Re: [FFmpeg-devel] [PATCH] [RFC] avformat: Add basic same origin check

[Hendrik Leppkes <h.leppkes@gmail.com>]

On Wed, May 3, 2023 at 12:49 PM Michael Niedermayer
<michael@niedermayer.cc> wrote:
>
> On Wed, May 03, 2023 at 12:05:54PM +0200, Hendrik Leppkes wrote:
> > On Tue, May 2, 2023 at 10:57 PM James Almer <jamrial@gmail.com> wrote:
> > > >
> > > > added
> > > > +{"same_none"  , "same origin check off"                       , 0 , AV_OPT_TYPE_CONST, { .i64 = AVFMT_SAME_ORIGIN_CHECK_NONE }, 0, INT_MAX, D|E, "same_origin"},
> > >
> > > "none" sounds more natural.
> > >
> > > >
> > > >
> > > >> And do we want check_path to be default? It's a change
> > > >> in behavior.
> > > >
> > > > is it usefull if its not enabled by default ?
> > >
> > > It is, since it can be enabled, like the whitelists and blacklists, but
> > > the question is if it's preferable to have it enabled. If you consider
> > > it so, then it's good and i wont oppose it.
> > >
> >
> > Is there any estimation how many legitimate streams would be broken by
> > these options?
> > If any major streams don't work with this, then its not a good option,
> > and eg. library users will likely just turn it off or to a lower
> > setting, as proper streams just have to work - and log output is
> > pretty much useless for API usage cases.
> >
> > A quick check for example shows that even something as simple as the
> > HLS BBC Radio streams will fail _all_ checks, since the playlists are
> > hosted on another host entirely as the media, thanks to akamai live
> > streaming.
> > Playlist here, as an example:
> > http://a.files.bbci.co.uk/media/live/manifesto/audio/simulcast/hls/nonuk/sbr_low/ak/bbc_radio_one.m3u8
>
> yes, thats why it says RFC in the subject, i had expected that a bit already
>
> still OTOH, blocking these by default is the safer option, i mean if a user
> does a
> ./ffplay http://trustedfoobar.org/cutevideo.avi
>
> would she expect that video to access http://127.0.0.1/ and later http://evilhost/localwebscan-success
> I think this should not be possible by default settings, its unexpected
>

Coming from the other side -- If the user needs to set the flag for
nearly all streams, then they are not going to check in the future and
just set it, defeating the purpose of them. At which point we might as
well not burden them.

- Hendrik
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