[Soot-list] dava Error : Could not verify approximated Synchronized body

[mbatch at cs.mcgill.ca]

On Tue, June 19, 2007 10:33 am, Dionne, Sebastien wrote:
> I'm trying to decompile a class but I got an error.  There is a way to
> fix it ?
>
> I try with JAD and I obtain this (if that could help)

Dionne,

It appears as though the class you are decompiling has some complicated
control flow containing some synchronized blocks. It is difficult to
identify the exact problem without seeing the class file itself, but you
are basically seeing the same problem with both Jad and Dava. Jad handles
problems by just spitting out the class-level bytecode instructions if it
cannot figure out how to translate them to java source. This is why you
get the line "JVM INSTR monitorexit ;" for example.

Dava is just slightly more clear on the problem, by failing with an
exception. It is telling you exactly what the problem is: "Could not
verify approximated Synchronized body".

While the class may be "correct" bytecode and even verifiable, this does
not guarantee that automatic tools such as Dava or Jad can necessarily
decompile them. This is especially a problem for bytecode generated by
third-party tools such as bytecode instrumenters or other frameworks that
compile their own code with a non-standard compiler.

I suspect, too, that this code might have been semi-obfuscated, given the
program method and variable names. The entire point of obfuscating is to
complicate decompilation attempts and this might be exactly what is
happening here.

Michael Batchelder

>
>
>
> private void a(BFContext bfcontext) {
> label0:
> {
> synchronized(y) {
> if(bfcontext.d < 0 || bfcontext.d >= z.size() || a(bfcontext.d) !=
> bfcontext) break label0; }
> return; }
> if(ab == null) {
> bfcontext.d = z.size(); z.addElement(bfcontext); } else
> {
> bfcontext.d = ab.intValue(); ab = (Integer)z.elementAt(ab.intValue());
> z.setElementAt(bfcontext, bfcontext.d); }
> if(a()) b(bfcontext.d, "+++"); abyte0; JVM INSTR monitorexit ;
> goto _L1 exception; throw exception; _L1:
> }
>
>
>
>
> -------------------------------------------------------------------------
> ---
> --------------------------------------------------------------------------
> --
> ----------------------------------
>
>
>
>
> C:\workspace-test\test-soot-bf>java -Xmx400m -classpath
> sootclasses-2.2.4.jar;polyglot.jar;C:\workspace-test\test-soot-b
> f\classes;C:\jdk_5\jre\lib\rt.jar;C:\jdk_5\jre\lib\jsse.jar;C:\jdk_5\jre\l
> ib \jce.jar;C:\jdk_5\jre\lib\charsets.jar;C:\jd
> k_5\jre\lib\ext\dnsns.jar;C:\jdk_5\jre\lib\ext\localedata.jar;C:\jdk_5\jre
> \l
> ib\ext\sunjce_provider.jar;C:\jdk_5\jre\lib\
> ext\sunmscapi.jar;C:\jdk_5\jre\lib\ext\sunpkcs11.jar soot.Main --cp
> sootclasses-2.2.4.jar;polyglot.jar;C:\workspace-test
> \test-soot-bf\classes;C:\jdk_5\jre\lib\rt.jar;C:\jdk_5\jre\lib\jsse.jar;C:
> \j
> dk_5\jre\lib\jce.jar;C:\jdk_5\jre\lib\charse
> ts.jar;C:\jdk_5\jre\lib\ext\dnsns.jar;C:\jdk_5\jre\lib\ext\localedata.jar;
> C:
> \jdk_5\jre\lib\ext\sunjce_provider.jar;C:\jd
> k_5\jre\lib\ext\sunmscapi.jar;C:\jdk_5\jre\lib\ext\sunpkcs11.jar
> --process-dir C:\workspace-test\test-soot-bf\classes -d
> C:\workspace-test\test-soot-bf\sootOutput\ -f dava
> Soot started on Tue Jun 19 10:19:28 EDT 2007
> Verifying exception handling.. Warning: using incomplete callgraph
> containing only application classes. [Call Graph] For information on where
> the call graph may be incomplete, use the verbose option to the cg phase. .
>
>
> Decompiling com.bridge.feed.server.BFContext...
> Decompiling com.bridge.feed.server.BFContextAdmin...
> Decompiling com.bridge.feed.server.BFContextLogin...
> Decompiling com.bridge.feed.server.BFContextStartup...
> Decompiling com.bridge.feed.server.BFCrypt...
> Decompiling com.bridge.feed.server.BFDriver...
> Exception in thread "main" java.lang.RuntimeException: Could not verify
> approximated Synchronized body at
> soot.dava.toolkits.base.finders.SynchronizedBlockFinder.find(Synchronized
> Blo
> ckFinder.java:163)
> at soot.dava.DavaBody.<init>(DavaBody.java:331) at
> soot.dava.Dava.newBody(Dava.java:84)
> at soot.PackManager.runBodyPacks(PackManager.java:807) at
> soot.PackManager.runBodyPacks(PackManager.java:451)
> at soot.PackManager.runBodyPacks(PackManager.java:370) at
> soot.PackManager.runPacks(PackManager.java:347)
> at soot.Main.run(Main.java:203) at soot.Main.main(Main.java:146)
>
> Sébastien Dionne ing. jr.
> Financière Banque Nationale
> Analyste programmeur Senior
> tel : 514-879-3107 courriel : sebastien.dionne at fbn.ca
>
>
>
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