Track difference between scriptPubKey and P2SH execution in IsMine

Inside IsMine we care about the distinction between scriptPubKey execution
and P2SH redeemScript execution. The consensus code does not care about this
distinction, and thus SigVersion does not have a field for P2SH. As the IsMine
code will care, it uses a separate enum with more fields.

Author: sipa

src/script/ismine.cpp

@@ -13,12 +13,24 @@
 
 typedef std::vector<unsigned char> valtype;
 
+/**
+ * This is an enum that tracks the execution context of a script, similar to
+ * SigVersion in script/interpreter. It is separate however because we want to
+ * distinguish between top-level scriptPubKey execution and P2SH redeemScript
+ * execution (a distinction that has no impact on consensus rules).
+ */
 enum class IsMineSigVersion
 {
-    BASE = 0,
-    WITNESS_V0 = 1
+    TOP = 0,        //! scriptPubKey execution
+    P2SH = 1,       //! P2SH redeemScript
+    WITNESS_V0 = 2  //! P2WSH witness script execution
 };
 
+static bool PermitsUncompressed(IsMineSigVersion sigversion)
+{
+    return sigversion == IsMineSigVersion::TOP || sigversion == IsMineSigVersion::P2SH;
+}
+
 static bool HaveKeys(const std::vector<valtype>& pubkeys, const CKeyStore& keystore)
 {
     for (const valtype& pubkey : pubkeys) {
@@ -49,7 +61,7 @@ static isminetype IsMineInner(const CKeyStore& keystore, const CScript& scriptPu
         break;
     case TX_PUBKEY:
         keyID = CPubKey(vSolutions[0]).GetID();
-        if (sigversion != IsMineSigVersion::BASE && vSolutions[0].size() != 33) {
+        if (!PermitsUncompressed(sigversion) && vSolutions[0].size() != 33) {
             isInvalid = true;
             return ISMINE_NO;
         }
@@ -71,7 +83,7 @@ static isminetype IsMineInner(const CKeyStore& keystore, const CScript& scriptPu
     }
     case TX_PUBKEYHASH:
         keyID = CKeyID(uint160(vSolutions[0]));
-        if (sigversion != IsMineSigVersion::BASE) {
+        if (!PermitsUncompressed(sigversion)) {
             CPubKey pubkey;
             if (keystore.GetPubKey(keyID, pubkey) && !pubkey.IsCompressed()) {
                 isInvalid = true;
@@ -86,7 +98,7 @@ static isminetype IsMineInner(const CKeyStore& keystore, const CScript& scriptPu
         CScriptID scriptID = CScriptID(uint160(vSolutions[0]));
         CScript subscript;
         if (keystore.GetCScript(scriptID, subscript)) {
-            isminetype ret = IsMineInner(keystore, subscript, isInvalid, IsMineSigVersion::BASE);
+            isminetype ret = IsMineInner(keystore, subscript, isInvalid, IsMineSigVersion::P2SH);
             if (ret == ISMINE_SPENDABLE || ret == ISMINE_WATCH_SOLVABLE || (ret == ISMINE_NO && isInvalid))
                 return ret;
         }
@@ -117,7 +129,7 @@ static isminetype IsMineInner(const CKeyStore& keystore, const CScript& scriptPu
         // them) enable spend-out-from-under-you attacks, especially
         // in shared-wallet situations.
         std::vector<valtype> keys(vSolutions.begin()+1, vSolutions.begin()+vSolutions.size()-1);
-        if (sigversion != IsMineSigVersion::BASE) {
+        if (!PermitsUncompressed(sigversion)) {
             for (size_t i = 0; i < keys.size(); i++) {
                 if (keys[i].size() != 33) {
                     isInvalid = true;
@@ -141,7 +153,7 @@ static isminetype IsMineInner(const CKeyStore& keystore, const CScript& scriptPu
 
 isminetype IsMine(const CKeyStore& keystore, const CScript& scriptPubKey, bool& isInvalid)
 {
-    return IsMineInner(keystore, scriptPubKey, isInvalid, IsMineSigVersion::BASE);
+    return IsMineInner(keystore, scriptPubKey, isInvalid, IsMineSigVersion::TOP);
 }
 
 isminetype IsMine(const CKeyStore& keystore, const CScript& scriptPubKey)