4 ms·

The PKWare Zip file spec is reasonably detailed. If you're not sure what the spec is trying to say, then either the PKZip binaries or the Info-ZIP zip/unzip so

by canucker2016 3y ago

The PKWare Zip file spec is reasonably detailed. If you're not sure what the spec is trying to say, then either the PKZip binaries or the Info-ZIP zip/unzip source code is your usual source of truth. When one unzip works but another unzip app doesn't, then you can usually point the finger at the last zip app that modified the zip file. There's some inconsistency in the zip file. Running "unzip -t -v" on the zip file in question may yield more info about the problem.

canucker2016 3y ago
Here's the link to the PKWARE APPNOTE.TXT https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT
Aachen 3y ago
The binaries you refer to as source of truth are a paid product (not sure if the trial version, which requires filling out a form that's currently not loading, includes all options, or how honest it is to use that to make an alternative to their software, or if the terms allow that) and don't seem to run on my operating system. I guess I could buy me a Windows license and read the pkzip EULA to see if you're allowed to use it for making a clone, but I figured the two decoders (that don't always agree with each other) I had on hand would do. If they agree about a field, it's good enough (and decoders can expect that unspecced fields are garbage)
- canucker2016 3y ago
  Info-ZIP is open source. Have you never used unzip?
  - Aachen 3y ago
    Isn't pkzip the original? I'm not sure I've heard of info-zip but unzip is a command I use regularly on Debian. I highly doubt that's the original commercial implementation though
canucker2016 3y ago
The only special thing about the Zip file format that springs to mind as causing ambiguity is the handling of the OS-specific extra field for a Zip archive entry. You don't have to include an OS-specific extra field unless you want the information in that specific extra field to be available by the party trying to extract the contents of the zipfile.

canucker2016 3y ago

Here's the link to the PKWARE APPNOTE.TXT https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT

Aachen 3y ago

The binaries you refer to as source of truth are a paid product (not sure if the trial version, which requires filling out a form that's currently not loading, includes all options, or how honest it is to use that to make an alternative to their software, or if the terms allow that) and don't seem to run on my operating system. I guess I could buy me a Windows license and read the pkzip EULA to see if you're allowed to use it for making a clone, but I figured the two decoders (that don't always agree with each other) I had on hand would do. If they agree about a field, it's good enough (and decoders can expect that unspecced fields are garbage)

canucker2016 3y ago
Info-ZIP is open source. Have you never used unzip?
- Aachen 3y ago
  Isn't pkzip the original? I'm not sure I've heard of info-zip but unzip is a command I use regularly on Debian. I highly doubt that's the original commercial implementation though

canucker2016 3y ago

The only special thing about the Zip file format that springs to mind as causing ambiguity is the handling of the OS-specific extra field for a Zip archive entry. You don't have to include an OS-specific extra field unless you want the information in that specific extra field to be available by the party trying to extract the contents of the zipfile.