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From: Andy Lutomirski <luto@kernel.org>
To: Florian Weimer <fweimer@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Andy Lutomirski <luto@kernel.org>,
	"Ahmed S. Darwish" <darwish.07@gmail.com>,
	Lennart Poettering <mzxreary@0pointer.de>,
	"Theodore Y. Ts'o" <tytso@mit.edu>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	"Alexander E. Patrakov" <patrakov@gmail.com>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	Willy Tarreau <w@1wt.eu>, Matthew Garrett <mjg59@srcf.ucam.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Ext4 Developers List <linux-ext4@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	linux-man <linux-man@vger.kernel.org>
Subject: Re: [PATCH RFC v4 1/1] random: WARN on large getrandom() waits and introduce getrandom2()
Date: Mon, 23 Sep 2019 11:33:21 -0700	[thread overview]
Message-ID: <CALCETrWM9opVj+BBrHnnTakTLunW_fB9RM+VSNpNSkR9drDjMw@mail.gmail.com> (raw)
In-Reply-To: <87blvefai7.fsf@oldenburg2.str.redhat.com>

On Fri, Sep 20, 2019 at 11:07 PM Florian Weimer <fweimer@redhat.com> wrote:
>
> * Linus Torvalds:
>
> > Violently agreed. And that's kind of what the GRND_EXPLICIT is really
> > aiming for.
> >
> > However, it's worth noting that nobody should ever use GRND_EXPLICIT
> > directly. That's just the name for the bit. The actual users would use
> > GRND_INSECURE or GRND_SECURE.
>
> Should we switch glibc's getentropy to GRND_EXPLICIT?  Or something
> else?
>
> I don't think we want to print a kernel warning for this function.
>

Contemplating this question, I think the answer is that we should just
not introduce GRND_EXPLICIT or anything like it.  glibc is going to
have to do *something*, and getentropy() is unlikely to just go away.
The explicitly documented semantics are that it blocks if the RNG
isn't seeded.

Similarly, FreeBSD has getrandom():

https://www.freebsd.org/cgi/man.cgi?query=getrandom&sektion=2&manpath=freebsd-release-ports

and if we make getrandom(..., 0) warn, then we have a situation where
the *correct* (if regrettable) way to use the function on FreeBSD
causes a warning on Linux.

Let's just add GRND_INSECURE, make the blocking mode work better, and,
if we're feeling a bit more adventurous, add GRND_SECURE_BLOCKING as a
better replacement for 0, convince FreeBSD to add it too, and then
worry about deprecating 0 once we at least get some agreement from the
FreeBSD camp.

  reply	other threads:[~2019-09-23 18:33 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAHk-=whW_AB0pZ0u6P9uVSWpqeb5t2NCX_sMpZNGy8shPDyDNg@mail.gmail.com>
     [not found] ` <CAHk-=wi_yXK5KSmRhgNRSmJSD55x+2-pRdZZPOT8Fm1B8w6jUw@mail.gmail.com>
     [not found]   ` <20190911173624.GI2740@mit.edu>
     [not found]     ` <20190912034421.GA2085@darwi-home-pc>
     [not found]       ` <20190912082530.GA27365@mit.edu>
     [not found]         ` <CAHk-=wjyH910+JRBdZf_Y9G54c1M=LBF8NKXB6vJcm9XjLnRfg@mail.gmail.com>
     [not found]           ` <20190914122500.GA1425@darwi-home-pc>
     [not found]             ` <008f17bc-102b-e762-a17c-e2766d48f515@gmail.com>
     [not found]               ` <20190915052242.GG19710@mit.edu>
     [not found]                 ` <CAHk-=wgg2T=3KxrO-BY3nHJgMEyApjnO3cwbQb_0vxsn9qKN8Q@mail.gmail.com>
2019-09-18 21:15                   ` [PATCH RFC v4 0/1] random: WARN on large getrandom() waits and introduce getrandom2() Ahmed S. Darwish
2019-09-18 21:17                     ` [PATCH RFC v4 1/1] " Ahmed S. Darwish
2019-09-18 23:57                       ` Linus Torvalds
2019-09-19 14:34                         ` Theodore Y. Ts'o
2019-09-19 15:20                           ` Linus Torvalds
2019-09-19 15:50                             ` Linus Torvalds
2019-09-20 13:13                               ` Theodore Y. Ts'o
2019-09-19 20:04                             ` Linus Torvalds
2019-09-19 20:45                               ` Alexander E. Patrakov
2019-09-19 21:47                                 ` Linus Torvalds
2019-09-19 22:23                                   ` Alexander E. Patrakov
2019-09-19 23:44                                     ` Alexander E. Patrakov
2019-09-20 13:16                                     ` Theodore Y. Ts'o
2019-09-23 11:55                               ` David Laight
2019-09-20 13:08                             ` Theodore Y. Ts'o
2019-09-20 13:46                         ` Ahmed S. Darwish
2019-09-20 14:33                           ` Andy Lutomirski
2019-09-20 16:29                             ` Linus Torvalds
2019-09-20 17:52                               ` Andy Lutomirski
2019-09-20 18:09                                 ` Linus Torvalds
2019-09-20 18:16                                   ` Willy Tarreau
2019-09-20 19:12                                   ` Andy Lutomirski
2019-09-20 19:51                                     ` Linus Torvalds
2019-09-20 20:11                                       ` Alexander E. Patrakov
2019-09-20 20:17                                       ` Matthew Garrett
2019-09-20 20:51                                       ` Andy Lutomirski
2019-09-20 22:44                                         ` Linus Torvalds
2019-09-20 23:30                                           ` Andy Lutomirski
2019-09-21  3:05                                             ` Willy Tarreau
2019-09-21  6:07                                   ` Florian Weimer
2019-09-23 18:33                                     ` Andy Lutomirski [this message]
2019-09-26 21:11                                       ` Ahmed S. Darwish
2019-09-20 18:12                                 ` Willy Tarreau
2019-09-20 19:22                                   ` Andy Lutomirski
2019-09-20 19:37                                     ` Willy Tarreau
2019-09-20 19:52                                       ` Andy Lutomirski
2019-09-20 20:02                                     ` Linus Torvalds
2019-09-20 18:15                                 ` Alexander E. Patrakov
2019-09-20 18:29                                   ` Andy Lutomirski
2019-09-20 17:26                           ` Willy Tarreau
2019-09-20 17:56                             ` Ahmed S. Darwish
2019-09-26 20:42                         ` [PATCH v5 0/1] random: getrandom(2): warn on large CRNG waits, introduce new flags Ahmed S. Darwish
2019-09-26 20:44                           ` [PATCH v5 1/1] " Ahmed S. Darwish
2019-09-26 21:39                             ` Andy Lutomirski
2019-09-28  9:30                               ` Ahmed S. Darwish

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