Fix bug in classifying things as MultiSigSPK that do not have enough public keys in the Script (#5371)

* Add test case for 3a8dd04bc1f8179d0b85c8e1a1e89d058833ae64a9a8c3681da3ca329297beb1

* Fix bug where we were classifying things are MultSigScriptPubKey that did not have maxSigs' number of public keys in the Script

* Remove redundant comment

core-test/src/test/scala/org/bitcoins/core/protocol/transaction/TransactionTest.scala

@@ -426,6 +426,14 @@ class TransactionTest extends BitcoinSUnitTest {
     assert(tx.hex == hex)
   }
 
+  it must "parse 3a8dd04bc1f8179d0b85c8e1a1e89d058833ae64a9a8c3681da3ca329297beb1" in {
+    //from testnet
+    val hex =
+      "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"
+    val tx = Transaction.fromHex(hex)
+    assert(tx.hex == hex)
+  }
+
   private def findInput(
       tx: Transaction,
       outPoint: TransactionOutPoint): Option[(TransactionInput, Int)] = {

core/src/main/scala/org/bitcoins/core/protocol/script/ScriptPubKey.scala

@@ -177,7 +177,7 @@ sealed trait MultiSignatureScriptPubKey extends RawScriptPubKey {
 
   /** Returns the public keys encoded into the `scriptPubKey` */
   def publicKeys: Seq[ECPublicKeyBytes] = {
-    MultiSignatureScriptPubKey.parsePublicKeys(maxSigs, asm)
+    MultiSignatureScriptPubKey.parsePublicKeys(asm)
   }
 
   override def toString = s"multi($requiredSigs,${publicKeys.mkString(",")})"
@@ -241,15 +241,12 @@ object MultiSignatureScriptPubKey
 
   def apply(asm: Seq[ScriptToken]): MultiSignatureScriptPubKey = fromAsm(asm)
 
+  private val opCmsOPs = Vector(OP_CHECKMULTISIG, OP_CHECKMULTISIGVERIFY)
+
   /** Determines if the given script tokens are a multisignature `scriptPubKey` */
   override def isValidAsm(asm: Seq[ScriptToken]): Boolean = {
-    val cmsIdx = if (asm.contains(OP_CHECKMULTISIG)) {
-      asm.indexOf(OP_CHECKMULTISIG)
-    } else asm.indexOf(OP_CHECKMULTISIGVERIFY)
-    val containsMultiSigOp = cmsIdx != -1
-
-    if (asm.nonEmpty && containsMultiSigOp) {
-
+    if (asm.nonEmpty && opCmsOPs.exists(_ == asm.last)) {
+      val cmsIdx = asm.size - 1
       //we need either the first or second asm operation to indicate how many signatures are required
       val hasRequiredSignaturesOpt: Option[Int] = {
         asm.headOption match {
@@ -285,7 +282,7 @@ object MultiSignatureScriptPubKey
               op == OP_CHECKMULTISIGVERIFY)
 
           val result =
-            asm.nonEmpty && containsMultiSigOp &&
+            asm.nonEmpty &&
               hasMaximumSignatures(maximumSignatures, asm) && isStandardOps
           result
         case (Some(_), None) => false
@@ -297,19 +294,19 @@ object MultiSignatureScriptPubKey
     }
   }
 
-  def parsePublicKeys(
-      maxSigs: Int,
-      asm: Seq[ScriptToken]): Seq[ECPublicKeyBytes] = {
-    asm
+  def parsePublicKeys(asm: Seq[ScriptToken]): Seq[ECPublicKeyBytes] = {
+    val keys = asm
+      .dropRight(2) //drop maxSigs, OP_CMS op
       .filter(_.isInstanceOf[ScriptConstant])
-      .slice(1, maxSigs + 1)
+      .slice(1, asm.length) // drop requiredSigs
       .map(t => ECPublicKeyBytes(t.bytes))
+    keys
   }
 
   private def hasMaximumSignatures(
       maxSigs: Int,
       asm: Seq[ScriptToken]): Boolean = {
-    parsePublicKeys(maxSigs, asm).size == maxSigs
+    parsePublicKeys(asm).size == maxSigs
   }
 
   /** Checks that the given script token is with the range of the maximum amount of