Added LOW_S script flag test case generator

examples/src/main/java/org/bitcoinj/examples/GenerateLowSTests.java

@@ -0,0 +1,170 @@
+/*
+ * Copyright 2015 Ross Nicoll.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.bitcoinj.examples;
+
+import java.io.IOException;
+import java.math.BigInteger;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+import java.util.EnumSet;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import org.bitcoinj.core.Coin;
+import org.bitcoinj.core.ECKey;
+import org.bitcoinj.core.NetworkParameters;
+import org.bitcoinj.core.ScriptException;
+import org.bitcoinj.core.Transaction;
+import org.bitcoinj.core.TransactionInput;
+import org.bitcoinj.core.TransactionOutput;
+import org.bitcoinj.core.Utils;
+import org.bitcoinj.crypto.TransactionSignature;
+import org.bitcoinj.params.MainNetParams;
+import org.bitcoinj.script.Script;
+import org.bitcoinj.script.ScriptBuilder;
+import org.bitcoinj.script.ScriptChunk;
+import static org.bitcoinj.script.ScriptOpCodes.getOpCodeName;
+import org.bitcoinj.signers.LocalTransactionSigner;
+import org.bitcoinj.signers.TransactionSigner.ProposedTransaction;
+import org.bitcoinj.wallet.KeyBag;
+import org.bitcoinj.wallet.RedeemData;
+
+/**
+ * Test case generator for transactions with low-S and high-S signatures, to
+ * test the LOW_S script validation flag.
+ *
+ * @author Ross Nicoll
+ */
+public class GenerateLowSTests {
+    public static final BigInteger HIGH_S_DIFFERENCE = new BigInteger("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141", 16);
+
+    public static void main(final String[] argv) throws NoSuchAlgorithmException, IOException {
+        final NetworkParameters params = new MainNetParams();
+        final LocalTransactionSigner signer = new LocalTransactionSigner();
+        final SecureRandom secureRandom = SecureRandom.getInstanceStrong();
+        final ECKey key = new ECKey(secureRandom);
+        final KeyBag bag = new KeyBag() {
+            @Override
+            public ECKey findKeyFromPubHash(byte[] pubkeyHash) {
+                return key;
+            }
+
+            @Override
+            public ECKey findKeyFromPubKey(byte[] pubkey) {
+                return key;
+            }
+
+            @Override
+            public RedeemData findRedeemDataFromScriptHash(byte[] scriptHash) {
+                return null;
+            }
+
+        };
+
+        // Generate a fictional output transaction we take values from, and
+        // an input transaction for the test case
+
+        final Transaction outputTransaction = new Transaction(params);
+        final Transaction inputTransaction = new Transaction(params);
+        final TransactionOutput output = new TransactionOutput(params, inputTransaction, Coin.ZERO, key.toAddress(params));
+
+        inputTransaction.addOutput(output);
+        outputTransaction.addInput(output);
+        outputTransaction.addOutput(Coin.ZERO, new ECKey(secureRandom).toAddress(params));
+
+        addOutputs(outputTransaction, bag);
+
+        // Sign the transaction
+        final ProposedTransaction proposedTransaction = new ProposedTransaction(outputTransaction);
+        signer.signInputs(proposedTransaction, bag);
+        final TransactionInput input = proposedTransaction.partialTx.getInput(0);
+
+        input.verify(output);
+        input.getScriptSig().correctlySpends(outputTransaction, 0, output.getScriptPubKey(),
+            EnumSet.of(Script.VerifyFlag.DERSIG, Script.VerifyFlag.P2SH));
+
+        final Script scriptSig = input.getScriptSig();
+        final TransactionSignature signature = TransactionSignature.decodeFromBitcoin(scriptSig.getChunks().get(0).data, true, false);
+
+        // First output a conventional low-S transaction with the LOW_S flag, for the tx_valid.json set
+        System.out.println("[\"A transaction with a low-S signature.\"],");
+        System.out.println("[[[\""
+            + inputTransaction.getHashAsString() + "\", "
+            + output.getIndex() + ", \""
+            + scriptToString(output.getScriptPubKey()) + "\"]],\n"
+            + "\"" + Utils.HEX.encode(proposedTransaction.partialTx.bitcoinSerialize()) + "\", \""
+            + Script.VerifyFlag.P2SH.name() + "," + Script.VerifyFlag.LOW_S.name() + "\"],");
+
+        final BigInteger highS = HIGH_S_DIFFERENCE.subtract(signature.s);
+        final TransactionSignature highSig = new TransactionSignature(signature.r, highS);
+        input.setScriptSig(new ScriptBuilder().data(highSig.encodeToBitcoin()).data(scriptSig.getChunks().get(1).data).build());
+        input.getScriptSig().correctlySpends(outputTransaction, 0, output.getScriptPubKey(),
+            EnumSet.of(Script.VerifyFlag.P2SH));
+
+        // A high-S transaction without the LOW_S flag, for the tx_valid.json set
+        System.out.println("[\"A transaction with a high-S signature.\"],");
+        System.out.println("[[[\""
+            + inputTransaction.getHashAsString() + "\", "
+            + output.getIndex() + ", \""
+            + scriptToString(output.getScriptPubKey()) + "\"]],\n"
+            + "\"" + Utils.HEX.encode(proposedTransaction.partialTx.bitcoinSerialize()) + "\", \""
+            + Script.VerifyFlag.P2SH.name() + "\"],");
+
+        // Lastly a conventional high-S transaction with the LOW_S flag, for the tx_invalid.json set
+        System.out.println("[\"A transaction with a high-S signature.\"],");
+        System.out.println("[[[\""
+            + inputTransaction.getHashAsString() + "\", "
+            + output.getIndex() + ", \""
+            + scriptToString(output.getScriptPubKey()) + "\"]],\n"
+            + "\"" + Utils.HEX.encode(proposedTransaction.partialTx.bitcoinSerialize()) + "\", \""
+            + Script.VerifyFlag.P2SH.name() + "," + Script.VerifyFlag.LOW_S.name() + "\"],");
+    }
+
+    private static void addOutputs(final Transaction outputTransaction, final KeyBag bag) throws ScriptException {
+        int numInputs = outputTransaction.getInputs().size();
+        for (int i = 0; i < numInputs; i++) {
+            TransactionInput txIn = outputTransaction.getInput(i);
+            Script scriptPubKey = txIn.getConnectedOutput().getScriptPubKey();
+            RedeemData redeemData = txIn.getConnectedRedeemData(bag);
+            checkNotNull(redeemData, "Transaction exists in wallet that we cannot redeem: %s", txIn.getOutpoint().getHash());
+            txIn.setScriptSig(scriptPubKey.createEmptyInputScript(redeemData.keys.get(0), redeemData.redeemScript));
+        }
+    }
+
+    /**
+     * Convert a script to a string format that suits the style expected in
+     * tx_valid.json and tx_invalid.json.
+     */
+    private static String scriptToString(Script scriptPubKey) {
+        final StringBuilder buf = new StringBuilder();
+        for (ScriptChunk chunk: scriptPubKey.getChunks()) {
+            if (buf.length() > 0) {
+                buf.append(" ");
+            }
+            if (chunk.isOpCode()) {
+                buf.append(getOpCodeName(chunk.opcode));
+            } else if (chunk.data != null) {
+                // Data chunk
+                buf.append("0x")
+                    .append(Integer.toString(chunk.opcode, 16)).append(" 0x")
+                    .append(Utils.HEX.encode(chunk.data));
+            } else {
+                buf.append(chunk.toString());
+            }
+        }
+        return buf.toString();
+    }
+}