From: Linus Torvalds <torvalds@linux-foundation.org> To: "Theodore Y. Ts'o" <tytso@mit.edu> Cc: "Ahmed S. Darwish" <darwish.07@gmail.com>, Lennart Poettering <mzxreary@0pointer.de>, "Eric W. Biederman" <ebiederm@xmission.com>, "Alexander E. Patrakov" <patrakov@gmail.com>, Michael Kerrisk <mtk.manpages@gmail.com>, lkml <linux-kernel@vger.kernel.org>, linux-ext4@vger.kernel.org, linux-man@vger.kernel.org Subject: Re: [PATCH RFC v4 1/1] random: WARN on large getrandom() waits and introduce getrandom2() Date: Thu, 19 Sep 2019 08:50:15 -0700 Message-ID: <CAHk-=wiRUqH1dch2VCaYqNT+_vPj6LXGHcP4oW9-M3zdSfXrTg@mail.gmail.com> (raw) In-Reply-To: <CAHk-=wgqbBy84ovtr8wPFqRo6U8jvp59rvQ8a6TvXuoyb-4L-Q@mail.gmail.com> [-- Attachment #1: Type: text/plain, Size: 1329 bytes --] On Thu, Sep 19, 2019 at 8:20 AM Linus Torvalds <torvalds@linux-foundation.org> wrote: > > The silly "reset crng_init_cnt" does absolutely nothing to help that, > but in fact what it does is to basically give the attacker a way to > get an infinite stream of data without any reseeding (because that > only happens after crng_read()), and able to extend that "block at > boot" time indefinitely while doing so. .. btw, instead of bad workarounds for a theoretical attack, here's something that should add actual *practical* real value: use the time of day (whether from an RTC device, or from ntp) to add noise to the random pool. If you let attackers in before you've set the clock on the device, you're doing something seriously wrong. And while this doesn't add much "serious" entropy, it does mean that the whole "let's look for identical state" which is a _real_ attack, goes out the window. In other words, this is about real security, not academic papers. Of course, attackers can still see possible bad random values from before the clock was set (possibly from things like TCP sequence numbers etc, orfrom that AT_RANDOM of a very early process, which was part of the Android the attack). But doing things like delaying reseeding sure isn't helping, which is what the crng_count reset does. Linus [-- Attachment #2: patch.diff --] [-- Type: text/x-patch, Size: 867 bytes --] kernel/time/timekeeping.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index ca69290bee2a..67e74f7f4198 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -22,6 +22,7 @@ #include <linux/pvclock_gtod.h> #include <linux/compiler.h> #include <linux/audit.h> +#include <linux/random.h> #include "tick-internal.h" #include "ntp_internal.h" @@ -1256,6 +1257,7 @@ int do_settimeofday64(const struct timespec64 *ts) /* signal hrtimers about time change */ clock_was_set(); + add_device_randomness(ts, sizeof(*ts)); if (!ret) audit_tk_injoffset(ts_delta); @@ -1304,6 +1306,7 @@ static int timekeeping_inject_offset(const struct timespec64 *ts) /* signal hrtimers about time change */ clock_was_set(); + add_device_randomness(ts, sizeof(*ts)); return ret; }
next prev parent reply index Thread overview: 211+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <CAHk-=whBQ+6c-h+htiv6pp8ndtv97+45AH9WvdZougDRM6M4VQ@mail.gmail.com> 2019-09-10 4:21 ` Linux 5.3-rc8 Ahmed S. Darwish 2019-09-10 11:33 ` Linus Torvalds 2019-09-10 12:21 ` Linus Torvalds 2019-09-10 17:33 ` Ahmed S. Darwish 2019-09-10 17:47 ` Reindl Harald 2019-09-10 18:21 ` Linus Torvalds 2019-09-11 16:07 ` Theodore Y. Ts'o 2019-09-11 16:45 ` Linus Torvalds 2019-09-11 17:00 ` Linus Torvalds 2019-09-11 17:36 ` Theodore Y. Ts'o 2019-09-12 3:44 ` Ahmed S. Darwish 2019-09-12 8:25 ` Theodore Y. Ts'o 2019-09-12 11:34 ` Linus Torvalds 2019-09-12 11:58 ` Willy Tarreau 2019-09-14 12:25 ` [PATCH RFC] random: getrandom(2): don't block on non-initialized entropy pool Ahmed S. Darwish 2019-09-14 14:08 ` Alexander E. Patrakov 2019-09-15 5:22 ` [PATCH RFC v2] random: optionally block in getrandom(2) when the CRNG is uninitialized Theodore Y. Ts'o 2019-09-15 8:17 ` [PATCH RFC v3] random: getrandom(2): optionally block when " Ahmed S. Darwish 2019-09-15 8:59 ` Lennart Poettering 2019-09-15 9:30 ` Willy Tarreau 2019-09-15 10:02 ` Ahmed S. Darwish 2019-09-15 10:40 ` Willy Tarreau 2019-09-15 10:55 ` Ahmed S. Darwish 2019-09-15 11:17 ` Willy Tarreau 2019-09-15 17:32 ` [PATCH RFC v2] random: optionally block in getrandom(2) when the " Linus Torvalds 2019-09-15 18:32 ` Willy Tarreau 2019-09-15 18:36 ` Willy Tarreau 2019-09-15 19:08 ` Linus Torvalds 2019-09-15 19:18 ` Willy Tarreau 2019-09-15 19:31 ` Linus Torvalds 2019-09-15 19:54 ` Willy Tarreau 2019-09-15 18:59 ` Linus Torvalds 2019-09-15 19:12 ` Willy Tarreau 2019-09-16 2:45 ` Ahmed S. Darwish 2019-09-16 18:08 ` Lennart Poettering 2019-09-16 19:16 ` Willy Tarreau 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 [this message] 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 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 2019-09-14 15:02 ` Linux 5.3-rc8 Ahmed S. Darwish 2019-09-14 16:30 ` Linus Torvalds 2019-09-14 16:35 ` Alexander E. Patrakov 2019-09-14 16:52 ` Linus Torvalds 2019-09-14 17:09 ` Alexander E. Patrakov 2019-09-14 19:19 ` Linus Torvalds 2019-09-15 6:56 ` Lennart Poettering 2019-09-15 7:01 ` Willy Tarreau 2019-09-15 7:05 ` Lennart Poettering 2019-09-15 7:07 ` Willy Tarreau 2019-09-15 8:34 ` Lennart Poettering 2019-09-15 17:02 ` Linus Torvalds 2019-09-16 3:23 ` Theodore Y. Ts'o 2019-09-16 3:40 ` Linus Torvalds 2019-09-16 3:56 ` Linus Torvalds 2019-09-16 17:00 ` Theodore Y. Ts'o 2019-09-16 17:07 ` Linus Torvalds 2019-09-14 21:11 ` Ahmed S. Darwish 2019-09-14 22:05 ` Martin Steigerwald 2019-09-14 22:24 ` Theodore Y. Ts'o 2019-09-14 22:32 ` Linus Torvalds 2019-09-15 1:00 ` Theodore Y. Ts'o 2019-09-15 1:10 ` Linus Torvalds 2019-09-15 2:05 ` Theodore Y. Ts'o 2019-09-15 2:11 ` Linus Torvalds 2019-09-15 6:33 ` Willy Tarreau 2019-09-15 6:53 ` Willy Tarreau 2019-09-15 6:51 ` Lennart Poettering 2019-09-15 7:27 ` Ahmed S. Darwish 2019-09-15 8:48 ` Lennart Poettering 2019-09-15 16:29 ` Linus Torvalds 2019-09-16 1:40 ` Ahmed S. Darwish 2019-09-16 1:48 ` Vito Caputo 2019-09-16 2:49 ` Theodore Y. Ts'o 2019-09-16 4:29 ` Willy Tarreau 2019-09-16 5:02 ` Linus Torvalds 2019-09-16 6:12 ` Willy Tarreau 2019-09-16 16:17 ` Linus Torvalds 2019-09-16 17:21 ` Theodore Y. Ts'o 2019-09-16 17:44 ` Linus Torvalds 2019-09-16 17:55 ` Serge Belyshev 2019-09-16 19:08 ` Willy Tarreau 2019-09-16 23:02 ` Matthew Garrett 2019-09-16 23:05 ` Linus Torvalds 2019-09-16 23:11 ` Matthew Garrett 2019-09-16 23:13 ` Alexander E. Patrakov 2019-09-16 23:15 ` Matthew Garrett 2019-09-16 23:18 ` Linus Torvalds 2019-09-16 23:29 ` Ahmed S. Darwish 2019-09-17 1:05 ` Linus Torvalds 2019-09-17 1:23 ` Matthew Garrett 2019-09-17 1:41 ` Linus Torvalds 2019-09-17 1:46 ` Matthew Garrett 2019-09-17 5:24 ` Willy Tarreau 2019-09-17 7:33 ` Martin Steigerwald 2019-09-17 8:35 ` Willy Tarreau 2019-09-17 8:44 ` Martin Steigerwald 2019-09-17 12:11 ` Theodore Y. Ts'o 2019-09-17 12:30 ` Ahmed S. Darwish 2019-09-17 12:46 ` Alexander E. Patrakov 2019-09-17 12:47 ` Willy Tarreau 2019-09-17 16:08 ` Lennart Poettering 2019-09-17 16:23 ` Linus Torvalds 2019-09-17 16:34 ` Reindl Harald 2019-09-17 17:42 ` Lennart Poettering 2019-09-17 18:01 ` Linus Torvalds 2019-09-17 20:28 ` Martin Steigerwald 2019-09-17 20:52 ` Ahmed S. Darwish 2019-09-17 21:38 ` Martin Steigerwald 2019-09-17 21:52 ` Matthew Garrett 2019-09-17 22:10 ` Martin Steigerwald 2019-09-18 13:53 ` Lennart Poettering 2019-09-19 7:28 ` Martin Steigerwald 2019-09-17 23:08 ` Linus Torvalds 2019-09-18 13:40 ` Lennart Poettering 2019-09-17 20:58 ` Linus Torvalds 2019-09-18 9:33 ` Rasmus Villemoes 2019-09-18 10:16 ` Willy Tarreau 2019-09-18 10:25 ` Alexander E. Patrakov 2019-09-18 10:42 ` Willy Tarreau 2019-09-18 19:31 ` Linus Torvalds 2019-09-18 19:56 ` Eric W. Biederman 2019-09-18 20:13 ` Linus Torvalds 2019-09-18 20:15 ` Alexander E. Patrakov 2019-09-18 20:26 ` Linus Torvalds 2019-09-18 22:12 ` Willy Tarreau 2019-09-27 13:57 ` Lennart Poettering 2019-09-27 15:58 ` Linus Torvalds 2019-09-29 9:05 ` Lennart Poettering 2019-09-17 13:11 ` Alexander E. Patrakov 2019-09-17 13:37 ` Alexander E. Patrakov 2019-09-17 15:57 ` Lennart Poettering 2019-09-17 16:21 ` Willy Tarreau 2019-09-17 17:13 ` Lennart Poettering 2019-09-17 17:29 ` Willy Tarreau 2019-09-17 20:42 ` Martin Steigerwald 2019-09-18 13:38 ` Lennart Poettering 2019-09-18 13:59 ` Alexander E. Patrakov 2019-09-18 14:50 ` Alexander E. Patrakov 2019-09-17 20:36 ` Martin Steigerwald 2019-09-17 16:27 ` Linus Torvalds 2019-09-17 16:34 ` Matthew Garrett 2019-09-17 17:16 ` Willy Tarreau 2019-09-17 17:20 ` Matthew Garrett 2019-09-17 17:23 ` Matthew Garrett 2019-09-17 17:57 ` Willy Tarreau 2019-09-17 16:58 ` Alexander E. Patrakov 2019-09-17 17:30 ` Lennart Poettering 2019-09-17 17:32 ` Willy Tarreau 2019-09-17 17:41 ` Alexander E. Patrakov 2019-09-17 17:28 ` Lennart Poettering 2019-09-17 0:03 ` Matthew Garrett 2019-09-17 0:40 ` Matthew Garrett 2019-09-17 7:15 ` a sane approach to random numbers (was: Re: Linux 5.3-rc8) Martin Steigerwald 2019-09-16 18:00 ` Linux 5.3-rc8 Alexander E. Patrakov 2019-09-16 19:53 ` Ahmed S. Darwish 2019-09-17 15:32 ` Lennart Poettering 2019-09-16 3:31 ` Linus Torvalds 2019-09-23 20:49 ` chaos generating driver was " Pavel Machek 2019-09-14 9:25 ` Ahmed S. Darwish 2019-09-14 16:27 ` Theodore Y. Ts'o 2019-09-11 21:41 ` Ahmed S. Darwish 2019-09-11 22:37 ` Ahmed S. Darwish 2019-09-16 3:52 ` Herbert Xu 2019-09-16 4:21 ` Linus Torvalds 2019-09-16 4:53 ` Willy Tarreau 2019-09-10 11:56 ` Theodore Y. Ts'o 2019-09-16 10:33 ` Christoph Hellwig 2019-10-03 21:10 ` Jon Masters 2019-10-03 21:31 ` Jon Masters
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