[Soot-list] SootClass.getMethodByName

[Steven Arzt]

Hi Eugen,

This behavior is expected given how the Soot resolver works. You only instruct it to load one specific class and nothing else. Consequently, nothing else is resolved. If you try to access a method inside a non-resolved class, it simply isn't there. The call to getMethod() triggers to resolver to find the target for that invocation expression, thereby loading the missing method. Afterwards, it's there and can be accessed.

My suggestion is to not use loadClassAndSupport or any of those methods. These are low-level methods, so unless you really know how the Soot resolver works internally, the results you will get can be quite surprising. The better method is to create a BodyTransformer, register it with the PackManager and then call Soot's normal main() method which will take care of all the required loading and initialization. There is a quite good introduction into the basic concepts of Soot in Eric's blog: http://www.bodden.de/2008/11/26/soot-packs/

Best regards,
  Steven

-----Ursprüngliche Nachricht-----
Von: Eugen Zalinescu [mailto:eugen.zalinescu at gmail.com] 
Gesendet: Dienstag, 12. Januar 2016 13:54
An: Steven Arzt
Cc: soot-list at cs.mcgill.ca
Betreff: Re: [Soot-list] SootClass.getMethodByName

Hi Steven,

Here are more details. Now I've also localized the call where the change in behavior occurs.

I'm doing an analysis (using ForwardFlowAnalysis) of a Java class, and the 'main' method looks something like this:

SootClass c = Scene.v().loadClassAndSupport("securibench.micro.basic.Basic30");
c.setApplicationClass();
SootMethod m = c.getMethodByName("doGet") Body b = m.retrieveActiveBody(); ExceptionalUnitGraph g = new ExceptionalUnitGraph(b); // build a ForwardFlowAnalysis object from g

Now, in the flowThrough method, for the unit d that is 'r3 = interfaceinvoke r1.<javax.servlet.http.HttpServletRequest:
java.lang.String getParameter(java.lang.String)>("name");' the code looks like this:

Main.testExists(); // here method not found SootMethod m = ((InvokeExpr)d).getMethod(); Main.testExists(); // here method found

where testExists in Main is:
static void testExists() {
        try {
            SootClass c =
Scene.v().getSootClass("javax.servlet.http.HttpServletRequest");
            c.getMethodByName("getParameter");
            System.out.println("IT WORKS!!!");
        } catch (RuntimeException e) {
            System.out.println("It does NOT work.");
        }
    }

So it seems that the call to InvokeExpr.getMethod() makes the difference. My main question is why is this, and my second question would be how to make Soot find the 'getParameter' method before starting the analysis.

Thanks,
Eugen







On Tue, Jan 12, 2016 at 12:05 PM, Steven Arzt <Steven.Arzt at cased.de> wrote:
> Hi Eugen,
>
> Without further details, it's hard to estimate what's happening there. 
> Maybe your first calls happens at a point in time when the class has 
> not been loaded yet. If you are using multiple threads in your code, 
> you might be trying to access  the method while Soot's resolver is 
> still loading the bodies.
>
> Best regards,
>   Steven
>
> -----Ursprüngliche Nachricht-----
> Von: soot-list-bounces at CS.McGill.CA 
> [mailto:soot-list-bounces at CS.McGill.CA]
> Im Auftrag von Eugen Zalinescu
> Gesendet: Montag, 11. Januar 2016 16:42
> An: soot-list at CS.McGill.CA
> Betreff: [Soot-list] SootClass.getMethodByName
>
> Hello,
>
> I get the following behavior. At some point in the program calling the 
> method SootClass.getMethodByName raises an exception, concretely:
>   Exception in thread "main" java.lang.RuntimeException: No method
> getParameter in class   javax.servlet.http.HttpServletRequest
> while calling the same method on the same SootClass object later 
> during the analysis, with the same arguments returns the looked for method.
>
> This seems strange to me, but maybe someone has an explanation for it?
>
> Thanks,
> Eugen
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