DEFCON 201 @defcon201@hostux.social

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The bulk of Tarfile extraction logic involves some shared code for reading Tarfiles with callback to copy the read data into new files.

This callback involves updating the reader's scanner, determining based on options whether to skip the file for its name starting with "../", otherwise determines whether to skip the file possibly involving a prompt if requested by adjusting the scanner, possibly decodes the header to output status, possibly evaluates queued `fstat` adjustments immediately, ...

... possibly carefully renames any existing files by this name to back them up, checks the header to determine which codepath to use to generate this file falling back to skipping the entry, & possibly attempts to restore the backedup file.

Extracting a file involves carefully opening the file setting correct attributes, running through a shellcommand, or outputting to stdout before adjusting the scanner, copying each block to that file handling with fastpath for contiguous files, ...

3/?

... updates scanner, possibly configures `fstat` info, & closes the file. Sparsefiles use a dispatch table presumably crossplatform portability.

For directories it validates the entry is safe & only contains files within the tarfile, decodes directory permissions, & carefully/repeatedly attempts to create it handling symlinks specially before enqueueing an operation to update the directory's `fstat` info.

For symlinks it might create placeholder file first to avoid complaints.

4/?

For hardlinks it might create a placeholder file (two conditions) or it'll repeatedly attempt to create the symlink before decoding the error if any.

For device files it syscalls `mknodat` before decoding the error & adjusting `fstat` info. For FIFOs it similarly syscalls `mkfifoat`.

Other filetypes issue warnings & are skipped. Then it validates results possibly removing the existing file, or checking timestamps.

5/? Next: reading tarfile.

  

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