Merge bitcoin/bitcoin#28246: wallet: Use CTxDestination in CRecipient instead of just scriptPubKey

ad0c469 wallet: Use CTxDestination in CRecipient rather than scriptPubKey (Andrew Chow)
07d3bdf Add PubKeyDestination for P2PK scripts (Andrew Chow)
1a98a51 Allow CNoDestination to represent a raw script (Andrew Chow)
8dd0670 Make WitnessUnknown members private (Andrew Chow)

Pull request description:

  For silent payments, we want to provide a `SilentPaymentsDestination` to be used as the recipient, which requires `CRecipient` to use something other than just the `scriptPubKey` as we cannot know the output script for a silent payment prior to transaction creation. `CTxDestination` seems like the obvious place to add a `SilentPaymentsDestination` as it is our internal representation of an address.

  In order to still allow paying to arbitrary scriptPubKeys (e.g. for data carrier outputs, or the user hand crafted a raw transaction that they have given to `fundrawtransaction`), `CNoDestination` is changed to contain raw scripts.

  Additionally, P2PK scripts are now interpreted as a new `PubKeyDestination` rather than `PKHash`. This results in some things that would have given an address for P2PK scripts to no longer do so. This is arguably more correct.

  `ExtractDestination`'s behavior is slightly changed for the above. It now returns `true` for those destinations that have addresses, so P2PK scripts now result in `false`. Even though it returns false for `CNoDestination`, the script will now be included in that `CNoDestination`.

  Builds on #28244

ACKs for top commit:
  josibake:
    ACK bitcoin/bitcoin@ad0c469

Tree-SHA512: ef3f8f3c7284779d9806c77c85b21caf910a79a1f7e7f1b51abcc0d7e074f14e00abf30f625a13075e41d94dad6202c10ddff462c0ee74c2ca4aab585b145a52

Author: fanquake

src/addresstype.cpp

@@ -54,11 +54,12 @@ bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet)
     switch (whichType) {
     case TxoutType::PUBKEY: {
         CPubKey pubKey(vSolutions[0]);
-        if (!pubKey.IsValid())
-            return false;
-
-        addressRet = PKHash(pubKey);
-        return true;
+        if (!pubKey.IsValid()) {
+            addressRet = CNoDestination(scriptPubKey);
+        } else {
+            addressRet = PubKeyDestination(pubKey);
+        }
+        return false;
     }
     case TxoutType::PUBKEYHASH: {
         addressRet = PKHash(uint160(vSolutions[0]));
@@ -87,16 +88,13 @@ bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet)
         return true;
     }
     case TxoutType::WITNESS_UNKNOWN: {
-        WitnessUnknown unk;
-        unk.version = vSolutions[0][0];
-        std::copy(vSolutions[1].begin(), vSolutions[1].end(), unk.program);
-        unk.length = vSolutions[1].size();
-        addressRet = unk;
+        addressRet = WitnessUnknown{vSolutions[0][0], vSolutions[1]};
         return true;
     }
     case TxoutType::MULTISIG:
     case TxoutType::NULL_DATA:
     case TxoutType::NONSTANDARD:
+        addressRet = CNoDestination(scriptPubKey);
         return false;
     } // no default case, so the compiler can warn about missing cases
     assert(false);
@@ -108,7 +106,12 @@ class CScriptVisitor
 public:
     CScript operator()(const CNoDestination& dest) const
     {
-        return CScript();
+        return dest.GetScript();
+    }
+
+    CScript operator()(const PubKeyDestination& dest) const
+    {
+        return CScript() << ToByteVector(dest.GetPubKey()) << OP_CHECKSIG;
     }
 
     CScript operator()(const PKHash& keyID) const
@@ -138,9 +141,22 @@ class CScriptVisitor
 
     CScript operator()(const WitnessUnknown& id) const
     {
-        return CScript() << CScript::EncodeOP_N(id.version) << std::vector<unsigned char>(id.program, id.program + id.length);
+        return CScript() << CScript::EncodeOP_N(id.GetWitnessVersion()) << id.GetWitnessProgram();
     }
 };
+
+class ValidDestinationVisitor
+{
+public:
+    bool operator()(const CNoDestination& dest) const { return false; }
+    bool operator()(const PubKeyDestination& dest) const { return false; }
+    bool operator()(const PKHash& dest) const { return true; }
+    bool operator()(const ScriptHash& dest) const { return true; }
+    bool operator()(const WitnessV0KeyHash& dest) const { return true; }
+    bool operator()(const WitnessV0ScriptHash& dest) const { return true; }
+    bool operator()(const WitnessV1Taproot& dest) const { return true; }
+    bool operator()(const WitnessUnknown& dest) const { return true; }
+};
 } // namespace
 
 CScript GetScriptForDestination(const CTxDestination& dest)
@@ -149,5 +165,5 @@ CScript GetScriptForDestination(const CTxDestination& dest)
 }
 
 bool IsValidDestination(const CTxDestination& dest) {
-    return dest.index() != 0;
+    return std::visit(ValidDestinationVisitor(), dest);
 }

src/addresstype.h

@@ -14,9 +14,30 @@
 #include <algorithm>
 
 class CNoDestination {
+private:
+    CScript m_script;
+
+public:
+    CNoDestination() = default;
+    CNoDestination(const CScript& script) : m_script(script) {}
+
+    const CScript& GetScript() const { return m_script; }
+
+    friend bool operator==(const CNoDestination& a, const CNoDestination& b) { return a.GetScript() == b.GetScript(); }
+    friend bool operator<(const CNoDestination& a, const CNoDestination& b) { return a.GetScript() < b.GetScript(); }
+};
+
+struct PubKeyDestination {
+private:
+    CPubKey m_pubkey;
+
 public:
-    friend bool operator==(const CNoDestination &a, const CNoDestination &b) { return true; }
-    friend bool operator<(const CNoDestination &a, const CNoDestination &b) { return true; }
+    PubKeyDestination(const CPubKey& pubkey) : m_pubkey(pubkey) {}
+
+    const CPubKey& GetPubKey() const LIFETIMEBOUND { return m_pubkey; }
+
+    friend bool operator==(const PubKeyDestination& a, const PubKeyDestination& b) { return a.GetPubKey() == b.GetPubKey(); }
+    friend bool operator<(const PubKeyDestination& a, const PubKeyDestination& b) { return a.GetPubKey() < b.GetPubKey(); }
 };
 
 struct PKHash : public BaseHash<uint160>
@@ -69,45 +90,55 @@ struct WitnessV1Taproot : public XOnlyPubKey
 //! CTxDestination subtype to encode any future Witness version
 struct WitnessUnknown
 {
-    unsigned int version;
-    unsigned int length;
-    unsigned char program[40];
+private:
+    unsigned int m_version;
+    std::vector<unsigned char> m_program;
+
+public:
+    WitnessUnknown(unsigned int version, const std::vector<unsigned char>& program) : m_version(version), m_program(program) {}
+    WitnessUnknown(int version, const std::vector<unsigned char>& program) : m_version(static_cast<unsigned int>(version)), m_program(program) {}
+
+    unsigned int GetWitnessVersion() const { return m_version; }
+    const std::vector<unsigned char>& GetWitnessProgram() const LIFETIMEBOUND { return m_program; }
 
     friend bool operator==(const WitnessUnknown& w1, const WitnessUnknown& w2) {
-        if (w1.version != w2.version) return false;
-        if (w1.length != w2.length) return false;
-        return std::equal(w1.program, w1.program + w1.length, w2.program);
+        if (w1.GetWitnessVersion() != w2.GetWitnessVersion()) return false;
+        return w1.GetWitnessProgram() == w2.GetWitnessProgram();
     }
 
     friend bool operator<(const WitnessUnknown& w1, const WitnessUnknown& w2) {
-        if (w1.version < w2.version) return true;
-        if (w1.version > w2.version) return false;
-        if (w1.length < w2.length) return true;
-        if (w1.length > w2.length) return false;
-        return std::lexicographical_compare(w1.program, w1.program + w1.length, w2.program, w2.program + w2.length);
+        if (w1.GetWitnessVersion() < w2.GetWitnessVersion()) return true;
+        if (w1.GetWitnessVersion() > w2.GetWitnessVersion()) return false;
+        return w1.GetWitnessProgram() < w2.GetWitnessProgram();
     }
 };
 
 /**
- * A txout script template with a specific destination. It is either:
- *  * CNoDestination: no destination set
- *  * PKHash: TxoutType::PUBKEYHASH destination (P2PKH)
- *  * ScriptHash: TxoutType::SCRIPTHASH destination (P2SH)
- *  * WitnessV0ScriptHash: TxoutType::WITNESS_V0_SCRIPTHASH destination (P2WSH)
- *  * WitnessV0KeyHash: TxoutType::WITNESS_V0_KEYHASH destination (P2WPKH)
- *  * WitnessV1Taproot: TxoutType::WITNESS_V1_TAPROOT destination (P2TR)
- *  * WitnessUnknown: TxoutType::WITNESS_UNKNOWN destination (P2W???)
+ * A txout script categorized into standard templates.
+ *  * CNoDestination: Optionally a script, no corresponding address.
+ *  * PubKeyDestination: TxoutType::PUBKEY (P2PK), no corresponding address
+ *  * PKHash: TxoutType::PUBKEYHASH destination (P2PKH address)
+ *  * ScriptHash: TxoutType::SCRIPTHASH destination (P2SH address)
+ *  * WitnessV0ScriptHash: TxoutType::WITNESS_V0_SCRIPTHASH destination (P2WSH address)
+ *  * WitnessV0KeyHash: TxoutType::WITNESS_V0_KEYHASH destination (P2WPKH address)
+ *  * WitnessV1Taproot: TxoutType::WITNESS_V1_TAPROOT destination (P2TR address)
+ *  * WitnessUnknown: TxoutType::WITNESS_UNKNOWN destination (P2W??? address)
  *  A CTxDestination is the internal data type encoded in a bitcoin address
  */
-using CTxDestination = std::variant<CNoDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>;
+using CTxDestination = std::variant<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>;
 
-/** Check whether a CTxDestination is a CNoDestination. */
+/** Check whether a CTxDestination corresponds to one with an address. */
 bool IsValidDestination(const CTxDestination& dest);
 
 /**
- * Parse a standard scriptPubKey for the destination address. Assigns result to
- * the addressRet parameter and returns true if successful. Currently only works for P2PK,
- * P2PKH, P2SH, P2WPKH, and P2WSH scripts.
+ * Parse a scriptPubKey for the destination.
+ *
+ * For standard scripts that have addresses (and P2PK as an exception), a corresponding CTxDestination
+ * is assigned to addressRet.
+ * For all other scripts. addressRet is assigned as a CNoDestination containing the scriptPubKey.
+ *
+ * Returns true for standard destinations with addresses - P2PKH, P2SH, P2WPKH, P2WSH, P2TR and P2W??? scripts.
+ * Returns false for non-standard destinations and those without addresses - P2PK, bare multisig, null data, and nonstandard scripts.
  */
 bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet);
 

src/key_io.cpp

@@ -67,16 +67,18 @@ class DestinationEncoder
 
     std::string operator()(const WitnessUnknown& id) const
     {
-        if (id.version < 1 || id.version > 16 || id.length < 2 || id.length > 40) {
+        const std::vector<unsigned char>& program = id.GetWitnessProgram();
+        if (id.GetWitnessVersion() < 1 || id.GetWitnessVersion() > 16 || program.size() < 2 || program.size() > 40) {
             return {};
         }
-        std::vector<unsigned char> data = {(unsigned char)id.version};
-        data.reserve(1 + (id.length * 8 + 4) / 5);
-        ConvertBits<8, 5, true>([&](unsigned char c) { data.push_back(c); }, id.program, id.program + id.length);
+        std::vector<unsigned char> data = {(unsigned char)id.GetWitnessVersion()};
+        data.reserve(1 + (program.size() * 8 + 4) / 5);
+        ConvertBits<8, 5, true>([&](unsigned char c) { data.push_back(c); }, program.begin(), program.end());
         return bech32::Encode(bech32::Encoding::BECH32M, m_params.Bech32HRP(), data);
     }
 
     std::string operator()(const CNoDestination& no) const { return {}; }
+    std::string operator()(const PubKeyDestination& pk) const { return {}; }
 };
 
 CTxDestination DecodeDestination(const std::string& str, const CChainParams& params, std::string& error_str, std::vector<int>* error_locations)
@@ -189,11 +191,7 @@ CTxDestination DecodeDestination(const std::string& str, const CChainParams& par
                 return CNoDestination();
             }
 
-            WitnessUnknown unk;
-            unk.version = version;
-            std::copy(data.begin(), data.end(), unk.program);
-            unk.length = data.size();
-            return unk;
+            return WitnessUnknown{version, data};
         } else {
             error_str = strprintf("Invalid padding in Bech32 data section");
             return CNoDestination();

src/rpc/output_script.cpp

@@ -280,6 +280,11 @@ static RPCHelpMan deriveaddresses()
                 for (const CScript& script : scripts) {
                     CTxDestination dest;
                     if (!ExtractDestination(script, dest)) {
+                        // ExtractDestination no longer returns true for P2PK since it doesn't have a corresponding address
+                        // However combo will output P2PK and should just ignore that script
+                        if (scripts.size() > 1 && std::get_if<PubKeyDestination>(&dest)) {
+                            continue;
+                        }
                         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Descriptor does not have a corresponding address");
                     }
 

src/rpc/util.cpp

@@ -253,6 +253,11 @@ class DescribeAddressVisitor
         return UniValue(UniValue::VOBJ);
     }
 
+    UniValue operator()(const PubKeyDestination& dest) const
+    {
+        return UniValue(UniValue::VOBJ);
+    }
+
     UniValue operator()(const PKHash& keyID) const
     {
         UniValue obj(UniValue::VOBJ);
@@ -303,8 +308,8 @@ class DescribeAddressVisitor
     {
         UniValue obj(UniValue::VOBJ);
         obj.pushKV("iswitness", true);
-        obj.pushKV("witness_version", (int)id.version);
-        obj.pushKV("witness_program", HexStr({id.program, id.length}));
+        obj.pushKV("witness_version", id.GetWitnessVersion());
+        obj.pushKV("witness_program", HexStr(id.GetWitnessProgram()));
         return obj;
     }
 };

src/test/fuzz/key.cpp

@@ -186,7 +186,7 @@ FUZZ_TARGET(key, .init = initialize_key)
         const CTxDestination tx_destination = GetDestinationForKey(pubkey, output_type);
         assert(output_type == OutputType::LEGACY);
         assert(IsValidDestination(tx_destination));
-        assert(CTxDestination{PKHash{pubkey}} == tx_destination);
+        assert(PKHash{pubkey} == *std::get_if<PKHash>(&tx_destination));
 
         const CScript script_for_destination = GetScriptForDestination(tx_destination);
         assert(script_for_destination.size() == 25);

src/test/fuzz/script.cpp

@@ -149,13 +149,16 @@ FUZZ_TARGET(script, .init = initialize_script)
         const CTxDestination tx_destination_2{ConsumeTxDestination(fuzzed_data_provider)};
         const std::string encoded_dest{EncodeDestination(tx_destination_1)};
         const UniValue json_dest{DescribeAddress(tx_destination_1)};
-        Assert(tx_destination_1 == DecodeDestination(encoded_dest));
         (void)GetKeyForDestination(/*store=*/{}, tx_destination_1);
         const CScript dest{GetScriptForDestination(tx_destination_1)};
         const bool valid{IsValidDestination(tx_destination_1)};
-        Assert(dest.empty() != valid);
 
-        Assert(valid == IsValidDestinationString(encoded_dest));
+        if (!std::get_if<PubKeyDestination>(&tx_destination_1)) {
+            // Only try to round trip non-pubkey destinations since PubKeyDestination has no encoding
+            Assert(dest.empty() != valid);
+            Assert(tx_destination_1 == DecodeDestination(encoded_dest));
+            Assert(valid == IsValidDestinationString(encoded_dest));
+        }
 
         (void)(tx_destination_1 < tx_destination_2);
         if (tx_destination_1 == tx_destination_2) {

src/test/fuzz/util.cpp

@@ -172,6 +172,15 @@ CTxDestination ConsumeTxDestination(FuzzedDataProvider& fuzzed_data_provider) no
         [&] {
             tx_destination = CNoDestination{};
         },
+        [&] {
+            bool compressed = fuzzed_data_provider.ConsumeBool();
+            CPubKey pk{ConstructPubKeyBytes(
+                    fuzzed_data_provider,
+                    ConsumeFixedLengthByteVector(fuzzed_data_provider, (compressed ? CPubKey::COMPRESSED_SIZE : CPubKey::SIZE)),
+                    compressed
+            )};
+            tx_destination = PubKeyDestination{pk};
+        },
         [&] {
             tx_destination = PKHash{ConsumeUInt160(fuzzed_data_provider)};
         },
@@ -188,15 +197,11 @@ CTxDestination ConsumeTxDestination(FuzzedDataProvider& fuzzed_data_provider) no
             tx_destination = WitnessV1Taproot{XOnlyPubKey{ConsumeUInt256(fuzzed_data_provider)}};
         },
         [&] {
-            WitnessUnknown witness_unknown{};
-            witness_unknown.version = fuzzed_data_provider.ConsumeIntegralInRange(2, 16);
-            std::vector<uint8_t> witness_unknown_program_1{fuzzed_data_provider.ConsumeBytes<uint8_t>(40)};
-            if (witness_unknown_program_1.size() < 2) {
-                witness_unknown_program_1 = {0, 0};
+            std::vector<unsigned char> program{ConsumeRandomLengthByteVector(fuzzed_data_provider, /*max_length=*/40)};
+            if (program.size() < 2) {
+                program = {0, 0};
             }
-            witness_unknown.length = witness_unknown_program_1.size();
-            std::copy(witness_unknown_program_1.begin(), witness_unknown_program_1.end(), witness_unknown.program);
-            tx_destination = witness_unknown;
+            tx_destination = WitnessUnknown{fuzzed_data_provider.ConsumeIntegralInRange<unsigned int>(2, 16), program};
         })};
     Assert(call_size == std::variant_size_v<CTxDestination>);
     return tx_destination;

src/test/script_standard_tests.cpp

@@ -203,8 +203,8 @@ BOOST_AUTO_TEST_CASE(script_standard_ExtractDestination)
     // TxoutType::PUBKEY
     s.clear();
     s << ToByteVector(pubkey) << OP_CHECKSIG;
-    BOOST_CHECK(ExtractDestination(s, address));
-    BOOST_CHECK(std::get<PKHash>(address) == PKHash(pubkey));
+    BOOST_CHECK(!ExtractDestination(s, address));
+    BOOST_CHECK(std::get<PubKeyDestination>(address) == PubKeyDestination(pubkey));
 
     // TxoutType::PUBKEYHASH
     s.clear();
@@ -249,10 +249,7 @@ BOOST_AUTO_TEST_CASE(script_standard_ExtractDestination)
     s.clear();
     s << OP_1 << ToByteVector(pubkey);
     BOOST_CHECK(ExtractDestination(s, address));
-    WitnessUnknown unk;
-    unk.length = 33;
-    unk.version = 1;
-    std::copy(pubkey.begin(), pubkey.end(), unk.program);
+    WitnessUnknown unk{1, ToByteVector(pubkey)};
     BOOST_CHECK(std::get<WitnessUnknown>(address) == unk);
 }
 

src/util/message.cpp

@@ -47,7 +47,7 @@ MessageVerificationResult MessageVerify(
         return MessageVerificationResult::ERR_PUBKEY_NOT_RECOVERED;
     }
 
-    if (!(CTxDestination(PKHash(pubkey)) == destination)) {
+    if (!(PKHash(pubkey) == *std::get_if<PKHash>(&destination))) {
         return MessageVerificationResult::ERR_NOT_SIGNED;
     }