Re: [FFmpeg-devel] [PATCH 1/2] lavu: add syntax for loading AV_OPT_TYPE_BINARY from files

[Anton Khirnov <anton@khirnov.net>]

Quoting Niklas Haas (2022-03-04 16:03:06)
> From: Niklas Haas <git@haasn.dev>
> 
> I arbitrarily decided to use the syntax 'opt=@filename' to match e.g.
> `curl -Ffield=@filename`, and also because @ is not a valid hex
> character, nor does it conflict with any other common shell or ffmpeg
> syntax.
> 
> This is arguably somewhat clunky because it does not round-trip with
> av_opt_get - you will get back a hex interpretation of the loaded file,
> rather than the filename it was loaded from. It also implies a (perhaps
> unnecessary) memcpy from mapped file memory into a allocated memory.
> This is unfortunately necessary because there's no way for us to know
> whether av_free or av_file_unmap is needed to clean up previous option
> values.
> 
> The motivating use case was the introduction of several new binary
> options for vf_libplacebo, but other filters that currently rely on
> manual file-path loading could benefit from it as well.

Sorry, I think having an arbitrary file loader in the options parser
will be an endless security nightmare.

The alternative I had in mind was having ffmpeg.c itself do the file
loading. This will be require some modification of the options parsing
code in cmdutils.c and also extending the mechanisms we use to pass
options to filters.

I can try to make a POC in a few days.

-- 
Anton Khirnov
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