Add support for creating multisig inputs scripts that redeem P2SH outputs

core/src/main/java/com/google/bitcoin/script/ScriptBuilder.java

@@ -21,6 +21,7 @@ import com.google.bitcoin.core.ECKey;
 import com.google.bitcoin.crypto.TransactionSignature;
 import com.google.common.collect.Lists;
 
+import javax.annotation.Nullable;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -116,10 +117,7 @@ public class ScriptBuilder {
 
     /** Create a program that satisfies an OP_CHECKMULTISIG program. */
     public static Script createMultiSigInputScript(List<TransactionSignature> signatures) {
-        List<byte[]> sigs = new ArrayList<byte[]>(signatures.size());
+        return createP2SHMultiSigInputScript(signatures, null);
-        for (TransactionSignature signature : signatures)
-            sigs.add(signature.encodeToBitcoin());
-        return createMultiSigInputScriptBytes(sigs);
     }
 
     /** Create a program that satisfies an OP_CHECKMULTISIG program. */
@@ -129,11 +127,30 @@ public class ScriptBuilder {
 
     /** Create a program that satisfies an OP_CHECKMULTISIG program, using pre-encoded signatures. */
     public static Script createMultiSigInputScriptBytes(List<byte[]> signatures) {
+    	return createMultiSigInputScriptBytes(signatures, null);
+    }
+
+    /** Create a program that satisfies a pay-to-script hashed OP_CHECKMULTISIG program. */
+    public static Script createP2SHMultiSigInputScript(List<TransactionSignature> signatures,
+                                                       byte[] multisigProgramBytes) {
+        List<byte[]> sigs = new ArrayList<byte[]>(signatures.size());
+        for (TransactionSignature signature : signatures)
+            sigs.add(signature.encodeToBitcoin());
+        return createMultiSigInputScriptBytes(sigs, multisigProgramBytes);
+    }
+
+    /** 
+     * Create a program that satisfies an OP_CHECKMULTISIG program, using pre-encoded signatures. 
+     * Optionally, appends the script program bytes if spending a P2SH output.
+     */
+    public static Script createMultiSigInputScriptBytes(List<byte[]> signatures, @Nullable byte[] multisigProgramBytes) {
         checkArgument(signatures.size() <= 16);
         ScriptBuilder builder = new ScriptBuilder();
         builder.smallNum(0);  // Work around a bug in CHECKMULTISIG that is now a required part of the protocol.
         for (byte[] signature : signatures)
             builder.data(signature);
+        if (multisigProgramBytes!= null)
+        	builder.data(multisigProgramBytes);
         return builder.build();
     }
 

core/src/test/java/com/google/bitcoin/script/ScriptTest.java

@@ -18,10 +18,16 @@
 package com.google.bitcoin.script;
 
 import com.google.bitcoin.core.*;
+import com.google.bitcoin.core.Transaction.SigHash;
+import com.google.bitcoin.crypto.TransactionSignature;
 import com.google.bitcoin.params.MainNetParams;
 import com.google.bitcoin.params.TestNet3Params;
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Lists;
 
+import org.hamcrest.core.IsEqual;
+import org.hamcrest.core.IsNot;
+import org.junit.Assert;
 import org.junit.Test;
 import org.spongycastle.util.encoders.Hex;
 
@@ -30,6 +36,7 @@ import java.io.InputStreamReader;
 import java.math.BigInteger;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -102,6 +109,50 @@ public class ScriptTest {
         assertTrue(s.isSentToRawPubKey());
     }
     
+    @Test
+    public void testCreateMultiSigInputScript() throws AddressFormatException {
+        // Setup transaction and signatures
+        ECKey key1 = new DumpedPrivateKey(params, "cVLwRLTvz3BxDAWkvS3yzT9pUcTCup7kQnfT2smRjvmmm1wAP6QT").getKey();
+        ECKey key2 = new DumpedPrivateKey(params, "cTine92s8GLpVqvebi8rYce3FrUYq78ZGQffBYCS1HmDPJdSTxUo").getKey();
+        ECKey key3 = new DumpedPrivateKey(params, "cVHwXSPRZmL9adctwBwmn4oTZdZMbaCsR5XF6VznqMgcvt1FDDxg").getKey();
+        Script multisigScript = ScriptBuilder.createMultiSigOutputScript(2, Arrays.asList(key1, key2, key3));
+        byte[] bytes = Hex.decode("01000000013df681ff83b43b6585fa32dd0e12b0b502e6481e04ee52ff0fdaf55a16a4ef61000000006b483045022100a84acca7906c13c5895a1314c165d33621cdcf8696145080895cbf301119b7cf0220730ff511106aa0e0a8570ff00ee57d7a6f24e30f592a10cae1deffac9e13b990012102b8d567bcd6328fd48a429f9cf4b315b859a58fd28c5088ef3cb1d98125fc4e8dffffffff02364f1c00000000001976a91439a02793b418de8ec748dd75382656453dc99bcb88ac40420f000000000017a9145780b80be32e117f675d6e0ada13ba799bf248e98700000000");
+        Transaction transaction = new Transaction(params, bytes);
+        TransactionOutput output = transaction.getOutput(1);
+        Transaction spendTx = new Transaction(params);
+        Address address = new Address(params, "n3CFiCmBXVt5d3HXKQ15EFZyhPz4yj5F3H");
+        Script outputScript = ScriptBuilder.createOutputScript(address);
+        spendTx.addOutput(output.getValue(), outputScript);
+        spendTx.addInput(output);
+        Sha256Hash sighash = spendTx.hashForSignature(0, multisigScript, SigHash.ALL, false);
+        ECKey.ECDSASignature party1Signature = key1.sign(sighash);
+        ECKey.ECDSASignature party2Signature = key2.sign(sighash);
+        TransactionSignature party1TransactionSignature = new TransactionSignature(party1Signature, SigHash.ALL, false);
+        TransactionSignature party2TransactionSignature = new TransactionSignature(party2Signature, SigHash.ALL, false);
+
+        // Create p2sh multisig input script
+        Script inputScript = ScriptBuilder.createP2SHMultiSigInputScript(ImmutableList.of(party1TransactionSignature, party2TransactionSignature), multisigScript.getProgram());
+
+        // Assert that the input script contains 4 chunks
+        assertTrue(inputScript.getChunks().size() == 4);
+
+        // Assert that the input script created contains the original multisig
+        // script as the last chunk
+        ScriptChunk scriptChunk = inputScript.getChunks().get(inputScript.getChunks().size() - 1);
+        Assert.assertArrayEquals(scriptChunk.data, multisigScript.getProgram());
+
+        // Create regular multisig input script
+        inputScript = ScriptBuilder.createMultiSigInputScript(ImmutableList.of(party1TransactionSignature, party2TransactionSignature));
+
+        // Assert that the input script only contains 3 chunks
+        assertTrue(inputScript.getChunks().size() == 3);
+
+        // Assert that the input script created does not end with the original
+        // multisig script
+        scriptChunk = inputScript.getChunks().get(inputScript.getChunks().size() - 1);
+        Assert.assertThat(scriptChunk.data, IsNot.not(IsEqual.equalTo(multisigScript.getProgram())));
+    }
+    
     private Script parseScriptString(String string) throws Exception {
         String[] words = string.split("[ \\t\\n]");