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 <common/compat/string.h>
  20 #include <stddef.h>
  21 #include <stdint.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <time.h>
  26
  27 #include "uuid.h"
  28
  29 static const lttng_uuid nil_uuid;
  30 static bool lttng_uuid_is_init;
  31
  32 void lttng_uuid_to_str(const lttng_uuid uuid, char *uuid_str)
  33 {
  34         sprintf(uuid_str, LTTNG_UUID_FMT, LTTNG_UUID_FMT_VALUES(uuid));
  35 }
  36
  37 int lttng_uuid_from_str(const char *str_in, lttng_uuid uuid_out)
  38 {
  39         int ret = 0;
  40         lttng_uuid uuid_scan;
  41
  42         if ((str_in == NULL) || (uuid_out == NULL)) {
  43                 ret = -1;
  44                 goto end;
  45         }
  46
  47         if (lttng_strnlen(str_in, LTTNG_UUID_STR_LEN) != LTTNG_UUID_STR_LEN - 1) {
  48                 ret = -1;
  49                 goto end;
  50         }
  51
  52         /* Scan to a temporary location in case of a partial match. */
  53         if (sscanf(str_in, LTTNG_UUID_FMT, LTTNG_UUID_SCAN_VALUES(uuid_scan)) !=
  54                         LTTNG_UUID_LEN) {
  55                 ret = -1;
  56         }
  57
  58         lttng_uuid_copy(uuid_out, uuid_scan);
  59 end:
  60         return ret;
  61 }
  62
  63 bool lttng_uuid_is_equal(const lttng_uuid a, const lttng_uuid b)
  64 {
  65         return memcmp(a, b, LTTNG_UUID_LEN) == 0;
  66 }
  67
  68 bool lttng_uuid_is_nil(const lttng_uuid uuid)
  69 {
  70         return memcmp(nil_uuid, uuid, sizeof(lttng_uuid)) == 0;
  71 }
  72
  73 void lttng_uuid_copy(lttng_uuid dst, const lttng_uuid src)
  74 {
  75         memcpy(dst, src, LTTNG_UUID_LEN);
  76 }
  77
  78 /*
  79  * Generate a random UUID according to RFC4122, section 4.4.
  80  */
  81 int lttng_uuid_generate(lttng_uuid uuid_out)
  82 {
  83         int i, ret = 0;
  84
  85         if (uuid_out == NULL) {
  86                 ret = -1;
  87                 goto end;
  88         }
  89
  90         if (!lttng_uuid_is_init) {
  91                 /*
  92                  * We don't need cryptographic quality randomness to
  93                  * generate UUIDs, seed rand with the epoch.
  94                  */
  95                 const time_t epoch = time(NULL);
  96
  97                 if (epoch == (time_t) -1) {
  98                         ret = -1;
  99                         goto end;
 100                 }
 101                 srand(epoch);
 102
 103                 lttng_uuid_is_init = true;
 104         }
 105
 106         /*
 107          * Generate 16 bytes of random bits.
 108          */
 109         for (i = 0; i < LTTNG_UUID_LEN; i++) {
 110                 uuid_out[i] = (uint8_t) rand();
 111         }
 112
 113         /*
 114          * Set the two most significant bits (bits 6 and 7) of the
 115          * clock_seq_hi_and_reserved to zero and one, respectively.
 116          */
 117         uuid_out[8] &= ~(1 << 6);
 118         uuid_out[8] |= (1 << 7);
 119
 120         /*
 121          * Set the four most significant bits (bits 12 through 15) of the
 122          * time_hi_and_version field to the 4-bit version number from
 123          * Section 4.1.3.
 124          */
 125         uuid_out[6] &= 0x0f;
 126         uuid_out[6] |= (LTTNG_UUID_VER << 4);
 127
 128 end:
 129         return ret;
 130 }