Add DummySignatureCreator which just creates zeroed sigs

src/script/sign.cpp

@@ -281,3 +281,39 @@ CScript CombineSignatures(const CScript& scriptPubKey, const BaseSignatureChecke
 
     return CombineSignatures(scriptPubKey, checker, txType, vSolutions, stack1, stack2);
 }
+
+namespace {
+/** Dummy signature checker which accepts all signatures. */
+class DummySignatureChecker : public BaseSignatureChecker
+{
+public:
+    DummySignatureChecker() {}
+
+    bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode) const
+    {
+        return true;
+    }
+};
+const DummySignatureChecker dummyChecker;
+}
+
+const BaseSignatureChecker& DummySignatureCreator::Checker() const
+{
+    return dummyChecker;
+}
+
+bool DummySignatureCreator::CreateSig(std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode) 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;
+}

src/script/sign.h

@@ -43,6 +43,14 @@ public:
     bool CreateSig(std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode) const;
 };
 
+/** A signature creator that just produces 72-byte empty signatyres. */
+class DummySignatureCreator : public BaseSignatureCreator {
+public:
+    DummySignatureCreator(const CKeyStore* keystoreIn) : BaseSignatureCreator(keystoreIn) {}
+    const BaseSignatureChecker& Checker() const;
+    bool CreateSig(std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode) const;
+};
+
 /** Produce a script signature using a generic signature creator. */
 bool ProduceSignature(const BaseSignatureCreator& creator, const CScript& scriptPubKey, CScript& scriptSig);