Joseph Shraibman wrote:
>
> And this is a big security problem? Access specifiers are meant to
> protect programmers from doing stupid things, not protect security. Of
IMHO, I'd say they are also there to protect security. Encapsulation =
Security.
References to objects can be handed around like, say, referenes to
files. We can give a whole lot of people a handle to a file that
contains, say, our private key or our address book. And that doesn't
(and shouldn't) mean everybody can open it and look at what's in there.
With this bug and given a reference to a graph of objects, it seems once
can traverse and examine the entire graph without any problem, breaking
all encapsulation. Seems easy - just introduce a class that does it.
> course if you hack the jvm you will be able to get access to a private
> field. So just what is the security concern here?
No need to hack the jvm. A single malicious piece of user code being
executed is enough.
Wolfgang.
> Wolfgang Hoschek wrote:
> >
> > There is a serious security bug in a major fraction of VMs.
> > Some VMs do not check access specifiers at runtime. This allows you to
> > access private data with either a hacked compiler, direct editing of
> > byte code, or a simple recompile.
> > For details, see http://metalab.unc.edu/javafaq/
> >
> > I checked the mini program given there on a number of Linux and Solaris
> > VMs.
> >
> > "NOT OK" means the access specifiers are not checked at runtime
> > "OK" means they are checked and the runtime correctly refuses the class.
> >
> > Interestingly BlackdownRC4 with Inprise's jitter was "NOT OK" whereas
> > BlackdownRC4 with sunwjit SIGSEV'd which is also not quite ok.
> > Here the builds I checked:
> >
> > Solaris@Spars
> > ------------
> > - NOT OK: java version "1.3.0", Java Hotspot(TM) Client VM (build
> > 1.3-beta, mixed mode)
> > - OK: (IncompatibleClassChangeError) java version "1.2.2", Solaris VM
> > (build Solaris_JDK_1.2.2_05a, native threads, sunwjit)
> >
> > RedHat6.1@Intel
> > ------------
> > - NOT OK: java full version "JDK 1.1.8 IBM build l118-20000515 (JIT
> > enabled: jitc)"
> > - NOT OK: java version "1.2.2", Classic VM (build Linux_JDK_1.2.2_RC4,
> > nativethreads, javacomp)
> > - HALF OK (segmentation violation): java version "1.2.2", Classic VM
> > (build Linux_JDK_1.2.2_RC4, nativethreads, sunwjit)
> > - NOT OK: java version "1.3.0", Java(TM) 2 Runtime Environment, Standard
> > Edition (build 1.3.0), Classic VM (build 1.3.0, J2RE 1.3.0 IBM build
> > cx130-20000605 (JIT enabled: jitc))
> > - NOT OK: java version "1.3.0", Classic VM (build 1.3.0, J2RE 1.3.0 IBM
> > build cx130-20000502 (JIT enabled: jitc))
> > - NOT OK: java version "1.3.0beta1", Java(TM) 2 RuntimeEnvironment,
> > Standard Edition (build 1.3.0beta-b07), Java Hotspot(TM) Client VM
> > (build 1.3.0beta-b04, mixed mode)
> >
> > Cheers,
> > Wolfgang.
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