Re: ZipFile bug

[Michael Koch]

On Tue, Dec 09, 2003 at 10:27:02PM +0100, Mark Wielaard wrote:
> Hi,
> 
> On Tue, 2003-12-09 at 20:20, Archie Cobbs wrote:
> > The web site still seems to be down, so here is a bug report FWIW...
> > 
> >     public class xx {
> >     public static void main(String[] args) throws Exception {
> >         ZipFile f = new ZipFile("/dev/null");
> >     }
> >     }
> > 
> > This program generates a ZipException on JDK, but Classpath
> > does not try to verify the file at all so doesn't throw any
> > exception... even if you then try to read the file's entries.
> > 
> > Instead what happens is you get null back from ZipFile.entries()
> > which is not according to spec. The ZipFile constructor should try
> > to do some minimal verification of the files's signature, etc.
> 
> Thanks for the report. Still don't know when savannah will be up again.
> During a large part of the day all the other gnu servers were also down.
> They are up again now. But I don't know why.
> 
> > I think a simple fix would be to try to read the directory
> > (which you are most likely going to have to do later anyway)
> > in the constructor(s).
> 
> I believe that was what the code did in the past. But some programs open
> lots of zip/jar files while starting up and we didn't want to read the
> whole zip directory and construct all those ZipEntries during opening
> when the entries might not be needed much later (or at all).
> 
> A good fix would be to only put the check that the file starts with
> LOCSIG (PK\003\004) in the constructor, but not explicitly try to read
> all entries.
> 
> Also nice would be to make the reading/construction of the whole
> directory lazy and stop when the entry that was needed is found. But
> that is much more work since you then have to remember where in the
> directory you were when another entry is needed that is not yet in the
> map but you haven't read the complete directory yet.

I dont checked if the JDK reads the file or only the directory entry.
/dev/null is no normal file. its a char driver:

crw-rw-rw-    1 root     root       1,   3 2003-10-29 11:18 /dev/null

ZipFile uses RandomAccessFile and this should throw an exception if
the file is not a regular file and char driver files are not regular
files.


Michael