Re: HDCP blob still present

[Denis 'GNUtoo' Carikli]

On Sun, 3 Nov 2024 02:29:07 +0100
Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org> wrote:

> On Tue, 29 Oct 2024 12:58:08 +0000
> Leah Rowe via Gnuboot-patches <gnuboot-patches@gnu.org> wrote:
> 
> > Dear gnuboot developers,  
> Hi,
> 
> > I checked your source code, and you seem to have this binary in some
> > of your coreboot trees:
> > 
> > 3rdparty/arm-trusted-firmware/plat/rockchip/rk3399/drivers/dp/hdcp.bin
> > 
> > This appears to be an executable, and I could not find source code; 
> > someone correct me if I'm wrong, but this appears to be a
> > proprietary  
> Thanks, I didn't see that arm-trusted-firmware included Rockchip
> firmwares as well. The hdcp.bin is also signed if I recall well.
I made a confusion with dptx.bin which is another firmware for RK3399
that is involved in making external display work on the Pinebook PRO
which uses the same System on a chip. I assumed that dptx.bin was
signed and nonfree because of HDCP.

According to the commit c76631c52b0b1550ff182c177555485700274314
("rockchip: include hdcp.bin and declare hdcp key decryption handler")
of ARM trusted firmware, the hdcp.bin is code that is included as-is
inside arm trusted firmware.

I'm unsure how the HDCP stack works in practice though, especially how
it is enabled/disabled, but to fix it in distributions other than GNU
Boot it might be possible to either re-implement it as free software
since HDCP is known to be broken, or to just disable it. For the later
I'm unsure of the impact regarding compatibility with hardware as I'm
unsure how HDCP get enabled or not on GNU/Linux.

Denis.

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