common/io/random.c

	random.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 *
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 * Random number generator pseudo-driver
 *
 * This is a lightweight driver which calls in to the Kernel Cryptographic
 * Framework to do the real work. Kernel modules should NOT depend on this
 * driver for /dev/random kernel API.
 *
 * Applications may ask for 2 types of random bits:
 * . High quality random by reading from /dev/random. The output is extracted
 *   only when a minimum amount of entropy is available.
 * . Pseudo-random, by reading from /dev/urandom, that can be generated any
 *   time.
 */

#include <sys/types.h>
#include <sys/errno.h>
#include <sys/stat.h>

#include <sys/file.h>
#include <sys/open.h>
#include <sys/poll.h>
#include <sys/uio.h>
#include <sys/cred.h>
#include <sys/modctl.h>
#include <sys/conf.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#include <sys/random.h>
#include <sys/crypto/impl.h>

#define DEVRANDOM       0
#define DEVURANDOM      1

#define HASHSIZE        20  /* Assuming a SHA1 hash algorithm */
#define WRITEBUFSIZE        512 /* Size of buffer for write request */
#define MAXRETBYTES     1040    /* Max bytes returned per read. */
                    /* Must be a multiple of HASHSIZE */
static dev_info_t *rnd_dip;

static int rnd_open(dev_t *, int, int, cred_t *);
static int rnd_close(dev_t, int, int, cred_t *);
static int rnd_read(dev_t, struct uio *, cred_t *);
static int rnd_write(dev_t, struct uio *, cred_t *);
static int rnd_chpoll(dev_t, short, int, short *, struct pollhead **);
static int rnd_attach(dev_info_t *, ddi_attach_cmd_t);
static int rnd_detach(dev_info_t *, ddi_detach_cmd_t);
static int rnd_getinfo(dev_info_t *, ddi_info_cmd_t, void *, void **);

/* DDI declarations */
static struct cb_ops rnd_cb_ops = {
    rnd_open,       /* open */
    rnd_close,      /* close */
    nodev,          /* strategy */
    nodev,          /* print */
    nodev,          /* dump */
    rnd_read,       /* read */
    rnd_write,      /* write */
    nodev,          /* ioctl */
    nodev,          /* devmap */
    nodev,          /* mmap */
    nodev,          /* segmap */
    rnd_chpoll,     /* chpoll */
    ddi_prop_op,        /* prop_op */
    NULL,           /* streamtab  */
    (D_NEW | D_MP),     /* cb_flag */
    CB_REV,         /* cb_rev */
    nodev,          /* aread */
    nodev           /* awrite */
};

static struct dev_ops rnd_ops = {
    DEVO_REV,       /* devo_rev, */
    0,          /* refcnt  */
    rnd_getinfo,        /* get_dev_info */
    nulldev,        /* identify */
    nulldev,        /* probe */
    rnd_attach,     /* attach */
    rnd_detach,     /* detach */
    nodev,          /* reset */
    &rnd_cb_ops,        /* driver operations */
    NULL,           /* bus operations */
    NULL            /* power */
};

/* Modlinkage */
static struct modldrv modldrv = {
    &mod_driverops,
    "random number device v%I%",
    &rnd_ops
};

static struct modlinkage modlinkage = { MODREV_1, { &modldrv, NULL } };


/* DDI glue */

int
_init(void)
{
    return (mod_install(&modlinkage));
}

int
_fini(void)
{
    return (mod_remove(&modlinkage));
}

int
_info(struct modinfo *modinfop)
{
    return (mod_info(&modlinkage, modinfop));
}

static int
rnd_attach(dev_info_t *dip, ddi_attach_cmd_t cmd)
{
    if (cmd != DDI_ATTACH)
        return (DDI_FAILURE);

    if (ddi_create_minor_node(dip, "random", S_IFCHR, DEVRANDOM,
        DDI_PSEUDO, 0) == DDI_FAILURE) {
        ddi_remove_minor_node(dip, NULL);
        return (DDI_FAILURE);
    }
    if (ddi_create_minor_node(dip, "urandom", S_IFCHR, DEVURANDOM,
        DDI_PSEUDO, 0) == DDI_FAILURE) {
        ddi_remove_minor_node(dip, NULL);
        return (DDI_FAILURE);
    }

    rnd_dip = dip;

    return (DDI_SUCCESS);
}

static int
rnd_detach(dev_info_t *dip, ddi_detach_cmd_t cmd)
{
    if (cmd != DDI_DETACH)
        return (DDI_FAILURE);

    rnd_dip = NULL;
    ddi_remove_minor_node(dip, NULL);

    return (DDI_SUCCESS);
}

/*ARGSUSED*/
static int
rnd_getinfo(dev_info_t *dip, ddi_info_cmd_t infocmd, void *arg, void **result)
{
    int error;

    switch (infocmd) {
    case DDI_INFO_DEVT2DEVINFO:
        *result = rnd_dip;
        error = DDI_SUCCESS;
        break;
    case DDI_INFO_DEVT2INSTANCE:
        *result = (void *)0;
        error = DDI_SUCCESS;
        break;
    default:
        error = DDI_FAILURE;
    }
    return (error);
}

/*ARGSUSED3*/
static int
rnd_open(dev_t *devp, int flag, int otyp, cred_t *credp)
{
    switch (getminor(*devp)) {
    case DEVRANDOM:
        if (!kcf_rngprov_check())
            return (ENXIO);
        break;
    case DEVURANDOM:
        break;
    default:
        return (ENXIO);
    }
    if (otyp != OTYP_CHR)
        return (EINVAL);

    if (flag & FEXCL)
        return (EINVAL);
    return (0);
}

/*ARGSUSED*/
static int
rnd_close(dev_t dev, int flag, int otyp, cred_t *credp)
{
    return (0);
}

/*ARGSUSED2*/
static int
rnd_read(dev_t dev, struct uio *uiop, cred_t *credp)
{
    size_t len;
    minor_t devno;
    int error = 0;
    int nbytes = 0;
    uint8_t random_bytes[2 * HASHSIZE];

    devno = getminor(dev);

    while (error == 0 && uiop->uio_resid > 0) {
        len = min(sizeof (random_bytes), uiop->uio_resid);
        switch (devno) {
        case DEVRANDOM:
            error = kcf_rnd_get_bytes(random_bytes, len,
                uiop->uio_fmode & (FNDELAY|FNONBLOCK), B_TRUE);
            break;
        case DEVURANDOM:
            error = kcf_rnd_get_pseudo_bytes(random_bytes, len);
            break;
        default:
            return (ENXIO);
        }

        if (error == 0) {
            /*
             * /dev/[u]random is not a seekable device. To prevent
             * uio offset from growing and eventually exceeding
             * the maximum, reset the offset here for every call.
             */
            uiop->uio_loffset = 0;
            error = uiomove(random_bytes, len, UIO_READ, uiop);

            nbytes += len;

            if (nbytes >= MAXRETBYTES)
                break;

        } else if ((error == EAGAIN) && (nbytes > 0)) {
            error = 0;
            break;
        }
    }
    return (error);
}

/*ARGSUSED*/
static int
rnd_write(dev_t dev, struct uio *uiop, cred_t *credp)
{
    int error;
    uint8_t buf[WRITEBUFSIZE];
    size_t bytes;

    while (uiop->uio_resid > 0) {
        bytes = min(sizeof (buf), uiop->uio_resid);

        /* See comments in rnd_read() */
        uiop->uio_loffset = 0;
        if ((error = uiomove(buf, bytes, UIO_WRITE, uiop)) != 0)
            return (error);

        /* Add bytes to the pool but don't change the entropy level */
        if ((error = random_add_entropy(buf, bytes, 0)) != 0)
            return (error);
    }

    return (0);
}

/*
 * poll(2) is supported as follows:
 * . Only POLLIN, POLLOUT, and POLLRDNORM events are valid.
 * . POLLOUT always succeeds.
 * . POLLIN and POLLRDNORM from /dev/urandom always succeeds.
 * . POLLIN and POLLRDNORM from /dev/random will block until a
 *   minimum amount of entropy is available.
 */
static int
rnd_chpoll(dev_t dev, short events, int anyyet, short *reventsp,
    struct pollhead **phpp)
{
    switch (getminor(dev)) {
    case DEVURANDOM:
        *reventsp = events & (POLLOUT | POLLIN | POLLRDNORM);

        /* We're being polled for non-supported events */
        if (*reventsp == 0 && !anyyet)
            return (EINVAL);

        break;
    case DEVRANDOM:
        *reventsp = events & POLLOUT;

        /* Either POLLOUT only or unsupported event */
        if ((events & (POLLIN | POLLRDNORM)) == 0) {
            if (*reventsp == 0 && !anyyet)
                return (EINVAL);
            break;
        }

        kcf_rnd_chpoll(anyyet, reventsp, phpp);
        break;
    default:
        return (ENXIO);
    }

    return (0);
}