[Privoxy-users] External filter never executes

[Tibor Pataky]

Thanks Fabian!

The problem was indeed that I did not set up HTTPS inspection correctly!
After going through the steps in the howto, everything works now as it
should!

Kind regards,
Tibor Pataky

On Sun, 17 Aug 2025 at 17:43, Fabian Keil via Privoxy-users <
privoxy-users at lists.privoxy.org> wrote:

> Tibor Pataky via Privoxy-users <privoxy-users at lists.privoxy.org> wrote on
> 2025-08-17 at 16:25:59:
>
> > I've only just recently discovered privoxy and I thought I'll give it a
> try!
>
> Great.
>
> > One thing I can't get to work though is external filters (perhaps any
> > filters at all?).
> > I stripped down the config as much as possible, my user.action and
> > user.filter files look like this:
> > user.action:
> > { +external-filter{my-filter} }
> > /
> >
> > user.filter:
> > EXTERNAL-FILTER: my-filter why you no work?
> > /usr/bin/tee /var/tmp/privoxy/out
> >
> > When I run privoxy with: --no-daemon /etc/privoxy/config
> > and run the following: curl --proxy localhost:8118
> https://www.privoxy.org/
> > I get the following output:
> > 2025-08-17 15:01:41.411 7ad19d4f0740 Info: Privoxy version 4.0.0
> > 2025-08-17 15:01:41.411 7ad19d4f0740 Info: Program name:
> > /workdir/privoxy/privoxy
> > 2025-08-17 15:01:41.413 7ad19d4f0740 Error: Config option single-threaded
> > disables connection keep-alive.
> > 2025-08-17 15:01:41.413 7ad19d4f0740 Info: Loading filter file:
> > /etc/privoxy/user.filter
> > 2025-08-17 15:01:41.413 7ad19d4f0740 Re-Filter: Reading in filter
> > "timed-filter" ("why you no work?")
> > 2025-08-17 15:01:41.413 7ad19d4f0740 Info: Loading actions file:
> > /etc/privoxy/user.action
> > 2025-08-17 15:01:41.413 7ad19d4f0740 Info: Listening on port 8118 on IP
> > address 0.0.0.0
> > 2025-08-17 15:01:48.322 7ad19d4f0740 Request: www.privoxy.org:443/
> > 2025-08-17 15:01:48.322 7ad19d4f0740 Actions: +external-filter{my-filter}
> >
> > This deceptively shows that it executes my-filter, but it never actually
> > runs the tee command, the file under /var/tmp/privoxy never appeared.
>
> Actually the "Actions:" message only shows that the external-filter{}
> action
> "applies".
>
> To actually execute any filters Privoxy has to buffer the content and it
> looks like you didn't enable HTTPS inspection so Privoxy isn't doing that.
>
> > I got to the point where I built privoxy from source (the v_4_0_0 tag)
> with
> > debug symbols and ran it under gdb.
> > I set various breakpoints in handle_established_connection, but couldn't
> > really figure out what is going wrong. What I noticed is that the
> variable
> > buffer_and_filter_content which guards the call to
> execute_content_filters
> > is only ever set where it is declared. The main loop in
> > handle_established_connection exits after a couple of iterations when it
> > runs onto the break statement at line 3413. As far as I can tell the only
> > place where buffer_and_filter_content is possibly set to a nonzero value
> is
> > in line 4111, but execution never reaches this line.
> >
> > At this point I'm really out of ideas what to try next...
>
> For a quick test, try a http:// URL.
>
> > Is there some extra config I forgot to set to enable external filters?
>
> As mentioned above, to filter https:// content you have to enable
> HTTPS inspection. There's a HOWTO at:
> <https://www.privoxy.org/user-manual/howto.html#H2-HTTPS-INSPECTION>
>
> > Is it a header that's behind this?
>
> No.
>
> > What should I check for in gdb?
>
> Enabling HTTPS inspection should be sufficient to solve this without
> involving gdb.
>
> Don't forget to remove the single-threaded directive again as it results
> in poor performance.
>
> Fabian
> _______________________________________________
> Privoxy-users mailing list
> Privoxy-users at lists.privoxy.org
> https://lists.privoxy.org/mailman/listinfo/privoxy-users
>