Valerie Snyder 31dcec1e42 libclamav: Add engine option to toggle temp directory recursion ...

Temp directory recursion in ClamAV is when each layer of a scan gets its
own temp directory in the parent layer's temp directory.

In addition to temp directory recursion, ClamAV has been creating a new
subdirectory for each file scan as a risk-adverse method to ensure
no temporary file leaks fill up the disk.
Creating a directory is relatively slow on Windows in particular if
scanning a lot of very small files.

This commit:

1. Separates the temp directory recursion feature from the leave-temps
   feature so that libclamav can leave temp files without making
   subdirectories for each file scanned.

2. Makes it so that when temp directory recursion is off, libclamav
   will just use the configure temp directory for all files.

The new option to enable temp directory recursion is for libclamav-only
at this time. It is off by default, and you can enable it like this:

```c
cl_engine_set_num(engine, CL_ENGINE_TMPDIR_RECURSION, 1);
```

For the `clamscan` and `clamd` programs, temp directory recursion will
be enabled when `--leave-temps` / `LeaveTemporaryFiles` is enabled.

The difference is that when disabled, it will return to using the
configured temp directory without making a subdirectory for each file
scanned, so as to improve scan performance for small files, mostly on
Windows.

Under the hood, this commit also:

1. Cleans up how we keep track of tmpdirs for each layer.
   The goal here is to align how we keep track of layer-specific stuff
   using the scan_layer structure.

2. Cleans up how we record metadata JSON for embedded files.
   Note: Embedded files being different from Contained files, as they
         are extracted not with a parser, but by finding them with
         file type magic signatures.

CLAM-1583

2025-08-14 22:38:58 -04:00

69 KiB

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