/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (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 (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright 2014, OmniTI Computer Consulting, Inc. All rights reserved.
 */

#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <locale.h>
#include <stdarg.h>
#include <cryptoutil.h>
#include <pthread.h>

#pragma init(pkcs11_random_init)

static pthread_mutex_t  random_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t  urandom_mutex = PTHREAD_MUTEX_INITIALIZER;

static pthread_mutex_t  random_seed_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t  urandom_seed_mutex = PTHREAD_MUTEX_INITIALIZER;

#define RANDOM_DEVICE           "/dev/random"   /* random device name */
#define URANDOM_DEVICE          "/dev/urandom"  /* urandom device name */

static int      random_fd = -1;
static int      urandom_fd = -1;

static int      random_seed_fd = -1;
static int      urandom_seed_fd = -1;


/*
 * Equivalent of open(2) insulated from EINTR.
 * Also sets close-on-exec.
 */
int
open_nointr(const char *path, int oflag, ...)
{
        int     fd;
        mode_t  pmode;
        va_list alist;

        va_start(alist, oflag);
        pmode = va_arg(alist, mode_t);
        va_end(alist);

        do {
                if ((fd = open(path, oflag, pmode)) >= 0) {
                        (void) fcntl(fd, F_SETFD, FD_CLOEXEC);
                        break;
                }
                /* errno definitely set by failed open() */
        } while (errno == EINTR);
        return (fd);
}

/*
 * Equivalent of read(2) insulated from EINTR.
 */
ssize_t
readn_nointr(int fd, void *dbuf, size_t dlen)
{
        char    *marker = dbuf;
        size_t  left = dlen;
        ssize_t nread = 0, err;

        for (err = 0; left > 0 && nread != -1; marker += nread, left -= nread) {
                if ((nread = read(fd, marker, left)) < 0) {
                        if (errno == EINTR) {   /* keep trying */
                                nread = 0;
                                continue;
                        }
                        err = nread;            /* hard error */
                        break;
                } else if (nread == 0) {
                        break;
                }
        }
        return (err != 0 ? err : dlen - left);
}

/*
 * Equivalent of write(2) insulated from EINTR.
 */
ssize_t
writen_nointr(int fd, void *dbuf, size_t dlen)
{
        char    *marker = dbuf;
        size_t  left = dlen;
        ssize_t nwrite = 0, err;

        for (err = 0; left > 0 && nwrite != -1; marker += nwrite,
            left -= nwrite) {
                if ((nwrite = write(fd, marker, left)) < 0) {
                        if (errno == EINTR) {   /* keep trying */
                                nwrite = 0;
                                continue;
                        }
                        err = nwrite;           /* hard error */
                        break;
                } else if (nwrite == 0) {
                        break;
                }
        }
        return (err != 0 ? err : dlen - left);
}

/*
 * Opens the random number generator devices if not already open.
 * Always returns the opened fd of the device, or error.
 */
static int
pkcs11_open_common(int *fd, pthread_mutex_t *mtx, const char *dev, int oflag)
{
        (void) pthread_mutex_lock(mtx);
        if (*fd < 0)
                *fd = open_nointr(dev, oflag);
        (void) pthread_mutex_unlock(mtx);

        return (*fd);
}

static int
pkcs11_open_random(void)
{
        return (pkcs11_open_common(&random_fd, &random_mutex,
            RANDOM_DEVICE, O_RDONLY));
}

static int
pkcs11_open_urandom(void)
{
        return (pkcs11_open_common(&urandom_fd, &urandom_mutex,
            URANDOM_DEVICE, O_RDONLY));
}

static int
pkcs11_open_random_seed(void)
{
        return (pkcs11_open_common(&random_seed_fd, &random_seed_mutex,
            RANDOM_DEVICE, O_WRONLY));
}

static int
pkcs11_open_urandom_seed(void)
{
        return (pkcs11_open_common(&urandom_seed_fd, &urandom_seed_mutex,
            URANDOM_DEVICE, O_WRONLY));
}

/*
 * Close the random number generator devices if already open.
 */
static void
pkcs11_close_common(int *fd, pthread_mutex_t *mtx)
{
        (void) pthread_mutex_lock(mtx);
        (void) close(*fd);
        *fd = -1;
        (void) pthread_mutex_unlock(mtx);
}

static void
pkcs11_close_random(void)
{
        pkcs11_close_common(&random_fd, &random_mutex);
}

static void
pkcs11_close_urandom(void)
{
        pkcs11_close_common(&urandom_fd, &urandom_mutex);
}

static void
pkcs11_close_random_seed(void)
{
        pkcs11_close_common(&random_seed_fd, &random_seed_mutex);
}

static void
pkcs11_close_urandom_seed(void)
{
        pkcs11_close_common(&urandom_seed_fd, &urandom_seed_mutex);
}

/*
 * Read from the random number generator devices.
 */
static size_t
pkcs11_read_common(int *fd, pthread_mutex_t *mtx, void *dbuf, size_t dlen)
{
        size_t  n;

        (void) pthread_mutex_lock(mtx);
        n = readn_nointr(*fd, dbuf, dlen);
        (void) pthread_mutex_unlock(mtx);

        return (n);
}

static size_t
pkcs11_read_random(void *dbuf, size_t dlen)
{
        return (pkcs11_read_common(&random_fd, &random_mutex, dbuf, dlen));
}

static size_t
pkcs11_read_urandom(void *dbuf, size_t dlen)
{
        return (pkcs11_read_common(&urandom_fd, &urandom_mutex, dbuf, dlen));
}

/*
 * Write to the random number generator devices.
 */
static size_t
pkcs11_write_common(int *fd, pthread_mutex_t *mtx, void *dbuf, size_t dlen)
{
        size_t  n;

        (void) pthread_mutex_lock(mtx);
        n = writen_nointr(*fd, dbuf, dlen);
        (void) pthread_mutex_unlock(mtx);

        return (n);
}

static size_t
pkcs11_write_random_seed(void *dbuf, size_t dlen)
{
        return (pkcs11_write_common(&random_seed_fd, &random_seed_mutex,
            dbuf, dlen));
}

static size_t
pkcs11_write_urandom_seed(void *dbuf, size_t dlen)
{
        return (pkcs11_write_common(&urandom_seed_fd, &urandom_seed_mutex,
            dbuf, dlen));
}

/*
 * Seed /dev/random with the data in the buffer.
 */
int
pkcs11_seed_random(void *sbuf, size_t slen)
{
        int     rv;

        if (sbuf == NULL || slen == 0)
                return (0);

        /* Seeding error could mean it's not supported (errno = EACCES) */
        if (pkcs11_open_random_seed() < 0)
                return (-1);

        rv = -1;
        if (pkcs11_write_random_seed(sbuf, slen) == slen)
                rv = 0;

        pkcs11_close_random_seed();
        return (rv);
}

/*
 * Seed /dev/urandom with the data in the buffer.
 */
int
pkcs11_seed_urandom(void *sbuf, size_t slen)
{
        int     rv;

        if (sbuf == NULL || slen == 0)
                return (0);

        /* Seeding error could mean it's not supported (errno = EACCES) */
        if (pkcs11_open_urandom_seed() < 0)
                return (-1);

        rv = -1;
        if (pkcs11_write_urandom_seed(sbuf, slen) == slen)
                rv = 0;

        pkcs11_close_urandom_seed();
        return (rv);
}

/*
 * Put the requested amount of random data into a preallocated buffer.
 * Good for token key data, persistent objects.
 */
int
pkcs11_get_random(void *dbuf, size_t dlen)
{
        if (dbuf == NULL || dlen == 0)
                return (0);

        /* Read random data directly from /dev/random */
        if (pkcs11_open_random() < 0)
                return (-1);

        if (pkcs11_read_random(dbuf, dlen) == dlen)
                return (0);
        return (-1);
}

/*
 * Put the requested amount of random data into a preallocated buffer.
 * Good for passphrase salts, initialization vectors.
 */
int
pkcs11_get_urandom(void *dbuf, size_t dlen)
{
        if (dbuf == NULL || dlen == 0)
                return (0);

        /* Read random data directly from /dev/urandom */
        if (pkcs11_open_urandom() < 0)
                return (-1);

        if (pkcs11_read_urandom(dbuf, dlen) == dlen)
                return (0);
        return (-1);
}

/*
 * Same as pkcs11_get_urandom but ensures non zero data.
 */
int
pkcs11_get_nzero_urandom(void *dbuf, size_t dlen)
{
        char    extrarand[32];
        size_t  bytesleft = 0;
        size_t  i = 0;

        /* Start with some random data */
        if (pkcs11_get_urandom(dbuf, dlen) < 0)
                return (-1);

        /* Walk through data replacing any 0 bytes with more random data */
        while (i < dlen) {
                if (((char *)dbuf)[i] != 0) {
                        i++;
                        continue;
                }

                if (bytesleft == 0) {
                        bytesleft = sizeof (extrarand);
                        if (pkcs11_get_urandom(extrarand, bytesleft) < 0)
                                return (-1);
                }
                bytesleft--;

                ((char *)dbuf)[i] = extrarand[bytesleft];
        }
        return (0);
}

static void
pkcs11_random_prepare(void)
{
        /*
         * NOTE - None of these are acquired more than one at a time.
         * I can therefore acquire all four without fear of deadlock.
         */
        (void) pthread_mutex_lock(&random_mutex);
        (void) pthread_mutex_lock(&urandom_mutex);
        (void) pthread_mutex_lock(&random_seed_mutex);
        (void) pthread_mutex_lock(&urandom_seed_mutex);
}

static void
pkcs11_random_parent_post(void)
{
        /* Drop the mutexes and get back to work! */
        (void) pthread_mutex_unlock(&urandom_seed_mutex);
        (void) pthread_mutex_unlock(&random_seed_mutex);
        (void) pthread_mutex_unlock(&urandom_mutex);
        (void) pthread_mutex_unlock(&random_mutex);
}

static void
pkcs11_random_child_post(void)
{
        pkcs11_random_parent_post();

        /* Also, close the FDs, just in case. */
        pkcs11_close_random();
        pkcs11_close_urandom();
        pkcs11_close_random_seed();
        pkcs11_close_urandom_seed();
}

static void
pkcs11_random_init(void)
{
        (void) pthread_atfork(pkcs11_random_prepare, pkcs11_random_parent_post,
            pkcs11_random_child_post);
}