Fixed incomplete JSON body on count request making org.elasticsearch.rest.action.RestActions#parseTopLevelQueryBuilder go into endless loop

core/src/main/java/org/elasticsearch/rest/action/RestActions.java

@@ -243,6 +243,15 @@ public RestResponse buildResponse(NodesResponse response, XContentBuilder builde
     private static QueryBuilder parseTopLevelQueryBuilder(XContentParser parser) {
         try {
             QueryBuilder queryBuilder = null;
+            XContentParser.Token first = parser.nextToken();
+            if (first == null) {
+                return null;
+            } else if (first != XContentParser.Token.START_OBJECT) {
+                throw new ParsingException(
+                    parser.getTokenLocation(), "Expected [" + XContentParser.Token.START_OBJECT +
+                    "] but found [" + first + "]", parser.getTokenLocation()
+                );
+            }
             for (XContentParser.Token token = parser.nextToken(); token != XContentParser.Token.END_OBJECT; token = parser.nextToken()) {
                 if (token == XContentParser.Token.FIELD_NAME) {
                     String fieldName = parser.currentName();

core/src/test/java/org/elasticsearch/rest/action/RestActionsTests.java

@@ -19,6 +19,8 @@
 
 package org.elasticsearch.rest.action;
 
+import com.fasterxml.jackson.core.io.JsonEOFException;
+import java.util.Arrays;
 import org.elasticsearch.common.ParsingException;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.NamedXContentRegistry;
@@ -59,10 +61,32 @@ public void testParseTopLevelBuilder() throws IOException {
     }
 
     public void testParseTopLevelBuilderEmptyObject() throws IOException {
-        String requestBody = "{}";
-        try (XContentParser parser = createParser(JsonXContent.jsonXContent, requestBody)) {
-            QueryBuilder query = RestActions.getQueryContent(parser);
-            assertNull(query);
+        for (String requestBody : Arrays.asList("{}", "")) {
+            try (XContentParser parser = createParser(JsonXContent.jsonXContent, requestBody)) {
+                QueryBuilder query = RestActions.getQueryContent(parser);
+                assertNull(query);
+            }
+        }
+    }
+
+    public void testParseTopLevelBuilderMalformedJson() throws IOException {
+        for (String requestBody : Arrays.asList("\"\"", "\"someString\"", "\"{\"")) {
+            try (XContentParser parser = createParser(JsonXContent.jsonXContent, requestBody)) {
+                ParsingException exception =
+                    expectThrows(ParsingException.class, () -> RestActions.getQueryContent(parser));
+                assertEquals("Expected [START_OBJECT] but found [VALUE_STRING]", exception.getMessage());
+            }
+        }
+    }
+
+    public void testParseTopLevelBuilderIncompleteJson() throws IOException {
+        for (String requestBody : Arrays.asList("{", "{ \"query\" :")) {
+            try (XContentParser parser = createParser(JsonXContent.jsonXContent, requestBody)) {
+                ParsingException exception =
+                    expectThrows(ParsingException.class, () -> RestActions.getQueryContent(parser));
+                assertEquals("Failed to parse", exception.getMessage());
+                assertEquals(JsonEOFException.class, exception.getRootCause().getClass());
+            }
         }
     }