NetBSD/sys/dev/rnd.c

/*	$NetBSD: rnd.c,v 1.86 2011/11/23 10:47:48 tls Exp $	*/

/*-
 * Copyright (c) 1997-2011 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Michael Graff <explorer@flame.org> and Thor Lancelot Simon.
 * This code uses ideas and algorithms from the Linux driver written by
 * Ted Ts'o.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: rnd.c,v 1.86 2011/11/23 10:47:48 tls Exp $");

#include <sys/param.h>
#include <sys/ioctl.h>
#include <sys/fcntl.h>
#include <sys/select.h>
#include <sys/poll.h>
#include <sys/kmem.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/systm.h>
#include <sys/callout.h>
#include <sys/rnd.h>
#include <sys/vnode.h>
#include <sys/pool.h>
#include <sys/kauth.h>
#include <sys/once.h>
#include <sys/rngtest.h>
#include <sys/cpu.h>	/* XXX temporary, see rnd_detach_source */

#if defined(__HAVE_CPU_COUNTER) && !defined(_RUMPKERNEL) /* XXX: bad pooka */
#include <machine/cpu_counter.h>
#endif

#ifdef RND_DEBUG
#define	DPRINTF(l,x)      if (rnd_debug & (l)) printf x
int	rnd_debug = 0;
#else
#define	DPRINTF(l,x)
#endif

#define	RND_DEBUG_WRITE		0x0001
#define	RND_DEBUG_READ		0x0002
#define	RND_DEBUG_IOCTL		0x0004
#define	RND_DEBUG_SNOOZE	0x0008

/*
 * list devices attached
 */
#if 0
#define	RND_VERBOSE
#endif

/*
 * The size of a temporary buffer, kmem_alloc()ed when needed, and used for
 * reading and writing data.
 */
#define	RND_TEMP_BUFFER_SIZE	128

/*
 * This is a little bit of state information attached to each device that we
 * collect entropy from.  This is simply a collection buffer, and when it
 * is full it will be "detached" from the source and added to the entropy
 * pool after entropy is distilled as much as possible.
 */
#define	RND_SAMPLE_COUNT	64	/* collect N samples, then compress */
typedef struct _rnd_sample_t {
	SIMPLEQ_ENTRY(_rnd_sample_t) next;
	krndsource_t	*source;
	int		cursor;
	int		entropy;
	u_int32_t	ts[RND_SAMPLE_COUNT];
	u_int32_t	values[RND_SAMPLE_COUNT];
} rnd_sample_t;

/*
 * The event queue.  Fields are altered at an interrupt level.
 * All accesses must be protected with the mutex.
 */
volatile int			rnd_timeout_pending;
SIMPLEQ_HEAD(, _rnd_sample_t)	rnd_samples;
kmutex_t			rnd_mtx;

/*
 * Entropy sinks: usually other generators waiting to be rekeyed.
 *
 * A sink's callback MUST NOT re-add the sink to the list, or
 * list corruption will occur.
 */
TAILQ_HEAD(, rndsink)		rnd_sinks;

/*
 * our select/poll queue
 */
struct selinfo rnd_selq;

/*
 * Memory pool for sample buffers
 */
static struct pool rnd_mempool;

/*
 * Our random pool.  This is defined here rather than using the general
 * purpose one defined in rndpool.c.
 *
 * Samples are collected and queued into a separate mutex-protected queue
 * (rnd_samples, see above), and processed in a timeout routine; therefore,
 * the mutex protecting the random pool is at IPL_SOFTCLOCK() as well.
 */
rndpool_t rnd_pool;
kmutex_t  rndpool_mtx;
kcondvar_t rndpool_cv;

/*
 * This source is used to easily "remove" queue entries when the source
 * which actually generated the events is going away.
 */
static krndsource_t rnd_source_no_collect = {
	/* LIST_ENTRY list */
	.name = { 'N', 'o', 'C', 'o', 'l', 'l', 'e', 'c', 't',
		   0, 0, 0, 0, 0, 0, 0 },
	.last_time = 0, .last_delta = 0, .last_delta2 = 0, .total = 0,
	.type = RND_TYPE_UNKNOWN,
	.flags = (RND_FLAG_NO_COLLECT |
		  RND_FLAG_NO_ESTIMATE |
		  RND_TYPE_UNKNOWN),
	.state = NULL,
	.test_cnt = 0,
	.test = NULL
};

struct callout rnd_callout;

void	rndattach(int);

dev_type_open(rndopen);
dev_type_read(rndread);
dev_type_write(rndwrite);
dev_type_ioctl(rndioctl);
dev_type_poll(rndpoll);
dev_type_kqfilter(rndkqfilter);

const struct cdevsw rnd_cdevsw = {
	rndopen, nullclose, rndread, rndwrite, rndioctl,
	nostop, notty, rndpoll, nommap, rndkqfilter, D_OTHER|D_MPSAFE,
};

static inline void	rnd_wakeup_readers(void);
static inline u_int32_t rnd_estimate_entropy(krndsource_t *, u_int32_t);
static inline u_int32_t rnd_counter(void);
static        void	rnd_timeout(void *);
static	      void	rnd_process_events(void *);
static u_int32_t	rnd_extract_data_locked(void *, u_int32_t, u_int32_t);

static int		rnd_ready = 0;
static int		rnd_have_entropy = 0;
static int		rnd_tested = 0;

LIST_HEAD(, krndsource)	rnd_sources;

/*
 * Generate a 32-bit counter.  This should be more machine dependent,
 * using cycle counters and the like when possible.
 */
static inline u_int32_t
rnd_counter(void)
{
	struct timeval tv;

#if defined(__HAVE_CPU_COUNTER) && !defined(_RUMPKERNEL) /* XXX: bad pooka */
	if (cpu_hascounter())
		return (cpu_counter32());
#endif
	if (rnd_ready) {
		microtime(&tv);
		return (tv.tv_sec * 1000000 + tv.tv_usec);
	}
	/* when called from rnd_init, its too early to call microtime safely */
	return (0);
}

/*
 * Check to see if there are readers waiting on us.  If so, kick them.
 */
static inline void
rnd_wakeup_readers(void)
{
	rndsink_t *sink, *tsink;
	TAILQ_HEAD(, rndsink) sunk = TAILQ_HEAD_INITIALIZER(sunk);

	mutex_spin_enter(&rndpool_mtx);
	if (rndpool_get_entropy_count(&rnd_pool) < RND_ENTROPY_THRESHOLD * 8) {
		mutex_spin_exit(&rndpool_mtx);
		return;
	}

	/*
	 * First, take care of in-kernel consumers needing rekeying.
	 */
	TAILQ_FOREACH_SAFE(sink, &rnd_sinks, tailq, tsink) {
		if ((sink->len + RND_ENTROPY_THRESHOLD) * 8 <
			rndpool_get_entropy_count(&rnd_pool)) {
			/* We have enough entropy to sink some here. */
			if (rndpool_extract_data(&rnd_pool, sink->data,
						 sink->len, RND_EXTRACT_GOOD)
			    != sink->len) {
				panic("could not extract estimated "
				      "entropy from pool");
			}
			/* Move this sink to the list of pending callbacks */
			TAILQ_REMOVE(&rnd_sinks, sink, tailq);
			TAILQ_INSERT_HEAD(&sunk, sink, tailq);
		}
	}
		
	/*
	 * If we still have enough new bits to do something, feed userspace.
	 */
	if (rndpool_get_entropy_count(&rnd_pool) > RND_ENTROPY_THRESHOLD * 8) {
#ifdef RND_VERBOSE
		if (!rnd_have_entropy)
			printf("rnd: have initial entropy (%u)\n",
			       rndpool_get_entropy_count(&rnd_pool));
#endif
		rnd_have_entropy = 1;
		cv_broadcast(&rndpool_cv);
		mutex_spin_exit(&rndpool_mtx);
		selnotify(&rnd_selq, 0, 0);
	} else {
		mutex_spin_exit(&rndpool_mtx);
	}

	/*
	 * Now that we have dropped the mutex, we can run sinks' callbacks.
	 * Since we have reused the "tailq" member of the sink structure for
	 * this temporary on-stack queue, the callback must NEVER re-add
	 * the sink to the main queue, or our on-stack queue will become
	 * corrupt.
	 */
	while ((sink = TAILQ_FIRST(&sunk))) {
#ifdef RND_VERBOSE
		printf("supplying %d bytes to entropy sink \"%s\""
		       " (cb %p, arg %p).\n",
		       (int)sink->len, sink->name, sink->cb, sink->arg);
#endif
		sink->cb(sink->arg);
		TAILQ_REMOVE(&sunk, sink, tailq);
	}
}

/*
 * Use the timing of the event to estimate the entropy gathered.
 * If all the differentials (first, second, and third) are non-zero, return
 * non-zero.  If any of these are zero, return zero.
 */
static inline u_int32_t
rnd_estimate_entropy(krndsource_t *rs, u_int32_t t)
{
	int32_t delta, delta2, delta3;

	/*
	 * If the time counter has overflowed, calculate the real difference.
	 * If it has not, it is simplier.
	 */
	if (t < rs->last_time)
		delta = UINT_MAX - rs->last_time + t;
	else
		delta = rs->last_time - t;

	if (delta < 0)
		delta = -delta;

	/*
	 * Calculate the second and third order differentials
	 */
	delta2 = rs->last_delta - delta;
	if (delta2 < 0)
		delta2 = -delta2;

	delta3 = rs->last_delta2 - delta2;
	if (delta3 < 0)
		delta3 = -delta3;

	rs->last_time = t;
	rs->last_delta = delta;
	rs->last_delta2 = delta2;

	/*
	 * If any delta is 0, we got no entropy.  If all are non-zero, we
	 * might have something.
	 */
	if (delta == 0 || delta2 == 0 || delta3 == 0)
		return (0);

	return (1);
}

static int
rnd_mempool_init(void)
{

	pool_init(&rnd_mempool, sizeof(rnd_sample_t), 0, 0, 0, "rndsample",
	    NULL, IPL_VM);
	return 0;
}
static ONCE_DECL(rnd_mempoolinit_ctrl);

/*
 * "Attach" the random device. This is an (almost) empty stub, since
 * pseudo-devices don't get attached until after config, after the
 * entropy sources will attach. We just use the timing of this event
 * as another potential source of initial entropy.
 */
void
rndattach(int num)
{
	u_int32_t c;

	RUN_ONCE(&rnd_mempoolinit_ctrl, rnd_mempool_init);

	/* Trap unwary players who don't call rnd_init() early */
	KASSERT(rnd_ready);

	/* mix in another counter */
	c = rnd_counter();
	mutex_spin_enter(&rndpool_mtx);
	rndpool_add_data(&rnd_pool, &c, sizeof(u_int32_t), 1);
	mutex_spin_exit(&rndpool_mtx);
}

/*
 * initialize the global random pool for our use.
 * rnd_init() must be called very early on in the boot process, so
 * the pool is ready for other devices to attach as sources.
 */
void
rnd_init(void)
{
	u_int32_t c;

	if (rnd_ready)
		return;

	mutex_init(&rnd_mtx, MUTEX_DEFAULT, IPL_VM);

	callout_init(&rnd_callout, CALLOUT_MPSAFE);
	callout_setfunc(&rnd_callout, rnd_timeout, NULL);

	/*
	 * take a counter early, hoping that there's some variance in
	 * the following operations
	 */
	c = rnd_counter();

	LIST_INIT(&rnd_sources);
	SIMPLEQ_INIT(&rnd_samples);
	TAILQ_INIT(&rnd_sinks);
	selinit(&rnd_selq);

	rndpool_init(&rnd_pool);
	mutex_init(&rndpool_mtx, MUTEX_DEFAULT, IPL_VM);
	cv_init(&rndpool_cv, "rndread");

	/* Mix *something*, *anything* into the pool to help it get started.
	 * However, it's not safe for rnd_counter() to call microtime() yet,
	 * so on some platforms we might just end up with zeros anyway.
	 * XXX more things to add would be nice.
	 */
	if (c) {
		mutex_spin_enter(&rndpool_mtx);
		rndpool_add_data(&rnd_pool, &c, sizeof(c), 1);
		c = rnd_counter();
		rndpool_add_data(&rnd_pool, &c, sizeof(c), 1);
		mutex_spin_exit(&rndpool_mtx);
	}

	rnd_ready = 1;

#ifdef RND_VERBOSE
	printf("rnd: initialised (%u)%s", RND_POOLBITS,
	       c ? " with counter\n" : "\n");
#endif
}

int
rndopen(dev_t dev, int flags, int ifmt,
    struct lwp *l)
{

	if (rnd_ready == 0)
		return (ENXIO);

	if (minor(dev) == RND_DEV_URANDOM || minor(dev) == RND_DEV_RANDOM)
		return (0);

	return (ENXIO);
}

int
rndread(dev_t dev, struct uio *uio, int ioflag)
{
	u_int8_t *bf;
	u_int32_t entcnt, mode, n, nread;
	int ret;

	DPRINTF(RND_DEBUG_READ,
	    ("Random:  Read of %zu requested, flags 0x%08x\n",
	    uio->uio_resid, ioflag));

	if (uio->uio_resid == 0)
		return (0);

	switch (minor(dev)) {
	case RND_DEV_RANDOM:
		mode = RND_EXTRACT_GOOD;
		break;
	case RND_DEV_URANDOM:
		mode = RND_EXTRACT_ANY;
		break;
	default:
		/* Can't happen, but this is cheap */
		return (ENXIO);
	}

	ret = 0;
	bf = kmem_alloc(RND_TEMP_BUFFER_SIZE, KM_SLEEP);
	while (uio->uio_resid > 0) {
		n = min(RND_TEMP_BUFFER_SIZE, uio->uio_resid);

		/*
		 * Make certain there is data available.  If there
		 * is, do the I/O even if it is partial.  If not,
		 * sleep unless the user has requested non-blocking
		 * I/O.
		 *
		 * If not requesting strong randomness, we can always read.
		 */
		mutex_spin_enter(&rndpool_mtx);
		if (mode != RND_EXTRACT_ANY) {
			for (;;) {
				/*
				 * How much entropy do we have?
				 * If it is enough for one hash, we can read.
				 */
				entcnt = rndpool_get_entropy_count(&rnd_pool);
				if (entcnt >= RND_ENTROPY_THRESHOLD * 8)
					break;

				/*
				 * Data is not available.
				 */
				if (ioflag & IO_NDELAY) {
					mutex_spin_exit(&rndpool_mtx);
					ret = EWOULDBLOCK;
					goto out;
				}
				ret = cv_wait_sig(&rndpool_cv, &rndpool_mtx);
				if (ret) {
					mutex_spin_exit(&rndpool_mtx);
					goto out;
				}
			}
		}
		nread = rnd_extract_data_locked(bf, n, mode);
		mutex_spin_exit(&rndpool_mtx);

		/*
		 * Copy (possibly partial) data to the user.
		 * If an error occurs, or this is a partial
		 * read, bail out.
		 */
		ret = uiomove((void *)bf, nread, uio);
		if (ret != 0 || nread != n)
			goto out;
	}

out:
	kmem_free(bf, RND_TEMP_BUFFER_SIZE);
	return (ret);
}

int
rndwrite(dev_t dev, struct uio *uio, int ioflag)
{
	u_int8_t *bf;
	int n, ret = 0, estimate_ok = 0, estimate = 0, added = 0;

	ret = kauth_authorize_device(curlwp->l_cred,
	    KAUTH_DEVICE_RND_ADDDATA, NULL, NULL, NULL, NULL);
	if (ret) {
		return (ret);
	}
	estimate_ok = !kauth_authorize_device(curlwp->l_cred,
	    KAUTH_DEVICE_RND_ADDDATA_ESTIMATE, NULL, NULL, NULL, NULL);

	DPRINTF(RND_DEBUG_WRITE,
	    ("Random: Write of %zu requested\n", uio->uio_resid));

	if (uio->uio_resid == 0)
		return (0);
	ret = 0;
	bf = kmem_alloc(RND_TEMP_BUFFER_SIZE, KM_SLEEP);
	while (uio->uio_resid > 0) {
		/*
		 * Don't flood the pool.
		 */
		if (added > RND_POOLWORDS * sizeof(int)) {
			printf("rnd: added %d already, adding no more.\n",
			       added);
			break;
		}
		n = min(RND_TEMP_BUFFER_SIZE, uio->uio_resid);

		ret = uiomove((void *)bf, n, uio);
		if (ret != 0)
			break;

		if (estimate_ok) {
			/*
			 * Don't cause samples to be discarded by taking
			 * the pool's entropy estimate to the max.
			 */
			if (added > RND_POOLWORDS / 2)
				estimate = 0;
			else
				estimate = n * NBBY / 2;
			printf("rnd: adding on write, %d bytes, estimate %d\n",
			       n, estimate);
		} else {
			printf("rnd: kauth says no entropy.\n");
		}

		/*
		 * Mix in the bytes.
		 */
		mutex_spin_enter(&rndpool_mtx);
		rndpool_add_data(&rnd_pool, bf, n, estimate);
		mutex_spin_exit(&rndpool_mtx);

		added += n;
		DPRINTF(RND_DEBUG_WRITE, ("Random: Copied in %d bytes\n", n));
	}
	kmem_free(bf, RND_TEMP_BUFFER_SIZE);
	return (ret);
}

static void
krndsource_to_rndsource(krndsource_t *kr, rndsource_t *r)
{
	memset(r, 0, sizeof(*r));
	strlcpy(r->name, kr->name, sizeof(r->name));
        r->total = kr->total;
        r->type = kr->type;
        r->flags = kr->flags;
}

int
rndioctl(dev_t dev, u_long cmd, void *addr, int flag,
    struct lwp *l)
{
	krndsource_t *kr;
	rndstat_t *rst;
	rndstat_name_t *rstnm;
	rndctl_t *rctl;
	rnddata_t *rnddata;
	u_int32_t count, start;
	int ret = 0;
	int estimate_ok = 0, estimate = 0;

	switch (cmd) {
	case FIONBIO:
	case FIOASYNC:
	case RNDGETENTCNT:
		break;

	case RNDGETPOOLSTAT:
	case RNDGETSRCNUM:
	case RNDGETSRCNAME:
		ret = kauth_authorize_device(l->l_cred,
		    KAUTH_DEVICE_RND_GETPRIV, NULL, NULL, NULL, NULL);
		if (ret)
			return (ret);
		break;

	case RNDCTL:
		ret = kauth_authorize_device(l->l_cred,
		    KAUTH_DEVICE_RND_SETPRIV, NULL, NULL, NULL, NULL);
		if (ret)
			return (ret);
		break;

	case RNDADDDATA:
		ret = kauth_authorize_device(l->l_cred,
		    KAUTH_DEVICE_RND_ADDDATA, NULL, NULL, NULL, NULL);
		if (ret)
			return (ret);
		estimate_ok = !kauth_authorize_device(l->l_cred,
		    KAUTH_DEVICE_RND_ADDDATA_ESTIMATE, NULL, NULL, NULL, NULL);
		break;

	default:
		return (EINVAL);
	}

	switch (cmd) {

	/*
	 * Handled in upper layer really, but we have to return zero
	 * for it to be accepted by the upper layer.
	 */
	case FIONBIO:
	case FIOASYNC:
		break;

	case RNDGETENTCNT:
		mutex_spin_enter(&rndpool_mtx);
		*(u_int32_t *)addr = rndpool_get_entropy_count(&rnd_pool);
		mutex_spin_exit(&rndpool_mtx);
		break;

	case RNDGETPOOLSTAT:
		mutex_spin_enter(&rndpool_mtx);
		rndpool_get_stats(&rnd_pool, addr, sizeof(rndpoolstat_t));
		mutex_spin_exit(&rndpool_mtx);
		break;

	case RNDGETSRCNUM:
		rst = (rndstat_t *)addr;

		if (rst->count == 0)
			break;

		if (rst->count > RND_MAXSTATCOUNT)
			return (EINVAL);

		/*
		 * Find the starting source by running through the
		 * list of sources.
		 */
		kr = rnd_sources.lh_first;
		start = rst->start;
		while (kr != NULL && start >= 1) {
			kr = kr->list.le_next;
			start--;
		}

		/*
		 * Return up to as many structures as the user asked
		 * for.  If we run out of sources, a count of zero
		 * will be returned, without an error.
		 */
		for (count = 0; count < rst->count && kr != NULL; count++) {
			krndsource_to_rndsource(kr, &rst->source[count]);
			kr = kr->list.le_next;
		}

		rst->count = count;

		break;

	case RNDGETSRCNAME:
		/*
		 * Scan through the list, trying to find the name.
		 */
		rstnm = (rndstat_name_t *)addr;
		kr = rnd_sources.lh_first;
		while (kr != NULL) {
			if (strncmp(kr->name, rstnm->name,
				    MIN(sizeof(kr->name),
					sizeof(*rstnm))) == 0) {
				krndsource_to_rndsource(kr, &rstnm->source);
				return (0);
			}
			kr = kr->list.le_next;
		}

		ret = ENOENT;		/* name not found */

		break;

	case RNDCTL:
		/*
		 * Set flags to enable/disable entropy counting and/or
		 * collection.
		 */
		rctl = (rndctl_t *)addr;
		kr = rnd_sources.lh_first;

		/*
		 * Flags set apply to all sources of this type.
		 */
		if (rctl->type != 0xff) {
			while (kr != NULL) {
				if (kr->type == rctl->type) {
					kr->flags &= ~rctl->mask;
					kr->flags |=
					    (rctl->flags & rctl->mask);
				}
				kr = kr->list.le_next;
			}

			return (0);
		}

		/*
		 * scan through the list, trying to find the name
		 */
		while (kr != NULL) {
			if (strncmp(kr->name, rctl->name,
				    MIN(sizeof(kr->name),
                                        sizeof(rctl->name))) == 0) {
				kr->flags &= ~rctl->mask;
				kr->flags |= (rctl->flags & rctl->mask);

				return (0);
			}
			kr = kr->list.le_next;
		}

		ret = ENOENT;		/* name not found */

		break;

	case RNDADDDATA:
		rnddata = (rnddata_t *)addr;

		if (rnddata->len > sizeof(rnddata->data))
			return EINVAL;

		if (estimate_ok) {
			/*
			 * Do not accept absurd entropy estimates, and
			 * do not flood the pool with entropy such that
			 * new samples are discarded henceforth.
			 */
			estimate = MIN((rnddata->len * NBBY) / 2,
				       MIN(rnddata->entropy,
					   RND_POOLWORDS * sizeof(int) *
					   NBBY / 2));
		} else {
			estimate = 0;
		}

		mutex_spin_enter(&rndpool_mtx);
		rndpool_add_data(&rnd_pool, rnddata->data, rnddata->len,
				 estimate);
		mutex_spin_exit(&rndpool_mtx);

		rnd_wakeup_readers();

		break;

	default:
		return (EINVAL);
	}

	return (ret);
}

int
rndpoll(dev_t dev, int events, struct lwp *l)
{
	u_int32_t entcnt;
	int revents;

	/*
	 * We are always writable.
	 */
	revents = events & (POLLOUT | POLLWRNORM);

	/*
	 * Save some work if not checking for reads.
	 */
	if ((events & (POLLIN | POLLRDNORM)) == 0)
		return (revents);

	/*
	 * If the minor device is not /dev/random, we are always readable.
	 */
	if (minor(dev) != RND_DEV_RANDOM) {
		revents |= events & (POLLIN | POLLRDNORM);
		return (revents);
	}

	/*
	 * Make certain we have enough entropy to be readable.
	 */
	mutex_spin_enter(&rndpool_mtx);
	entcnt = rndpool_get_entropy_count(&rnd_pool);
	mutex_spin_exit(&rndpool_mtx);
	if (entcnt >= RND_ENTROPY_THRESHOLD * 8)
		revents |= events & (POLLIN | POLLRDNORM);
	else
		selrecord(l, &rnd_selq);

	return (revents);
}

static void
filt_rnddetach(struct knote *kn)
{
	mutex_spin_enter(&rndpool_mtx);
	SLIST_REMOVE(&rnd_selq.sel_klist, kn, knote, kn_selnext);
	mutex_spin_exit(&rndpool_mtx);
}

static int
filt_rndread(struct knote *kn, long hint)
{
	uint32_t entcnt;

	mutex_spin_enter(&rndpool_mtx);
	entcnt = rndpool_get_entropy_count(&rnd_pool);
	mutex_spin_exit(&rndpool_mtx);
	if (entcnt >= RND_ENTROPY_THRESHOLD * 8) {
		kn->kn_data = RND_TEMP_BUFFER_SIZE;
		return (1);
	}
	return (0);
}

static const struct filterops rnd_seltrue_filtops =
	{ 1, NULL, filt_rnddetach, filt_seltrue };

static const struct filterops rndread_filtops =
	{ 1, NULL, filt_rnddetach, filt_rndread };

int
rndkqfilter(dev_t dev, struct knote *kn)
{
	struct klist *klist;

	switch (kn->kn_filter) {
	case EVFILT_READ:
		klist = &rnd_selq.sel_klist;
		if (minor(dev) == RND_DEV_URANDOM)
			kn->kn_fop = &rnd_seltrue_filtops;
		else
			kn->kn_fop = &rndread_filtops;
		break;

	case EVFILT_WRITE:
		klist = &rnd_selq.sel_klist;
		kn->kn_fop = &rnd_seltrue_filtops;
		break;

	default:
		return (EINVAL);
	}

	kn->kn_hook = NULL;

	mutex_spin_enter(&rndpool_mtx);
	SLIST_INSERT_HEAD(klist, kn, kn_selnext);
	mutex_spin_exit(&rndpool_mtx);

	return (0);
}

static rnd_sample_t *
rnd_sample_allocate(krndsource_t *source)
{
	rnd_sample_t *c;

	c = pool_get(&rnd_mempool, PR_WAITOK);
	if (c == NULL)
		return (NULL);

	c->source = source;
	c->cursor = 0;
	c->entropy = 0;

	return (c);
}

/*
 * Don't wait on allocation.  To be used in an interrupt context.
 */
static rnd_sample_t *
rnd_sample_allocate_isr(krndsource_t *source)
{
	rnd_sample_t *c;

	c = pool_get(&rnd_mempool, PR_NOWAIT);
	if (c == NULL)
		return (NULL);

	c->source = source;
	c->cursor = 0;
	c->entropy = 0;

	return (c);
}

static void
rnd_sample_free(rnd_sample_t *c)
{
	memset(c, 0, sizeof(*c));
	pool_put(&rnd_mempool, c);
}

/*
 * Add a source to our list of sources.
 */
void
rnd_attach_source(krndsource_t *rs, const char *name, u_int32_t type,
    u_int32_t flags)
{
	u_int32_t ts;

	RUN_ONCE(&rnd_mempoolinit_ctrl, rnd_mempool_init);

	ts = rnd_counter();

	strlcpy(rs->name, name, sizeof(rs->name));
	rs->last_time = ts;
	rs->last_delta = 0;
	rs->last_delta2 = 0;
	rs->total = 0;

	/*
	 * Force network devices to not collect any entropy by
	 * default.
	 */
	if (type == RND_TYPE_NET)
		flags |= (RND_FLAG_NO_COLLECT | RND_FLAG_NO_ESTIMATE);

	/*
 	 * Hardware RNGs get extra space for statistical testing.
	 */
	if (type == RND_TYPE_RNG) {
		rs->test = kmem_alloc(sizeof(rngtest_t), KM_NOSLEEP);
		rs->test_cnt = 0;
	} else {
		rs->test = NULL;
		rs->test_cnt = -1;
	}

	rs->type = type;
	rs->flags = flags;

	rs->state = rnd_sample_allocate(rs);

	mutex_spin_enter(&rndpool_mtx);
	LIST_INSERT_HEAD(&rnd_sources, rs, list);

#ifdef RND_VERBOSE
	printf("rnd: %s attached as an entropy source (", rs->name);
	if (!(flags & RND_FLAG_NO_COLLECT)) {
		printf("collecting");
		if (flags & RND_FLAG_NO_ESTIMATE)
			printf(" without estimation");
	}
	else
		printf("off");
	printf(")\n");
#endif

	/*
	 * Again, put some more initial junk in the pool.
	 * XXX Bogus, but harder to guess than zeros.
	 */
	rndpool_add_data(&rnd_pool, &ts, sizeof(u_int32_t), 1);
	mutex_spin_exit(&rndpool_mtx);
}

/*
 * Remove a source from our list of sources.
 */
void
rnd_detach_source(krndsource_t *source)
{
	rnd_sample_t *sample;

	mutex_spin_enter(&rnd_mtx);

	LIST_REMOVE(source, list);

	/*
	 * If there are samples queued up "remove" them from the sample queue
	 * by setting the source to the no-collect pseudosource.
	 */
	sample = SIMPLEQ_FIRST(&rnd_samples);
	while (sample != NULL) {
		if (sample->source == source)
			sample->source = &rnd_source_no_collect;

		sample = SIMPLEQ_NEXT(sample, next);
	}

	mutex_spin_exit(&rnd_mtx);

	if (!cpu_softintr_p()) {	/* XXX XXX very temporary "fix" */
		if (source->state) {
			rnd_sample_free(source->state);
			source->state = NULL;
		}

		if (source->test) {
			kmem_free(source->test, sizeof(rngtest_t));
		}
	}

#ifdef RND_VERBOSE
	printf("rnd: %s detached as an entropy source\n", source->name);
#endif
}

/*
 * Add a value to the entropy pool. The rs parameter should point to the
 * source-specific source structure.
 */
void
rnd_add_uint32(krndsource_t *rs, u_int32_t val)
{
	u_int32_t ts;
	u_int32_t entropy = 0;

	if (rs->flags & RND_FLAG_NO_COLLECT)
		return;

	/*
	 * Sample the counter as soon as possible to avoid
	 * entropy overestimation.
	 */
	ts = rnd_counter();

	/*
	 * If we are estimating entropy on this source,
	 * calculate differentials.
	 */

	if ((rs->flags & RND_FLAG_NO_ESTIMATE) == 0) {
		entropy = rnd_estimate_entropy(rs, ts);
	}

	rnd_add_data(rs, &val, sizeof(val), entropy);
}

void
rnd_add_data(krndsource_t *rs, const void *const data, u_int32_t len,
    u_int32_t entropy)
{
	rnd_sample_t *state = NULL;
	uint32_t ts;
	const uint32_t *dint = data;
	int todo, done, filled = 0;
	SIMPLEQ_HEAD(, _rnd_sample_t) tmp_samples =
	    		SIMPLEQ_HEAD_INITIALIZER(tmp_samples);

	if (rs->flags & RND_FLAG_NO_COLLECT) {
		return;
	}

        /*
         * Sample the counter as soon as possible to avoid entropy
         * overestimation.
         */
        ts = rnd_counter();

	/*
	 * Loop over data packaging it into sample buffers.
	 * If a sample buffer allocation fails, drop all data.
	 */
	todo = len / sizeof(*dint);
	for (done = 0; done < todo ; done++) {
		state = rs->state;
		if (state == NULL) {
			state = rnd_sample_allocate_isr(rs);
			if (__predict_false(state == NULL)) {
				break;
			}
			rs->state = state;
		}

		state->ts[state->cursor] = ts;
		state->values[state->cursor] = dint[done];
		state->cursor++;

		if (state->cursor == RND_SAMPLE_COUNT) {
			SIMPLEQ_INSERT_HEAD(&tmp_samples, state, next);
			filled++;
			rs->state = NULL;
		}
	}

	if (__predict_false(state == NULL)) {
		while ((state = SIMPLEQ_FIRST(&tmp_samples))) {
			SIMPLEQ_REMOVE_HEAD(&tmp_samples, next);
			rnd_sample_free(state);
		}
		return;
	}

	/*
	 * Claim all the entropy on the last one we send to
	 * the pool, so we don't rely on it being evenly distributed
	 * in the supplied data.
	 *
	 * XXX The rndpool code must accept samples with more
	 * XXX claimed entropy than bits for this to work right.
	 */
	state->entropy += entropy;
	rs->total += entropy;

	/*
	 * If we didn't finish any sample buffers, we're done.
	 */
	if (!filled) {
		return;
	}

	mutex_spin_enter(&rnd_mtx);
	while ((state = SIMPLEQ_FIRST(&tmp_samples))) {
		SIMPLEQ_REMOVE_HEAD(&tmp_samples, next);
		SIMPLEQ_INSERT_HEAD(&rnd_samples, state, next);
	}

	/*
	 * If we are still starting up, cause immediate processing of
	 * the queued samples.  Otherwise, if the timeout isn't
	 * pending, have it run in the near future.
	 */
	if (__predict_false(cold)) {
#ifdef RND_VERBOSE
		printf("rnd: directly processing boot-time events.\n");
#endif
		rnd_process_events(NULL);	/* Drops lock! */
		return;
	}
	if (rnd_timeout_pending == 0) {
		rnd_timeout_pending = 1;
		mutex_spin_exit(&rnd_mtx);
		callout_schedule(&rnd_callout, 1);
		return;
	}
	mutex_spin_exit(&rnd_mtx);
}

static int
rnd_hwrng_test(rnd_sample_t *sample)
{
	krndsource_t *source = sample->source;
	size_t cmplen;
	uint8_t *v1, *v2;
	size_t resid, totest;

	KASSERT(source->type = RND_TYPE_RNG);

	/*
	 * Continuous-output test: compare two halves of the
	 * sample buffer to each other.  The sample buffer (64 ints,
	 * so either 256 or 512 bytes on any modern machine) should be
	 * much larger than a typical hardware RNG output, so this seems
	 * a reasonable way to do it without retaining extra data.
	 */
	cmplen = sizeof(sample->values) / 2;
	v1 = (uint8_t *)sample->values;
	v2 = (uint8_t *)sample->values + cmplen;

	if (__predict_false(!memcmp(v1, v2, cmplen))) {
		int *dump;
		printf("rnd: source \"%s\" failed continuous-output test.\n",
		       source->name);
		printf("rnd: bad buffer: ");
		for (dump = (int *)sample->values;
		     dump < (int *)((uint8_t *)sample->values +
		     sizeof(sample->values)); dump += sizeof(int)) {
			printf("%x ", *dump);
		}
		printf("\n");
		return 1;
	}

	/*
	 * FIPS 140 statistical RNG test.  We must accumulate 20,000 bits.
	 */
	if (__predict_true(source->test_cnt == -1)) {
		/* already passed the test */
		return 0;
	}
	resid = FIPS140_RNG_TEST_BYTES - source->test_cnt;
	totest = MIN(RND_SAMPLE_COUNT * 4, resid);
	memcpy(source->test->rt_b + source->test_cnt, sample->values, totest);
	resid -= totest;
	source->test_cnt += totest;
	if (resid == 0) {
		strlcpy(source->test->rt_name, source->name,
			sizeof(source->test->rt_name));
		if (rngtest(source->test)) {
			printf("rnd: source \"%s\" failed statistical test.",
			       source->name);
			return 1;
		}
		source->test_cnt = -1;
		memset(source->test, 0, sizeof(*source->test));
	}
	return 0;
}

/*
 * Process the events in the ring buffer.  Called by rnd_timeout or
 * by the add routines directly if the callout has never fired (that
 * is, if we are "cold" -- just booted).
 *
 * Call with rnd_mtx held -- WILL RELEASE IT.
 */
static void
rnd_process_events(void *arg)
{
	rnd_sample_t *sample;
	krndsource_t *source, *badsource = NULL;
	u_int32_t entropy;
	SIMPLEQ_HEAD(, _rnd_sample_t) dq_samples =
			SIMPLEQ_HEAD_INITIALIZER(dq_samples);
	SIMPLEQ_HEAD(, _rnd_sample_t) df_samples =
			SIMPLEQ_HEAD_INITIALIZER(df_samples);
        TAILQ_HEAD(, rndsink) sunk = TAILQ_HEAD_INITIALIZER(sunk);

	/*
	 * Sample queue is protected by rnd_mtx, drain to onstack queue
	 * and drop lock.
	 */

	while ((sample = SIMPLEQ_FIRST(&rnd_samples))) {
		SIMPLEQ_REMOVE_HEAD(&rnd_samples, next);
		/*
		 * We repeat this check here, since it is possible
		 * the source was disabled before we were called, but
		 * after the entry was queued.
		 */
		if (__predict_false(sample->source->flags
				    & RND_FLAG_NO_COLLECT)) {
			SIMPLEQ_INSERT_TAIL(&df_samples, sample, next);
		} else {
			SIMPLEQ_INSERT_TAIL(&dq_samples, sample, next);
		}
	}
	mutex_spin_exit(&rnd_mtx);

	/* Don't thrash the rndpool mtx either.  Hold, add all samples. */
	mutex_spin_enter(&rndpool_mtx);
	while ((sample = SIMPLEQ_FIRST(&dq_samples))) {
		SIMPLEQ_REMOVE_HEAD(&dq_samples, next);
		source = sample->source;
		entropy = sample->entropy;
		if (source->flags & RND_FLAG_NO_ESTIMATE)
			entropy = 0;

		/*
		 * Hardware generators are great but sometimes they
		 * have...hardware issues.  Don't use any data from
		 * them unless it passes some tests.
		 */
		if (source->type == RND_TYPE_RNG) {
			if (__predict_false(rnd_hwrng_test(sample))) {
				/*
				 * Detach the bad source.  See below.
				 */
				badsource = source;
				printf("rnd: detaching source \"%s\".",
				       badsource->name);
				break;
			}
		}
		rndpool_add_data(&rnd_pool, sample->values,
		    RND_SAMPLE_COUNT * 4, 0);

		rndpool_add_data(&rnd_pool, sample->ts,
		    RND_SAMPLE_COUNT * 4, entropy);

		source->total += sample->entropy;
		SIMPLEQ_INSERT_TAIL(&df_samples, sample, next);
	}
	mutex_spin_exit(&rndpool_mtx);

	/* Now we hold no locks: clean up. */
	if (__predict_false(badsource)) {
		/*
		 * The detach routine frees any samples we have not
		 * dequeued ourselves.  For sanity's sake, we simply
		 * free (without using) all dequeued samples from the
		 * point at which we detected a problem onwards.
		 */
		rnd_detach_source(badsource);
		while ((sample = SIMPLEQ_FIRST(&dq_samples))) {
			SIMPLEQ_REMOVE_HEAD(&dq_samples, next);
			rnd_sample_free(sample);
		}
	}
	while ((sample = SIMPLEQ_FIRST(&df_samples))) {
		SIMPLEQ_REMOVE_HEAD(&df_samples, next);
		rnd_sample_free(sample);
	}

	/*
	 * Wake up any potential readers waiting.
	 */
	rnd_wakeup_readers();
}

/*
 * Timeout, run to process the events in the ring buffer.
 */
static void
rnd_timeout(void *arg)
{
        mutex_spin_enter(&rnd_mtx);
        rnd_timeout_pending = 0;
        rnd_process_events(arg);
}

static u_int32_t
rnd_extract_data_locked(void *p, u_int32_t len, u_int32_t flags)
{

	KASSERT(mutex_owned(&rndpool_mtx));
	if (!rnd_have_entropy) {
		u_int32_t c;

#ifdef RND_VERBOSE
		printf("rnd: WARNING! initial entropy low (%u).\n",
		       rndpool_get_entropy_count(&rnd_pool));
#endif
		/* Try once again to put something in the pool */
		c = rnd_counter();
		rndpool_add_data(&rnd_pool, &c, sizeof(u_int32_t), 1);
	}
	if (!rnd_tested) {
		rngtest_t rt;
		uint8_t testbits[sizeof(rt.rt_b)];
		int entropy_count;

		entropy_count = rndpool_get_entropy_count(&rnd_pool);
#ifdef RND_VERBOSE
		printf("rnd: starting statistical RNG test, entropy = %d.\n",
			entropy_count);
#endif
		if (rndpool_extract_data(&rnd_pool, rt.rt_b,
		    sizeof(rt.rt_b), RND_EXTRACT_ANY) != sizeof(rt.rt_b)) {
			panic("rnd: could not get bits for statistical test");
		}
		/*
		 * Stash the tested bits so we can put them back in the
		 * pool, restoring the entropy count.  DO NOT rely on
		 * rngtest to maintain the bits pristine -- we could end
		 * up adding back non-random data claiming it were pure
		 * entropy.
		 */
		memcpy(testbits, rt.rt_b, sizeof(rt.rt_b));
		strlcpy(rt.rt_name, "entropy pool", sizeof(rt.rt_name));
		if (rngtest(&rt)) {
			/*
			 * The probabiliity of a Type I error is 3/10000,
			 * but note this can only happen at boot time.
			 * The relevant standard says to reset the module,
			 * so that's what we do.
			 */
			panic("rnd: entropy pool failed statistical test");
		}
		memset(&rt, 0, sizeof(rt));
		rndpool_add_data(&rnd_pool, testbits, sizeof(testbits),
				 entropy_count);
		memset(testbits, 0, sizeof(testbits));
#ifdef RND_VERBOSE
		printf("rnd: statistical RNG test done, entropy = %d.\n",
		       rndpool_get_entropy_count(&rnd_pool));
#endif
		rnd_tested++;
	}
	return rndpool_extract_data(&rnd_pool, p, len, flags);
}

u_int32_t
rnd_extract_data(void *p, u_int32_t len, u_int32_t flags)
{
	uint32_t retval;

	mutex_spin_enter(&rndpool_mtx);
	retval = rnd_extract_data_locked(p, len, flags);
	mutex_spin_exit(&rndpool_mtx);
	return retval;
}

void
rndsink_attach(rndsink_t *rs)
{
#ifdef RND_VERBOSE
	printf("rnd: entropy sink \"%s\" wants %d bytes of data.\n",
	       rs->name, (int)rs->len);
#endif
	mutex_spin_enter(&rndpool_mtx);
	TAILQ_INSERT_TAIL(&rnd_sinks, rs, tailq);
	mutex_spin_exit(&rndpool_mtx);
	mutex_spin_enter(&rnd_mtx);
	if (rnd_timeout_pending == 0) {
		rnd_timeout_pending = 1;
		callout_schedule(&rnd_callout, 1);
	}
	mutex_spin_exit(&rnd_mtx);
}

void
rndsink_detach(rndsink_t *rs)
{
	rndsink_t *sink, *tsink;
#ifdef RND_VERBOSE
	printf("rnd: entropy sink \"%s\" no longer wants data.\n", rs->name);
#endif
	mutex_spin_enter(&rndpool_mtx);
	TAILQ_FOREACH_SAFE(sink, &rnd_sinks, tailq, tsink) {
		if (sink == rs) {
			TAILQ_REMOVE(&rnd_sinks, rs, tailq);
		}
	}
	mutex_spin_exit(&rndpool_mtx);
}