Stop runtime script from emitting too many values (#61938)

This prevent `keyword` valued runtime scripts from emitting too many
values or values that take up too much space. Without this you can put
allocate a ton of memory with the script by sticking it into a tight
loop. Painless has some protections against this but:
1. I don't want to rely on them out of sheer paranoia
2. They don't really kick in when the script uses callbacks like we do
   anyway.

Relates to #59332

Author: nik9000

x-pack/plugin/runtime-fields/src/main/java/org/elasticsearch/xpack/runtimefields/AbstractLongScriptFieldScript.java

@@ -19,8 +19,8 @@ public abstract class AbstractLongScriptFieldScript extends AbstractScriptFieldS
     private long[] values = new long[1];
     private int count;
 
-    public AbstractLongScriptFieldScript(Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
-        super(params, searchLookup, ctx);
+    public AbstractLongScriptFieldScript(String fieldName, Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
+        super(fieldName, params, searchLookup, ctx);
     }
 
     /**
@@ -50,6 +50,7 @@ public final int count() {
     }
 
     protected final void emitValue(long v) {
+        checkMaxSize(count);
         if (values.length < count + 1) {
             values = ArrayUtil.grow(values, count + 1);
         }

x-pack/plugin/runtime-fields/src/main/java/org/elasticsearch/xpack/runtimefields/AbstractScriptFieldScript.java

@@ -17,6 +17,7 @@
 import org.elasticsearch.search.lookup.SourceLookup;
 
 import java.util.HashMap;
+import java.util.Locale;
 import java.util.Map;
 import java.util.function.Function;
 
@@ -27,6 +28,11 @@
  * {@link AggregationScript} but hopefully with less historical baggage.
  */
 public abstract class AbstractScriptFieldScript {
+    /**
+     * The maximum number of values a script should be allowed to emit.
+     */
+    static final int MAX_VALUES = 100;
+
     public static <F> ScriptContext<F> newContext(String name, Class<F> factoryClass) {
         return new ScriptContext<F>(
             name + "_script_field",
@@ -54,10 +60,12 @@ public static <F> ScriptContext<F> newContext(String name, Class<F> factoryClass
         value -> ((SourceLookup) value).loadSourceIfNeeded()
     );
 
+    protected final String fieldName;
     private final Map<String, Object> params;
     private final LeafSearchLookup leafSearchLookup;
 
-    public AbstractScriptFieldScript(Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
+    public AbstractScriptFieldScript(String fieldName, Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
+        this.fieldName = fieldName;
         this.leafSearchLookup = searchLookup.getLeafSearchLookup(ctx);
         params = new HashMap<>(params);
         params.put("_source", leafSearchLookup.source());
@@ -93,5 +101,23 @@ public final Map<String, ScriptDocValues<?>> getDoc() {
         return leafSearchLookup.doc();
     }
 
+    /**
+     * Check if the we can add another value to the list of values.
+     * @param currentSize the current size of the list
+     */
+    protected final void checkMaxSize(int currentSize) {
+        if (currentSize >= MAX_VALUES) {
+            throw new IllegalArgumentException(
+                String.format(
+                    Locale.ROOT,
+                    "Runtime field [%s] is emitting [%s] values while the maximum number of values allowed is [%s]",
+                    fieldName,
+                    currentSize + 1,
+                    MAX_VALUES
+                )
+            );
+        }
+    }
+
     public abstract void execute();
 }

x-pack/plugin/runtime-fields/src/main/java/org/elasticsearch/xpack/runtimefields/BooleanScriptFieldScript.java

@@ -28,7 +28,7 @@ static List<Whitelist> whitelist() {
     public static final String[] PARAMETERS = {};
 
     public interface Factory extends ScriptFactory {
-        LeafFactory newFactory(Map<String, Object> params, SearchLookup searchLookup);
+        LeafFactory newFactory(String fieldName, Map<String, Object> params, SearchLookup searchLookup);
     }
 
     public interface LeafFactory {
@@ -38,8 +38,8 @@ public interface LeafFactory {
     private int trues;
     private int falses;
 
-    public BooleanScriptFieldScript(Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
-        super(params, searchLookup, ctx);
+    public BooleanScriptFieldScript(String fieldName, Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
+        super(fieldName, params, searchLookup, ctx);
     }
 
     /**

x-pack/plugin/runtime-fields/src/main/java/org/elasticsearch/xpack/runtimefields/DateScriptFieldScript.java

@@ -30,7 +30,7 @@ static List<Whitelist> whitelist() {
     public static final String[] PARAMETERS = {};
 
     public interface Factory extends ScriptFactory {
-        LeafFactory newFactory(Map<String, Object> params, SearchLookup searchLookup, DateFormatter formatter);
+        LeafFactory newFactory(String fieldName, Map<String, Object> params, SearchLookup searchLookup, DateFormatter formatter);
     }
 
     public interface LeafFactory {
@@ -39,8 +39,14 @@ public interface LeafFactory {
 
     private final DateFormatter formatter;
 
-    public DateScriptFieldScript(Map<String, Object> params, SearchLookup searchLookup, DateFormatter formatter, LeafReaderContext ctx) {
-        super(params, searchLookup, ctx);
+    public DateScriptFieldScript(
+        String fieldName,
+        Map<String, Object> params,
+        SearchLookup searchLookup,
+        DateFormatter formatter,
+        LeafReaderContext ctx
+    ) {
+        super(fieldName, params, searchLookup, ctx);
         this.formatter = formatter;
     }
 

x-pack/plugin/runtime-fields/src/main/java/org/elasticsearch/xpack/runtimefields/DoubleScriptFieldScript.java

@@ -28,7 +28,7 @@ static List<Whitelist> whitelist() {
     public static final String[] PARAMETERS = {};
 
     public interface Factory extends ScriptFactory {
-        LeafFactory newFactory(Map<String, Object> params, SearchLookup searchLookup);
+        LeafFactory newFactory(String fieldName, Map<String, Object> params, SearchLookup searchLookup);
     }
 
     public interface LeafFactory {
@@ -38,8 +38,8 @@ public interface LeafFactory {
     private double[] values = new double[1];
     private int count;
 
-    public DoubleScriptFieldScript(Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
-        super(params, searchLookup, ctx);
+    public DoubleScriptFieldScript(String fieldName, Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
+        super(fieldName, params, searchLookup, ctx);
     }
 
     /**
@@ -69,6 +69,7 @@ public final int count() {
     }
 
     protected final void emitValue(double v) {
+        checkMaxSize(count);
         if (values.length < count + 1) {
             values = ArrayUtil.grow(values, count + 1);
         }

x-pack/plugin/runtime-fields/src/main/java/org/elasticsearch/xpack/runtimefields/IpScriptFieldScript.java

@@ -49,7 +49,7 @@ static List<Whitelist> whitelist() {
     public static final String[] PARAMETERS = {};
 
     public interface Factory extends ScriptFactory {
-        LeafFactory newFactory(Map<String, Object> params, SearchLookup searchLookup);
+        LeafFactory newFactory(String fieldName, Map<String, Object> params, SearchLookup searchLookup);
     }
 
     public interface LeafFactory {
@@ -59,8 +59,8 @@ public interface LeafFactory {
     private BytesRef[] values = new BytesRef[1];
     private int count;
 
-    public IpScriptFieldScript(Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
-        super(params, searchLookup, ctx);
+    public IpScriptFieldScript(String fieldName, Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
+        super(fieldName, params, searchLookup, ctx);
     }
 
     /**
@@ -93,6 +93,7 @@ public final int count() {
     }
 
     protected final void emitValue(String v) {
+        checkMaxSize(count);
         if (values.length < count + 1) {
             values = ArrayUtil.grow(values, count + 1);
         }

x-pack/plugin/runtime-fields/src/main/java/org/elasticsearch/xpack/runtimefields/LongScriptFieldScript.java

@@ -27,15 +27,15 @@ static List<Whitelist> whitelist() {
     public static final String[] PARAMETERS = {};
 
     public interface Factory extends ScriptFactory {
-        LeafFactory newFactory(Map<String, Object> params, SearchLookup searchLookup);
+        LeafFactory newFactory(String fieldName, Map<String, Object> params, SearchLookup searchLookup);
     }
 
     public interface LeafFactory {
         LongScriptFieldScript newInstance(LeafReaderContext ctx) throws IOException;
     }
 
-    public LongScriptFieldScript(Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
-        super(params, searchLookup, ctx);
+    public LongScriptFieldScript(String fieldName, Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
+        super(fieldName, params, searchLookup, ctx);
     }
 
     public static class EmitValue {

x-pack/plugin/runtime-fields/src/main/java/org/elasticsearch/xpack/runtimefields/StringScriptFieldScript.java

@@ -16,9 +16,15 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 
 public abstract class StringScriptFieldScript extends AbstractScriptFieldScript {
+    /**
+     * The maximum number of chars a script should be allowed to emit.
+     */
+    public static final long MAX_CHARS = 1024 * 1024;
+
     public static final ScriptContext<Factory> CONTEXT = newContext("string_script_field", Factory.class);
 
     static List<Whitelist> whitelist() {
@@ -28,17 +34,18 @@ static List<Whitelist> whitelist() {
     public static final String[] PARAMETERS = {};
 
     public interface Factory extends ScriptFactory {
-        LeafFactory newFactory(Map<String, Object> params, SearchLookup searchLookup);
+        LeafFactory newFactory(String fieldName, Map<String, Object> params, SearchLookup searchLookup);
     }
 
     public interface LeafFactory {
         StringScriptFieldScript newInstance(LeafReaderContext ctx) throws IOException;
     }
 
     private final List<String> results = new ArrayList<>();
+    private long chars;
 
-    public StringScriptFieldScript(Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
-        super(params, searchLookup, ctx);
+    public StringScriptFieldScript(String fieldName, Map<String, Object> params, SearchLookup searchLookup, LeafReaderContext ctx) {
+        super(fieldName, params, searchLookup, ctx);
     }
 
     /**
@@ -49,12 +56,26 @@ public StringScriptFieldScript(Map<String, Object> params, SearchLookup searchLo
      */
     public final List<String> resultsForDoc(int docId) {
         results.clear();
+        chars = 0;
         setDocument(docId);
         execute();
         return results;
     }
 
     protected final void emitValue(String v) {
+        checkMaxSize(results.size());
+        chars += v.length();
+        if (chars > MAX_CHARS) {
+            throw new IllegalArgumentException(
+                String.format(
+                    Locale.ROOT,
+                    "Runtime field [%s] is emitting [%s] characters while the maximum number of values allowed is [%s]",
+                    fieldName,
+                    chars,
+                    MAX_CHARS
+                )
+            );
+        }
         results.add(v);
     }
 

x-pack/plugin/runtime-fields/src/main/java/org/elasticsearch/xpack/runtimefields/mapper/ScriptBooleanMappedFieldType.java

@@ -72,7 +72,7 @@ public ScriptBooleanFieldData.Builder fielddataBuilder(String fullyQualifiedInde
     }
 
     private BooleanScriptFieldScript.LeafFactory leafFactory(SearchLookup searchLookup) {
-        return scriptFactory.newFactory(script.getParams(), searchLookup);
+        return scriptFactory.newFactory(name(), script.getParams(), searchLookup);
     }
 
     @Override

x-pack/plugin/runtime-fields/src/main/java/org/elasticsearch/xpack/runtimefields/mapper/ScriptDateMappedFieldType.java

@@ -85,7 +85,7 @@ public ScriptDateFieldData.Builder fielddataBuilder(String fullyQualifiedIndexNa
     }
 
     private DateScriptFieldScript.LeafFactory leafFactory(SearchLookup lookup) {
-        return scriptFactory.newFactory(script.getParams(), lookup, dateTimeFormatter);
+        return scriptFactory.newFactory(name(), script.getParams(), lookup, dateTimeFormatter);
     }
 
     @Override