Date: Wed, 23 Apr 2003 20:59:45 -0700 (PDT)
From: Linus Torvalds <torvalds@transmeta.com>
To: Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Flame Linus to a crisp!
——————————-
Ok,
there’s no way to do this gracefully, so I won’t even try. I’m
going to just hunker down for some really impressive extended
flaming, and my asbestos underwear is firmly in place, and
extremely uncomfortable.
I want to make it clear that DRM is perfectly ok with Linux!
There, I’ve said it. I’m out of the closet. So bring it
on…
I’ve had some private discussions with various people about this
already, and I do realize that a lot of people want to use the
kernel in some way to just make DRM go away, at least as far as
Linux is concerned. Either by some policy decision or by extending
the GPL to just not allow it.
In some ways the discussion was very similar to some of the
software patent related GPL-NG discussions from a year or so ago:
“we don’t like it, and we should change the license to make it not
work somehow”.
And like the software patent issue, I also don’t necessarily
like DRM myself, but I still ended up feeling the same: I’m an
“Oppenheimer”, and I refuse to play politics with Linux, and I
think you can use Linux for whatever you want to – which very much
includes things I don’t necessarily personally approve of.
The GPL requires you to give out sources to the kernel, but it
doesn’t limit what you can _do_ with the kernel. On the whole, this
is just another example of why rms calls me “just an engineer” and
thinks I have no ideals.
[ Personally, I see it as a virtue – trying to make the world a
slightly better place _without_ trying to impose your moral values
on other people. You do whatever the h*ll rings your bell, I’m just
an engineer who wants to make the best OS possible. ]
In short, it’s perfectly ok to sign a kernel image – I do it
myself indirectly every day through the kernel.org, as kernel.org
will sign the tar-balls I upload to make sure people can at least
verify that they came that way. Doing the same thing on the binary
is no different: signing a binary is a perfectly fine way to show
the world that you’re the one behind it, and that _you_ trust
it.
And since I can imaging signing binaries myself, I don’t feel
that I can disallow anybody else doing so.
Another part of the DRM discussion is the fact that signing is
only the first step: _acting_ on the fact whether a binary is
signed or not (by refusing to load it, for example, or by refusing
to give it a secret key) is required too.
But since the signature is pointless unless you _use_ it for
something, and since the decision how to use the signature is
clearly outside of the scope of the kernel itself (and thus not a
“derived work” or anything like that), I have to convince myself
that not only is it clearly ok to act on the knowledge of whather
the kernel is signed or not, it’s also outside of the scope of what
the GPL talks about, and thus irrelevant to the license.
That’s the short and sweet of it. I wanted to bring this out in
the open, because I know there are people who think that signed
binaries are an act of “subversion” (or “perversion”) of the GPL,
and I wanted to make sure that people don’t live under
mis-apprehension that it can’t be done.
I think there are many quite valid reasons to sign (and verify)
your kernel images, and while some of the uses of signing are
odious, I don’t see any sane way to distinguish between “good”
signers and “bad” signers.
Comments? I’d love to get some real discussion about this, but
in the end I’m personally convinced that we have to allow it.
Btw, one thing that is clearly _not_ allowed by the GPL is
hiding private keys in the binary. You can sign the binary that is
a result of the build process, but you can _not_ make a binary that
is aware of certain keys without making those keys public – because
those keys will obviously have been part of the kernel build
itself.
So don’t get these two things confused – one is an external key
that is applied _to_ the kernel (ok, and outside the license), and
the other one is embedding a key _into_ the kernel (still ok, but
the GPL requires that such a key has to be made available as
“source” to the kernel).
Linus