Merge #12803: Make BaseSignatureCreator a pure interface

be67831 Make DummySignatureCreator a singleton (Pieter Wuille)
190b8d2 Make BaseSignatureCreator a pure interface (Pieter Wuille)

Pull request description:

  * Removes the `m_provider` field from `BaseSignatureCreator`. Instead both a `SigningProvider` (which provides keys and scripts) and a `BaseSignatureCreator` (which implements the transaction-specific (or other) signing logic) are passed into and down in `ProduceSignature`, making the two concepts orthogonal.
  * Makes `BaseSignatureCreator` a pure interface without constructor, making it easier to implement new derivations of it (for example for message signing).
  * As `DummySignatureCreator` now becomes a stateless object, turn it into a singleton `DUMMY_SIGNATURE_CREATOR`.

Tree-SHA512: 5f1f4512e4ea7d02a31df7b9ede55008efa716c5b74a2630ca1c2fc6599584d8bf5f5641487266127f4b3788033803539fbd22b03ef1219c83c10da2d3da3dcd

3 files changed, 52 insertions, 65 deletions

diff --git a/src/script/ismine.cpp b/src/script/ismine.cpp
index 05bc5e9bd6..b826bcfe20 100644
--- a/src/script/ismine.cpp
+++ b/src/script/ismine.cpp
@@ -146,7 +146,7 @@ isminetype IsMine(const CKeyStore &keystore, const CScript& scriptPubKey, bool&
     if (keystore.HaveWatchOnly(scriptPubKey)) {
         // TODO: This could be optimized some by doing some work after the above solver
         SignatureData sigs;
-        return ProduceSignature(DummySignatureCreator(&keystore), scriptPubKey, sigs) ? ISMINE_WATCH_SOLVABLE : ISMINE_WATCH_UNSOLVABLE;
+        return ProduceSignature(keystore, DUMMY_SIGNATURE_CREATOR, scriptPubKey, sigs) ? ISMINE_WATCH_SOLVABLE : ISMINE_WATCH_UNSOLVABLE;
     }
     return ISMINE_NO;
 }
diff --git a/src/script/sign.cpp b/src/script/sign.cpp
index 910bb39ce6..ac35f17f3e 100644
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -14,12 +14,12 @@
 
 typedef std::vector<unsigned char> valtype;
 
-TransactionSignatureCreator::TransactionSignatureCreator(const SigningProvider* provider, const CTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, int nHashTypeIn) : BaseSignatureCreator(provider), txTo(txToIn), nIn(nInIn), nHashType(nHashTypeIn), amount(amountIn), checker(txTo, nIn, amountIn) {}
+TransactionSignatureCreator::TransactionSignatureCreator(const CTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, int nHashTypeIn) : txTo(txToIn), nIn(nInIn), nHashType(nHashTypeIn), amount(amountIn), checker(txTo, nIn, amountIn) {}
 
-bool TransactionSignatureCreator::CreateSig(std::vector<unsigned char>& vchSig, const CKeyID& address, const CScript& scriptCode, SigVersion sigversion) const
+bool TransactionSignatureCreator::CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& address, const CScript& scriptCode, SigVersion sigversion) const
 {
     CKey key;
-    if (!m_provider->GetKey(address, key))
+    if (!provider.GetKey(address, key))
         return false;
 
     // Signing with uncompressed keys is disabled in witness scripts
@@ -33,16 +33,16 @@ bool TransactionSignatureCreator::CreateSig(std::vector<unsigned char>& vchSig,
     return true;
 }
 
-static bool Sign1(const CKeyID& address, const BaseSignatureCreator& creator, const CScript& scriptCode, std::vector<valtype>& ret, SigVersion sigversion)
+static bool Sign1(const SigningProvider& provider, const CKeyID& address, const BaseSignatureCreator& creator, const CScript& scriptCode, std::vector<valtype>& ret, SigVersion sigversion)
 {
     std::vector<unsigned char> vchSig;
-    if (!creator.CreateSig(vchSig, address, scriptCode, sigversion))
+    if (!creator.CreateSig(provider, vchSig, address, scriptCode, sigversion))
         return false;
     ret.push_back(vchSig);
     return true;
 }
 
-static bool SignN(const std::vector<valtype>& multisigdata, const BaseSignatureCreator& creator, const CScript& scriptCode, std::vector<valtype>& ret, SigVersion sigversion)
+static bool SignN(const SigningProvider& provider, const std::vector<valtype>& multisigdata, const BaseSignatureCreator& creator, const CScript& scriptCode, std::vector<valtype>& ret, SigVersion sigversion)
 {
     int nSigned = 0;
     int nRequired = multisigdata.front()[0];
@@ -50,7 +50,7 @@ static bool SignN(const std::vector<valtype>& multisigdata, const BaseSignatureC
     {
         const valtype& pubkey = multisigdata[i];
         CKeyID keyID = CPubKey(pubkey).GetID();
-        if (Sign1(keyID, creator, scriptCode, ret, sigversion))
+        if (Sign1(provider, keyID, creator, scriptCode, ret, sigversion))
             ++nSigned;
     }
     return nSigned==nRequired;
@@ -62,7 +62,7 @@ static bool SignN(const std::vector<valtype>& multisigdata, const BaseSignatureC
  * unless whichTypeRet is TX_SCRIPTHASH, in which case scriptSigRet is the redemption script.
  * Returns false if scriptPubKey could not be completely satisfied.
  */
-static bool SignStep(const BaseSignatureCreator& creator, const CScript& scriptPubKey,
+static bool SignStep(const SigningProvider& provider, const BaseSignatureCreator& creator, const CScript& scriptPubKey,
                      std::vector<valtype>& ret, txnouttype& whichTypeRet, SigVersion sigversion)
 {
     CScript scriptRet;
@@ -82,20 +82,20 @@ static bool SignStep(const BaseSignatureCreator& creator, const CScript& scriptP
         return false;
     case TX_PUBKEY:
         keyID = CPubKey(vSolutions[0]).GetID();
-        return Sign1(keyID, creator, scriptPubKey, ret, sigversion);
+        return Sign1(provider, keyID, creator, scriptPubKey, ret, sigversion);
     case TX_PUBKEYHASH:
         keyID = CKeyID(uint160(vSolutions[0]));
-        if (!Sign1(keyID, creator, scriptPubKey, ret, sigversion))
+        if (!Sign1(provider, keyID, creator, scriptPubKey, ret, sigversion))
             return false;
         else
         {
             CPubKey vch;
-            creator.Provider().GetPubKey(keyID, vch);
+            provider.GetPubKey(keyID, vch);
             ret.push_back(ToByteVector(vch));
         }
         return true;
     case TX_SCRIPTHASH:
-        if (creator.Provider().GetCScript(uint160(vSolutions[0]), scriptRet)) {
+        if (provider.GetCScript(uint160(vSolutions[0]), scriptRet)) {
             ret.push_back(std::vector<unsigned char>(scriptRet.begin(), scriptRet.end()));
             return true;
         }
@@ -103,7 +103,7 @@ static bool SignStep(const BaseSignatureCreator& creator, const CScript& scriptP
 
     case TX_MULTISIG:
         ret.push_back(valtype()); // workaround CHECKMULTISIG bug
-        return (SignN(vSolutions, creator, scriptPubKey, ret, sigversion));
+        return (SignN(provider, vSolutions, creator, scriptPubKey, ret, sigversion));
 
     case TX_WITNESS_V0_KEYHASH:
         ret.push_back(vSolutions[0]);
@@ -111,7 +111,7 @@ static bool SignStep(const BaseSignatureCreator& creator, const CScript& scriptP
 
     case TX_WITNESS_V0_SCRIPTHASH:
         CRIPEMD160().Write(&vSolutions[0][0], vSolutions[0].size()).Finalize(h160.begin());
-        if (creator.Provider().GetCScript(h160, scriptRet)) {
+        if (provider.GetCScript(h160, scriptRet)) {
             ret.push_back(std::vector<unsigned char>(scriptRet.begin(), scriptRet.end()));
             return true;
         }
@@ -137,11 +137,11 @@ static CScript PushAll(const std::vector<valtype>& values)
     return result;
 }
 
-bool ProduceSignature(const BaseSignatureCreator& creator, const CScript& fromPubKey, SignatureData& sigdata)
+bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreator& creator, const CScript& fromPubKey, SignatureData& sigdata)
 {
     std::vector<valtype> result;
     txnouttype whichType;
-    bool solved = SignStep(creator, fromPubKey, result, whichType, SigVersion::BASE);
+    bool solved = SignStep(provider, creator, fromPubKey, result, whichType, SigVersion::BASE);
     bool P2SH = false;
     CScript subscript;
     sigdata.scriptWitness.stack.clear();
@@ -152,7 +152,7 @@ bool ProduceSignature(const BaseSignatureCreator& creator, const CScript& fromPu
         // the final scriptSig is the signatures from that
         // and then the serialized subscript:
         subscript = CScript(result[0].begin(), result[0].end());
-        solved = solved && SignStep(creator, subscript, result, whichType, SigVersion::BASE) && whichType != TX_SCRIPTHASH;
+        solved = solved && SignStep(provider, creator, subscript, result, whichType, SigVersion::BASE) && whichType != TX_SCRIPTHASH;
         P2SH = true;
     }
 
@@ -161,7 +161,7 @@ bool ProduceSignature(const BaseSignatureCreator& creator, const CScript& fromPu
         CScript witnessscript;
         witnessscript << OP_DUP << OP_HASH160 << ToByteVector(result[0]) << OP_EQUALVERIFY << OP_CHECKSIG;
         txnouttype subType;
-        solved = solved && SignStep(creator, witnessscript, result, subType, SigVersion::WITNESS_V0);
+        solved = solved && SignStep(provider, creator, witnessscript, result, subType, SigVersion::WITNESS_V0);
         sigdata.scriptWitness.stack = result;
         result.clear();
     }
@@ -169,7 +169,7 @@ bool ProduceSignature(const BaseSignatureCreator& creator, const CScript& fromPu
     {
         CScript witnessscript(result[0].begin(), result[0].end());
         txnouttype subType;
-        solved = solved && SignStep(creator, witnessscript, result, subType, SigVersion::WITNESS_V0) && subType != TX_SCRIPTHASH && subType != TX_WITNESS_V0_SCRIPTHASH && subType != TX_WITNESS_V0_KEYHASH;
+        solved = solved && SignStep(provider, creator, witnessscript, result, subType, SigVersion::WITNESS_V0) && subType != TX_SCRIPTHASH && subType != TX_WITNESS_V0_SCRIPTHASH && subType != TX_WITNESS_V0_KEYHASH;
         result.push_back(std::vector<unsigned char>(witnessscript.begin(), witnessscript.end()));
         sigdata.scriptWitness.stack = result;
         result.clear();
@@ -210,10 +210,10 @@ bool SignSignature(const SigningProvider &provider, const CScript& fromPubKey, C
     assert(nIn < txTo.vin.size());
 
     CTransaction txToConst(txTo);
-    TransactionSignatureCreator creator(&provider, &txToConst, nIn, amount, nHashType);
+    TransactionSignatureCreator creator(&txToConst, nIn, amount, nHashType);
 
     SignatureData sigdata;
-    bool ret = ProduceSignature(creator, fromPubKey, sigdata);
+    bool ret = ProduceSignature(provider, creator, fromPubKey, sigdata);
     UpdateTransaction(txTo, nIn, sigdata);
     return ret;
 }
@@ -392,39 +392,37 @@ SignatureData CombineSignatures(const CScript& scriptPubKey, const BaseSignature
 
 namespace {
 /** Dummy signature checker which accepts all signatures. */
-class DummySignatureChecker : public BaseSignatureChecker
+class DummySignatureChecker final : public BaseSignatureChecker
 {
 public:
     DummySignatureChecker() {}
+    bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const override { return true; }
+};
+const DummySignatureChecker DUMMY_CHECKER;
 
-    bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const override
+class DummySignatureCreator final : public BaseSignatureCreator {
+public:
+    DummySignatureCreator() {}
+    const BaseSignatureChecker& Checker() const override { return DUMMY_CHECKER; }
+    bool CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const override
     {
+        // Create a dummy signature that is a valid DER-encoding
+        vchSig.assign(72, '\000');
+        vchSig[0] = 0x30;
+        vchSig[1] = 69;
+        vchSig[2] = 0x02;
+        vchSig[3] = 33;
+        vchSig[4] = 0x01;
+        vchSig[4 + 33] = 0x02;
+        vchSig[5 + 33] = 32;
+        vchSig[6 + 33] = 0x01;
+        vchSig[6 + 33 + 32] = SIGHASH_ALL;
         return true;
     }
 };
-const DummySignatureChecker dummyChecker;
-} // namespace
-
-const BaseSignatureChecker& DummySignatureCreator::Checker() const
-{
-    return dummyChecker;
 }
 
-bool DummySignatureCreator::CreateSig(std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const
-{
-    // Create a dummy signature that is a valid DER-encoding
-    vchSig.assign(72, '\000');
-    vchSig[0] = 0x30;
-    vchSig[1] = 69;
-    vchSig[2] = 0x02;
-    vchSig[3] = 33;
-    vchSig[4] = 0x01;
-    vchSig[4 + 33] = 0x02;
-    vchSig[5 + 33] = 32;
-    vchSig[6 + 33] = 0x01;
-    vchSig[6 + 33 + 32] = SIGHASH_ALL;
-    return true;
-}
+const BaseSignatureCreator& DUMMY_SIGNATURE_CREATOR = DummySignatureCreator();
 
 bool IsSolvable(const SigningProvider& provider, const CScript& script)
 {
@@ -432,14 +430,13 @@ bool IsSolvable(const SigningProvider& provider, const CScript& script)
     // if we were to have the private keys. This is just to make sure that the script is valid and that,
     // if found in a transaction, we would still accept and relay that transaction. In particular,
     // it will reject witness outputs that require signing with an uncompressed public key.
-    DummySignatureCreator creator(&provider);
     SignatureData sigs;
     // Make sure that STANDARD_SCRIPT_VERIFY_FLAGS includes SCRIPT_VERIFY_WITNESS_PUBKEYTYPE, the most
     // important property this function is designed to test for.
     static_assert(STANDARD_SCRIPT_VERIFY_FLAGS & SCRIPT_VERIFY_WITNESS_PUBKEYTYPE, "IsSolvable requires standard script flags to include WITNESS_PUBKEYTYPE");
-    if (ProduceSignature(creator, script, sigs)) {
+    if (ProduceSignature(provider, DUMMY_SIGNATURE_CREATOR, script, sigs)) {
         // VerifyScript check is just defensive, and should never fail.
-        assert(VerifyScript(sigs.scriptSig, script, &sigs.scriptWitness, STANDARD_SCRIPT_VERIFY_FLAGS, creator.Checker()));
+        assert(VerifyScript(sigs.scriptSig, script, &sigs.scriptWitness, STANDARD_SCRIPT_VERIFY_FLAGS, DUMMY_CHECKER));
         return true;
     }
     return false;
diff --git a/src/script/sign.h b/src/script/sign.h
index c301f0544f..cf3651c1de 100644
--- a/src/script/sign.h
+++ b/src/script/sign.h
@@ -26,19 +26,14 @@ public:
     virtual bool GetKey(const CKeyID &address, CKey& key) const =0;
 };
 
-/** Virtual base class for signature creators. */
+/** Interface for signature creators. */
 class BaseSignatureCreator {
-protected:
-    const SigningProvider* m_provider;
-
 public:
-    explicit BaseSignatureCreator(const SigningProvider* provider) : m_provider(provider) {}
-    const SigningProvider& Provider() const { return *m_provider; }
     virtual ~BaseSignatureCreator() {}
     virtual const BaseSignatureChecker& Checker() const =0;
 
     /** Create a singular (non-script) signature. */
-    virtual bool CreateSig(std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const =0;
+    virtual bool CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const =0;
 };
 
 /** A signature creator for transactions. */
@@ -50,25 +45,20 @@ class TransactionSignatureCreator : public BaseSignatureCreator {
     const TransactionSignatureChecker checker;
 
 public:
-    TransactionSignatureCreator(const SigningProvider* provider, const CTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, int nHashTypeIn=SIGHASH_ALL);
+    TransactionSignatureCreator(const CTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, int nHashTypeIn=SIGHASH_ALL);
     const BaseSignatureChecker& Checker() const override { return checker; }
-    bool CreateSig(std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const override;
+    bool CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const override;
 };
 
 class MutableTransactionSignatureCreator : public TransactionSignatureCreator {
     CTransaction tx;
 
 public:
-    MutableTransactionSignatureCreator(const SigningProvider* provider, const CMutableTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, int nHashTypeIn) : TransactionSignatureCreator(provider, &tx, nInIn, amountIn, nHashTypeIn), tx(*txToIn) {}
+    MutableTransactionSignatureCreator(const CMutableTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, int nHashTypeIn) : TransactionSignatureCreator(&tx, nInIn, amountIn, nHashTypeIn), tx(*txToIn) {}
 };
 
 /** A signature creator that just produces 72-byte empty signatures. */
-class DummySignatureCreator : public BaseSignatureCreator {
-public:
-    explicit DummySignatureCreator(const SigningProvider* provider) : BaseSignatureCreator(provider) {}
-    const BaseSignatureChecker& Checker() const override;
-    bool CreateSig(std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const override;
-};
+extern const BaseSignatureCreator& DUMMY_SIGNATURE_CREATOR;
 
 struct SignatureData {
     CScript scriptSig;
@@ -79,7 +69,7 @@ struct SignatureData {
 };
 
 /** Produce a script signature using a generic signature creator. */
-bool ProduceSignature(const BaseSignatureCreator& creator, const CScript& scriptPubKey, SignatureData& sigdata);
+bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreator& creator, const CScript& scriptPubKey, SignatureData& sigdata);
 
 /** Produce a script signature for a transaction. */
 bool SignSignature(const SigningProvider &provider, const CScript& fromPubKey, CMutableTransaction& txTo, unsigned int nIn, const CAmount& amount, int nHashType);