partial merge bitcoin#11403: Abstract out IsSolvable from Witnessifier

UdjinM6 · Jun 27, 2021 · 01fccc4 · 01fccc4
1 parent c8ee5e1
commit 01fccc4
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Showing 3 changed files with 37 additions and 16 deletions.
diff --git a/src/policy/policy.h b/src/policy/policy.h
@@ -43,26 +43,26 @@ static const unsigned int DUST_RELAY_TX_FEE = 3000;
  * with. However scripts violating these flags may still be present in valid
  * blocks and we must accept those blocks.
  */
-static const unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY_FLAGS |
-                                                         SCRIPT_VERIFY_DERSIG |
-                                                         SCRIPT_VERIFY_STRICTENC |
-                                                         SCRIPT_VERIFY_MINIMALDATA |
-                                                         SCRIPT_VERIFY_NULLDUMMY |
-                                                         SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS |
-                                                         SCRIPT_VERIFY_CLEANSTACK |
-                                                         SCRIPT_VERIFY_NULLFAIL |
-                                                         SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY |
-                                                         SCRIPT_VERIFY_CHECKSEQUENCEVERIFY |
-                                                         SCRIPT_VERIFY_LOW_S |
-                                                         SCRIPT_ENABLE_DIP0020_OPCODES |
-                                                         SCRIPT_VERIFY_CONST_SCRIPTCODE;
+static constexpr unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY_FLAGS |
+                                                             SCRIPT_VERIFY_DERSIG |
+                                                             SCRIPT_VERIFY_STRICTENC |
+                                                             SCRIPT_VERIFY_MINIMALDATA |
+                                                             SCRIPT_VERIFY_NULLDUMMY |
+                                                             SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS |
+                                                             SCRIPT_VERIFY_CLEANSTACK |
+                                                             SCRIPT_VERIFY_NULLFAIL |
+                                                             SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY |
+                                                             SCRIPT_VERIFY_CHECKSEQUENCEVERIFY |
+                                                             SCRIPT_VERIFY_LOW_S |
+                                                             SCRIPT_ENABLE_DIP0020_OPCODES |
+                                                             SCRIPT_VERIFY_CONST_SCRIPTCODE;
 
 /** For convenience, standard but not mandatory verify flags. */
-static const unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS = STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS;
+static constexpr unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS = STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS;
 
 /** Used as the flags parameter to sequence and nLocktime checks in non-consensus code. */
-static const unsigned int STANDARD_LOCKTIME_VERIFY_FLAGS = LOCKTIME_VERIFY_SEQUENCE |
-                                                           LOCKTIME_MEDIAN_TIME_PAST;
+static constexpr unsigned int STANDARD_LOCKTIME_VERIFY_FLAGS = LOCKTIME_VERIFY_SEQUENCE |
+                                                               LOCKTIME_MEDIAN_TIME_PAST;
 
 CAmount GetDustThreshold(const CTxOut& txout, const CFeeRate& dustRelayFee);
 

diff --git a/src/script/sign.cpp b/src/script/sign.cpp
@@ -352,3 +352,18 @@ class DummySignatureCreator final : public BaseSignatureCreator {
 }
 
 const BaseSignatureCreator& DUMMY_SIGNATURE_CREATOR = DummySignatureCreator();
+
+bool IsSolvable(const CKeyStore& store, const CScript& script)
+{
+    // This check is to make sure that the script we created can actually be solved for and signed by us
+    // 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.
+    DummySignatureCreator creator(&store);
+    SignatureData sigs;
+    if (ProduceSignature(creator, script, sigs)) {
+        // VerifyScript check is just defensive, and should never fail.
+        assert(VerifyScript(sigs.scriptSig, script, STANDARD_SCRIPT_VERIFY_FLAGS, creator.Checker()));
+        return true;
+    }
+    return false;
+}
diff --git a/src/script/sign.h b/src/script/sign.h
@@ -82,4 +82,10 @@ SignatureData DataFromTransaction(const CMutableTransaction& tx, unsigned int nI
 void UpdateTransaction(CMutableTransaction& tx, unsigned int nIn, const SignatureData& data);
 void UpdateInput(CTxIn& input, const SignatureData& data);
 
+/* Check whether we know how to sign for an output like this, assuming we
+ * have all private keys. While this function does not need private keys, the passed
+ * keystore is used to look up public keys and redeemscripts by hash.
+ * Solvability is unrelated to whether we consider this output to be ours. */
+bool IsSolvable(const CKeyStore& store, const CScript& script);
+
 #endif // BITCOIN_SCRIPT_SIGN_H