Fuzz JSON with Peach - json

Question

I have made a small REST based webservice in Flask by reading http://blog.miguelgrinberg.com/post/designing-a-restful-api-with-python-and-flask and now I wanted to fuzz the JSON using Peach framework. I know it's uses a pit file(XML) for fuzzing but my small brain is not able to make the pit file that can serve my purpose. I googled a lot for peach pit file but all goes in vain.
I need a pit file or anyone can tell how to create a pit file for fuzzing payload.

Answer 1

There is a nice tutorial about peach available there.
Several elements need to be defined:
a data model describing the format of the data you want to send.
a state model describing the behavior of the fuzzer.
an agent runnning and monitoring the applications under fuzzing.
a test bringing all definitions together.
Here is an example of a Peach Pit file from the tutorial.
<Peach xmlns="http://peachfuzzer.com/2012/Peach" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://peachfuzzer.com/2012/Peach ../peach.xsd">
<DataModel name="DataHTER">
<String value="HTER " mutable="false" token="true"/>
<String value=""/>
<String value="\r\n" mutable="false" token="true"/>
</DataModel>
<StateModel name="StateHTER" initialState="Initial">
<State name="Initial">
<Action type="input" ><DataModel ref="DataResponse"/></Action>
<Action type="output"><DataModel ref="DataHTER"/></Action>
<Action type="input" ><DataModel ref="DataResponse"/></Action>
</State>
</StateModel>
<DataModel name="DataResponse">
<String value=""/>
</DataModel>
<Agent name="RemoteAgent" location="tcp://127.0.0.1:9001">
<!-- Run and attach windbg to a vulnerable server. -->
<Monitor class="WindowsDebugger">
<Param name="CommandLine" value="C:\Documents and Settings\Administrator\Desktop\vulnserver\vulnserver.exe"/>
<Param name="WinDbgPath" value="C:\Program Files\Debugging Tools for Windows (x86)" />
</Monitor>
</Agent>
<Test name="TestHTER">
<Agent ref="RemoteAgent"/>
<StateModel ref="StateHTER"/>
<Publisher class="TcpClient">
<Param name="Host" value="127.0.0.1"/>
<Param name="Port" value="9999"/>
</Publisher>
<Logger class="File">
<Param name="Path" value="Logs"/>
</Logger>
</Test>
If you want to use a JSON data model, you can follow the recommendation of one of the peach architect.
1)Define a data model corresponding to the JSON.
JSON Object
{
"name":"John Smith",
"address":{
"address1":"555 Main St.",
"city":"Seattle"
}
}
Data model
<DataModel>
<String name="name" value="John Smith" />
<Block name="address">
<String name="address1" value="555 Main St." />
<String name="city" value="Seattle" />
</Block>
</DataModel>
You then have to write your own custom publisher in C#. Here is a tutorial for this.