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  * This file may be redistributed under the terms of the GNU
   8  * Library General Public License.
   9  * %End-Header%
  10  */
  11
  12 /*
  13  * Force inclusion of SVID stuff since we need it if we're compiling in
  14  * gcc-wall wall mode
  15  */
  16 #define _SVID_SOURCE
  17
  18 #ifdef HAVE_UNISTD_H
  19 #include <unistd.h>
  20 #endif
  21 #ifdef HAVE_STDLIB_H
  22 #include <stdlib.h>
  23 #endif
  24 #include <string.h>
  25 #include <fcntl.h>
  26 #include <errno.h>
  27 #include <sys/types.h>
  28 #include <sys/time.h>
  29 #include <sys/stat.h>
  30 #include <sys/file.h>
  31 #ifdef HAVE_SYS_IOCTL_H
  32 #include <sys/ioctl.h>
  33 #endif
  34 #ifdef HAVE_SYS_SOCKET_H
  35 #include <sys/socket.h>
  36 #endif
  37 #ifdef HAVE_SYS_SOCKIO_H
  38 #include <sys/sockio.h>
  39 #endif
  40 #ifdef HAVE_NET_IF_H
  41 #include <net/if.h>
  42 #endif
  43 #ifdef HAVE_NETINET_IN_H
  44 #include <netinet/in.h>
  45 #endif
  46
  47 #include "uuidP.h"
  48
  49 #ifdef HAVE_SRANDOM
  50 #define srand(x)        srandom(x)
  51 #define rand()          random()
  52 #endif
  53
  54 static int get_random_fd(void)
  55 {
  56         struct timeval  tv;
  57         static int      fd = -2;
  58         int             i;
  59
  60         if (fd == -2) {
  61                 gettimeofday(&tv, 0);
  62                 fd = open("/dev/urandom", O_RDONLY);
  63                 if (fd == -1)
  64                         fd = open("/dev/random", O_RDONLY | O_NONBLOCK);
  65                 srand((getpid() << 16) ^ getuid() ^ tv.tv_sec ^ tv.tv_usec);
  66         }
  67         /* Crank the random number generator a few times */
  68         gettimeofday(&tv, 0);
  69         for (i = (tv.tv_sec ^ tv.tv_usec) & 0x1F; i > 0; i--)
  70                 rand();
  71         return fd;
  72 }
  73
  74
  75 /*
  76  * Generate a series of random bytes.  Use /dev/urandom if possible,
  77  * and if not, use srandom/random.
  78  */
  79 static void get_random_bytes(void *buf, int nbytes)
  80 {
  81         int i, n = nbytes, fd = get_random_fd();
  82         int lose_counter = 0;
  83         unsigned char *cp = (unsigned char *) buf;
  84
  85         if (fd >= 0) {
  86                 while (n > 0) {
  87                         i = read(fd, cp, n);
  88                         if (i <= 0) {
  89                                 if (lose_counter++ > 16)
  90                                         break;
  91                                 continue;
  92                         }
  93                         n -= i;
  94                         cp += i;
  95                         lose_counter = 0;
  96                 }
  97         }
  98
  99         /*
 100          * We do this all the time, but this is the only source of
 101          * randomness if /dev/random/urandom is out to lunch.
 102          */
 103         for (cp = buf, i = 0; i < nbytes; i++)
 104                 *cp++ ^= (rand() >> 7) & 0xFF;
 105         return;
 106 }
 107
 108 /*
 109  * Get the ethernet hardware address, if we can find it...
 110  */
 111 static int get_node_id(unsigned char *node_id)
 112 {
 113 #ifdef HAVE_NET_IF_H
 114         int             sd;
 115         struct ifreq    ifr, *ifrp;
 116         struct ifconf   ifc;
 117         char buf[1024];
 118         int             n, i;
 119         unsigned char   *a;
 120
 121 /*
 122  * BSD 4.4 defines the size of an ifreq to be
 123  * max(sizeof(ifreq), sizeof(ifreq.ifr_name)+ifreq.ifr_addr.sa_len
 124  * However, under earlier systems, sa_len isn't present, so the size is
 125  * just sizeof(struct ifreq)
 126  */
 127 #ifdef HAVE_SA_LEN
 128 #ifndef max
 129 #define max(a,b) ((a) > (b) ? (a) : (b))
 130 #endif
 131 #define ifreq_size(i) max(sizeof(struct ifreq),\
 132      sizeof((i).ifr_name)+(i).ifr_addr.sa_len)
 133 #else
 134 #define ifreq_size(i) sizeof(struct ifreq)
 135 #endif /* HAVE_SA_LEN*/
 136
 137         sd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
 138         if (sd < 0) {
 139                 return -1;
 140         }
 141         memset(buf, 0, sizeof(buf));
 142         ifc.ifc_len = sizeof(buf);
 143         ifc.ifc_buf = buf;
 144         if (ioctl (sd, SIOCGIFCONF, (char *)&ifc) < 0) {
 145                 close(sd);
 146                 return -1;
 147         }
 148         n = ifc.ifc_len;
 149         for (i = 0; i < n; i+= ifreq_size(*ifr) ) {
 150                 ifrp = (struct ifreq *)((char *) ifc.ifc_buf+i);
 151                 strncpy(ifr.ifr_name, ifrp->ifr_name, IFNAMSIZ);
 152 #ifdef SIOCGIFHWADDR
 153                 if (ioctl(sd, SIOCGIFHWADDR, &ifr) < 0)
 154                         continue;
 155                 a = (unsigned char *) &ifr.ifr_hwaddr.sa_data;
 156 #else
 157 #ifdef SIOCGENADDR
 158                 if (ioctl(sd, SIOCGENADDR, &ifr) < 0)
 159                         continue;
 160                 a = (unsigned char *) ifr.ifr_enaddr;
 161 #else
 162                 /*
 163                  * XXX we don't have a way of getting the hardware
 164                  * address
 165                  */
 166                 close(sd);
 167                 return 0;
 168 #endif /* SIOCGENADDR */
 169 #endif /* SIOCGIFHWADDR */
 170                 if (!a[0] && !a[1] && !a[2] && !a[3] && !a[4] && !a[5])
 171                         continue;
 172                 if (node_id) {
 173                         memcpy(node_id, a, 6);
 174                         close(sd);
 175                         return 1;
 176                 }
 177         }
 178         close(sd);
 179 #endif
 180         return 0;
 181 }
 182
 183 /* Assume that the gettimeofday() has microsecond granularity */
 184 #define MAX_ADJUSTMENT 10
 185
 186 static int get_clock(__u32 *clock_high, __u32 *clock_low, __u16 *ret_clock_seq)
 187 {
 188         static int                      adjustment = 0;
 189         static struct timeval           last = {0, 0};
 190         static __u16                    clock_seq;
 191         struct timeval                  tv;
 192         unsigned long long              clock_reg;
 193
 194 try_again:
 195         gettimeofday(&tv, 0);
 196         if ((last.tv_sec == 0) && (last.tv_usec == 0)) {
 197                 get_random_bytes(&clock_seq, sizeof(clock_seq));
 198                 clock_seq &= 0x1FFF;
 199                 last = tv;
 200                 last.tv_sec--;
 201         }
 202         if ((tv.tv_sec < last.tv_sec) ||
 203             ((tv.tv_sec == last.tv_sec) &&
 204              (tv.tv_usec < last.tv_usec))) {
 205                 clock_seq = (clock_seq+1) & 0x1FFF;
 206                 adjustment = 0;
 207                 last = tv;
 208         } else if ((tv.tv_sec == last.tv_sec) &&
 209             (tv.tv_usec == last.tv_usec)) {
 210                 if (adjustment >= MAX_ADJUSTMENT)
 211                         goto try_again;
 212                 adjustment++;
 213         } else {
 214                 adjustment = 0;
 215                 last = tv;
 216         }
 217
 218         clock_reg = tv.tv_usec*10 + adjustment;
 219         clock_reg += ((unsigned long long) tv.tv_sec)*10000000;
 220         clock_reg += (((unsigned long long) 0x01B21DD2) << 32) + 0x13814000;
 221
 222         *clock_high = clock_reg >> 32;
 223         *clock_low = clock_reg;
 224         *ret_clock_seq = clock_seq;
 225         return 0;
 226 }
 227
 228 void uuid_generate_time(uuid_t out)
 229 {
 230         static unsigned char node_id[6];
 231         static int has_init = 0;
 232         struct uuid uu;
 233         __u32   clock_mid;
 234
 235         if (!has_init) {
 236                 if (get_node_id(node_id) <= 0) {
 237                         get_random_bytes(node_id, 6);
 238                         /*
 239                          * Set multicast bit, to prevent conflicts
 240                          * with IEEE 802 addresses obtained from
 241                          * network cards
 242                          */
 243                         node_id[0] |= 0x01;
 244                 }
 245                 has_init = 1;
 246         }
 247         get_clock(&clock_mid, &uu.time_low, &uu.clock_seq);
 248         uu.clock_seq |= 0x8000;
 249         uu.time_mid = (__u16) clock_mid;
 250         uu.time_hi_and_version = (clock_mid >> 16) | 0x1000;
 251         memcpy(uu.node, node_id, 6);
 252         uuid_pack(&uu, out);
 253 }
 254
 255 void uuid_generate_random(uuid_t out)
 256 {
 257         uuid_t  buf;
 258         struct uuid uu;
 259
 260         get_random_bytes(buf, sizeof(buf));
 261         uuid_unpack(buf, &uu);
 262
 263         uu.clock_seq = (uu.clock_seq & 0x3FFF) | 0x8000;
 264         uu.time_hi_and_version = (uu.time_hi_and_version & 0x0FFF) | 0x4000;
 265         uuid_pack(&uu, out);
 266 }
 267
 268 /*
 269  * This is the generic front-end to uuid_generate_random and
 270  * uuid_generate_time.  It uses uuid_generate_random only if
 271  * /dev/urandom is available, since otherwise we won't have
 272  * high-quality randomness.
 273  */
 274 void uuid_generate(uuid_t out)
 275 {
 276         if (get_random_fd() >= 0)
 277                 uuid_generate_random(out);
 278         else
 279                 uuid_generate_time(out);
 280 }