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 std::string lttng::utils::uuid_to_str(const lttng_uuid& uuid)
  30 {
  31         std::string uuid_str(LTTNG_UUID_STR_LEN, '\0');
  32
  33         ::lttng_uuid_to_str(uuid, &uuid_str[0]);
  34
  35         /* Don't include '\0' in the C++ string. */
  36         uuid_str.resize(uuid_str.size() - 1);
  37
  38         return uuid_str;
  39 }
  40
  41 int lttng_uuid_from_str(const char *str_in, lttng_uuid& uuid_out)
  42 {
  43         int ret = 0;
  44         lttng_uuid uuid_scan;
  45
  46         if (str_in == nullptr) {
  47                 ret = -1;
  48                 goto end;
  49         }
  50
  51         if (lttng_strnlen(str_in, LTTNG_UUID_STR_LEN) != LTTNG_UUID_STR_LEN - 1) {
  52                 ret = -1;
  53                 goto end;
  54         }
  55
  56         /* Scan to a temporary location in case of a partial match. */
  57         if (sscanf(str_in, LTTNG_UUID_FMT, LTTNG_UUID_SCAN_VALUES(uuid_scan)) !=
  58                         LTTNG_UUID_LEN) {
  59                 ret = -1;
  60         }
  61
  62         uuid_out = uuid_scan;
  63 end:
  64         return ret;
  65 }
  66
  67 bool lttng_uuid_is_nil(const lttng_uuid& uuid)
  68 {
  69         return uuid == nil_uuid;
  70 }
  71
  72 /*
  73  * Generate a random UUID according to RFC4122, section 4.4.
  74  */
  75 int lttng_uuid_generate(lttng_uuid& uuid_out)
  76 {
  77         int i, ret = 0;
  78
  79         if (!lttng_uuid_is_init) {
  80                 /*
  81                  * We don't need cryptographic quality randomness to
  82                  * generate UUIDs, seed rand with the epoch.
  83                  */
  84                 const time_t epoch = time(NULL);
  85
  86                 if (epoch == (time_t) -1) {
  87                         ret = -1;
  88                         goto end;
  89                 }
  90
  91                 srand(epoch);
  92                 lttng_uuid_is_init = true;
  93         }
  94
  95         /*
  96          * Generate 16 bytes of random bits.
  97          */
  98         for (i = 0; i < LTTNG_UUID_LEN; i++) {
  99                 uuid_out[i] = (uint8_t) rand();
 100         }
 101
 102         /*
 103          * Set the two most significant bits (bits 6 and 7) of the
 104          * clock_seq_hi_and_reserved to zero and one, respectively.
 105          */
 106         uuid_out[8] &= ~(1 << 6);
 107         uuid_out[8] |= (1 << 7);
 108
 109         /*
 110          * Set the four most significant bits (bits 12 through 15) of the
 111          * time_hi_and_version field to the 4-bit version number from
 112          * Section 4.1.3.
 113          */
 114         uuid_out[6] &= 0x0f;
 115         uuid_out[6] |= (LTTNG_UUID_VER << 4);
 116
 117 end:
 118         return ret;
 119 }