Hello,
Based on the discussion here, I have reverted back to something more
similar to webrev.02, but with a few changes. Mainly fixing a bug that
caused JVM_FEATURES_hardened to not actually be the same as for server
(if you have custom additions in configure). I also added a check so
that configure fails if you try to enable either variant hardened or
feature no-speculative-cti and the flags aren't available.
Webrev: http://cr.openjdk.java.net/~erikj/8202384/webrev.05/index.html
/Erik
On 2018-06-11 00:10, Magnus Ihse Bursie wrote:
On 2018-06-08 23:50, Erik Joelsson wrote:
On 2018-06-07 17:30, David Holmes wrote:
On 8/06/2018 6:11 AM, Erik Joelsson wrote:
I just don't think the extra work is warranted or should be
prioritized at this point. I also cannot think of a combination of
options required for what you are suggesting that wouldn't be
confusing to the user. If someone truly feels like these flags are
forced on them and can't live with them, we or preferably that
person can fix it then. I don't think that's dictatorship. OpenJDK
is still open source and anyone can contribute.
I don't see why --enable-hardened-jdk and --enable-hardened-hotspot
to add to the right flags would be either complicated or confusing.
For me the confusion surrounds the difference between
--enable-hardened-hotspot and --with-jvm-variants=server, hardened
and making the user understand it. But sure, it is doable. Here is a
new webrev with those two options as I interpret them. Here is the
help text:
--enable-hardened-jdk enable hardenening compiler flags for all jdk
libraries (except the JVM), typically
disabling
speculative cti. [disabled]
--enable-hardened-hotspot
enable hardenening compiler flags for
hotspot (all
jvm variants), typically disabling
speculative cti.
To make hardening of hotspot a runtime choice,
consider the "hardened" jvm variant instead
of this
option. [disabled]
Note that this changes the default for jdk libraries to not enable
hardening unless the user requests it.
Webrev: http://cr.openjdk.java.net/~erikj/8202384/webrev.04/
Hold it, hold it! I'm not sure how we ended up here, but I don't like
it at all. :-(
I think Eriks initial patch is much better than this. Some arguments
in random order to defend this position:
1) Why should we have a configure option to disable security relevant
flags for the JDK, if there has been no measured negative effect? We
don't do this for any other compiler flags, especially not security
relevant ones!
I've re-read the entire thread to see if I could understand what could
possibly motivate this, but the only thing I can find is David Holmes
vague fear that these flags would not be well-tested enough. Let me
counter with my own vague guesses: I believe the spectre mitigation
methods to have been fully and properly tested, since they are
rolled-out massively on all products. And let me complement with my
own fear: the PR catastrophe if OpenJDK were *not* built with spectre
mitigations, and someone were to exploit that!
In fact, I could even argue that "server" should be hardened *by
default*, and that we should instead introduce a non-hardened JVM
named something akin to "quick-but-dangerous-server" instead. But I
realize that a 25% performance hit is hard to swallow, so I won't push
this agenda.
2) It is by no means clear that "--enable-hardened-jdk" does not
harden all aspects of the JDK! If we should keep the option (which I
definitely do not think we should!) it should be renamed to
"--enable-hardened-libraries", or something like that. And it should
be on by default, so it should be a "--disabled-hardened-jdk-libraries".
Also, the general-sounding name "hardened" sounds like it might
encompass more things than it does. What if I disabled a hardened jdk
build, should I still get stack banging protection? If so, you need to
move a lot more security-related flags to this option. (And, just to
be absolutely clear: I don't think you should do that.)
3) Having two completely different ways of turning on Spectre
protection for hotspot is just utterly confusing! This was a perfect
example of how to use the JVM features, just as in the original patch.
If you want to have spectre mitigation enabled for both server and
client, by default, you would just need to run "configure
--with-jvm-variants=server,client
--with-jvm-features=no-speculative-cti", which will enable that
feature for all variants. That's not really hard *at all* for anyone
building OpenJDK. And it's way clearer what will happen, than a
--enable-hardened-hotspot.
4) If you are a downstream provider building OpenJDK and you are dead
set on not including Spectre mitigations in the JDK libraries, despite
being shown to have no negative effects, then you can do just as any
other downstream user with highly specialized requirements, and patch
the source. I have no sympathies for this; I can't stop it but I don't
think there's any reason for us to complicate the code to support this
unlikely case.
So, to recap, I think the webrev as published in
http://cr.openjdk.java.net/~erikj/8202384/webrev.02/ (with "altserver"
renamed to "hardened") is the way to go.
/Magnus
/Erik
