[LON-CAPA-users] need help with odd error

[Gerd Kortemeyer]

Hi,

There are two reasons I can think of:

* Peter Riegler just described one of the two possible reasons. Do you use https?

* My other guess is that something the student entered looks like a "quoted execution," i.e., something that is supposed to be executed on the command line. Most likely, she entered backticks, and more than likely, she did so inadvertently. The problem itself is not dangerous, after all, this got caught by the safe environment. The only problem is that it reveals part of the source code. It would be good to know exactly what the student entered on which problem. We could then filter out the characters before they are caught by the "last resort" safeeval code.

- Gerd.


On Nov 29, 2010, at 3:38 PM, Sally S Hunnicutt/FS/VCU wrote:

> Hello, 
> 
> One of our students is enrolled in three different LC courses on campus.  In one of those courses, she gets errors like the one at the end of this email.  This happens for about 1/3 of her problems, but only toward the latter half of the course.  This does not happen for any other students in this course, nor in any of her other courses.  It happens when she uses IE or Firefox as her browser on a PC (not a Mac).  Eric Harvey suggested it might be something  to do with a Perl security feature - but that still doesn't seem to explain why the problem comes up so randomly.  I am the author of these problems.   
> 
> Any ideas?  Thanks. 
> 
>  'quoted execution (``, qx)' trapped by operation maskCompilation failed in require at /usr/lib/perl5/5.8.8/AutoLoader.pm line 92.
> at /usr/lib/perl5/vendor_perl/5.8.8/IO/Socket/SSL.pm line 401
> occurred while running #Enter the computations here
> $reaction=&chemparse("H2(g)+I2(g)->2HI(g)");
> 
> $K=&format(129,'3s');
> 
> $PHI=&format(&random(0.01,10.0,0.005),'3s');
> $PH2=&format(&random(0.01,1.0,0.005),'3s');
> $PI2=$PH2;
> $Q=&format(&pow($PHI,2)/($PH2*$PI2),'3s');
> $sqrtK=&format(&sqrt($K),'3s');
> if ( $Q>$K ) {
>   $x=&format(((-$sqrtK*$PH2+$PHI)/($sqrtK+2)),'3s');
>   @shifttrue=("The reaction shifts left.","More reactants will form from products.");
>   @shiftfalse1=("The reaction shifts right.","More products will form from reactants.");
>   @shiftfalse2=("The reaction is at equilibrium.","The concentrations of products and reactants will not change.");
>   $PHIe=&format($PHI-2*$x,'3s');
>   $PH2e=&format($PH2+$x,'3s');
>   $PI2e=$PH2e;
>   }
> elsif ( $QThis error occurred while processing part 0The error occurred on host vcua1 
> <Mail Attachment.jpeg>