From 93012e43ea03411456c20e7cec1ede73ff46b7d2 Mon Sep 17 00:00:00 2001
From: Fransisco Fernandez Castano <francisco.castano@datastax.com>
Date: Sun, 22 Apr 2018 13:08:26 +0200
Subject: [PATCH] Ignore empty Counter cells on digest calculation.
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patch by Francisco Fernández Castaño; reviewed by Sylvain Lebresne for CASSANDRA-14167
---
 CHANGES.txt                                   |  1 +
 .../cassandra/db/context/CounterContext.java  |  3 +++
 .../apache/cassandra/db/CounterCellTest.java  | 23 +++++++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/CHANGES.txt b/CHANGES.txt
index ee957182bd..00944dc1ff 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,4 +1,5 @@
 3.0.17
+ * Fix potential IndexOutOfBoundsException with counters (CASSANDRA-14167)
  * Restore resumable hints delivery, backport CASSANDRA-11960 (CASSANDRA-14419)
  * Always close RT markers returned by ReadCommand#executeLocally() (CASSANDRA-14515)
  * Reverse order queries with range tombstones can cause data loss (CASSANDRA-14513)
diff --git a/src/java/org/apache/cassandra/db/context/CounterContext.java b/src/java/org/apache/cassandra/db/context/CounterContext.java
index 29e5cfcf7b..b40246455d 100644
--- a/src/java/org/apache/cassandra/db/context/CounterContext.java
+++ b/src/java/org/apache/cassandra/db/context/CounterContext.java
@@ -692,6 +692,9 @@ public class CounterContext
      */
     public void updateDigest(MessageDigest message, ByteBuffer context)
     {
+        // context can be empty due to the optimization from CASSANDRA-10657
+        if (!context.hasRemaining())
+            return;
         ByteBuffer dup = context.duplicate();
         dup.position(context.position() + headerLength(context));
         message.update(dup);
diff --git a/test/unit/org/apache/cassandra/db/CounterCellTest.java b/test/unit/org/apache/cassandra/db/CounterCellTest.java
index a8ddfccc8f..8859fc671f 100644
--- a/test/unit/org/apache/cassandra/db/CounterCellTest.java
+++ b/test/unit/org/apache/cassandra/db/CounterCellTest.java
@@ -29,13 +29,16 @@ import org.junit.Test;
 
 import org.apache.cassandra.SchemaLoader;
 import org.apache.cassandra.config.ColumnDefinition;
+import org.apache.cassandra.db.rows.BTreeRow;
 import org.apache.cassandra.db.rows.BufferCell;
 import org.apache.cassandra.db.rows.Cell;
 import org.apache.cassandra.db.rows.CellPath;
 import org.apache.cassandra.db.rows.Cells;
 import org.apache.cassandra.db.context.CounterContext;
+import org.apache.cassandra.db.rows.Row;
 import org.apache.cassandra.exceptions.ConfigurationException;
 import org.apache.cassandra.schema.KeyspaceParams;
+import org.apache.cassandra.serializers.AsciiSerializer;
 import org.apache.cassandra.utils.*;
 
 import static org.junit.Assert.*;
@@ -281,4 +284,24 @@ public class CounterCellTest
 
         assert Arrays.equals(digest1.digest(), digest2.digest());
     }
+
+    @Test
+    public void testDigestWithEmptyCells() throws Exception
+    {
+        // For DB-1881
+        ColumnFamilyStore cfs = Keyspace.open(KEYSPACE1).getColumnFamilyStore(COUNTER1);
+
+        ColumnDefinition emptyColDef = cfs.metadata.getColumnDefinition(ByteBufferUtil.bytes("val2"));
+        BufferCell emptyCell = BufferCell.live(emptyColDef, 0, ByteBuffer.allocate(0));
+
+        Row.Builder builder = BTreeRow.unsortedBuilder(0);
+        builder.newRow(Clustering.make(AsciiSerializer.instance.serialize("test")));
+        builder.addCell(emptyCell);
+        Row row = builder.build();
+
+        MessageDigest digest = MessageDigest.getInstance("md5");
+        row.digest(digest);
+        assertNotNull(digest.digest());
+    }
+
 }