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weichsel / ZIPFoundation

Effortless ZIP Handling in Swift
MIT License
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Unzip Method Should Perform CRC Verification #248

Closed VaslD closed 2 years ago

VaslD commented 2 years ago

Summary

Extension method on FileManager currently ignores CRC return from the actual extract call.

https://github.com/weichsel/ZIPFoundation/blob/bad07a8f3dfefb0cf9faa8f9c89b6a762c92ebb0/Sources/ZIPFoundation/FileManager%2BZIP.swift#L127

This successfully extracts the following corrupt archive, which fails to extract using other software, except when using Apple's Archive Utility (that's another mystery because even UNIX unzip reports CRC error).

Printer Driver.zip

In my opinion, archiver tools should verify content integrity by default. Therefore, when skipCRC32 is false, unzipItem as a one-shot helper should perform this default behavior by comparing extract return with CRC from each zip entry. Not to mention when calling this helper method, there is no other way for the caller to really step in and compare CRCs themselves; skipCRC32 == false should suggest that they want integrity checks performed after calculating CRCs. (Otherwise why would you want to calculate something that you can never get or use?)

Steps to Reproduce

Expected Results

Method throws because the archive was corrupted.

Actual Results

Call completes and creates (corrupted) files in target directory, as if the archive was intact.

Regression & Version

0.9.14

Related Link

None

weichsel commented 2 years ago

Thanks for reporting this - this was an oversight. CRC32 checksums will be properly evaluated when using the FileManager convenience unzip method in the next release.