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PK Zippers self destruct (Announce)

posted by Doug(R) E-mail, 09.09.2016, 06:46

It might not be a bug! I'm wondering if it might be a security device to prevent "snooping"....

Because i've had this issue as well... but only under a particular condition. Have you (or someone else) unpacked/decompressed the .EXE files? That's when it began happening to me (with both PKZIP and PKUNZIP).

I just tested it again to verify (plain MS-DOS v7.1). Unpack/decompress the binaries (i used IUP or UNPKLITE -- same behavior after either), run the binaries (parameters not required!), and the binary files change datestamp to current, and PKUNZIP changes size as such:

               ------  --------  -----------
  PKUNZIP.EXE  34,583  44,562    65,535
  PKZIP  .EXE  50,663  68,370    68,370

When you next run them, they crash. Examining the binaries reveals that their EXE headers have been overwritten!

Setting the file attribute of the binaries to Read-Only does indeed prevent them from being trashed.

The original (compressed) binaries do not exhibit this issue -- only the decompressed binaries self-destruct.

The version i tested/used was PKZip/PKUnzip 2.50 (03-01-1999). However, i abandoned PK many years ago in favor of the (freeware/open-source) Info-Zip alternatives -- newer and more capable. There are 16-bit and 32-bit DOS versions that have a much-greater memory capacity. And the syntax is easier, in my opinion.

- Doug B.


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