Merge bitcoin#31242: wallet, desc spkm: Return SigningProvider only i…

…f we have the privkey

f6a6d91 test: add check for getting SigningProvider for a CPubKey (Sebastian Falbesoner)
62a95f5 test: refactor: move `CreateDescriptor` helper to wallet test util module (Sebastian Falbesoner)
4936567 desc spkm: Return SigningProvider only if we have the privkey (Ava Chow)

Pull request description:

  If we know about a pubkey that's in our descriptor, but we don't have the private key, don't return a SigningProvider for that pubkey.

  This is specifically an issue for Taproot outputs that use the H point as the resulting PSBTs may end up containing irrelevant information because the H point was detected as a pubkey each unrelated descriptor knew about.

  Split from bitcoin#29675

ACKs for top commit:
  fjahr:
    ACK f6a6d91
  theStack:
    re-ACK f6a6d91
  furszy:
    utACK f6a6d91. Only reviewed the actual change in detail, not the test commit.

Tree-SHA512: 30a196e611a0c5d9ebe5baf6d896caaa6af66f1615463dbb0c31e52604d53cf342922bb9967b3c697b47083d76b0485c77a5f545bd6381247c8bc44321c70f97

src/script/signingprovider.cpp

@@ -62,6 +62,11 @@ bool FlatSigningProvider::GetKeyOrigin(const CKeyID& keyid, KeyOriginInfo& info)
     if (ret) info = std::move(out.second);
     return ret;
 }
+bool FlatSigningProvider::HaveKey(const CKeyID &keyid) const
+{
+    CKey key;
+    return LookupHelper(keys, keyid, key);
+}
 bool FlatSigningProvider::GetKey(const CKeyID& keyid, CKey& key) const { return LookupHelper(keys, keyid, key); }
 bool FlatSigningProvider::GetTaprootSpendData(const XOnlyPubKey& output_key, TaprootSpendData& spenddata) const
 {

src/script/signingprovider.h

@@ -215,6 +215,7 @@ struct FlatSigningProvider final : public SigningProvider
     bool GetCScript(const CScriptID& scriptid, CScript& script) const override;
     bool GetPubKey(const CKeyID& keyid, CPubKey& pubkey) const override;
     bool GetKeyOrigin(const CKeyID& keyid, KeyOriginInfo& info) const override;
+    bool HaveKey(const CKeyID &keyid) const override;
     bool GetKey(const CKeyID& keyid, CKey& key) const override;
     bool GetTaprootSpendData(const XOnlyPubKey& output_key, TaprootSpendData& spenddata) const override;
     bool GetTaprootBuilder(const XOnlyPubKey& output_key, TaprootBuilder& builder) const override;

src/wallet/scriptpubkeyman.cpp

@@ -2468,7 +2468,11 @@ std::unique_ptr<FlatSigningProvider> DescriptorScriptPubKeyMan::GetSigningProvid
     int32_t index = it->second;
 
     // Always try to get the signing provider with private keys. This function should only be called during signing anyways
-    return GetSigningProvider(index, true);
+    std::unique_ptr<FlatSigningProvider> out = GetSigningProvider(index, true);
+    if (!out->HaveKey(pubkey.GetID())) {
+        return nullptr;
+    }
+    return out;
 }
 
 std::unique_ptr<FlatSigningProvider> DescriptorScriptPubKeyMan::GetSigningProvider(int32_t index, bool include_private) const

src/wallet/scriptpubkeyman.h

@@ -613,8 +613,6 @@ class DescriptorScriptPubKeyMan : public ScriptPubKeyMan
     mutable std::map<int32_t, FlatSigningProvider> m_map_signing_providers;
     // Fetch the SigningProvider for the given script and optionally include private keys
     std::unique_ptr<FlatSigningProvider> GetSigningProvider(const CScript& script, bool include_private = false) const;
-    // Fetch the SigningProvider for the given pubkey and always include private keys. This should only be called by signing code.
-    std::unique_ptr<FlatSigningProvider> GetSigningProvider(const CPubKey& pubkey) const;
     // Fetch the SigningProvider for a given index and optionally include private keys. Called by the above functions.
     std::unique_ptr<FlatSigningProvider> GetSigningProvider(int32_t index, bool include_private = false) const EXCLUSIVE_LOCKS_REQUIRED(cs_desc_man);
 
@@ -678,6 +676,9 @@ class DescriptorScriptPubKeyMan : public ScriptPubKeyMan
 
     bool CanProvide(const CScript& script, SignatureData& sigdata) override;
 
+    // Fetch the SigningProvider for the given pubkey and always include private keys. This should only be called by signing code.
+    std::unique_ptr<FlatSigningProvider> GetSigningProvider(const CPubKey& pubkey) const;
+
     bool SignTransaction(CMutableTransaction& tx, const std::map<COutPoint, Coin>& coins, int sighash, std::map<int, bilingual_str>& input_errors) const override;
     SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const override;
     std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = SIGHASH_DEFAULT, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;

src/wallet/test/ismine_tests.cpp

@@ -20,26 +20,6 @@ using namespace util::hex_literals;
 namespace wallet {
 BOOST_FIXTURE_TEST_SUITE(ismine_tests, BasicTestingSetup)
 
-wallet::ScriptPubKeyMan* CreateDescriptor(CWallet& keystore, const std::string& desc_str, const bool success)
-{
-    keystore.SetWalletFlag(WALLET_FLAG_DESCRIPTORS);
-
-    FlatSigningProvider keys;
-    std::string error;
-    auto parsed_descs = Parse(desc_str, keys, error, false);
-    BOOST_CHECK(success == (!parsed_descs.empty()));
-    if (!success) return nullptr;
-    auto& desc = parsed_descs.at(0);
-
-    const int64_t range_start = 0, range_end = 1, next_index = 0, timestamp = 1;
-
-    WalletDescriptor w_desc(std::move(desc), timestamp, range_start, range_end, next_index);
-
-    LOCK(keystore.cs_wallet);
-
-    return Assert(keystore.AddWalletDescriptor(w_desc, keys,/*label=*/"", /*internal=*/false));
-};
-
 BOOST_AUTO_TEST_CASE(ismine_standard)
 {
     CKey keys[2];

src/wallet/test/scriptpubkeyman_tests.cpp

@@ -3,6 +3,7 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <key.h>
+#include <key_io.h>
 #include <test/util/setup_common.h>
 #include <script/solver.h>
 #include <wallet/scriptpubkeyman.h>
@@ -40,5 +41,27 @@ BOOST_AUTO_TEST_CASE(CanProvide)
     BOOST_CHECK(keyman.CanProvide(p2sh_script, data));
 }
 
+BOOST_AUTO_TEST_CASE(DescriptorScriptPubKeyManTests)
+{
+    std::unique_ptr<interfaces::Chain>& chain = m_node.chain;
+
+    CWallet keystore(chain.get(), "", CreateMockableWalletDatabase());
+    auto key_scriptpath = GenerateRandomKey();
+
+    // Verify that a SigningProvider for a pubkey is only returned if its corresponding private key is available
+    auto key_internal = GenerateRandomKey();
+    std::string desc_str = "tr(" + EncodeSecret(key_internal) + ",pk(" + HexStr(key_scriptpath.GetPubKey()) + "))";
+    auto spk_man1 = dynamic_cast<DescriptorScriptPubKeyMan*>(CreateDescriptor(keystore, desc_str, true));
+    BOOST_CHECK(spk_man1 != nullptr);
+    auto signprov_keypath_spendable = spk_man1->GetSigningProvider(key_internal.GetPubKey());
+    BOOST_CHECK(signprov_keypath_spendable != nullptr);
+
+    desc_str = "tr(" + HexStr(XOnlyPubKey::NUMS_H) + ",pk(" + HexStr(key_scriptpath.GetPubKey()) + "))";
+    auto spk_man2 = dynamic_cast<DescriptorScriptPubKeyMan*>(CreateDescriptor(keystore, desc_str, true));
+    BOOST_CHECK(spk_man2 != nullptr);
+    auto signprov_keypath_nums_h = spk_man2->GetSigningProvider(XOnlyPubKey::NUMS_H.GetEvenCorrespondingCPubKey());
+    BOOST_CHECK(signprov_keypath_nums_h == nullptr);
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 } // namespace wallet

src/wallet/test/util.cpp

@@ -192,4 +192,24 @@ MockableDatabase& GetMockableDatabase(CWallet& wallet)
 {
     return dynamic_cast<MockableDatabase&>(wallet.GetDatabase());
 }
+
+wallet::ScriptPubKeyMan* CreateDescriptor(CWallet& keystore, const std::string& desc_str, const bool success)
+{
+    keystore.SetWalletFlag(WALLET_FLAG_DESCRIPTORS);
+
+    FlatSigningProvider keys;
+    std::string error;
+    auto parsed_descs = Parse(desc_str, keys, error, false);
+    Assert(success == (!parsed_descs.empty()));
+    if (!success) return nullptr;
+    auto& desc = parsed_descs.at(0);
+
+    const int64_t range_start = 0, range_end = 1, next_index = 0, timestamp = 1;
+
+    WalletDescriptor w_desc(std::move(desc), timestamp, range_start, range_end, next_index);
+
+    LOCK(keystore.cs_wallet);
+
+    return Assert(keystore.AddWalletDescriptor(w_desc, keys,/*label=*/"", /*internal=*/false));
+};
 } // namespace wallet

src/wallet/test/util.h

@@ -9,6 +9,7 @@
 
 #include <addresstype.h>
 #include <wallet/db.h>
+#include <wallet/scriptpubkeyman.h>
 
 #include <memory>
 
@@ -127,8 +128,9 @@ class MockableDatabase : public WalletDatabase
 };
 
 std::unique_ptr<WalletDatabase> CreateMockableWalletDatabase(MockableData records = {});
-
 MockableDatabase& GetMockableDatabase(CWallet& wallet);
+
+ScriptPubKeyMan* CreateDescriptor(CWallet& keystore, const std::string& desc_str, const bool success);
 } // namespace wallet
 
 #endif // BITCOIN_WALLET_TEST_UTIL_H