Merge #14780: PSBT backports to 0.17

7bee41452b Add test for conversion from non-witness to witness UTXO (Pieter Wuille)
ff56bb9b44 Add regression test for PSBT signing bug #14473 (Glenn Willen)
db445d4e5a Refactor PSBTInput signing to enforce invariant (Glenn Willen)
ad94165db9 Simplify arguments to SignPSBTInput (Glenn Willen)
39ece4fc28 Add bool PSBTInputSigned (Glenn Willen)
70ee1f8709 New PartiallySignedTransaction constructor from CTransction (Glenn Willen)
a9eab081d5 Remove redundant txConst parameter to FillPSBT (Glenn Willen)
cfdd6b2f6c More concise conversion of CDataStream to string (Glenn Willen)
a3fe125490 check that a separator is found for psbt inputs, outputs, and global map (Andrew Chow)

Pull request description:

  This is a backport of #14588, #14377, and #14197's test to 0.17.

Tree-SHA512: 07535ec69a878a63b549e5e463345e233f34662dff805202614cf2ffc896c6d1981363e6d06d02db2e02d815075ad8ebdc5f93f637052cff8c8cbe6c8dfa096a

6 files changed, 106 insertions, 71 deletions

diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 314184ab06..7de3638f4e 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -1643,13 +1643,14 @@ UniValue finalizepsbt(const JSONRPCRequest& request)
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("TX decode failed %s", error));
     }
 
-    // Get all of the previous transactions
+    // Finalize input signatures -- in case we have partial signatures that add up to a complete
+    //   signature, but have not combined them yet (e.g. because the combiner that created this
+    //   PartiallySignedTransaction did not understand them), this will combine them into a final
+    //   script.
     bool complete = true;
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
-        PSBTInput& input = psbtx.inputs.at(i);
-
         SignatureData sigdata;
-        complete &= SignPSBTInput(DUMMY_SIGNING_PROVIDER, *psbtx.tx, input, sigdata, i, 1);
+        complete &= SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, sigdata, i, SIGHASH_ALL);
     }
 
     UniValue result(UniValue::VOBJ);
@@ -1662,10 +1663,10 @@ UniValue finalizepsbt(const JSONRPCRequest& request)
             mtx.vin[i].scriptWitness = psbtx.inputs[i].final_script_witness;
         }
         ssTx << mtx;
-        result.pushKV("hex", HexStr(ssTx.begin(), ssTx.end()));
+        result.pushKV("hex", HexStr(ssTx.str()));
     } else {
         ssTx << psbtx;
-        result.pushKV("psbt", EncodeBase64((unsigned char*)ssTx.data(), ssTx.size()));
+        result.pushKV("psbt", EncodeBase64(ssTx.str()));
     }
     result.pushKV("complete", complete);
 
diff --git a/src/script/sign.cpp b/src/script/sign.cpp
index 1ab5051ff7..f97d6a2533 100644
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -233,10 +233,17 @@ bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreato
     return sigdata.complete;
 }
 
-bool SignPSBTInput(const SigningProvider& provider, const CMutableTransaction& tx, PSBTInput& input, SignatureData& sigdata, int index, int sighash)
+bool PSBTInputSigned(PSBTInput& input)
 {
-    // if this input has a final scriptsig or scriptwitness, don't do anything with it
-    if (!input.final_script_sig.empty() || !input.final_script_witness.IsNull()) {
+    return !input.final_script_sig.empty() || !input.final_script_witness.IsNull();
+}
+
+bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, SignatureData& sigdata, int index, int sighash)
+{
+    PSBTInput& input = psbt.inputs.at(index);
+    const CMutableTransaction& tx = *psbt.tx;
+
+    if (PSBTInputSigned(input)) {
         return true;
     }
 
@@ -246,15 +253,19 @@ bool SignPSBTInput(const SigningProvider& provider, const CMutableTransaction& t
     // Get UTXO
     bool require_witness_sig = false;
     CTxOut utxo;
+
+    // Verify input sanity, which checks that at most one of witness or non-witness utxos is provided.
+    if (!input.IsSane()) {
+        return false;
+    }
+
     if (input.non_witness_utxo) {
         // If we're taking our information from a non-witness UTXO, verify that it matches the prevout.
-        if (input.non_witness_utxo->GetHash() != tx.vin[index].prevout.hash) return false;
-        // If both witness and non-witness UTXO are provided, verify that they match. This check shouldn't
-        // matter, as the PSBT deserializer enforces only one of both is provided, and the only way both
-        // can be present is when they're added simultaneously by FillPSBT (in which case they always match).
-        // Still, check in order to not rely on callers to enforce this.
-        if (!input.witness_utxo.IsNull() && input.non_witness_utxo->vout[tx.vin[index].prevout.n] != input.witness_utxo) return false;
-        utxo = input.non_witness_utxo->vout[tx.vin[index].prevout.n];
+        COutPoint prevout = tx.vin[index].prevout;
+        if (input.non_witness_utxo->GetHash() != prevout.hash) {
+            return false;
+        }
+        utxo = input.non_witness_utxo->vout[prevout.n];
     } else if (!input.witness_utxo.IsNull()) {
         utxo = input.witness_utxo;
         // When we're taking our information from a witness UTXO, we can't verify it is actually data from
@@ -272,6 +283,13 @@ bool SignPSBTInput(const SigningProvider& provider, const CMutableTransaction& t
     // Verify that a witness signature was produced in case one was required.
     if (require_witness_sig && !sigdata.witness) return false;
     input.FromSignatureData(sigdata);
+
+    // If we have a witness signature, use the smaller witness UTXO.
+    if (sigdata.witness) {
+        input.witness_utxo = utxo;
+        input.non_witness_utxo = nullptr;
+    }
+
     return sig_complete;
 }
 
@@ -491,6 +509,12 @@ bool IsSolvable(const SigningProvider& provider, const CScript& script)
     return false;
 }
 
+PartiallySignedTransaction::PartiallySignedTransaction(const CTransaction& tx) : tx(tx)
+{
+    inputs.resize(tx.vin.size());
+    outputs.resize(tx.vout.size());
+}
+
 bool PartiallySignedTransaction::IsNull() const
 {
     return !tx && inputs.empty() && outputs.empty() && unknown.empty();
diff --git a/src/script/sign.h b/src/script/sign.h
index 245b15410f..f24d77cb31 100644
--- a/src/script/sign.h
+++ b/src/script/sign.h
@@ -286,6 +286,7 @@ struct PSBTInput
     template <typename Stream>
     inline void Unserialize(Stream& s) {
         // Read loop
+        bool found_sep = false;
         while(!s.empty()) {
             // Read
             std::vector<unsigned char> key;
@@ -293,7 +294,10 @@ struct PSBTInput
 
             // the key is empty if that was actually a separator byte
             // This is a special case for key lengths 0 as those are not allowed (except for separator)
-            if (key.empty()) return;
+            if (key.empty()) {
+                found_sep = true;
+                break;
+            }
 
             // First byte of key is the type
             unsigned char type = key[0];
@@ -408,6 +412,10 @@ struct PSBTInput
                     break;
             }
         }
+
+        if (!found_sep) {
+            throw std::ios_base::failure("Separator is missing at the end of an input map");
+        }
     }
 
     template <typename Stream>
@@ -461,6 +469,7 @@ struct PSBTOutput
     template <typename Stream>
     inline void Unserialize(Stream& s) {
         // Read loop
+        bool found_sep = false;
         while(!s.empty()) {
             // Read
             std::vector<unsigned char> key;
@@ -468,7 +477,10 @@ struct PSBTOutput
 
             // the key is empty if that was actually a separator byte
             // This is a special case for key lengths 0 as those are not allowed (except for separator)
-            if (key.empty()) return;
+            if (key.empty()) {
+                found_sep = true;
+                break;
+            }
 
             // First byte of key is the type
             unsigned char type = key[0];
@@ -513,6 +525,10 @@ struct PSBTOutput
                 }
             }
         }
+
+        if (!found_sep) {
+            throw std::ios_base::failure("Separator is missing at the end of an output map");
+        }
     }
 
     template <typename Stream>
@@ -534,6 +550,7 @@ struct PartiallySignedTransaction
     bool IsSane() const;
     PartiallySignedTransaction() {}
     PartiallySignedTransaction(const PartiallySignedTransaction& psbt_in) : tx(psbt_in.tx), inputs(psbt_in.inputs), outputs(psbt_in.outputs), unknown(psbt_in.unknown) {}
+    explicit PartiallySignedTransaction(const CTransaction& tx);
 
     // Only checks if they refer to the same transaction
     friend bool operator==(const PartiallySignedTransaction& a, const PartiallySignedTransaction &b)
@@ -588,6 +605,7 @@ struct PartiallySignedTransaction
         }
 
         // Read global data
+        bool found_sep = false;
         while(!s.empty()) {
             // Read
             std::vector<unsigned char> key;
@@ -595,7 +613,10 @@ struct PartiallySignedTransaction
 
             // the key is empty if that was actually a separator byte
             // This is a special case for key lengths 0 as those are not allowed (except for separator)
-            if (key.empty()) break;
+            if (key.empty()) {
+                found_sep = true;
+                break;
+            }
 
             // First byte of key is the type
             unsigned char type = key[0];
@@ -635,6 +656,10 @@ struct PartiallySignedTransaction
             }
         }
 
+        if (!found_sep) {
+            throw std::ios_base::failure("Separator is missing at the end of the global map");
+        }
+
         // Make sure that we got an unsigned tx
         if (!tx) {
             throw std::ios_base::failure("No unsigned transcation was provided");
@@ -689,8 +714,11 @@ bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreato
 bool SignSignature(const SigningProvider &provider, const CScript& fromPubKey, CMutableTransaction& txTo, unsigned int nIn, const CAmount& amount, int nHashType);
 bool SignSignature(const SigningProvider &provider, const CTransaction& txFrom, CMutableTransaction& txTo, unsigned int nIn, int nHashType);
 
+/** Checks whether a PSBTInput is already signed. */
+bool PSBTInputSigned(PSBTInput& input);
+
 /** Signs a PSBTInput, verifying that all provided data matches what is being signed. */
-bool SignPSBTInput(const SigningProvider& provider, const CMutableTransaction& tx, PSBTInput& input, SignatureData& sigdata, int index, int sighash = 1);
+bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, SignatureData& sigdata, int index, int sighash = SIGHASH_ALL);
 
 /** Extract signature data from a transaction input, and insert it. */
 SignatureData DataFromTransaction(const CMutableTransaction& tx, unsigned int nIn, const CTxOut& txout);
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 0a9242327b..6400b4470f 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -4502,24 +4502,34 @@ void AddKeypathToMap(const CWallet* pwallet, const CKeyID& keyID, std::map<CPubK
     hd_keypaths.emplace(vchPubKey, keypath);
 }
 
-bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, const CTransaction* txConst, int sighash_type, bool sign, bool bip32derivs)
+bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, int sighash_type, bool sign, bool bip32derivs)
 {
     LOCK(pwallet->cs_wallet);
     // Get all of the previous transactions
     bool complete = true;
-    for (unsigned int i = 0; i < txConst->vin.size(); ++i) {
-        const CTxIn& txin = txConst->vin[i];
+    for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
+        const CTxIn& txin = psbtx.tx->vin[i];
         PSBTInput& input = psbtx.inputs.at(i);
 
-        // If we don't know about this input, skip it and let someone else deal with it
-        const uint256& txhash = txin.prevout.hash;
-        const auto it = pwallet->mapWallet.find(txhash);
-        if (it != pwallet->mapWallet.end()) {
-            const CWalletTx& wtx = it->second;
-            CTxOut utxo = wtx.tx->vout[txin.prevout.n];
-            // Update both UTXOs from the wallet.
-            input.non_witness_utxo = wtx.tx;
-            input.witness_utxo = utxo;
+        if (PSBTInputSigned(input)) {
+            continue;
+        }
+
+        // Verify input looks sane. This will check that we have at most one uxto, witness or non-witness.
+        if (!input.IsSane()) {
+            throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "PSBT input is not sane.");
+        }
+
+        // If we have no utxo, grab it from the wallet.
+        if (!input.non_witness_utxo && input.witness_utxo.IsNull()) {
+            const uint256& txhash = txin.prevout.hash;
+            const auto it = pwallet->mapWallet.find(txhash);
+            if (it != pwallet->mapWallet.end()) {
+                const CWalletTx& wtx = it->second;
+                // We only need the non_witness_utxo, which is a superset of the witness_utxo.
+                //   The signing code will switch to the smaller witness_utxo if this is ok.
+                input.non_witness_utxo = wtx.tx;
+            }
         }
 
         // Get the Sighash type
@@ -4529,9 +4539,9 @@ bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, const C
 
         SignatureData sigdata;
         if (sign) {
-            complete &= SignPSBTInput(*pwallet, *psbtx.tx, input, sigdata, i, sighash_type);
+            complete &= SignPSBTInput(*pwallet, psbtx, sigdata, i, sighash_type);
         } else {
-            complete &= SignPSBTInput(PublicOnlySigningProvider(pwallet), *psbtx.tx, input, sigdata, i, sighash_type);
+            complete &= SignPSBTInput(PublicOnlySigningProvider(pwallet), psbtx, sigdata, i, sighash_type);
         }
 
         if (sigdata.witness) {
@@ -4541,15 +4551,6 @@ bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, const C
             }
         }
 
-        // If both UTXO types are present, drop the unnecessary one.
-        if (input.non_witness_utxo && !input.witness_utxo.IsNull()) {
-            if (sigdata.witness) {
-                input.non_witness_utxo = nullptr;
-            } else {
-                input.witness_utxo.SetNull();
-            }
-        }
-
         // Get public key paths
         if (bip32derivs) {
             for (const auto& pubkey_it : sigdata.misc_pubkeys) {
@@ -4559,8 +4560,8 @@ bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, const C
     }
 
     // Fill in the bip32 keypaths and redeemscripts for the outputs so that hardware wallets can identify change
-    for (unsigned int i = 0; i < txConst->vout.size(); ++i) {
-        const CTxOut& out = txConst->vout.at(i);
+    for (unsigned int i = 0; i < psbtx.tx->vout.size(); ++i) {
+        const CTxOut& out = psbtx.tx->vout.at(i);
         PSBTOutput& psbt_out = psbtx.outputs.at(i);
 
         // Dummy tx so we can use ProduceSignature to get stuff out
@@ -4637,19 +4638,15 @@ UniValue walletprocesspsbt(const JSONRPCRequest& request)
     // Get the sighash type
     int nHashType = ParseSighashString(request.params[2]);
 
-    // Use CTransaction for the constant parts of the
-    // transaction to avoid rehashing.
-    const CTransaction txConst(*psbtx.tx);
-
     // Fill transaction with our data and also sign
     bool sign = request.params[1].isNull() ? true : request.params[1].get_bool();
     bool bip32derivs = request.params[3].isNull() ? false : request.params[3].get_bool();
-    bool complete = FillPSBT(pwallet, psbtx, &txConst, nHashType, sign, bip32derivs);
+    bool complete = FillPSBT(pwallet, psbtx, nHashType, sign, bip32derivs);
 
     UniValue result(UniValue::VOBJ);
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
     ssTx << psbtx;
-    result.pushKV("psbt", EncodeBase64((unsigned char*)ssTx.data(), ssTx.size()));
+    result.pushKV("psbt", EncodeBase64(ssTx.str()));
     result.pushKV("complete", complete);
 
     return result;
@@ -4741,29 +4738,18 @@ UniValue walletcreatefundedpsbt(const JSONRPCRequest& request)
     FundTransaction(pwallet, rawTx, fee, change_position, request.params[3]);
 
     // Make a blank psbt
-    PartiallySignedTransaction psbtx;
-    psbtx.tx = rawTx;
-    for (unsigned int i = 0; i < rawTx.vin.size(); ++i) {
-        psbtx.inputs.push_back(PSBTInput());
-    }
-    for (unsigned int i = 0; i < rawTx.vout.size(); ++i) {
-        psbtx.outputs.push_back(PSBTOutput());
-    }
-
-    // Use CTransaction for the constant parts of the
-    // transaction to avoid rehashing.
-    const CTransaction txConst(*psbtx.tx);
+    PartiallySignedTransaction psbtx(rawTx);
 
     // Fill transaction with out data but don't sign
     bool bip32derivs = request.params[4].isNull() ? false : request.params[4].get_bool();
-    FillPSBT(pwallet, psbtx, &txConst, 1, false, bip32derivs);
+    FillPSBT(pwallet, psbtx, 1, false, bip32derivs);
 
     // Serialize the PSBT
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
     ssTx << psbtx;
 
     UniValue result(UniValue::VOBJ);
-    result.pushKV("psbt", EncodeBase64((unsigned char*)ssTx.data(), ssTx.size()));
+    result.pushKV("psbt", EncodeBase64(ssTx.str()));
     result.pushKV("fee", ValueFromAmount(fee));
     result.pushKV("changepos", change_position);
     return result;
diff --git a/src/wallet/rpcwallet.h b/src/wallet/rpcwallet.h
index 9b9a159b86..abd7750874 100644
--- a/src/wallet/rpcwallet.h
+++ b/src/wallet/rpcwallet.h
@@ -30,5 +30,5 @@ bool EnsureWalletIsAvailable(CWallet *, bool avoidException);
 
 UniValue getaddressinfo(const JSONRPCRequest& request);
 UniValue signrawtransactionwithwallet(const JSONRPCRequest& request);
-bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, const CTransaction* txConst, int sighash_type = 1, bool sign = true, bool bip32derivs = false);
+bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false);
 #endif //BITCOIN_WALLET_RPCWALLET_H
diff --git a/src/wallet/test/psbt_wallet_tests.cpp b/src/wallet/test/psbt_wallet_tests.cpp
index 61c3fa94a6..8d46718a7d 100644
--- a/src/wallet/test/psbt_wallet_tests.cpp
+++ b/src/wallet/test/psbt_wallet_tests.cpp
@@ -59,12 +59,8 @@ BOOST_AUTO_TEST_CASE(psbt_updater_test)
     CDataStream ssData(ParseHex("70736274ff01009a020000000258e87a21b56daf0c23be8e7070456c336f7cbaa5c8757924f545887bb2abdd750000000000ffffffff838d0427d0ec650a68aa46bb0b098aea4422c071b2ca78352a077959d07cea1d0100000000ffffffff0270aaf00800000000160014d85c2b71d0060b09c9886aeb815e50991dda124d00e1f5050000000016001400aea9a2e5f0f876a588df5546e8742d1d87008f000000000000000000"), SER_NETWORK, PROTOCOL_VERSION);
     ssData >> psbtx;
 
-    // Use CTransaction for the constant parts of the
-    // transaction to avoid rehashing.
-    const CTransaction txConst(*psbtx.tx);
-
     // Fill transaction with our data
-    FillPSBT(&m_wallet, psbtx, &txConst, 1, false, true);
+    FillPSBT(&m_wallet, psbtx, SIGHASH_ALL, false, true);
 
     // Get the final tx
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);