common/syscall/getrandom.c

	getrandom.c revision 9d12795f87b63c2e39e87bff369182edd34677d3
/*
 * This file and its contents are supplied under the terms of the
 * Common Development and Distribution License ("CDDL"), version 1.0.
 * You may only use this file in accordance with the terms of version
 * 1.0 of the CDDL.
 *
 * A full copy of the text of the CDDL should have accompanied this
 * source.  A copy of the CDDL is also available via the Internet at
 * http://www.illumos.org/license/CDDL.
 */

/*
 * Copyright (c) 2015, Joyent, Inc.
 */

/*
 * getrandom system call implementation
 */

#include <sys/types.h>
#include <sys/errno.h>
#include <sys/systm.h>
#include <sys/random.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#include <sys/sysmacros.h>

#include <sys/random.h>

/*
 * Impose a maximum upper bound on the number of bytes that we'll read in one
 * go, ala a read of /dev/random. For /dev/urandom, we clamp it based on our
 * return value, because the system call returns an int, we can't handle more
 * than INT_MAX.
 */
#define MAXRANDBYTES    1024
#define MAXURANDBYTES   INT_MAX

int
getrandom(void *bufp, size_t buflen, int flags)
{
    int out = 0;
    uint8_t rbytes[128];
    uint8_t *buf = bufp;

    if (flags & ~(GRND_NONBLOCK | GRND_RANDOM))
        return (set_errno(EINVAL));

    if ((flags & GRND_RANDOM) && buflen > MAXRANDBYTES) {
        buflen = MAXRANDBYTES;
    } else if (buflen > MAXURANDBYTES) {
        buflen = MAXURANDBYTES;
    }

    while (buflen > out) {
        int err;
        size_t len = MIN(sizeof (rbytes), buflen);

        if (flags & GRND_RANDOM) {
            if (flags & GRND_NONBLOCK)
                err = random_get_bytes(rbytes, len);
            else
                err = random_get_blocking_bytes(rbytes, len);
        } else {
            err = random_get_pseudo_bytes(rbytes, len);
        }

        if (err == 0) {
            if (ddi_copyout(rbytes, buf + out, len, 0) != 0)
                return (set_errno(EFAULT));
            out += len;
        } else if (err == EAGAIN && out > 0) {
            break;
        } else {
            return (set_errno(err));
        }
    }

    return (out);
}