How to taint class instance

[raylax]

Hi~

java code

String tainted = xxx;
StringBuilder sb = new StringBuilder();
sb.append(tainted);
sink(sb.toString());

jimple IR

$stack7 = new java.lang.StringBuilder;
specialinvoke $stack7.<java.lang.StringBuilder: void <init>()>();
sb = $stack7;
$stack8 = virtualinvoke sb.<java.lang.StringBuilder: java.lang.StringBuilder append(java.lang.String)>(tainted);
$stack9 = virtualinvoke sb.<java.lang.StringBuilder: java.lang.String toString()>();
specialinvoke this.<ClassA: void sink(java.lang.String)>($stack9);

How to mark sb when the parameter passed to method append is tainted?

my code

if (callArgs[0].equivTo(source.value)) {
    ret.add(invokeExpr.base) // maybe not working
    ret.add(leftOp)
}

Thanks :)

[Eric Bodden]

Hello. I am not sure what's going wrong in your case. Taint generation usually happens within the call-to-return-flow function. Is this where your code is located?

Cheers
Eric