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PK Zippers self destruct - NOT BUG it checks PSP for PK sig (Announce)

posted by Arjay(R), 20.09.2016, 19:15

> I'm not looking for a solution but
> both the old PKZIP and PKUNZIP
> programs at times self destruct on
> my new I5 system.
>
> When this happens the size of the
> program will be found to be 65535
> bytes. Yep.

Yes still alive (just)... first post/login in a here in a very long time just to answer this question as I know the exact answer. Phil Katz implemented an anti-hack check to see if the PSP (Program Segment Prefix) contains his initials PK at an offset which his PKLite unpacker adds, if the initials are not present then in the case of PKZIP it runs a bit of code which grabs 64k of from memory which it then uses to overwrite over the top of the EXE before then cleanly exciting.
If I remember correctly Phil also un-readonly's a file as well. I did write my own code to counter this for other situations but if you use Ben Castricum's UNP ( http://unp.bencastricum.nl/ ) as follows: "unp -k+ pkunzip.exe" and "unp -k+ pkzip.exe" then the EXE's will be unpacked which might resolve any other issues and the PKLite fake signature code will be added which will fool Phil's overwriting code.

 

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