Commit Graph

133 Commits

Author SHA1 Message Date
Linus Torvalds 0891ad829d The /dev/random changes for 3.13 including a number of improvements in
the following areas: performance, avoiding waste of entropy, better
 tracking of entropy estimates, support for non-x86 platforms that have
 a register which can't be used for fine-grained timekeeping, but which
 might be good enough for the random driver.
 
 Also add some printk's so that we can see how quickly /dev/urandom can
 get initialized, and when programs try to use /dev/urandom before it
 is fully initialized (since this could be a security issue).  This
 shouldn't be an issue on x86 desktop/laptops --- a test on my Lenovo
 T430s laptop shows that /dev/urandom is getting fully initialized
 approximately two seconds before the root file system is mounted
 read/write --- this may be an issue with ARM and MIPS embedded/mobile
 systems, though.  These printk's will be a useful canary before
 potentially adding a future change to start blocking processes which
 try to read from /dev/urandom before it is initialized, which is
 something FreeBSD does already for security reasons, and which
 security folks have been agitating for Linux to also adopt.
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Merge tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random

Pull /dev/random changes from Ted Ts'o:
 "The /dev/random changes for 3.13 including a number of improvements in
  the following areas: performance, avoiding waste of entropy, better
  tracking of entropy estimates, support for non-x86 platforms that have
  a register which can't be used for fine-grained timekeeping, but which
  might be good enough for the random driver.

  Also add some printk's so that we can see how quickly /dev/urandom can
  get initialized, and when programs try to use /dev/urandom before it
  is fully initialized (since this could be a security issue).  This
  shouldn't be an issue on x86 desktop/laptops --- a test on my Lenovo
  T430s laptop shows that /dev/urandom is getting fully initialized
  approximately two seconds before the root file system is mounted
  read/write --- this may be an issue with ARM and MIPS embedded/mobile
  systems, though.  These printk's will be a useful canary before
  potentially adding a future change to start blocking processes which
  try to read from /dev/urandom before it is initialized, which is
  something FreeBSD does already for security reasons, and which
  security folks have been agitating for Linux to also adopt"

* tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  random: add debugging code to detect early use of get_random_bytes()
  random: initialize the last_time field in struct timer_rand_state
  random: don't zap entropy count in rand_initialize()
  random: printk notifications for urandom pool initialization
  random: make add_timer_randomness() fill the nonblocking pool first
  random: convert DEBUG_ENT to tracepoints
  random: push extra entropy to the output pools
  random: drop trickle mode
  random: adjust the generator polynomials in the mixing function slightly
  random: speed up the fast_mix function by a factor of four
  random: cap the rate which the /dev/urandom pool gets reseeded
  random: optimize the entropy_store structure
  random: optimize spinlock use in add_device_randomness()
  random: fix the tracepoint for get_random_bytes(_arch)
  random: account for entropy loss due to overwrites
  random: allow fractional bits to be tracked
  random: statically compute poolbitshift, poolbytes, poolbits
  random: mix in architectural randomness earlier in extract_buf()
2013-11-16 10:19:15 -08:00
Hannes Frederic Sowa 4af712e8df random32: add prandom_reseed_late() and call when nonblocking pool becomes initialized
The Tausworthe PRNG is initialized at late_initcall time. At that time the
entropy pool serving get_random_bytes is not filled sufficiently. This
patch adds an additional reseeding step as soon as the nonblocking pool
gets marked as initialized.

On some machines it might be possible that late_initcall gets called after
the pool has been initialized. In this situation we won't reseed again.

(A call to prandom_seed_late blocks later invocations of early reseed
attempts.)

Joint work with Daniel Borkmann.

Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
2013-11-11 14:32:14 -05:00
Theodore Ts'o 392a546dc8 random: add debugging code to detect early use of get_random_bytes()
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-11-03 18:24:08 -05:00
Theodore Ts'o 644008df89 random: initialize the last_time field in struct timer_rand_state
Since we initialize jiffies to wrap five minutes before boot (see
INITIAL_JIFFIES defined in include/linux/jiffies.h) it's important to
make sure the last_time field is initialized to INITIAL_JIFFIES.
Otherwise, the entropy estimator will overestimate the amount of
entropy resulting from the first call to add_timer_randomness(),
generally by about 8 bits.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-11-03 18:20:05 -05:00
Theodore Ts'o ae9ecd92dd random: don't zap entropy count in rand_initialize()
The rand_initialize() function was being run fairly late in the kernel
boot sequence.  This was unfortunate, since it zero'ed the entropy
counters, thus throwing away credit that was accumulated earlier in
the boot sequence, and it also meant that initcall functions run
before rand_initialize were using a minimally initialized pool.

To fix this, fix init_std_data() to no longer zap the entropy counter;
it wasn't necessary, and move rand_initialize() to be an early
initcall.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-11-03 18:18:49 -05:00
Theodore Ts'o 301f0595c0 random: printk notifications for urandom pool initialization
Print a notification to the console when the nonblocking pool is
initialized.  Also printk a warning when a process tries reading from
/dev/urandom before it is fully initialized.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-11-03 18:18:48 -05:00
Theodore Ts'o 40db23e533 random: make add_timer_randomness() fill the nonblocking pool first
Change add_timer_randomness() so that it directs incoming entropy to
the nonblocking pool first if it hasn't been fully initialized yet.
This matches the strategy we use in add_interrupt_randomness(), which
allows us to push the randomness where we need it the most during when
the system is first booting up, so that get_random_bytes() and
/dev/urandom become safe to use as soon as possible.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-11-03 18:18:47 -05:00
Linus Torvalds f715729ee4 These patches are designed to enable improvements to /dev/random for
non-x86 platforms, in particular MIPS and ARM.
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Merge tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random

Pull /dev/random changes from Ted Ts'o:
 "These patches are designed to enable improvements to /dev/random for
  non-x86 platforms, in particular MIPS and ARM"

* tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  random: allow architectures to optionally define random_get_entropy()
  random: run random_int_secret_init() run after all late_initcalls
2013-10-10 12:31:43 -07:00
Theodore Ts'o f80bbd8b92 random: convert DEBUG_ENT to tracepoints
Instead of using the random driver's ad-hoc DEBUG_ENT() mechanism, use
tracepoints instead.  This allows for a much more fine-grained control
of which debugging mechanism which a developer might need, and unifies
the debugging messages with all of the existing tracepoints.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-10-10 14:32:23 -04:00
Theodore Ts'o 6265e169cd random: push extra entropy to the output pools
As the input pool gets filled, start transfering entropy to the output
pools until they get filled.  This allows us to use the output pools
to store more system entropy.  Waste not, want not....

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-10-10 14:32:22 -04:00
Theodore Ts'o 95b709b6be random: drop trickle mode
The add_timer_randomness() used to drop into trickle mode when entropy
pool was estimated to be 87.5% full.  This was important when
add_timer_randomness() was used to sample interrupts.  It's not used
for this any more --- add_interrupt_randomness() now uses fast_mix()
instead.  By elimitating trickle mode, it allows us to fully utilize
entropy provided by add_input_randomness() and add_disk_randomness()
even when the input pool is above the old trickle threshold of 87.5%.

This helps to answer the criticism in [1] in their hypothetical
scenario where our entropy estimator was inaccurate, even though the
measurements in [2] seem to indicate that our entropy estimator given
real-life entropy collection is actually pretty good, albeit on the
conservative side (which was as it was designed).

[1] http://eprint.iacr.org/2013/338.pdf
[2] http://eprint.iacr.org/2012/251.pdf

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-10-10 14:32:21 -04:00
Theodore Ts'o 6e9fa2c8a6 random: adjust the generator polynomials in the mixing function slightly
Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
Videau in their paper, "The Linux Pseudorandom Number Generator
Revisited" (see: http://eprint.iacr.org/2012/251.pdf).

They suggested a slight change to improve our mixing functions
slightly.  I also adjusted the comments to better explain what is
going on, and to document why the polynomials were changed.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-10-10 14:32:21 -04:00
Theodore Ts'o 655b226470 random: speed up the fast_mix function by a factor of four
By mixing the entropy in chunks of 32-bit words instead of byte by
byte, we can speed up the fast_mix function significantly.  Since it
is called on every single interrupt, on systems with a very heavy
interrupt load, this can make a noticeable difference.

Also fix a compilation warning in add_interrupt_randomness() and avoid
xor'ing cycles and jiffies together just in case we have an
architecture which tries to define random_get_entropy() by returning
jiffies.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reported-by: Jörn Engel <joern@logfs.org>
2013-10-10 14:32:20 -04:00
Theodore Ts'o f5c2742c23 random: cap the rate which the /dev/urandom pool gets reseeded
In order to avoid draining the input pool of its entropy at too high
of a rate, enforce a minimum time interval between reseedings of the
urandom pool.  This is set to 60 seconds by default.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-10-10 14:32:19 -04:00
Theodore Ts'o c59974aea4 random: optimize the entropy_store structure
Use smaller types to slightly shrink the size of the entropy store
structure.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-10-10 14:32:18 -04:00
Theodore Ts'o 3ef4cb2d65 random: optimize spinlock use in add_device_randomness()
The add_device_randomness() function calls mix_pool_bytes() twice for
the input pool and the non-blocking pool, for a total of four times.
By using _mix_pool_byte() and taking the spinlock in
add_device_randomness(), we can halve the number of times we need
take each pool's spinlock.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-10-10 14:32:17 -04:00
Theodore Ts'o 5910895f0e random: fix the tracepoint for get_random_bytes(_arch)
Fix a problem where get_random_bytes_arch() was calling the tracepoint
get_random_bytes().  So add a new tracepoint for
get_random_bytes_arch(), and make get_random_bytes() and
get_random_bytes_arch() call their correct tracepoint.

Also, add a new tracepoint for add_device_randomness()

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-10-10 14:32:16 -04:00
H. Peter Anvin 30e37ec516 random: account for entropy loss due to overwrites
When we write entropy into a non-empty pool, we currently don't
account at all for the fact that we will probabilistically overwrite
some of the entropy in that pool.  This means that unless the pool is
fully empty, we are currently *guaranteed* to overestimate the amount
of entropy in the pool!

Assuming Shannon entropy with zero correlations we end up with an
exponentally decaying value of new entropy added:

	entropy <- entropy + (pool_size - entropy) *
		(1 - exp(-add_entropy/pool_size))

However, calculations involving fractional exponentials are not
practical in the kernel, so apply a piecewise linearization:

	  For add_entropy <= pool_size/2 then

	  (1 - exp(-add_entropy/pool_size)) >= (add_entropy/pool_size)*0.7869...

	  ... so we can approximate the exponential with
	  3/4*add_entropy/pool_size and still be on the
	  safe side by adding at most pool_size/2 at a time.

In order for the loop not to take arbitrary amounts of time if a bad
ioctl is received, terminate if we are within one bit of full.  This
way the loop is guaranteed to terminate after no more than
log2(poolsize) iterations, no matter what the input value is.  The
vast majority of the time the loop will be executed exactly once.

The piecewise linearization is very conservative, approaching 3/4 of
the usable input value for small inputs, however, our entropy
estimation is pretty weak at best, especially for small values; we
have no handle on correlation; and the Shannon entropy measure (Rényi
entropy of order 1) is not the correct one to use in the first place,
but rather the correct entropy measure is the min-entropy, the Rényi
entropy of infinite order.

As such, this conservatism seems more than justified.

This does introduce fractional bit values.  I have left it to have 3
bits of fraction, so that with a pool of 2^12 bits the multiply in
credit_entropy_bits() can still fit into an int, as 2*(3+12) < 31.  It
is definitely possible to allow for more fractional accounting, but
that multiply then would have to be turned into a 32*32 -> 64 multiply.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: DJ Johnston <dj.johnston@intel.com>
2013-10-10 14:32:15 -04:00
H. Peter Anvin a283b5c459 random: allow fractional bits to be tracked
Allow fractional bits of entropy to be tracked by scaling the entropy
counter (fixed point).  This will be used in a subsequent patch that
accounts for entropy lost due to overwrites.

[ Modified by tytso to fix up a few missing places where the
  entropy_count wasn't properly converted from fractional bits to
  bits. ]

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2013-10-10 14:32:14 -04:00
H. Peter Anvin 9ed17b70b4 random: statically compute poolbitshift, poolbytes, poolbits
Use a macro to statically compute poolbitshift (will be used in a
subsequent patch), poolbytes, and poolbits.  On virtually all
architectures the cost of a memory load with an offset is the same as
the one of a memory load.

It is still possible for this to generate worse code since the C
compiler doesn't know the fixed relationship between these fields, but
that is somewhat unlikely.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2013-10-10 14:32:13 -04:00
Theodore Ts'o 85a1f77716 random: mix in architectural randomness earlier in extract_buf()
Previously if CPU chip had a built-in random number generator (i.e.,
RDRAND on newer x86 chips), we mixed it in at the very end of
extract_buf() using an XOR operation.

We now mix it in right after the calculate a hash across the entire
pool.  This has the advantage that any contribution of entropy from
the CPU's HWRNG will get mixed back into the pool.  In addition, it
means that if the HWRNG has any defects (either accidentally or
maliciously introduced), this will be mitigated via the non-linear
transform of the SHA-1 hash function before we hand out generated
output.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-10-10 14:32:13 -04:00
Theodore Ts'o 61875f30da random: allow architectures to optionally define random_get_entropy()
Allow architectures which have a disabled get_cycles() function to
provide a random_get_entropy() function which provides a fine-grained,
rapidly changing counter that can be used by the /dev/random driver.

For example, an architecture might have a rapidly changing register
used to control random TLB cache eviction, or DRAM refresh that
doesn't meet the requirements of get_cycles(), but which is good
enough for the needs of the random driver.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
2013-10-10 14:30:53 -04:00
Theodore Ts'o 47d06e532e random: run random_int_secret_init() run after all late_initcalls
The some platforms (e.g., ARM) initializes their clocks as
late_initcalls for some unknown reason.  So make sure
random_int_secret_init() is run after all of the late_initcalls are
run.

Cc: stable@vger.kernel.org
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2013-09-23 06:35:06 -04:00
Martin Schwidefsky 0244ad004a Remove GENERIC_HARDIRQ config option
After the last architecture switched to generic hard irqs the config
options HAVE_GENERIC_HARDIRQS & GENERIC_HARDIRQS and the related code
for !CONFIG_GENERIC_HARDIRQS can be removed.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2013-09-13 15:09:52 +02:00
Joe Perches a151427ed0 char: Convert use of typedef ctl_table to struct ctl_table
This typedef is unnecessary and should just be removed.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-06-17 16:43:08 -07:00
Jiri Kosina 10b3a32d29 random: fix accounting race condition with lockless irq entropy_count update
Commit 902c098a36 ("random: use lockless techniques in the interrupt
path") turned IRQ path from being spinlock protected into lockless
cmpxchg-retry update.

That commit removed r->lock serialization between crediting entropy bits
from IRQ context and accounting when extracting entropy on userspace
read path, but didn't turn the r->entropy_count reads/updates in
account() to use cmpxchg as well.

It has been observed, that under certain circumstances this leads to
read() on /dev/urandom to return 0 (EOF), as r->entropy_count gets
corrupted and becomes negative, which in turn results in propagating 0
all the way from account() to the actual read() call.

Convert the accounting code to be the proper lockless counterpart of
what has been partially done by 902c098a36.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Greg KH <greg@kroah.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-24 16:22:52 -07:00
Jarod Wilson 1e7e2e05c1 drivers/char/random.c: fix priming of last_data
Commit ec8f02da9e ("random: prime last_data value per fips
requirements") added priming of last_data per fips requirements.

Unfortuantely, it did so in a way that can lead to multiple threads all
incrementing nbytes, but only one actually doing anything with the extra
data, which leads to some fun random corruption and panics.

The fix is to simply do everything needed to prime last_data in a single
shot, so there's no window for multiple cpus to increment nbytes -- in
fact, we won't even increment or decrement nbytes anymore, we'll just
extract the needed EXTRACT_SIZE one time per pool and then carry on with
the normal routine.

All these changes have been tested across multiple hosts and
architectures where panics were previously encoutered.  The code changes
are are strictly limited to areas only touched when when booted in fips
mode.

This change should also go into 3.8-stable, to make the myriads of fips
users on 3.8.x happy.

Signed-off-by: Jarod Wilson <jarod@redhat.com>
Tested-by: Jan Stancek <jstancek@redhat.com>
Tested-by: Jan Stodola <jstodola@redhat.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Matt Mackall <mpm@selenic.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-05-24 16:22:52 -07:00
Andy Shevchenko 16c7fa0582 lib/string_helpers: introduce generic string_unescape
There are several places in kernel where modules unescapes input to convert
C-Style Escape Sequences into byte codes.

The patch provides generic implementation of such approach. Test cases are
also included into the patch.

[akpm@linux-foundation.org: clarify comment]
[akpm@linux-foundation.org: export get_random_int() to modules]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: William Hubbs <w.d.hubbs@gmail.com>
Cc: Chris Brannon <chris@the-brannons.com>
Cc: Kirk Reiser <kirk@braille.uwo.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-04-30 17:04:03 -07:00
Linus Torvalds c77f8bf918 Fix a circular locking dependency in random's collection of cputime
used by a thread when it exits.
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Merge tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random

Pull random fixes from Ted Ts'o:
 "Fix a circular locking dependency in random's collection of cputime
  used by a thread when it exits."

* tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  random: fix locking dependency with the tasklist_lock
2013-03-08 14:42:16 -08:00
Theodore Ts'o b980955236 random: fix locking dependency with the tasklist_lock
Commit 6133705494 introduced a circular lock dependency because
posix_cpu_timers_exit() is called by release_task(), which is holding
a writer lock on tasklist_lock, and this can cause a deadlock since
kill_fasync() gets called with nonblocking_pool.lock taken.

There's no reason why kill_fasync() needs to be taken while the random
pool is locked, so move it out to fix this locking dependency.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reported-by: Russ Dill <Russ.Dill@gmail.com>
Cc: stable@kernel.org
2013-03-04 12:05:15 -05:00
Thomas Gleixner eece09ec21 locking: Various static lock initializer fixes
The static lock initializers want to be fed the proper name of the
lock and not some random string. In mainline random strings are
obfuscating the readability of debug output, but for RT they prevent
the spinlock substitution. Fix it up.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2013-02-19 08:42:45 +01:00
Jarod Wilson ec8f02da9e random: prime last_data value per fips requirements
The value stored in last_data must be primed for FIPS 140-2 purposes. Upon
first use, either on system startup or after an RNDCLEARPOOL ioctl, we
need to take an initial random sample, store it internally in last_data,
then pass along the value after that to the requester, so that consistency
checks aren't being run against stale and possibly known data.

CC: Herbert Xu <herbert@gondor.apana.org.au>
CC: "David S. Miller" <davem@davemloft.net>
CC: Matt Mackall <mpm@selenic.com>
CC: linux-crypto@vger.kernel.org
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2012-11-08 07:19:18 -05:00
Jiri Kosina 8eb2ffbf7b random: fix debug format strings
Fix the following warnings in formatting debug output:

drivers/char/random.c: In function ‘xfer_secondary_pool’:
drivers/char/random.c:827: warning: format ‘%d’ expects type ‘int’, but argument 7 has type ‘size_t’
drivers/char/random.c: In function ‘account’:
drivers/char/random.c:859: warning: format ‘%d’ expects type ‘int’, but argument 5 has type ‘size_t’
drivers/char/random.c:881: warning: format ‘%d’ expects type ‘int’, but argument 5 has type ‘size_t’
drivers/char/random.c: In function ‘random_read’:
drivers/char/random.c:1141: warning: format ‘%d’ expects type ‘int’, but argument 5 has type ‘ssize_t’
drivers/char/random.c:1145: warning: format ‘%d’ expects type ‘int’, but argument 5 has type ‘ssize_t’
drivers/char/random.c:1145: warning: format ‘%d’ expects type ‘int’, but argument 6 has type ‘long unsigned int’

by using '%zd' instead of '%d' to properly denote ssize_t/size_t conversion.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2012-11-08 07:12:20 -05:00
Jiri Kosina be5b779ae9 random: make it possible to enable debugging without rebuild
The module parameter that turns debugging mode (which basically means
printing a few extra lines during runtime) is in '#if 0' block. Forcing
everyone who would like to see how entropy is behaving on his system to
rebuild seems to be a little bit too harsh.

If we were concerned about speed, we could potentially turn 'debug' into a
static key, but I don't think it's necessary.

Drop the '#if 0' block to allow using the 'debug' parameter without rebuilding.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2012-10-15 23:24:39 -04:00
H. Peter Anvin d2e7c96af1 random: mix in architectural randomness in extract_buf()
Mix in any architectural randomness in extract_buf() instead of
xfer_secondary_buf().  This allows us to mix in more architectural
randomness, and it also makes xfer_secondary_buf() faster, moving a
tiny bit of additional CPU overhead to process which is extracting the
randomness.

[ Commit description modified by tytso to remove an extended
  advertisement for the RDRAND instruction. ]

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: DJ Johnston <dj.johnston@intel.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
2012-07-27 22:37:20 -04:00
Tony Luck cbc96b7594 random: Add comment to random_initialize()
Many platforms have per-machine instance data (serial numbers,
asset tags, etc.) squirreled away in areas that are accessed
during early system bringup. Mixing this data into the random
pools has a very high value in providing better random data,
so we should allow (and even encourage) architecture code to
call add_device_randomness() from the setup_arch() paths.

However, this limits our options for internal structure of
the random driver since random_initialize() is not called
until long after setup_arch().

Add a big fat comment to rand_initialize() spelling out
this requirement.

Suggested-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2012-07-24 13:16:41 -04:00
Theodore Ts'o c5857ccf29 random: remove rand_initialize_irq()
With the new interrupt sampling system, we are no longer using the
timer_rand_state structure in the irq descriptor, so we can stop
initializing it now.

[ Merged in fixes from Sedat to find some last missing references to
  rand_initialize_irq() ]

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Sedat Dilek <sedat.dilek@gmail.com>
2012-07-19 10:38:32 -04:00
Theodore Ts'o 00ce1db1a6 random: add tracepoints for easier debugging and verification
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2012-07-14 20:17:48 -04:00
Theodore Ts'o c2557a303a random: add new get_random_bytes_arch() function
Create a new function, get_random_bytes_arch() which will use the
architecture-specific hardware random number generator if it is
present.  Change get_random_bytes() to not use the HW RNG, even if it
is avaiable.

The reason for this is that the hw random number generator is fast (if
it is present), but it requires that we trust the hardware
manufacturer to have not put in a back door.  (For example, an
increasing counter encrypted by an AES key known to the NSA.)

It's unlikely that Intel (for example) was paid off by the US
Government to do this, but it's impossible for them to prove otherwise
--- especially since Bull Mountain is documented to use AES as a
whitener.  Hence, the output of an evil, trojan-horse version of
RDRAND is statistically indistinguishable from an RDRAND implemented
to the specifications claimed by Intel.  Short of using a tunnelling
electronic microscope to reverse engineer an Ivy Bridge chip and
disassembling and analyzing the CPU microcode, there's no way for us
to tell for sure.

Since users of get_random_bytes() in the Linux kernel need to be able
to support hardware systems where the HW RNG is not present, most
time-sensitive users of this interface have already created their own
cryptographic RNG interface which uses get_random_bytes() as a seed.
So it's much better to use the HW RNG to improve the existing random
number generator, by mixing in any entropy returned by the HW RNG into
/dev/random's entropy pool, but to always _use_ /dev/random's entropy
pool.

This way we get almost of the benefits of the HW RNG without any
potential liabilities.  The only benefits we forgo is the
speed/performance enhancements --- and generic kernel code can't
depend on depend on get_random_bytes() having the speed of a HW RNG
anyway.

For those places that really want access to the arch-specific HW RNG,
if it is available, we provide get_random_bytes_arch().

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
2012-07-14 20:17:47 -04:00
Theodore Ts'o e6d4947b12 random: use the arch-specific rng in xfer_secondary_pool
If the CPU supports a hardware random number generator, use it in
xfer_secondary_pool(), where it will significantly improve things and
where we can afford it.

Also, remove the use of the arch-specific rng in
add_timer_randomness(), since the call is significantly slower than
get_cycles(), and we're much better off using it in
xfer_secondary_pool() anyway.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
2012-07-14 20:17:46 -04:00
Linus Torvalds a2080a67ab random: create add_device_randomness() interface
Add a new interface, add_device_randomness() for adding data to the
random pool that is likely to differ between two devices (or possibly
even per boot).  This would be things like MAC addresses or serial
numbers, or the read-out of the RTC. This does *not* add any actual
entropy to the pool, but it initializes the pool to different values
for devices that might otherwise be identical and have very little
entropy available to them (particularly common in the embedded world).

[ Modified by tytso to mix in a timestamp, since there may be some
  variability caused by the time needed to detect/configure the hardware
  in question. ]

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
2012-07-14 20:17:44 -04:00
Theodore Ts'o 902c098a36 random: use lockless techniques in the interrupt path
The real-time Linux folks don't like add_interrupt_randomness() taking
a spinlock since it is called in the low-level interrupt routine.
This also allows us to reduce the overhead in the fast path, for the
random driver, which is the interrupt collection path.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
2012-07-14 20:17:43 -04:00
Theodore Ts'o 775f4b297b random: make 'add_interrupt_randomness()' do something sane
We've been moving away from add_interrupt_randomness() for various
reasons: it's too expensive to do on every interrupt, and flooding the
CPU with interrupts could theoretically cause bogus floods of entropy
from a somewhat externally controllable source.

This solves both problems by limiting the actual randomness addition
to just once a second or after 64 interrupts, whicever comes first.
During that time, the interrupt cycle data is buffered up in a per-cpu
pool.  Also, we make sure the the nonblocking pool used by urandom is
initialized before we start feeding the normal input pool.  This
assures that /dev/urandom is returning unpredictable data as soon as
possible.

(Based on an original patch by Linus, but significantly modified by
tytso.)

Tested-by: Eric Wustrow <ewust@umich.edu>
Reported-by: Eric Wustrow <ewust@umich.edu>
Reported-by: Nadia Heninger <nadiah@cs.ucsd.edu>
Reported-by: Zakir Durumeric <zakir@umich.edu>
Reported-by: J. Alex Halderman <jhalderm@umich.edu>.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
2012-07-14 20:17:28 -04:00
Theodore Ts'o 74feec5dd8 random: fix up sparse warnings
Add extern and static declarations to suppress sparse warnings

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2012-07-06 14:13:25 -04:00
Mathieu Desnoyers 44e4360fa3 drivers/char/random.c: fix boot id uniqueness race
/proc/sys/kernel/random/boot_id can be read concurrently by userspace
processes.  If two (or more) user-space processes concurrently read
boot_id when sysctl_bootid is not yet assigned, a race can occur making
boot_id differ between the reads.  Because the whole point of the boot id
is to be unique across a kernel execution, fix this by protecting this
operation with a spinlock.

Given that this operation is not frequently used, hitting the spinlock
on each call should not be an issue.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-04-12 13:12:12 -07:00
Linus Torvalds c2bc3a316a Merge branch 'x86/rdrand' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
* 'x86/rdrand' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  random: Adjust the number of loops when initializing
  random: Use arch-specific RNG to initialize the entropy store
2012-01-16 18:23:09 -08:00
H. Peter Anvin 2dac8e54f9 random: Adjust the number of loops when initializing
When we are initializing using arch_get_random_long() we only need to
loop enough times to touch all the bytes in the buffer; using
poolwords for that does twice the number of operations necessary on a
64-bit machine, since in the random number generator code "word" means
32 bits.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Link: http://lkml.kernel.org/r/1324589281-31931-1-git-send-email-tytso@mit.edu
2012-01-16 11:33:49 -08:00
Theodore Ts'o 3e88bdff1c random: Use arch-specific RNG to initialize the entropy store
If there is an architecture-specific random number generator (such as
RDRAND for Intel architectures), use it to initialize /dev/random's
entropy stores.  Even in the worst case, if RDRAND is something like
AES(NSA_KEY, counter++), it won't hurt, and it will definitely help
against any other adversaries.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Link: http://lkml.kernel.org/r/1324589281-31931-1-git-send-email-tytso@mit.edu
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2012-01-16 11:18:21 -08:00
Rusty Russell 90ab5ee941 module_param: make bool parameters really bool (drivers & misc)
module_param(bool) used to counter-intuitively take an int.  In
fddd5201 (mid-2009) we allowed bool or int/unsigned int using a messy
trick.

It's time to remove the int/unsigned int option.  For this version
it'll simply give a warning, but it'll break next kernel version.

Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2012-01-13 09:32:20 +10:30
Linus Torvalds cf833d0b99 random: Use arch_get_random_int instead of cycle counter if avail
We still don't use rdrand in /dev/random, which just seems stupid. We
accept the *cycle*counter* as a random input, but we don't accept
rdrand? That's just broken.

Sure, people can do things in user space (write to /dev/random, use
rdrand in addition to /dev/random themselves etc etc), but that
*still* seems to be a particularly stupid reason for saying "we
shouldn't bother to try to do better in /dev/random".

And even if somebody really doesn't trust rdrand as a source of random
bytes, it seems singularly stupid to trust the cycle counter *more*.

So I'd suggest the attached patch. I'm not going to even bother
arguing that we should add more bits to the entropy estimate, because
that's not the point - I don't care if /dev/random fills up slowly or
not, I think it's just stupid to not use the bits we can get from
rdrand and mix them into the strong randomness pool.

Link: http://lkml.kernel.org/r/CA%2B55aFwn59N1=m651QAyTy-1gO1noGbK18zwKDwvwqnravA84A@mail.gmail.com
Acked-by: "David S. Miller" <davem@davemloft.net>
Acked-by: "Theodore Ts'o" <tytso@mit.edu>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2011-12-29 16:49:45 -08:00