From 4a3d702397598fc2f217cc7b9da6782f8500f606 Mon Sep 17 00:00:00 2001
From: Ross Nicoll <jrn@jrn.me.uk>
Date: Sun, 18 Oct 2015 15:17:12 +0100
Subject: [PATCH] Correct coinbase height script validation

Changes coinbase height validation to check for the bytes at the start of
the coinbase script, and ignore everything after them. The validation then
matches Bitcoin Core.

Also update error messages to more closely match latest Bitcoin Core.
---
 .../java/org/bitcoinj/core/Transaction.java   | 28 +++++++------------
 .../org/bitcoinj/core/TransactionTest.java    | 22 ++++++++++++---
 2 files changed, 28 insertions(+), 22 deletions(-)

diff --git a/core/src/main/java/org/bitcoinj/core/Transaction.java b/core/src/main/java/org/bitcoinj/core/Transaction.java
index 7cea2009..1bb55f4b 100644
--- a/core/src/main/java/org/bitcoinj/core/Transaction.java
+++ b/core/src/main/java/org/bitcoinj/core/Transaction.java
@@ -1177,25 +1177,17 @@ public class Transaction extends ChildMessage {
 
         // Check block height is in coinbase input script
         final TransactionInput in = this.getInputs().get(0);
-        final List<ScriptChunk> chunks;
-        
-        try {
-            final Script scriptSig = in.getScriptSig();
-            chunks = scriptSig.getChunks();
-        } catch(ScriptException e) {
-            throw new VerificationException("Coinbase input script signature is invalid.", e);
+        final ScriptBuilder builder = new ScriptBuilder();
+        builder.data(ScriptBuilder.createHeightScriptData(height));
+        final byte[] expected = builder.build().getProgram();
+        final byte[] actual = in.getScriptBytes();
+        if (actual.length < expected.length) {
+            throw new VerificationException.CoinbaseHeightMismatch("Block height mismatch in coinbase.");
         }
-        if (chunks.isEmpty()) {
-            throw new VerificationException("Coinbase input script signature is empty.");
-        }
-        final ScriptChunk chunk = chunks.get(0);
-        if (!chunk.isPushData()) {
-            throw new VerificationException("First element of coinbase input script signature is not pushdata.");
-        }
-        final byte[] data = chunk.data;
-        final byte[] expected = ScriptBuilder.createHeightScriptData(height);
-        if (!Arrays.equals(data, expected)) {
-            throw new VerificationException.CoinbaseHeightMismatch("Coinbase height mismatch.");
+        for (int scriptIdx = 0; scriptIdx < expected.length; scriptIdx++) {
+            if (actual[scriptIdx] != expected[scriptIdx]) {
+                throw new VerificationException.CoinbaseHeightMismatch("Block height mismatch in coinbase.");
+            }
         }
     }
 
diff --git a/core/src/test/java/org/bitcoinj/core/TransactionTest.java b/core/src/test/java/org/bitcoinj/core/TransactionTest.java
index 812f063e..001dc28b 100644
--- a/core/src/test/java/org/bitcoinj/core/TransactionTest.java
+++ b/core/src/test/java/org/bitcoinj/core/TransactionTest.java
@@ -307,10 +307,6 @@ public class TransactionTest {
         assertEquals(79, tx1.getMessageSizeForPriorityCalc());
     }
 
-    /**
-     * 
-     * @throws VerificationException 
-     */
     @Test
     public void testCoinbaseHeightCheck() throws VerificationException {
         // Coinbase transaction from block 300,000
@@ -319,4 +315,22 @@ public class TransactionTest {
         final Transaction transaction = params.getDefaultSerializer().makeTransaction(transactionBytes);
         transaction.checkCoinBaseHeight(height);
     }
+
+    /**
+     * Test a coinbase transaction whose script has nonsense after the block height.
+     * See https://github.com/bitcoinj/bitcoinj/issues/1097
+     */
+    @Test
+    public void testCoinbaseHeightCheckWithDamagedScript() throws VerificationException {
+        // Coinbase transaction from block 224,430
+        final byte[] transactionBytes = HEX.decode(
+            "010000000100000000000000000000000000000000000000000000000000000000"
+            + "00000000ffffffff3b03ae6c0300044bd7031a0400000000522cfabe6d6d0000"
+            + "0000000000b7b8bf0100000068692066726f6d20706f6f6c7365727665726aac"
+            + "1eeeed88ffffffff01e0587597000000001976a91421c0d001728b3feaf11551"
+            + "5b7c135e779e9f442f88ac00000000");
+        final int height = 224430;
+        final Transaction transaction = params.getDefaultSerializer().makeTransaction(transactionBytes);
+        transaction.checkCoinBaseHeight(height);
+    }
 }
\ No newline at end of file