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

posted by Arjay(R), 20.09.2016, 19:28

> 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,

Checking Ben's code and reminded myself of when I looked into this about 15 years ago. Phil's PKLite professional code adds PK into 5Ch+5Dh of the loading programs PSP. Those offsets are the first 2 bytes of of a 16 byte array used for Unopened Standard FCB 1. FCB (File Control Blocks) were a C/PM legacy which had already been superseded by file handles by the time PKLite came out.

So basically to stop the anti-hack self destruct code in PKUNZIP/PKZip for DOS you just need to make sure the PK signature is present in some way in the PSP at 5Ch+5Dh when they run. Ben's code -K+ code in http://unp.bencastricum.nl/ is the easiest way.

 

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