On Wed 2017-11-29 22:08:56, Sean Paul wrote:
> This patch adds a new optional connector property to allow userspace to enable
> protection over the content it is displaying. This will typically be implemented
> by the driver using HDCP.
>
> The property is a tri-state with the following values:
> - OFF: Self explanatory, no content protection
> - DESIRED: Userspace requests that the driver enable protection
> - ENABLED: Once the driver has authenticated the link, it sets this value
>
> The driver is responsible for downgrading ENABLED to DESIRED if the link becomes
> unprotected. The driver should also maintain the desiredness of protection
> across hotplug/dpms/suspend.
Why would user of the machine want this to be something else than
'OFF'?
If kernel implements this, will it mean hardware vendors will have to
prevent user from updating kernel on machines they own?
If this is merged, does it open kernel developers to DMCA threats if
they try to change it?
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
On Tue, Dec 05, 2017 at 11:28:40AM +0100, Pavel Machek wrote:
> On Wed 2017-11-29 22:08:56, Sean Paul wrote:
> > This patch adds a new optional connector property to allow userspace to enable
> > protection over the content it is displaying. This will typically be implemented
> > by the driver using HDCP.
> >
> > The property is a tri-state with the following values:
> > - OFF: Self explanatory, no content protection
> > - DESIRED: Userspace requests that the driver enable protection
> > - ENABLED: Once the driver has authenticated the link, it sets this value
> >
> > The driver is responsible for downgrading ENABLED to DESIRED if the link becomes
> > unprotected. The driver should also maintain the desiredness of protection
> > across hotplug/dpms/suspend.
>
> Why would user of the machine want this to be something else than
> 'OFF'?
>
> If kernel implements this, will it mean hardware vendors will have to
> prevent user from updating kernel on machines they own?
>
> If this is merged, does it open kernel developers to DMCA threats if
> they try to change it?
Because this just implements one part of the content protection scheme.
This only gives you an option to enable HDCP (aka encryption, it's really
nothing else) on the cable. Just because it has Content Protection in the
name does _not_ mean it is (stand-alone) an effective nor complete content
protection scheme. It's simply encrypting data, that's all.
If you want to actually lock down a machine to implement content
protection, then you need secure boot without unlockable boot-loader and a
pile more bits in userspace. If you do all that, only then do you have
full content protection. And yes, then you don't really own the machine
fully, and I think users who are concerned with being able to update their
kernels and be able to exercise their software freedoms already know to
avoid such locked down systems.
So yeah it would be better to call this the "HDMI/DP cable encryption
support", but well, it's not what it's called really.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
On Tue 2017-12-05 11:45:38, Daniel Vetter wrote:
> On Tue, Dec 05, 2017 at 11:28:40AM +0100, Pavel Machek wrote:
> > On Wed 2017-11-29 22:08:56, Sean Paul wrote:
> > > This patch adds a new optional connector property to allow userspace to enable
> > > protection over the content it is displaying. This will typically be implemented
> > > by the driver using HDCP.
> > >
> > > The property is a tri-state with the following values:
> > > - OFF: Self explanatory, no content protection
> > > - DESIRED: Userspace requests that the driver enable protection
> > > - ENABLED: Once the driver has authenticated the link, it sets this value
> > >
> > > The driver is responsible for downgrading ENABLED to DESIRED if the link becomes
> > > unprotected. The driver should also maintain the desiredness of protection
> > > across hotplug/dpms/suspend.
> >
> > Why would user of the machine want this to be something else than
> > 'OFF'?
> >
> > If kernel implements this, will it mean hardware vendors will have to
> > prevent user from updating kernel on machines they own?
> >
> > If this is merged, does it open kernel developers to DMCA threats if
> > they try to change it?
>
> Because this just implements one part of the content protection scheme.
> This only gives you an option to enable HDCP (aka encryption, it's really
> nothing else) on the cable. Just because it has Content Protection in the
> name does _not_ mean it is (stand-alone) an effective nor complete content
> protection scheme. It's simply encrypting data, that's all.
Yep. So my first question was: why would user of the machine ever want
encryption "ENABLED" or "DESIRED"? Could you answer it?
> If you want to actually lock down a machine to implement content
> protection, then you need secure boot without unlockable boot-loader and a
> pile more bits in userspace. If you do all that, only then do you have
> full content protection. And yes, then you don't really own the machine
> fully, and I think users who are concerned with being able to update
> their
Yes, so... This patch makes it more likely to see machines with locked
down kernels, preventing developers from working with systems their
own, running hardware. That is evil, and direct threat to Free
software movement.
Users compiling their own kernels get no benefit from it. Actually it
looks like this only benefits Intel and Disney. We don't want that.
> kernels and be able to exercise their software freedoms already know to
> avoid such locked down systems.
>
> So yeah it would be better to call this the "HDMI/DP cable encryption
> support", but well, it's not what it's called really.
Well, it does not belong in kernel, no matter what is the name.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
On Tue, Dec 5, 2017 at 12:34 PM, Pavel Machek <[email protected]> wrote:
> On Tue 2017-12-05 11:45:38, Daniel Vetter wrote:
>> On Tue, Dec 05, 2017 at 11:28:40AM +0100, Pavel Machek wrote:
>> > On Wed 2017-11-29 22:08:56, Sean Paul wrote:
>> > > This patch adds a new optional connector property to allow userspace to enable
>> > > protection over the content it is displaying. This will typically be implemented
>> > > by the driver using HDCP.
>> > >
>> > > The property is a tri-state with the following values:
>> > > - OFF: Self explanatory, no content protection
>> > > - DESIRED: Userspace requests that the driver enable protection
>> > > - ENABLED: Once the driver has authenticated the link, it sets this value
>> > >
>> > > The driver is responsible for downgrading ENABLED to DESIRED if the link becomes
>> > > unprotected. The driver should also maintain the desiredness of protection
>> > > across hotplug/dpms/suspend.
>> >
>> > Why would user of the machine want this to be something else than
>> > 'OFF'?
>> >
>> > If kernel implements this, will it mean hardware vendors will have to
>> > prevent user from updating kernel on machines they own?
>> >
>> > If this is merged, does it open kernel developers to DMCA threats if
>> > they try to change it?
>>
>> Because this just implements one part of the content protection scheme.
>> This only gives you an option to enable HDCP (aka encryption, it's really
>> nothing else) on the cable. Just because it has Content Protection in the
>> name does _not_ mean it is (stand-alone) an effective nor complete content
>> protection scheme. It's simply encrypting data, that's all.
>
> Yep. So my first question was: why would user of the machine ever want
> encryption "ENABLED" or "DESIRED"? Could you answer it?
How about for sensitive video streams in government offices where you
want to avoid a spy potentially tapping the cable to see the video
stream?
>
>> If you want to actually lock down a machine to implement content
>> protection, then you need secure boot without unlockable boot-loader and a
>> pile more bits in userspace. If you do all that, only then do you have
>> full content protection. And yes, then you don't really own the machine
>> fully, and I think users who are concerned with being able to update
>> their
>
> Yes, so... This patch makes it more likely to see machines with locked
> down kernels, preventing developers from working with systems their
> own, running hardware. That is evil, and direct threat to Free
> software movement.
>
> Users compiling their own kernels get no benefit from it. Actually it
> looks like this only benefits Intel and Disney. We don't want that.
And just about every SoC manufacturer and google and amazon and a ton
of other companies and organizations. Who gets to decide who's
benefit gets taken into account?
>
>> kernels and be able to exercise their software freedoms already know to
>> avoid such locked down systems.
>>
>> So yeah it would be better to call this the "HDMI/DP cable encryption
>> support", but well, it's not what it's called really.
>
> Well, it does not belong in kernel, no matter what is the name.
Should we remove support for encrypted file systems and encrypted
virtual machines? Just like them the option is there is you want to
use it. If you don't want to, you don't have to.
Alex
Hi!
> >> > Why would user of the machine want this to be something else than
> >> > 'OFF'?
> >> >
> >> > If kernel implements this, will it mean hardware vendors will have to
> >> > prevent user from updating kernel on machines they own?
> >> >
> >> > If this is merged, does it open kernel developers to DMCA threats if
> >> > they try to change it?
> >>
> >> Because this just implements one part of the content protection scheme.
> >> This only gives you an option to enable HDCP (aka encryption, it's really
> >> nothing else) on the cable. Just because it has Content Protection in the
> >> name does _not_ mean it is (stand-alone) an effective nor complete content
> >> protection scheme. It's simply encrypting data, that's all.
> >
> > Yep. So my first question was: why would user of the machine ever want
> > encryption "ENABLED" or "DESIRED"? Could you answer it?
>
> How about for sensitive video streams in government offices where you
> want to avoid a spy potentially tapping the cable to see the video
> stream?
Except that spies already have the keys, as every monitor
manufacturer has them?
> >> kernels and be able to exercise their software freedoms already know to
> >> avoid such locked down systems.
> >>
> >> So yeah it would be better to call this the "HDMI/DP cable encryption
> >> support", but well, it's not what it's called really.
> >
> > Well, it does not belong in kernel, no matter what is the name.
>
> Should we remove support for encrypted file systems and encrypted
> virtual machines? Just like them the option is there is you want to
> use it. If you don't want to, you don't have to.
Encrypted file systems benefit users. Encrypted video is designed to
work against users. In particular, users don't have encryption keys
for video they generate. I'd have nothing against feature that would
let users encrypt video with keys they control.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
On Tue, Dec 5, 2017 at 12:34 PM, Pavel Machek <[email protected]> wrote:
> On Tue 2017-12-05 11:45:38, Daniel Vetter wrote:
>> On Tue, Dec 05, 2017 at 11:28:40AM +0100, Pavel Machek wrote:
>> > On Wed 2017-11-29 22:08:56, Sean Paul wrote:
>> > > This patch adds a new optional connector property to allow userspace to enable
>> > > protection over the content it is displaying. This will typically be implemented
>> > > by the driver using HDCP.
>> > >
>> > > The property is a tri-state with the following values:
>> > > - OFF: Self explanatory, no content protection
>> > > - DESIRED: Userspace requests that the driver enable protection
>> > > - ENABLED: Once the driver has authenticated the link, it sets this value
>> > >
>> > > The driver is responsible for downgrading ENABLED to DESIRED if the link becomes
>> > > unprotected. The driver should also maintain the desiredness of protection
>> > > across hotplug/dpms/suspend.
>> >
>> > Why would user of the machine want this to be something else than
>> > 'OFF'?
>> >
>> > If kernel implements this, will it mean hardware vendors will have to
>> > prevent user from updating kernel on machines they own?
>> >
>> > If this is merged, does it open kernel developers to DMCA threats if
>> > they try to change it?
>>
>> Because this just implements one part of the content protection scheme.
>> This only gives you an option to enable HDCP (aka encryption, it's really
>> nothing else) on the cable. Just because it has Content Protection in the
>> name does _not_ mean it is (stand-alone) an effective nor complete content
>> protection scheme. It's simply encrypting data, that's all.
>
> Yep. So my first question was: why would user of the machine ever want
> encryption "ENABLED" or "DESIRED"? Could you answer it?
>
Sure. We have a lot of Chrome OS users who would really like to enjoy
premium hd content on their tvs.
>> If you want to actually lock down a machine to implement content
>> protection, then you need secure boot without unlockable boot-loader and a
>> pile more bits in userspace. If you do all that, only then do you have
>> full content protection. And yes, then you don't really own the machine
>> fully, and I think users who are concerned with being able to update
>> their
>
> Yes, so... This patch makes it more likely to see machines with locked
> down kernels, preventing developers from working with systems their
> own, running hardware. That is evil, and direct threat to Free
> software movement.
>
> Users compiling their own kernels get no benefit from it. Actually it
> looks like this only benefits Intel and Disney. We don't want that.
>
Major citation needed here. Did you actually read the code? If you
did, you would realize that the feature is already latent in your
computer. This patchset merely exposes how that hardware can be
enabled to encrypt your video link. Would you have the same problems
with a new whizzbang video encoding format, or is it just the "Content
Protection" name? Perhaps you'd prefer this feature was implemented in
Intel's firmware, or a userspace blob? It wouldn't change the fact
that those registers exist and _can_ be used for HDCP, it's just that
now you know about it.
Having all of the code in the open allows users to see what is
happening with their hardware, how is this a bad thing?
Sean
>> kernels and be able to exercise their software freedoms already know to
>> avoid such locked down systems.
>>
>> So yeah it would be better to call this the "HDMI/DP cable encryption
>> support", but well, it's not what it's called really.
>
> Well, it does not belong in kernel, no matter what is the name.
>
> Pavel
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
Hi Pavel,
On 5 December 2017 at 17:34, Pavel Machek <[email protected]> wrote:
> Yes, so... This patch makes it more likely to see machines with locked
> down kernels, preventing developers from working with systems their
> own, running hardware. That is evil, and direct threat to Free
> software movement.
>
> Users compiling their own kernels get no benefit from it. Actually it
> looks like this only benefits Intel and Disney. We don't want that.
With all due respect, you can't claim to speak for the entire kernel
and FLOSS community of users and developers.
The feature is optional: it does not enforce additional constraints on
users, but exposes additional functionality already present in
hardware, for those who wish to opt in to it. Those who wish to avoid
it can do so, by simply not making active use of it.
Cheers,
Daniel
> If you want to actually lock down a machine to implement content
> protection, then you need secure boot without unlockable boot-loader and a
> pile more bits in userspace.
So let me take my Intel hat off for a moment.
The upstream policy has always been that we don't merge things which
don't have an open usable user space. Is the HDCP encryption feature
useful on its own ? What do users get from it ?
If this is just an enabler for a lump of binary stuff in ChromeOS then I
don't think it belongs, if it is useful standalone then it seems it does
belong ?
Alan
> How about for sensitive video streams in government offices where you
> want to avoid a spy potentially tapping the cable to see the video
> stream?
Last time I checked HDCP did not meet government security requirements -
which is hardly surprising since you can buy $10 boxes from China to
de-hdcp video streams 8)
Alan
On Thu, Dec 07, 2017 at 02:30:52PM +0000, Alan Cox wrote:
> > If you want to actually lock down a machine to implement content
> > protection, then you need secure boot without unlockable boot-loader and a
> > pile more bits in userspace.
>
> So let me take my Intel hat off for a moment.
>
> The upstream policy has always been that we don't merge things which
> don't have an open usable user space. Is the HDCP encryption feature
> useful on its own ? What do users get from it ?
>
> If this is just an enabler for a lump of binary stuff in ChromeOS then I
> don't think it belongs, if it is useful standalone then it seems it does
> belong ?
The cros side is ofc all open source. dri-devel is extremely strict with
not taking anything that doesn't fullfil this requirement, probably more
strict than anyone else. Sean has the link in the cover letter of his
patch series.
For more context, here's our documented expectations about the userspace
side of any uapi addition to drm:
https://dri.freedesktop.org/docs/drm/gpu/drm-uapi.html#open-source-userspace-requirements
Cheers, Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch