src/common/uuid.c

   1 /*
   2  * Copyright (C) 2018 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com>
   4  *
   5  * This library is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU Lesser General Public License, version 2.1 only,
   7  * as published by the Free Software Foundation.
   8  *
   9  * This library is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
  12  * for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public License
  15  * along with this library; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  17  */
  18
  19 #include <stddef.h>
  20 #include <stdint.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <time.h>
  25
  26 #include "uuid.h"
  27
  28 static const lttng_uuid nil_uuid;
  29 static bool lttng_uuid_is_init;
  30
  31 void lttng_uuid_to_str(const lttng_uuid uuid, char *uuid_str)
  32 {
  33         sprintf(uuid_str, LTTNG_UUID_FMT, LTTNG_UUID_FMT_VALUES(uuid));
  34 }
  35
  36 int lttng_uuid_from_str(const char *str_in, lttng_uuid uuid_out)
  37 {
  38         int ret = 0;
  39         lttng_uuid uuid_scan;
  40
  41         if ((str_in == NULL) || (uuid_out == NULL)) {
  42                 ret = -1;
  43                 goto end;
  44         }
  45
  46         if (strnlen(str_in, LTTNG_UUID_STR_LEN) != LTTNG_UUID_STR_LEN - 1) {
  47                 ret = -1;
  48                 goto end;
  49         }
  50
  51         /* Scan to a temporary location in case of a partial match. */
  52         if (sscanf(str_in, LTTNG_UUID_FMT, LTTNG_UUID_SCAN_VALUES(uuid_scan)) !=
  53                         LTTNG_UUID_LEN) {
  54                 ret = -1;
  55         }
  56
  57         lttng_uuid_copy(uuid_out, uuid_scan);
  58 end:
  59         return ret;
  60 }
  61
  62 bool lttng_uuid_is_equal(const lttng_uuid a, const lttng_uuid b)
  63 {
  64         return memcmp(a, b, LTTNG_UUID_LEN) == 0;
  65 }
  66
  67 bool lttng_uuid_is_nil(const lttng_uuid uuid)
  68 {
  69         return memcmp(nil_uuid, uuid, sizeof(lttng_uuid)) == 0;
  70 }
  71
  72 void lttng_uuid_copy(lttng_uuid dst, const lttng_uuid src)
  73 {
  74         memcpy(dst, src, LTTNG_UUID_LEN);
  75 }
  76
  77 /*
  78  * Generate a random UUID according to RFC4122, section 4.4.
  79  */
  80 int lttng_uuid_generate(lttng_uuid uuid_out)
  81 {
  82         int i, ret = 0;
  83
  84         if (uuid_out == NULL) {
  85                 ret = -1;
  86                 goto end;
  87         }
  88
  89         if (!lttng_uuid_is_init) {
  90                 /*
  91                  * We don't need cryptographic quality randomness to
  92                  * generate UUIDs, seed rand with the epoch.
  93                  */
  94                 const time_t epoch = time(NULL);
  95
  96                 if (epoch == (time_t) -1) {
  97                         ret = -1;
  98                         goto end;
  99                 }
 100                 srand(epoch);
 101
 102                 lttng_uuid_is_init = true;
 103         }
 104
 105         /*
 106          * Generate 16 bytes of random bits.
 107          */
 108         for (i = 0; i < LTTNG_UUID_LEN; i++) {
 109                 uuid_out[i] = (uint8_t) rand();
 110         }
 111
 112         /*
 113          * Set the two most significant bits (bits 6 and 7) of the
 114          * clock_seq_hi_and_reserved to zero and one, respectively.
 115          */
 116         uuid_out[8] &= ~(1 << 6);
 117         uuid_out[8] |= (1 << 7);
 118
 119         /*
 120          * Set the four most significant bits (bits 12 through 15) of the
 121          * time_hi_and_version field to the 4-bit version number from
 122          * Section 4.1.3.
 123          */
 124         uuid_out[6] &= 0x0f;
 125         uuid_out[6] |= (LTTNG_UUID_VER << 4);
 126
 127 end:
 128         return ret;
 129 }