Merge #16639: [0.17] abort when attempting to fund a transaction above -maxtxfee

0e7c7465bf2b9911da094d9790480f94e158f9a5 wallet: Fix -maxtxfee check by moving it to CWallet::CreateTransaction (João Barbosa)
e9adb96f8854d21a02d80b4295f1a2e57579cc18 [wallet] abort when attempting to fund a transaction above maxtxfee (Sjors Provoost)

Pull request description:

  Backport #16257.

  Cherry-picked from the 0.18 backport in #16414, but without the [wip] messages and without the last commit (which adds a test in a file that didn't exist in 0.17).

ACKs for top commit:
  laanwj:
    ACK 0e7c7465bf2b9911da094d9790480f94e158f9a5

Tree-SHA512: a0fd603518487854be0b3815f34a8dabd2ed258850c032b08894a7c55cb135df5d3c103f76c5294e8065fec6d610e064acf01d24c77f02eaf996698a1e45d512

8 files changed, 41 insertions, 10 deletions

diff --git a/doc/release-notes-0.18.1-16257.md b/doc/release-notes-0.18.1-16257.md
new file mode 100644
index 0000000000..21867b7fb2
--- /dev/null
+++ b/doc/release-notes-0.18.1-16257.md
@@ -0,0 +1,6 @@
+Wallet changes
+--------------
+When creating a transaction with a fee above `-maxtxfee` (default 0.1 BTC),
+the RPC commands `walletcreatefundedpsbt` and  `fundrawtransaction` will now fail
+instead of rounding down the fee. Beware that the `feeRate` argument is specified
+in BTC per kilobyte, not satoshi per byte.
diff --git a/src/policy/fees.cpp b/src/policy/fees.cpp
index aee6fbee1a..d9a5474056 100644
--- a/src/policy/fees.cpp
+++ b/src/policy/fees.cpp
@@ -38,7 +38,6 @@ std::string StringForFeeReason(FeeReason reason) {
         {FeeReason::PAYTXFEE, "PayTxFee set"},
         {FeeReason::FALLBACK, "Fallback fee"},
         {FeeReason::REQUIRED, "Minimum Required Fee"},
-        {FeeReason::MAXTXFEE, "MaxTxFee limit"}
     };
     auto reason_string = fee_reason_strings.find(reason);
 
diff --git a/src/policy/fees.h b/src/policy/fees.h
index 136fb481f7..d46738cefb 100644
--- a/src/policy/fees.h
+++ b/src/policy/fees.h
@@ -88,7 +88,6 @@ enum class FeeReason {
     PAYTXFEE,
     FALLBACK,
     REQUIRED,
-    MAXTXFEE,
 };
 
 std::string StringForFeeReason(FeeReason reason);
diff --git a/src/wallet/fees.cpp b/src/wallet/fees.cpp
index d620e25f2b..0cac42ba72 100644
--- a/src/wallet/fees.cpp
+++ b/src/wallet/fees.cpp
@@ -21,13 +21,7 @@ CAmount GetRequiredFee(const CWallet& wallet, unsigned int nTxBytes)
 
 CAmount GetMinimumFee(const CWallet& wallet, unsigned int nTxBytes, const CCoinControl& coin_control, const CTxMemPool& pool, const CBlockPolicyEstimator& estimator, FeeCalculation* feeCalc)
 {
-    CAmount fee_needed = GetMinimumFeeRate(wallet, coin_control, pool, estimator, feeCalc).GetFee(nTxBytes);
-    // Always obey the maximum
-    if (fee_needed > maxTxFee) {
-        fee_needed = maxTxFee;
-        if (feeCalc) feeCalc->reason = FeeReason::MAXTXFEE;
-    }
-    return fee_needed;
+    return GetMinimumFeeRate(wallet, coin_control, pool, estimator, feeCalc).GetFee(nTxBytes);
 }
 
 CFeeRate GetRequiredFeeRate(const CWallet& wallet)
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 8d52f7eeca..d5f5df381a 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -3075,6 +3075,11 @@ bool CWallet::CreateTransaction(const std::vector<CRecipient>& vecSend, CTransac
         }
     }
 
+    if (nFeeRet > maxTxFee) {
+        strFailReason = _("Fee exceeds maximum configured by -maxtxfee");
+        return false;
+    }
+
     if (gArgs.GetBoolArg("-walletrejectlongchains", DEFAULT_WALLET_REJECT_LONG_CHAINS)) {
         // Lastly, ensure this tx will pass the mempool's chain limits
         LockPoints lp;
diff --git a/test/functional/rpc_fundrawtransaction.py b/test/functional/rpc_fundrawtransaction.py
index 0c61e9ab62..019a9d4012 100755
--- a/test/functional/rpc_fundrawtransaction.py
+++ b/test/functional/rpc_fundrawtransaction.py
@@ -662,6 +662,7 @@ class RawTransactionsTest(BitcoinTestFramework):
         result = self.nodes[3].fundrawtransaction(rawtx) # uses min_relay_tx_fee (set by settxfee)
         result2 = self.nodes[3].fundrawtransaction(rawtx, {"feeRate": 2*min_relay_tx_fee})
         result3 = self.nodes[3].fundrawtransaction(rawtx, {"feeRate": 10*min_relay_tx_fee})
+        assert_raises_rpc_error(-4, "Fee exceeds maximum configured by -maxtxfee", self.nodes[3].fundrawtransaction, rawtx, {"feeRate": 1})
         result_fee_rate = result['fee'] * 1000 / count_bytes(result['hex'])
         assert_fee_amount(result2['fee'], count_bytes(result2['hex']), 2 * result_fee_rate)
         assert_fee_amount(result3['fee'], count_bytes(result3['hex']), 10 * result_fee_rate)
diff --git a/test/functional/rpc_psbt.py b/test/functional/rpc_psbt.py
index ef895dd13a..1beda6e832 100755
--- a/test/functional/rpc_psbt.py
+++ b/test/functional/rpc_psbt.py
@@ -6,7 +6,15 @@
 """
 
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal, assert_raises_rpc_error, find_output, disconnect_nodes, connect_nodes_bi, sync_blocks
+from test_framework.util import (
+    assert_equal,
+    assert_greater_than,
+    assert_raises_rpc_error,
+    connect_nodes_bi,
+    disconnect_nodes,
+    find_output,
+    sync_blocks,
+)
 
 import json
 import os
@@ -122,6 +130,15 @@ class PSBTTest(BitcoinTestFramework):
         assert_equal(walletprocesspsbt_out['complete'], True)
         self.nodes[1].sendrawtransaction(self.nodes[1].finalizepsbt(walletprocesspsbt_out['psbt'])['hex'])
 
+        # feeRate of 0.1 BTC / KB produces a total fee slightly below -maxtxfee (~0.05280000):
+        res = self.nodes[1].walletcreatefundedpsbt([{"txid":txid,"vout":p2wpkh_pos},{"txid":txid,"vout":p2sh_p2wpkh_pos},{"txid":txid,"vout":p2pkh_pos}], {self.nodes[1].getnewaddress():29.99}, 0, {"feeRate": 0.1})
+        assert_greater_than(res["fee"], 0.05)
+        assert_greater_than(0.06, res["fee"])
+
+        # feeRate of 10 BTC / KB produces a total fee well above -maxtxfee
+        # previously this was silently capped at -maxtxfee
+        assert_raises_rpc_error(-4, "Fee exceeds maximum configured by -maxtxfee", self.nodes[1].walletcreatefundedpsbt, [{"txid":txid,"vout":p2wpkh_pos},{"txid":txid,"vout":p2sh_p2wpkh_pos},{"txid":txid,"vout":p2pkh_pos}], {self.nodes[1].getnewaddress():29.99}, 0, {"feeRate": 10})
+
         # partially sign multisig things with node 1
         psbtx = self.nodes[1].walletcreatefundedpsbt([{"txid":txid,"vout":p2wsh_pos},{"txid":txid,"vout":p2sh_pos},{"txid":txid,"vout":p2sh_p2wsh_pos}], {self.nodes[1].getnewaddress():29.99})['psbt']
         walletprocesspsbt_out = self.nodes[1].walletprocesspsbt(psbtx)
diff --git a/test/functional/wallet_bumpfee.py b/test/functional/wallet_bumpfee.py
index e478347cd7..944fc7b131 100755
--- a/test/functional/wallet_bumpfee.py
+++ b/test/functional/wallet_bumpfee.py
@@ -76,6 +76,7 @@ class BumpFeeTest(BitcoinTestFramework):
         test_unconfirmed_not_spendable(rbf_node, rbf_node_address)
         test_bumpfee_metadata(rbf_node, dest_address)
         test_locked_wallet_fails(rbf_node, dest_address)
+        test_maxtxfee_fails(self, rbf_node, dest_address)
         self.log.info("Success")
 
 
@@ -206,6 +207,15 @@ def test_settxfee(rbf_node, dest_address):
     rbf_node.settxfee(Decimal("0.00000000"))  # unset paytxfee
 
 
+def test_maxtxfee_fails(test, rbf_node, dest_address):
+    test.restart_node(1, ['-maxtxfee=0.00003'] + test.extra_args[1])
+    rbf_node.walletpassphrase(WALLET_PASSPHRASE, WALLET_PASSPHRASE_TIMEOUT)
+    rbfid = spend_one_input(rbf_node, dest_address)
+    assert_raises_rpc_error(-4, "Specified or calculated fee 0.0000332 is too high (cannot be higher than maxTxFee 0.00003)", rbf_node.bumpfee, rbfid)
+    test.restart_node(1, test.extra_args[1])
+    rbf_node.walletpassphrase(WALLET_PASSPHRASE, WALLET_PASSPHRASE_TIMEOUT)
+
+
 def test_rebumping(rbf_node, dest_address):
     # check that re-bumping the original tx fails, but bumping the bumper succeeds
     rbfid = spend_one_input(rbf_node, dest_address)