8f30dde5fe
which juxtaposes nicely with the comment just above on how the harvest function must be cheap.
136 lines
4.0 KiB
C
136 lines
4.0 KiB
C
/*-
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* Copyright (c) 2000-2004 Mark R V Murray
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer
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* in this position and unchanged.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/kthread.h>
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/mutex.h>
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#include <sys/poll.h>
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#include <sys/queue.h>
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#include <sys/random.h>
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#include <sys/selinfo.h>
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#include <sys/systm.h>
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#include <sys/sysctl.h>
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#include <machine/cpu.h>
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#include <dev/random/randomdev_soft.h>
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static int read_random_phony(void *, int);
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/* Structure holding the desired entropy sources */
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struct harvest_select harvest = { 1, 1, 1, 0 };
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/* hold the address of the routine which is actually called if
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* the randomdev is loaded
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*/
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static void (*reap_func)(u_int64_t, const void *, u_int, u_int, u_int,
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enum esource) = NULL;
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static int (*read_func)(void *, int) = read_random_phony;
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/* Initialise the harvester at load time */
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void
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random_yarrow_init_harvester(void (*reaper)(u_int64_t, const void *, u_int,
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u_int, u_int, enum esource), int (*reader)(void *, int))
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{
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reap_func = reaper;
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read_func = reader;
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}
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/* Deinitialise the harvester at unload time */
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void
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random_yarrow_deinit_harvester(void)
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{
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reap_func = NULL;
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read_func = read_random_phony;
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}
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/* Entropy harvesting routine. This is supposed to be fast; do
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* not do anything slow in here!
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* Implemented as in indirect call to allow non-inclusion of
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* the entropy device.
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*
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* XXXRW: get_cyclecount() is cheap on most modern hardware, where cycle
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* counters are built in, but on older hardware it will do a real time clock
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* read which can be quite expensive.
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*/
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void
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random_harvest(void *entropy, u_int count, u_int bits, u_int frac,
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enum esource origin)
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{
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if (reap_func)
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(*reap_func)(get_cyclecount(), entropy, count, bits, frac,
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origin);
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}
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/* Userland-visible version of read_random */
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int
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read_random(void *buf, int count)
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{
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return ((*read_func)(buf, count));
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}
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/* If the entropy device is not loaded, make a token effort to
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* provide _some_ kind of randomness. This should only be used
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* inside other RNG's, like arc4random(9).
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*/
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static int
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read_random_phony(void *buf, int count)
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{
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u_long randval;
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int size, i;
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/* srandom() is called in kern/init_main.c:proc0_post() */
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/* Fill buf[] with random(9) output */
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for (i = 0; i < count; i+= (int)sizeof(u_long)) {
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randval = random();
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size = MIN(count - i, sizeof(u_long));
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memcpy(&((char *)buf)[i], &randval, (size_t)size);
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}
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return (count);
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}
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/* Helper routine to enable kthread_exit() to work while the module is
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* being (or has been) unloaded.
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* This routine is in this file because it is always linked into the kernel,
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* and will thus never be unloaded. This is critical for unloadable modules
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* that have threads.
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*/
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void
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random_set_wakeup_exit(void *control)
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{
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wakeup(control);
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kthread_exit(0);
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/* NOTREACHED */
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}
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