Hi Clinton,
> We intentionally have a corrupt file in a test suite to help test our error
> handling code. See attached.
>
> However, we are updating to use NetCDF 4.3 and are getting this problem when
> we run ncdump on the file.
>
> ncdump: ../../libsrc/v1hpg.c:1160: NC_computeshapes: Assertion `ncp->begin_var
> <= ncp->begin_rec' failed.
>
> Older versions of NetCDF could handle this gracefully and return an error to
> our code.
I'm curious what older version handled this any differently. I just tested
older versions
back to netCDF-3.6.1 (February 2006), and they all got the same assertion
violation.
Version 3.6.0 (December 2004) didn't get an assertion violation, but it also
didn't detect
any error! The ncdump from that version just emits zeros of the appropriate
type for all
the values of variable(s) past the truncation point.
I've got a fix that replaces the assertions in libsrc/v1hpg.c with code to
return the error
code NC_ENOTNC ("Not a netCDF file"). That passes all our tests, and makes
ncdump
behave like this on your corrupted file:
$ ncdump ~/test/truncated.g
ncdump: truncated.g: NetCDF: Unknown file format
I think that should qualify as more graceful handling, but note that there are
surely other
ways to corrupt a netCDF file that are not detected by this change, and no
possible way to
detect a maliciously modified netCDF file (e.g., if two variable names of the
same length
were swapped in the header). However, this modification would detect a lot of
simple
corruptions, such as truncation.
--Russ
> Thanks for your attention.
>
> --
> Clinton Stimpson
> Elemental Technologies, Inc
> Computational Simulation Software, LLC
> www.csimsoft.com
>
Russ Rew UCAR Unidata Program
address@hidden http://www.unidata.ucar.edu
Ticket Details
===================
Ticket ID: VUC-284716
Department: Support netCDF
Priority: Normal
Status: Closed
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