src/common/uuid.cpp

   1 /*
   2  * Copyright (C) 2018 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com>
   4  *
   5  * SPDX-License-Identifier: LGPL-2.1-only
   6  *
   7  */
   8
   9 #include <common/compat/string.hpp>
  10 #include <stddef.h>
  11 #include <stdint.h>
  12 #include <stdio.h>
  13 #include <stdlib.h>
  14 #include <string.h>
  15 #include <time.h>
  16
  17 #include "uuid.hpp"
  18
  19 namespace {
  20 const lttng_uuid nil_uuid = {};
  21 bool lttng_uuid_is_init;
  22 } /* namespace */
  23
  24 void lttng_uuid_to_str(const lttng_uuid& uuid, char *uuid_str)
  25 {
  26         sprintf(uuid_str, LTTNG_UUID_FMT, LTTNG_UUID_FMT_VALUES(uuid));
  27 }
  28
  29 int lttng_uuid_from_str(const char *str_in, lttng_uuid& uuid_out)
  30 {
  31         int ret = 0;
  32         lttng_uuid uuid_scan;
  33
  34         if (str_in == nullptr) {
  35                 ret = -1;
  36                 goto end;
  37         }
  38
  39         if (lttng_strnlen(str_in, LTTNG_UUID_STR_LEN) != LTTNG_UUID_STR_LEN - 1) {
  40                 ret = -1;
  41                 goto end;
  42         }
  43
  44         /* Scan to a temporary location in case of a partial match. */
  45         if (sscanf(str_in, LTTNG_UUID_FMT, LTTNG_UUID_SCAN_VALUES(uuid_scan)) !=
  46                         LTTNG_UUID_LEN) {
  47                 ret = -1;
  48         }
  49
  50         uuid_out = uuid_scan;
  51 end:
  52         return ret;
  53 }
  54
  55 bool lttng_uuid_is_nil(const lttng_uuid& uuid)
  56 {
  57         return uuid == nil_uuid;
  58 }
  59
  60 /*
  61  * Generate a random UUID according to RFC4122, section 4.4.
  62  */
  63 int lttng_uuid_generate(lttng_uuid& uuid_out)
  64 {
  65         int i, ret = 0;
  66
  67         if (!lttng_uuid_is_init) {
  68                 /*
  69                  * We don't need cryptographic quality randomness to
  70                  * generate UUIDs, seed rand with the epoch.
  71                  */
  72                 const time_t epoch = time(NULL);
  73
  74                 if (epoch == (time_t) -1) {
  75                         ret = -1;
  76                         goto end;
  77                 }
  78
  79                 srand(epoch);
  80                 lttng_uuid_is_init = true;
  81         }
  82
  83         /*
  84          * Generate 16 bytes of random bits.
  85          */
  86         for (i = 0; i < LTTNG_UUID_LEN; i++) {
  87                 uuid_out[i] = (uint8_t) rand();
  88         }
  89
  90         /*
  91          * Set the two most significant bits (bits 6 and 7) of the
  92          * clock_seq_hi_and_reserved to zero and one, respectively.
  93          */
  94         uuid_out[8] &= ~(1 << 6);
  95         uuid_out[8] |= (1 << 7);
  96
  97         /*
  98          * Set the four most significant bits (bits 12 through 15) of the
  99          * time_hi_and_version field to the 4-bit version number from
 100          * Section 4.1.3.
 101          */
 102         uuid_out[6] &= 0x0f;
 103         uuid_out[6] |= (LTTNG_UUID_VER << 4);
 104
 105 end:
 106         return ret;
 107 }