ey1afDFnn4886T7196doS9GPMzexD9gXpsZJDwVjeRVdFCSoHnv7KPbBeGpzJBzHRCAs9UxqeoyFQMYbqSWYTfJJQAWDm', 'amount': 1000000000000}
+        res = self.wallet[signers[0]].transfer([dst])
+        assert len(res.tx_hash) == 0 # not known yet
+        txid = res.tx_hash
+        assert len(res.tx_key) == 32*2
+        assert res.amount > 0
+        amount = res.amount
+        assert res.fee > 0
+        fee = res.fee
+        assert len(res.tx_blob) == 0
+        assert len(res.tx_metadata) == 0
+        assert len(res.multisig_txset) > 0
+        assert len(res.unsigned_txset) == 0
+        spent_key_images = res.spent_key_images.key_images
+        multisig_txset = res.multisig_txset
+
+        daemon.generateblocks('42ey1afDFnn4886T7196doS9GPMzexD9gXpsZJDwVjeRVdFCSoHnv7KPbBeGpzJBzHRCAs9UxqeoyFQMYbqSWYTfJJQAWDm', 1)
+        for i in range(len(self.wallet)):
+          self.wallet[i].refresh()
+
+        for i in range(len(signers[1:])):
+          # Check that each signer wallet has key image and it is not frozen
+          for ki in spent_key_images:
+            frozen = self.wallet[signers[i+1]].frozen(ki).frozen
+            assert not frozen
+
+        # Freeze key image involved with initiated transfer
+        assert len(spent_key_images)
+        ki0 = spent_key_images[0]
+        print("Freezing involved key image:", ki0)
+        self.wallet[signers[1]].freeze(ki0)
+        frozen = self.wallet[signers[1]].frozen(ki).frozen
+        assert frozen
+
+        # Try signing multisig (this operation should fail b/c of the frozen key image)
+        print("Attemping to sign with frozen key image. This should fail")
+        try:
+          res = self.wallet[signers[1]].sign_multisig(multisig_txset)
+          raise ValueError('sign_multisig should not have succeeded w/ fronzen enotes')
+        except AssertionError:
+          pass
+
+        # Thaw key image and continue transfer as normal
+        print("Thawing key image and continuing transfer as normal")
+        self.wallet[signers[1]].thaw(ki0)
+        frozen = self.wallet[signers[1]].frozen(ki).frozen
+        assert not frozen
+
+        for i in range(len(signers[1:])):
+          print('Signing multisig transaction with wallet ' + str(signers[i+1]))
+          res = self.wallet[signers[i+1]].describe_transfer(multisig_txset = multisig_txset)
+          assert len(res.desc) == 1
+          desc = res.desc[0]
+          assert desc.amount_in >= amount + fee
+          assert desc.amount_out == desc.amount_in - fee
+          assert desc.ring_size == 16
+          assert desc.unlock_time == 0
+          assert not 'payment_id' in desc or desc.payment_id in ['', '0000000000000000']
+          assert desc.change_amount == desc.amount_in - 1000000000000 - fee
+          assert desc.change_address == self.wallet_address
+          assert desc.fee == fee
+          assert len(desc.recipients) == 1
+          rec = desc.recipients[0]
+          assert rec.address == '42ey1afDFnn4886T7196doS9GPMzexD9gXpsZJDwVjeRVdFCSoHnv7KPbBeGpzJBzHRCAs9UxqeoyFQMYbqSWYTfJJQAWDm'
+          assert rec.amount == 1000000000000
+
+          res = self.wallet[signers[i+1]].sign_multisig(multisig_txset)
+          multisig_txset = res.tx_data_hex
+          assert len(res.tx_hash_list if 'tx_hash_list' in res else []) == (i == len(signers[1:]) - 1)
+
+          if i < len(signers[1:]) - 1:
+            print('Submitting multisig transaction prematurely with wallet ' + str(signers[-1]))
+            ok = False
+            try: self.wallet[signers[-1]].submit_multisig(multisig_txset)
+            except: ok = True
+            assert ok
+
+        print('Submitting multisig transaction with wallet ' + str(signers[-1]))
+        res = self.wallet[signers[-1]].submit_multisig(multisig_txset)
+        assert len(res.tx_hash_list) == 1
+        txid = res.tx_hash_list[0]
+
+        for i in range(len(self.wallet)):
+          self.wallet[i].refresh()
+          res = self.wallet[i].get_transfers()
+          assert len([x for x in (res['pending'] if 'pending' in res else []) if x.txid == txid]) == (1 if i == signers[-1] else 0)
+          assert len([x for x in (res['out'] if 'out' in res else []) if x.txid == txid]) == 0
+
+        daemon.generateblocks('42ey1afDFnn4886T7196doS9GPMzexD9gXpsZJDwVjeRVdFCSoHnv7KPbBeGpzJBzHRCAs9UxqeoyFQMYbqSWYTfJJQAWDm', 1)
+        return txid
+
     def check_transaction(self, txid):
         for i in range(len(self.wallet)):
           self.wallet[i].refresh()