/*	$OpenBSD$	*/

/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (c) 2002 Jason L. Wright (jason@thought.net)
 * All rights reserved.
 *
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by Jason L. Wright
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/callout.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/random.h>
#include <sys/sysctl.h>
#include <machine/stdarg.h>

#include <dev/rndtest/rndtest.h>

static	void rndtest_test(struct rndtest_state *);
static	void rndtest_timeout(void *);

/* The tests themselves */
static	int rndtest_monobit(struct rndtest_state *);
static	int rndtest_runs(struct rndtest_state *);
static	int rndtest_longruns(struct rndtest_state *);
static	int rndtest_chi_4(struct rndtest_state *);

static	int rndtest_runs_check(struct rndtest_state *, int, int *);
static	void rndtest_runs_record(struct rndtest_state *, int, int *);

static const struct rndtest_testfunc {
	int (*test)(struct rndtest_state *);
} rndtest_funcs[] = {
	{ rndtest_monobit },
	{ rndtest_runs },
	{ rndtest_chi_4 },
	{ rndtest_longruns },
};

#define	RNDTEST_NTESTS	nitems(rndtest_funcs)

static SYSCTL_NODE(_kern, OID_AUTO, rndtest, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
    "RNG test parameters");
static	int rndtest_retest = 120;		/* interval in seconds */
SYSCTL_INT(_kern_rndtest, OID_AUTO, retest, CTLFLAG_RW, &rndtest_retest,
	    0, "retest interval (seconds)");
static struct rndtest_stats rndstats;
SYSCTL_STRUCT(_kern_rndtest, OID_AUTO, stats, CTLFLAG_RD, &rndstats,
	    rndtest_stats, "RNG test statistics");
static	int rndtest_verbose = 1;		/* report only failures */
SYSCTL_INT(_kern_rndtest, OID_AUTO, verbose, CTLFLAG_RW, &rndtest_verbose,
	    0, "display results on console");

struct rndtest_state *
rndtest_attach(device_t dev)
{
	struct rndtest_state *rsp;

	rsp = malloc(sizeof (*rsp), M_DEVBUF, M_NOWAIT);
	if (rsp != NULL) {
		rsp->rs_begin = rsp->rs_buf;
		rsp->rs_end = rsp->rs_buf + sizeof(rsp->rs_buf);
		rsp->rs_current = rsp->rs_begin;
		rsp->rs_discard = 1;
		rsp->rs_collect = 1;
		rsp->rs_parent = dev;
		callout_init(&rsp->rs_to, 1);
	} else
		device_printf(dev, "rndtest_init: no memory for state block\n");
	return (rsp);
}

void
rndtest_detach(struct rndtest_state *rsp)
{
	callout_stop(&rsp->rs_to);
	free(rsp, M_DEVBUF);
}

void
rndtest_harvest(struct rndtest_state *rsp, void *buf, u_int len)
{
	size_t i;
	/*
	 * If enabled, collect data and run tests when we have enough.
	 */
	if (rsp->rs_collect) {
		for (i = 0; i < len; i++) {
			*rsp->rs_current = ((u_char *) buf)[i];
			if (++rsp->rs_current == rsp->rs_end) {
				rndtest_test(rsp);
				rsp->rs_current = rsp->rs_begin;
				/*
				 * If tests passed, turn off collection and
				 * schedule another test. Otherwise we keep
				 * testing until the data looks ok.
				 */
				if (!rsp->rs_discard && rndtest_retest != 0) {
					rsp->rs_collect = 0;
					callout_reset(&rsp->rs_to,
						hz * rndtest_retest,
						rndtest_timeout, rsp);
					break;
				}
			}
		}
	}
	/*
	 * Only stir entropy that passes muster into the pool.
	 */
	if (rsp->rs_discard)
		rndstats.rst_discard += len;
	else
	/* MarkM: FIX!! Check that this does not swamp the harvester! */
	random_harvest_queue(buf, len, RANDOM_PURE_RNDTEST);
}

static void
rndtest_test(struct rndtest_state *rsp)
{
	int i, rv = 0;

	rndstats.rst_tests++;
	for (i = 0; i < RNDTEST_NTESTS; i++)
		rv |= (*rndtest_funcs[i].test)(rsp);
	rsp->rs_discard = (rv != 0);
}

static void
rndtest_report(struct rndtest_state *rsp, int failure, const char *fmt, ...)
{
	char buf[80];
	va_list ap;

	if (rndtest_verbose == 0)
		return;
	if (!failure && rndtest_verbose == 1)	/* don't report successes */
		return;
	va_start(ap, fmt);
	vsnprintf(buf, sizeof (buf), fmt, ap);
	va_end(ap);
	device_printf(rsp->rs_parent, "rndtest: %s\n", buf);
}

#define	RNDTEST_MONOBIT_MINONES	9725
#define	RNDTEST_MONOBIT_MAXONES	10275

static int
rndtest_monobit(struct rndtest_state *rsp)
{
	int i, ones = 0, j;
	u_int8_t r;

	for (i = 0; i < RNDTEST_NBYTES; i++) {
		r = rsp->rs_buf[i];
		for (j = 0; j < 8; j++, r <<= 1)
			if (r & 0x80)
				ones++;
	}
	if (ones > RNDTEST_MONOBIT_MINONES &&
	    ones < RNDTEST_MONOBIT_MAXONES) {
		if (rndtest_verbose > 1)
			rndtest_report(rsp, 0, "monobit pass (%d < %d < %d)",
			    RNDTEST_MONOBIT_MINONES, ones,
			    RNDTEST_MONOBIT_MAXONES);
		return (0);
	} else {
		if (rndtest_verbose)
			rndtest_report(rsp, 1,
			    "monobit failed (%d ones)", ones);
		rndstats.rst_monobit++;
		return (-1);
	}
}

#define	RNDTEST_RUNS_NINTERVAL	6

static const struct rndtest_runs_tabs {
	u_int16_t min, max;
} rndtest_runs_tab[] = {
	{ 2343, 2657 },
	{ 1135, 1365 },
	{ 542, 708 },
	{ 251, 373 },
	{ 111, 201 },
	{ 111, 201 },
};

static int
rndtest_runs(struct rndtest_state *rsp)
{
	int i, j, ones, zeros, rv = 0;
	int onei[RNDTEST_RUNS_NINTERVAL], zeroi[RNDTEST_RUNS_NINTERVAL];
	u_int8_t c;

	bzero(onei, sizeof(onei));
	bzero(zeroi, sizeof(zeroi));
	ones = zeros = 0;
	for (i = 0; i < RNDTEST_NBYTES; i++) {
		c = rsp->rs_buf[i];
		for (j = 0; j < 8; j++, c <<= 1) {
			if (c & 0x80) {
				ones++;
				rndtest_runs_record(rsp, zeros, zeroi);
				zeros = 0;
			} else {
				zeros++;
				rndtest_runs_record(rsp, ones, onei);
				ones = 0;
			}
		}
	}
	rndtest_runs_record(rsp, ones, onei);
	rndtest_runs_record(rsp, zeros, zeroi);

	rv |= rndtest_runs_check(rsp, 0, zeroi);
	rv |= rndtest_runs_check(rsp, 1, onei);

	if (rv)
		rndstats.rst_runs++;

	return (rv);
}

static void
rndtest_runs_record(struct rndtest_state *rsp, int len, int *intrv)
{
	if (len == 0)
		return;
	if (len > RNDTEST_RUNS_NINTERVAL)
		len = RNDTEST_RUNS_NINTERVAL;
	len -= 1;
	intrv[len]++;
}

static int
rndtest_runs_check(struct rndtest_state *rsp, int val, int *src)
{
	int i, rv = 0;

	for (i = 0; i < RNDTEST_RUNS_NINTERVAL; i++) {
		if (src[i] < rndtest_runs_tab[i].min ||
		    src[i] > rndtest_runs_tab[i].max) {
			rndtest_report(rsp, 1,
			    "%s interval %d failed (%d, %d-%d)",
			    val ? "ones" : "zeros",
			    i + 1, src[i], rndtest_runs_tab[i].min,
			    rndtest_runs_tab[i].max);
			rv = -1;
		} else {
			rndtest_report(rsp, 0,
			    "runs pass %s interval %d (%d < %d < %d)",
			    val ? "ones" : "zeros",
			    i + 1, rndtest_runs_tab[i].min, src[i],
			    rndtest_runs_tab[i].max);
		}
	}
	return (rv);
}

static int
rndtest_longruns(struct rndtest_state *rsp)
{
	int i, j, ones = 0, zeros = 0, maxones = 0, maxzeros = 0;
	u_int8_t c;

	for (i = 0; i < RNDTEST_NBYTES; i++) {
		c = rsp->rs_buf[i];
		for (j = 0; j < 8; j++, c <<= 1) {
			if (c & 0x80) {
				zeros = 0;
				ones++;
				if (ones > maxones)
					maxones = ones;
			} else {
				ones = 0;
				zeros++;
				if (zeros > maxzeros)
					maxzeros = zeros;
			}
		}
	}

	if (maxones < 26 && maxzeros < 26) {
		rndtest_report(rsp, 0, "longruns pass (%d ones, %d zeros)",
			maxones, maxzeros);
		return (0);
	} else {
		rndtest_report(rsp, 1, "longruns fail (%d ones, %d zeros)",
			maxones, maxzeros);
		rndstats.rst_longruns++;
		return (-1);
	}
}

/*
 * chi^2 test over 4 bits: (this is called the poker test in FIPS 140-2,
 * but it is really the chi^2 test over 4 bits (the poker test as described
 * by Knuth vol 2 is something different, and I take him as authoritative
 * on nomenclature over NIST).
 */
#define	RNDTEST_CHI4_K	16
#define	RNDTEST_CHI4_K_MASK	(RNDTEST_CHI4_K - 1)

/*
 * The unnormalized values are used so that we don't have to worry about
 * fractional precision.  The "real" value is found by:
 *	(V - 1562500) * (16 / 5000) = Vn   (where V is the unnormalized value)
 */
#define	RNDTEST_CHI4_VMIN	1563181		/* 2.1792 */
#define	RNDTEST_CHI4_VMAX	1576929		/* 46.1728 */

static int
rndtest_chi_4(struct rndtest_state *rsp)
{
	unsigned int freq[RNDTEST_CHI4_K], i, sum;

	for (i = 0; i < RNDTEST_CHI4_K; i++)
		freq[i] = 0;

	/* Get number of occurrences of each 4 bit pattern */
	for (i = 0; i < RNDTEST_NBYTES; i++) {
		freq[(rsp->rs_buf[i] >> 4) & RNDTEST_CHI4_K_MASK]++;
		freq[(rsp->rs_buf[i] >> 0) & RNDTEST_CHI4_K_MASK]++;
	}

	for (i = 0, sum = 0; i < RNDTEST_CHI4_K; i++)
		sum += freq[i] * freq[i];

	if (sum >= 1563181 && sum <= 1576929) {
		rndtest_report(rsp, 0, "chi^2(4): pass (sum %u)", sum);
		return (0);
	} else {
		rndtest_report(rsp, 1, "chi^2(4): failed (sum %u)", sum);
		rndstats.rst_chi++;
		return (-1);
	}
}

static void
rndtest_timeout(void *xrsp)
{
	struct rndtest_state *rsp = xrsp;

	rsp->rs_collect = 1;
}

static int
rndtest_modevent(module_t mod, int type, void *unused)
{
	switch (type) {
	case MOD_LOAD:
		return 0;
	case MOD_UNLOAD:
		return 0;
	}
	return EINVAL;
}

static moduledata_t rndtest_mod = {
	"rndtest",
	rndtest_modevent,
	0
};
DECLARE_MODULE(rndtest, rndtest_mod, SI_SUB_DRIVERS, SI_ORDER_ANY);
MODULE_VERSION(rndtest, 1);