/*      $OpenBSD$       */

/*-
 * 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/stdarg.h>
#include <sys/sysctl.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);