[CVE-2021-30179]Pre-auth RCE via Java deserialization in the Generic filter

[Jun Liu <li...@apache.org>]

Hi

Severity: medium

Vendor:
The Dubbo Project Team

Versions Affected:
Dubbo 2.7.0 to 2.7.9
Dubbo 2.6.0 to 2.6.9
Dubbo all 2.5.x versions (not supported by official team any longer)


Description:
Apache Dubbo by default supports generic calls to arbitrary methods exposed by provider interfaces.
These invocations are handled by the GenericFilter which will find the service and method specified in the first arguments of the invocation and use the Java Reflection API to make the final call. The signature for the $invoke or $invokeAsync methods is Ljava/lang/String;[Ljava/lang/String;[Ljava/lang/Object; where the first argument is the name of the method to invoke, the second one is an array with the parameter types for the method being invoked and the third one is an array with the actual call arguments.

In addition, the caller also needs to set an RPC attachment specifying that the call is a generic call and how to decode the arguments. The possible values are:

- true
- raw.return
- nativejava
- bean
- protobuf-json

An attacker can control this RPC attachment and set it to nativejava to force the java deserialization of the byte array located in the third argument:


Mitigation:
Upgrade to 2.7.10+ or 2.6.9+ accordingly based on the version currently using. 
https://github.com/apache/dubbo/releases/tag/dubbo-2.7.10
https://dubbo.apache.org/en/blog/2020/05/18/past-releases/

Credit:
This issue was first reported by GitHub Security Lab

Jun