lib/uuid/gen_uuid.c

   1 /*
   2  * gen_uuid.c --- generate a DCE-compatible uuid
   3  *
   4  * Copyright (C) 1996, 1997, 1998, 1999 Theodore Ts'o.
   5  *
   6  * %Begin-Header%
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, and the entire permission notice in its entirety,
  12  *    including the disclaimer of warranties.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. The name of the author may not be used to endorse or promote
  17  *    products derived from this software without specific prior
  18  *    written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
  21  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  22  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
  23  * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
  24  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  25  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
  26  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  27  * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  28  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
  30  * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
  31  * DAMAGE.
  32  * %End-Header%
  33  */
  34
  35 /*
  36  * Force inclusion of SVID stuff since we need it if we're compiling in
  37  * gcc-wall wall mode
  38  */
  39 #define _SVID_SOURCE
  40
  41 #ifdef HAVE_UNISTD_H
  42 #include <unistd.h>
  43 #endif
  44 #ifdef HAVE_STDLIB_H
  45 #include <stdlib.h>
  46 #endif
  47 #include <string.h>
  48 #include <fcntl.h>
  49 #include <errno.h>
  50 #include <sys/types.h>
  51 #include <sys/time.h>
  52 #include <sys/stat.h>
  53 #include <sys/file.h>
  54 #ifdef HAVE_SYS_IOCTL_H
  55 #include <sys/ioctl.h>
  56 #endif
  57 #ifdef HAVE_SYS_SOCKET_H
  58 #include <sys/socket.h>
  59 #endif
  60 #ifdef HAVE_SYS_SOCKIO_H
  61 #include <sys/sockio.h>
  62 #endif
  63 #ifdef HAVE_NET_IF_H
  64 #include <net/if.h>
  65 #endif
  66 #ifdef HAVE_NETINET_IN_H
  67 #include <netinet/in.h>
  68 #endif
  69 #ifdef HAVE_NET_IF_DL_H
  70 #include <net/if_dl.h>
  71 #endif
  72
  73 #include "uuidP.h"
  74
  75 #ifdef HAVE_SRANDOM
  76 #define srand(x)        srandom(x)
  77 #define rand()          random()
  78 #endif
  79
  80 static int get_random_fd(void)
  81 {
  82         struct timeval  tv;
  83         static int      fd = -2;
  84         int             i;
  85
  86         if (fd == -2) {
  87                 gettimeofday(&tv, 0);
  88                 fd = open("/dev/urandom", O_RDONLY);
  89                 if (fd == -1)
  90                         fd = open("/dev/random", O_RDONLY | O_NONBLOCK);
  91                 if (fd >= 0) {
  92                         i = fcntl(fd, F_GETFD);
  93                         if (i >= 0)
  94                                 fcntl(fd, F_SETFD, i | FD_CLOEXEC);
  95                 }
  96                 srand((getpid() << 16) ^ getuid() ^ tv.tv_sec ^ tv.tv_usec);
  97         }
  98         /* Crank the random number generator a few times */
  99         gettimeofday(&tv, 0);
 100         for (i = (tv.tv_sec ^ tv.tv_usec) & 0x1F; i > 0; i--)
 101                 rand();
 102         return fd;
 103 }
 104
 105
 106 /*
 107  * Generate a series of random bytes.  Use /dev/urandom if possible,
 108  * and if not, use srandom/random.
 109  */
 110 static void get_random_bytes(void *buf, int nbytes)
 111 {
 112         int i, n = nbytes, fd = get_random_fd();
 113         int lose_counter = 0;
 114         unsigned char *cp = (unsigned char *) buf;
 115
 116         if (fd >= 0) {
 117                 while (n > 0) {
 118                         i = read(fd, cp, n);
 119                         if (i <= 0) {
 120                                 if (lose_counter++ > 16)
 121                                         break;
 122                                 continue;
 123                         }
 124                         n -= i;
 125                         cp += i;
 126                         lose_counter = 0;
 127                 }
 128         }
 129
 130         /*
 131          * We do this all the time, but this is the only source of
 132          * randomness if /dev/random/urandom is out to lunch.
 133          */
 134         for (cp = buf, i = 0; i < nbytes; i++)
 135                 *cp++ ^= (rand() >> 7) & 0xFF;
 136         return;
 137 }
 138
 139 /*
 140  * Get the ethernet hardware address, if we can find it...
 141  */
 142 static int get_node_id(unsigned char *node_id)
 143 {
 144 #ifdef HAVE_NET_IF_H
 145         int             sd;
 146         struct ifreq    ifr, *ifrp;
 147         struct ifconf   ifc;
 148         char buf[1024];
 149         int             n, i;
 150         unsigned char   *a;
 151 #ifdef HAVE_NET_IF_DL_H
 152         struct sockaddr_dl *sdlp;
 153 #endif
 154
 155 /*
 156  * BSD 4.4 defines the size of an ifreq to be
 157  * max(sizeof(ifreq), sizeof(ifreq.ifr_name)+ifreq.ifr_addr.sa_len
 158  * However, under earlier systems, sa_len isn't present, so the size is
 159  * just sizeof(struct ifreq)
 160  */
 161 #ifdef HAVE_SA_LEN
 162 #ifndef max
 163 #define max(a,b) ((a) > (b) ? (a) : (b))
 164 #endif
 165 #define ifreq_size(i) max(sizeof(struct ifreq),\
 166      sizeof((i).ifr_name)+(i).ifr_addr.sa_len)
 167 #else
 168 #define ifreq_size(i) sizeof(struct ifreq)
 169 #endif /* HAVE_SA_LEN*/
 170
 171         sd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
 172         if (sd < 0) {
 173                 return -1;
 174         }
 175         memset(buf, 0, sizeof(buf));
 176         ifc.ifc_len = sizeof(buf);
 177         ifc.ifc_buf = buf;
 178         if (ioctl (sd, SIOCGIFCONF, (char *)&ifc) < 0) {
 179                 close(sd);
 180                 return -1;
 181         }
 182         n = ifc.ifc_len;
 183         for (i = 0; i < n; i+= ifreq_size(*ifrp) ) {
 184                 ifrp = (struct ifreq *)((char *) ifc.ifc_buf+i);
 185                 strncpy(ifr.ifr_name, ifrp->ifr_name, IFNAMSIZ);
 186 #ifdef SIOCGIFHWADDR
 187                 if (ioctl(sd, SIOCGIFHWADDR, &ifr) < 0)
 188                         continue;
 189                 a = (unsigned char *) &ifr.ifr_hwaddr.sa_data;
 190 #else
 191 #ifdef SIOCGENADDR
 192                 if (ioctl(sd, SIOCGENADDR, &ifr) < 0)
 193                         continue;
 194                 a = (unsigned char *) ifr.ifr_enaddr;
 195 #else
 196 #ifdef HAVE_NET_IF_DL_H
 197                 sdlp = (struct sockaddr_dl *) &ifrp->ifr_addr;
 198                 if ((sdlp->sdl_family != AF_LINK) || (sdlp->sdl_alen != 6))
 199                         continue;
 200                 a = (unsigned char *) &sdlp->sdl_data[sdlp->sdl_nlen];
 201 #else
 202                 /*
 203                  * XXX we don't have a way of getting the hardware
 204                  * address
 205                  */
 206                 close(sd);
 207                 return 0;
 208 #endif /* HAVE_NET_IF_DL_H */
 209 #endif /* SIOCGENADDR */
 210 #endif /* SIOCGIFHWADDR */
 211                 if (!a[0] && !a[1] && !a[2] && !a[3] && !a[4] && !a[5])
 212                         continue;
 213                 if (node_id) {
 214                         memcpy(node_id, a, 6);
 215                         close(sd);
 216                         return 1;
 217                 }
 218         }
 219         close(sd);
 220 #endif
 221         return 0;
 222 }
 223
 224 /* Assume that the gettimeofday() has microsecond granularity */
 225 #define MAX_ADJUSTMENT 10
 226
 227 static int get_clock(uint32_t *clock_high, uint32_t *clock_low, uint16_t *ret_clock_seq)
 228 {
 229         static int                      adjustment = 0;
 230         static struct timeval           last = {0, 0};
 231         static uint16_t                 clock_seq;
 232         struct timeval                  tv;
 233         unsigned long long              clock_reg;
 234
 235 try_again:
 236         gettimeofday(&tv, 0);
 237         if ((last.tv_sec == 0) && (last.tv_usec == 0)) {
 238                 get_random_bytes(&clock_seq, sizeof(clock_seq));
 239                 clock_seq &= 0x3FFF;
 240                 last = tv;
 241                 last.tv_sec--;
 242         }
 243         if ((tv.tv_sec < last.tv_sec) ||
 244             ((tv.tv_sec == last.tv_sec) &&
 245              (tv.tv_usec < last.tv_usec))) {
 246                 clock_seq = (clock_seq+1) & 0x3FFF;
 247                 adjustment = 0;
 248                 last = tv;
 249         } else if ((tv.tv_sec == last.tv_sec) &&
 250             (tv.tv_usec == last.tv_usec)) {
 251                 if (adjustment >= MAX_ADJUSTMENT)
 252                         goto try_again;
 253                 adjustment++;
 254         } else {
 255                 adjustment = 0;
 256                 last = tv;
 257         }
 258
 259         clock_reg = tv.tv_usec*10 + adjustment;
 260         clock_reg += ((unsigned long long) tv.tv_sec)*10000000;
 261         clock_reg += (((unsigned long long) 0x01B21DD2) << 32) + 0x13814000;
 262
 263         *clock_high = clock_reg >> 32;
 264         *clock_low = clock_reg;
 265         *ret_clock_seq = clock_seq;
 266         return 0;
 267 }
 268
 269 void uuid_generate_time(uuid_t out)
 270 {
 271         static unsigned char node_id[6];
 272         static int has_init = 0;
 273         struct uuid uu;
 274         uint32_t        clock_mid;
 275
 276         if (!has_init) {
 277                 if (get_node_id(node_id) <= 0) {
 278                         get_random_bytes(node_id, 6);
 279                         /*
 280                          * Set multicast bit, to prevent conflicts
 281                          * with IEEE 802 addresses obtained from
 282                          * network cards
 283                          */
 284                         node_id[0] |= 0x01;
 285                 }
 286                 has_init = 1;
 287         }
 288         get_clock(&clock_mid, &uu.time_low, &uu.clock_seq);
 289         uu.clock_seq |= 0x8000;
 290         uu.time_mid = (uint16_t) clock_mid;
 291         uu.time_hi_and_version = ((clock_mid >> 16) & 0x0FFF) | 0x1000;
 292         memcpy(uu.node, node_id, 6);
 293         uuid_pack(&uu, out);
 294 }
 295
 296 void uuid_generate_random(uuid_t out)
 297 {
 298         uuid_t  buf;
 299         struct uuid uu;
 300
 301         get_random_bytes(buf, sizeof(buf));
 302         uuid_unpack(buf, &uu);
 303
 304         uu.clock_seq = (uu.clock_seq & 0x3FFF) | 0x8000;
 305         uu.time_hi_and_version = (uu.time_hi_and_version & 0x0FFF) | 0x4000;
 306         uuid_pack(&uu, out);
 307 }
 308
 309 /*
 310  * This is the generic front-end to uuid_generate_random and
 311  * uuid_generate_time.  It uses uuid_generate_random only if
 312  * /dev/urandom is available, since otherwise we won't have
 313  * high-quality randomness.
 314  */
 315 void uuid_generate(uuid_t out)
 316 {
 317         if (get_random_fd() >= 0)
 318                 uuid_generate_random(out);
 319         else
 320                 uuid_generate_time(out);
 321 }