Zkar : A Java Serialization Protocol Analysis Tool Implement In Go

ZKar is a Java serialization protocol analysis tool implement in Go. This tool is still work in progress, so no complete API document and contribution guide.

ZKar provides:

• A Java serialization payloads parser and viewer in pure Go, no CGO or JDK is required
• From the Java serialization protocol to a Go struct
• A Go library that can manipulate the Java serialization data
• WIP: ysoserial implement in Go
• WIP: Java class bytecodes parser, viewer and manipulation
• WIP: An implementation of RMI/LDAP in Go

Installing

Using ZKar is easy. use go get to install the ZKar along with the library and its dependencies:

go get -u github.com/phith0n/zkar

Next, use github.com/phith0n/zkar/* in your application:

package main
import (
“fmt”
“github.com/phith0n/zkar/serz”
“io/ioutil”
“log”
)
func main() {
data, _ := ioutil.ReadFile(“./testcases/ysoserial/CommonsCollections6.ser”)
serialization, err := serz.FromBytes(data)
if err != nil {
log.Fatal(“parse error”)
}
fmt.Println(serialization.ToString())
}

Command line utility tool

ZKar also provides a command line utility tool that you can use it directly:

$ go run main.go
NAME:
zkar – A Java serz tool
USAGE:
main [global options] command [command options] [arguments…]
COMMANDS:
generate generate Java serz attack payloads
dump parse the Java serz streams and dump the struct
help, h Shows a list of commands or help for one command
GLOBAL OPTIONS:
–help, -h show help (default: false)

For example, you are able to dump the payload CommonsBeanutils3 from ysoserial like:

$ go run main.go dump -f “$(pwd)/testcases/ysoserial/CommonsBeanutils3.ser”

Tests

ZKar is a well-tested tool that passed all ysoserial generated gadgets parsing and rebuilding tests. It means that gadget generating by ysoserial can be parsed by ZKar, and parsed struts can be converted back into bytes string which is equal to the original one.

Gadget	Package	Parse	Rebuild	Parse Time
AspectJWeaver	ysoserial	✅	✅	80.334µs
BeanShell1	ysoserial	✅	✅	782.613µs
C3P0	ysoserial	✅	✅	98.321µs
Click1	ysoserial	✅	✅	573.298µs
Clojure	ysoserial	✅	✅	72.415µs
CommonsBeanutils1	ysoserial	✅	✅	461.15µs
CommonsCollections1	ysoserial	✅	✅	64.484µs
CommonsCollections2	ysoserial	✅	✅	508.918µs
CommonsCollections3	ysoserial	✅	✅	564.071µs
CommonsCollections4	ysoserial	✅	✅	535.449µs
CommonsCollections5	ysoserial	✅	✅	137.609µs
CommonsCollections6	ysoserial	✅	✅	68.753µs
CommonsCollections7	ysoserial	✅	✅	178.549µs
FileUpload1	ysoserial	✅	✅	35.39µs
Groovy1	ysoserial	✅	✅	150.991µs
Hibernate1	ysoserial	✅	✅	789.674µs
Hibernate2	ysoserial	✅	✅	168.624µs
JBossInterceptors1	ysoserial	✅	✅	632.581µs
JRMPClient	ysoserial	✅	✅	32.967µs
JRMPListener	ysoserial	✅	✅	38.263µs
JSON1	ysoserial	✅	✅	2.157225ms
JavassistWeld1	ysoserial	✅	✅	468.596µs
Jdk7u21	ysoserial	✅	✅	355.01µs
Jython1	ysoserial	✅	✅	216.862µs
MozillaRhino1	ysoserial	✅	✅	1.775193ms
MozillaRhino2	ysoserial	✅	✅	409.124µs
Myfaces1	ysoserial	✅	✅	22.997µs
Myfaces2	ysoserial	✅	✅	38.131µs
ROME	ysoserial	✅	✅	485.804µs
Spring1	ysoserial	✅	✅	797.469µs
Spring2	ysoserial	✅	✅	358.041µs
URLDNS	ysoserial	✅	✅	21.502µs
Vaadin1	ysoserial	✅	✅	438.729µs
Wicket1	ysoserial	✅	✅	23.509µs
JDK8u20*	pwntester	✅	✅	529.3µs

Notice: For parsing JDK8u20 payload, you should add --jdk8u20 flag to dump command. As the payload is not a valid serialized data stream, it’s necessary to tell ZKar patches the data through this flag.