5152 /dev/random cache leads to duplicate uuids after fork

[unleashed.git] / usr / src / lib / libuuid / common / uuid.c

/*
 * 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 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 * Copyright 2012 Milan Jurik. All rights reserved.
 * Copyright 2014 Joyent, Inc. All rights reserved.
 * Copyright 2014 Andrew Stormont.
 */

/*
 * The copyright in this file is taken from the original Leach & Salz
 * UUID specification, from which this implementation is derived.
 */

/*
 * Copyright (c) 1990- 1993, 1996 Open Software Foundation, Inc.
 * Copyright (c) 1989 by Hewlett-Packard Company, Palo Alto, Ca. &
 * Digital Equipment Corporation, Maynard, Mass.  Copyright (c) 1998
 * Microsoft.  To anyone who acknowledges that this file is provided
 * "AS IS" without any express or implied warranty: permission to use,
 * copy, modify, and distribute this file for any purpose is hereby
 * granted without fee, provided that the above copyright notices and
 * this notice appears in all source code copies, and that none of the
 * names of Open Software Foundation, Inc., Hewlett-Packard Company,
 * or Digital Equipment Corporation be used in advertising or
 * publicity pertaining to distribution of the software without
 * specific, written prior permission.  Neither Open Software
 * Foundation, Inc., Hewlett-Packard Company, Microsoft, nor Digital
 * Equipment Corporation makes any representations about the
 * suitability of this software for any purpose.
 */

/*
 * This module is the workhorse for generating abstract
 * UUIDs.  It delegates system-specific tasks (such
 * as obtaining the node identifier or system time)
 * to the sysdep module.
 */

#include <ctype.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <fcntl.h>
#include <unistd.h>
#include <synch.h>
#include <sys/mman.h>
#include "uuid_misc.h"

shared_buffer_t         *data;

static  uuid_node_t     node_id_cache;
static  int             node_init;
static  int             file_type;
static  int             fd;

/*
 * The urandmtx mutex prevents multiple opens of /dev/urandom and protects the
 * cache.
 */
#define RCACHE_SIZE     65535
static  mutex_t         urandmtx;
static  int             fd_urand = -1;
static  char            rcache[RCACHE_SIZE];
static  char            *rcachep = rcache;

/*
 * misc routines
 */
uint16_t                get_random(void);
void                    get_current_time(uuid_time_t *);

void                    struct_to_string(uuid_t, struct uuid *);
void                    string_to_struct(struct uuid *, uuid_t);
int                     get_ethernet_address(uuid_node_t *);

/*
 * local functions
 */
static  int             map_state();
static  void            format_uuid(struct uuid *, uint16_t, uuid_time_t,
    uuid_node_t);
static  void            fill_random_bytes(uchar_t *, int);
static  int             uuid_create(struct uuid *);
static  void            gen_ethernet_address(uuid_node_t *);
static  void            revalidate_data(uuid_node_t *);

/*
 * Generates a uuid based on version 1 format.
 * Returns 0 on success and -1 on failure.
 */
static int
uuid_create(struct uuid *uuid)
{
        uuid_time_t     timestamp;
        uuid_node_t     system_node;
        int             ret, non_unique = 0;

        /*
         * Get the system MAC address and/or cache it
         */
        if (node_init) {
                bcopy(&node_id_cache, &system_node, sizeof (uuid_node_t));
        } else {
                gen_ethernet_address(&system_node);
                bcopy(&system_node, &node_id_cache, sizeof (uuid_node_t));
                node_init = 1;
        }

        /*
         * Access the state file, mmap it and initialize the shared lock.
         * file_type tells us whether we had access to the state file or
         * created a temporary one.
         */
        if (map_state() == -1)
                return (-1);

        /*
         * Acquire the lock
         */
        for (;;) {
                if ((ret = mutex_lock(&data->lock)) == 0)
                        break;
                else
                        switch (ret) {
                                case EOWNERDEAD:
                                        revalidate_data(&system_node);
                                        (void) mutex_consistent(&data->lock);
                                        (void) mutex_unlock(&data->lock);
                                        break;
                                case ENOTRECOVERABLE:
                                        return (ret);
                        }
        }

        /* State file is either new or is temporary, get a random clock seq */
        if (data->state.clock == 0) {
                data->state.clock = get_random();
                non_unique++;
        }

        if (memcmp(&system_node, &data->state.node, sizeof (uuid_node_t)) != 0)
                data->state.clock++;

        get_current_time(&timestamp);

        /*
         * If timestamp is not set or is not in the past, bump
         * data->state.clock
         */
        if ((data->state.ts == 0) || (data->state.ts >= timestamp)) {
                data->state.clock++;
                data->state.ts = timestamp;
        }

        if (non_unique)
                system_node.nodeID[0] |= 0x80;

        /* Stuff fields into the UUID struct */
        format_uuid(uuid, data->state.clock, timestamp, system_node);

        (void) mutex_unlock(&data->lock);

        return (0);
}

/*
 * Fills system_node with Ethernet address if available,
 * else fills random numbers
 */
static void
gen_ethernet_address(uuid_node_t *system_node)
{
        uchar_t         node[6];

        if (get_ethernet_address(system_node) != 0) {
                fill_random_bytes(node, 6);
                (void) memcpy(system_node->nodeID, node, 6);
                /*
                 * use 8:0:20 with the multicast bit set
                 * to avoid namespace collisions.
                 */
                system_node->nodeID[0] = 0x88;
                system_node->nodeID[1] = 0x00;
                system_node->nodeID[2] = 0x20;
        }
}

/*
 * Formats a UUID, given the clock_seq timestamp, and node address.
 * Fills in passed-in pointer with the resulting uuid.
 */
static void
format_uuid(struct uuid *uuid, uint16_t clock_seq,
    uuid_time_t timestamp, uuid_node_t node)
{

        /*
         * First set up the first 60 bits from the timestamp
         */
        uuid->time_low = (uint32_t)(timestamp & 0xFFFFFFFF);
        uuid->time_mid = (uint16_t)((timestamp >> 32) & 0xFFFF);
        uuid->time_hi_and_version = (uint16_t)((timestamp >> 48) & 0x0FFF);

        /*
         * This is version 1, so say so in the UUID version field (4 bits)
         */
        uuid->time_hi_and_version |= (1 << 12);

        /*
         * Now do the clock sequence
         */
        uuid->clock_seq_low = clock_seq & 0xFF;

        /*
         * We must save the most-significant 2 bits for the reserved field
         */
        uuid->clock_seq_hi_and_reserved = (clock_seq & 0x3F00) >> 8;

        /*
         * The variant for this format is the 2 high bits set to 10,
         * so here it is
         */
        uuid->clock_seq_hi_and_reserved |= 0x80;

        /*
         * write result to passed-in pointer
         */
        (void) memcpy(&uuid->node_addr, &node, sizeof (uuid->node_addr));
}

/*
 * Opens/creates the state file, falling back to a tmp
 */
static int
map_state()
{
        FILE    *tmp;

        /* If file's mapped, return */
        if (file_type != 0)
                return (1);

        if ((fd = open(STATE_LOCATION, O_RDWR)) < 0) {
                file_type = TEMP_FILE;

                if ((tmp = tmpfile()) == NULL)
                        return (-1);
                else
                        fd = fileno(tmp);
        } else {
                file_type = STATE_FILE;
        }

        (void) ftruncate(fd, (off_t)sizeof (shared_buffer_t));

        /* LINTED - alignment */
        data = (shared_buffer_t *)mmap(NULL, sizeof (shared_buffer_t),
            PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);

        if (data == MAP_FAILED)
                return (-1);

        (void) mutex_init(&data->lock, USYNC_PROCESS|LOCK_ROBUST, 0);

        (void) close(fd);

        return (1);
}

static void
revalidate_data(uuid_node_t *node)
{
        int i;

        data->state.ts = 0;

        for (i = 0; i < sizeof (data->state.node.nodeID); i++)
                data->state.node.nodeID[i] = 0;

        data->state.clock = 0;

        gen_ethernet_address(node);
        bcopy(node, &node_id_cache, sizeof (uuid_node_t));
        node_init = 1;
}

/*
 * Prints a nicely-formatted uuid to stdout.
 */
void
uuid_print(struct uuid u)
{
        int i;

        (void) printf("%8.8x-%4.4x-%4.4x-%2.2x%2.2x-", u.time_low, u.time_mid,
            u.time_hi_and_version, u.clock_seq_hi_and_reserved,
            u.clock_seq_low);
        for (i = 0; i < 6; i++)
                (void) printf("%2.2x", u.node_addr[i]);
        (void) printf("\n");
}

/*
 * Only called with urandmtx held.
 * Fills/refills the cache of randomness. We know that our allocations of
 * randomness are always much less than the total size of the cache.
 * Tries to use /dev/urandom random number generator - if that fails for some
 * reason, it retries MAX_RETRY times then sets rcachep to NULL so we no
 * longer use the cache.
 */
static void
load_cache()
{
        int i, retries = 0;
        int nbytes = RCACHE_SIZE;
        char *buf = rcache;

        while (nbytes > 0) {
                i = read(fd_urand, buf, nbytes);
                if ((i < 0) && (errno == EINTR)) {
                        continue;
                }
                if (i <= 0) {
                        if (retries++ == MAX_RETRY)
                                break;
                        continue;
                }
                nbytes -= i;
                buf += i;
                retries = 0;
        }
        if (nbytes == 0)
                rcachep = rcache;
        else
                rcachep = NULL;
}

static void
close_pre()
{
        (void) mutex_lock(&urandmtx);
}

static void
close_parent()
{
        (void) mutex_unlock(&urandmtx);
}

static void
close_child()
{
        if (fd_urand != -1) {
                (void) close(fd_urand);
                fd_urand = -1;
        }
        (void) mutex_unlock(&urandmtx);
}

#pragma init(cache_init)
static void
cache_init(void)
{
        (void) pthread_atfork(close_pre, close_parent, close_child);
}

/*
 * Fills buf with random numbers - nbytes is the number of bytes
 * to fill-in. Tries to use cached data from the /dev/urandom random number
 * generator - if that fails for some reason, it uses srand48(3C)
 */
static void
fill_random_bytes(uchar_t *buf, int nbytes)
{
        int i;

        if (fd_urand == -1) {
                (void) mutex_lock(&urandmtx);
                /* check again now that we have the mutex */
                if (fd_urand == -1) {
                        if ((fd_urand = open(URANDOM_PATH,
                            O_RDONLY | O_CLOEXEC)) >= 0)
                                load_cache();
                }
                (void) mutex_unlock(&urandmtx);
        }
        if (fd_urand >= 0 && rcachep != NULL) {
                int cnt;

                (void) mutex_lock(&urandmtx);
                if (rcachep != NULL &&
                    (rcachep + nbytes) >= (rcache + RCACHE_SIZE))
                        load_cache();

                if (rcachep != NULL) {
                        for (cnt = 0; cnt < nbytes; cnt++)
                                *buf++ = *rcachep++;
                        (void) mutex_unlock(&urandmtx);
                        return;
                }
                (void) mutex_unlock(&urandmtx);
        }
        for (i = 0; i < nbytes; i++) {
                *buf++ = get_random() & 0xFF;
        }
}

/*
 * Unpacks the structure members in "struct uuid" to a char string "uuid_t".
 */
void
struct_to_string(uuid_t ptr, struct uuid *uu)
{
        uint_t          tmp;
        uchar_t         *out = ptr;

        tmp = uu->time_low;
        out[3] = (uchar_t)tmp;
        tmp >>= 8;
        out[2] = (uchar_t)tmp;
        tmp >>= 8;
        out[1] = (uchar_t)tmp;
        tmp >>= 8;
        out[0] = (uchar_t)tmp;

        tmp = uu->time_mid;
        out[5] = (uchar_t)tmp;
        tmp >>= 8;
        out[4] = (uchar_t)tmp;

        tmp = uu->time_hi_and_version;
        out[7] = (uchar_t)tmp;
        tmp >>= 8;
        out[6] = (uchar_t)tmp;

        tmp = uu->clock_seq_hi_and_reserved;
        out[8] = (uchar_t)tmp;
        tmp = uu->clock_seq_low;
        out[9] = (uchar_t)tmp;

        (void) memcpy(out+10, uu->node_addr, 6);

}

/*
 * Packs the values in the "uuid_t" string into "struct uuid".
 */
void
string_to_struct(struct uuid *uuid, uuid_t in)
{
        uchar_t *ptr;
        uint_t  tmp;

        ptr = in;

        tmp = *ptr++;
        tmp = (tmp << 8) | *ptr++;
        tmp = (tmp << 8) | *ptr++;
        tmp = (tmp << 8) | *ptr++;
        uuid->time_low = tmp;

        tmp = *ptr++;
        tmp = (tmp << 8) | *ptr++;
        uuid->time_mid = tmp;

        tmp = *ptr++;
        tmp = (tmp << 8) | *ptr++;
        uuid->time_hi_and_version = tmp;

        tmp = *ptr++;
        uuid->clock_seq_hi_and_reserved = tmp;

        tmp = *ptr++;
        uuid->clock_seq_low = tmp;

        (void) memcpy(uuid->node_addr, ptr, 6);

}

/*
 * Generates UUID based on DCE Version 4
 */
void
uuid_generate_random(uuid_t uu)
{
        struct uuid     uuid;

        if (uu == NULL)
                return;

        (void) memset(uu, 0, sizeof (uuid_t));
        (void) memset(&uuid, 0, sizeof (struct uuid));

        fill_random_bytes(uu, sizeof (uuid_t));
        string_to_struct(&uuid, uu);
        /*
         * This is version 4, so say so in the UUID version field (4 bits)
         */
        uuid.time_hi_and_version |= (1 << 14);
        /*
         * we don't want the bit 1 to be set also which is for version 1
         */
        uuid.time_hi_and_version &= VER1_MASK;

        /*
         * The variant for this format is the 2 high bits set to 10,
         * so here it is
         */
        uuid.clock_seq_hi_and_reserved |= 0x80;

        /*
         * Set MSB of Ethernet address to 1 to indicate that it was generated
         * randomly
         */
        uuid.node_addr[0] |= 0x80;
        struct_to_string(uu, &uuid);
}

/*
 * Generates UUID based on DCE Version 1.
 */
void
uuid_generate_time(uuid_t uu)
{
        struct  uuid uuid;

        if (uu == NULL)
                return;

        if (uuid_create(&uuid) < 0) {
                uuid_generate_random(uu);
                return;
        }

        struct_to_string(uu, &uuid);
}

/*
 * Creates a new UUID. The uuid will be generated based on high-quality
 * randomness from /dev/urandom, if available by calling uuid_generate_random.
 * If it failed to generate UUID then uuid_generate will call
 * uuid_generate_time.
 */
void
uuid_generate(uuid_t uu)
{
        if (uu == NULL) {
                return;
        }
        if (fd_urand == -1) {
                (void) mutex_lock(&urandmtx);
                /* check again now that we have the mutex */
                if (fd_urand == -1) {
                        if ((fd_urand = open(URANDOM_PATH, O_RDONLY)) >= 0)
                                load_cache();
                }
                (void) mutex_unlock(&urandmtx);
        }
        if (fd_urand >= 0) {
                uuid_generate_random(uu);
        } else {
                (void) uuid_generate_time(uu);
        }
}

/*
 * Copies the UUID variable src to dst.
 */
void
uuid_copy(uuid_t dst, uuid_t src)
{
        (void) memcpy(dst, src, UUID_LEN);
}

/*
 * Sets the value of the supplied uuid variable uu, to the NULL value.
 */
void
uuid_clear(uuid_t uu)
{
        (void) memset(uu, 0, UUID_LEN);
}

/*
 * This function converts the supplied UUID uu from the internal
 * binary format into a 36-byte string (plus trailing null char)
 * and stores this value in the character string pointed to by out.
 */
static void
uuid_unparse_common(uuid_t uu, char *out, boolean_t upper)
{
        struct uuid     uuid;
        uint16_t        clock_seq;
        char            etheraddr[13];
        int             index = 0, i;

        /* basic sanity checking */
        if (uu == NULL) {
                return;
        }

        string_to_struct(&uuid, uu);
        clock_seq = uuid.clock_seq_hi_and_reserved;
        clock_seq = (clock_seq  << 8) | uuid.clock_seq_low;
        for (i = 0; i < 6; i++) {
                (void) sprintf(&etheraddr[index++], upper ? "%.2X" : "%.2x",
                    uuid.node_addr[i]);
                index++;
        }
        etheraddr[index] = '\0';

        (void) snprintf(out, 25,
            upper ? "%08X-%04X-%04X-%04X-" : "%08x-%04x-%04x-%04x-",
            uuid.time_low, uuid.time_mid, uuid.time_hi_and_version, clock_seq);
        (void) strlcat(out, etheraddr, UUID_PRINTABLE_STRING_LENGTH);
}

void
uuid_unparse_upper(uuid_t uu, char *out)
{
        uuid_unparse_common(uu, out, B_TRUE);
}

void
uuid_unparse_lower(uuid_t uu, char *out)
{
        uuid_unparse_common(uu, out, B_FALSE);
}

void
uuid_unparse(uuid_t uu, char *out)
{
        /*
         * Historically uuid_unparse on Solaris returns lower case,
         * for compatibility we preserve this behaviour.
         */
        uuid_unparse_common(uu, out, B_FALSE);
}

/*
 * The uuid_is_null function compares the value of the supplied
 * UUID variable uu to the NULL value. If the value is equal
 * to the NULL UUID, 1 is returned, otherwise 0 is returned.
 */
int
uuid_is_null(uuid_t uu)
{
        int             i;
        uuid_t          null_uu;

        (void) memset(null_uu, 0, sizeof (uuid_t));
        i = memcmp(uu, null_uu, sizeof (uuid_t));
        if (i == 0) {
                /* uu is NULL uuid */
                return (1);
        } else {
                return (0);
        }
}

/*
 * uuid_parse converts the UUID string given by 'in' into the
 * internal uuid_t format. The input UUID is a string of the form
 * cefa7a9c-1dd2-11b2-8350-880020adbeef in printf(3C) format.
 * Upon successfully parsing the input string, UUID is stored
 * in the location pointed to by uu
 */
int
uuid_parse(char *in, uuid_t uu)
{

        char            *ptr, buf[3];
        int             i;
        struct uuid     uuid;
        uint16_t        clock_seq;

        /* do some sanity checking */
        if ((strlen(in) != 36) || (uu == NULL) || (in[36] != '\0')) {
                return (-1);
        }

        ptr = in;
        for (i = 0; i < 36; i++, ptr++) {
                if ((i == 8) || (i == 13) || (i == 18) || (i == 23)) {
                        if (*ptr != '-') {
                                return (-1);
                        }
                } else {
                        if (!isxdigit(*ptr)) {
                                return (-1);
                        }
                }
        }

        uuid.time_low = strtoul(in, NULL, 16);
        uuid.time_mid = strtoul(in+9, NULL, 16);
        uuid.time_hi_and_version = strtoul(in+14, NULL, 16);
        clock_seq = strtoul(in+19, NULL, 16);
        uuid.clock_seq_hi_and_reserved = (clock_seq & 0xFF00) >> 8;
        uuid.clock_seq_low = (clock_seq & 0xFF);

        ptr = in+24;
        buf[2] = '\0';
        for (i = 0; i < 6; i++) {
                buf[0] = *ptr++;
                buf[1] = *ptr++;
                uuid.node_addr[i] = strtoul(buf, NULL, 16);
        }
        struct_to_string(uu, &uuid);
        return (0);
}

/*
 * uuid_time extracts the time at which the supplied UUID uu
 * was created. This function can only extract the creation
 * time for UUIDs created with the uuid_generate_time function.
 * The time at which the UUID was created, in seconds and
 * microseconds since the epoch is stored in the location
 * pointed to by ret_tv.
 */
time_t
uuid_time(uuid_t uu, struct timeval *ret_tv)
{
        struct uuid     uuid;
        uint_t          high;
        struct timeval  tv;
        u_longlong_t    clock_reg;
        uint_t          tmp;
        uint8_t         clk;

        string_to_struct(&uuid, uu);
        tmp = (uuid.time_hi_and_version & 0xF000) >> 12;
        clk = uuid.clock_seq_hi_and_reserved;

        /* check if uu is NULL, Version = 1 of DCE and Variant = 0b10x */
        if ((uu == NULL) || ((tmp & 0x01) != 0x01) || ((clk & 0x80) != 0x80)) {
                return (-1);
        }
        high = uuid.time_mid | ((uuid.time_hi_and_version & 0xFFF) << 16);
        clock_reg = uuid.time_low | ((u_longlong_t)high << 32);

        clock_reg -= (((u_longlong_t)0x01B21DD2) << 32) + 0x13814000;
        tv.tv_sec = clock_reg / 10000000;
        tv.tv_usec = (clock_reg % 10000000) / 10;

        if (ret_tv) {
                *ret_tv = tv;
        }

        return (tv.tv_sec);
}