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  * SPDX-License-Identifier: LGPL-2.1-only
   6  *
   7  */
   8
   9 #include <common/compat/string.h>
  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.h"
  18
  19 static const lttng_uuid nil_uuid;
  20 static bool lttng_uuid_is_init;
  21
  22 void lttng_uuid_to_str(const lttng_uuid uuid, char *uuid_str)
  23 {
  24         sprintf(uuid_str, LTTNG_UUID_FMT, LTTNG_UUID_FMT_VALUES(uuid));
  25 }
  26
  27 int lttng_uuid_from_str(const char *str_in, lttng_uuid uuid_out)
  28 {
  29         int ret = 0;
  30         lttng_uuid uuid_scan;
  31
  32         if ((str_in == NULL) || (uuid_out == NULL)) {
  33                 ret = -1;
  34                 goto end;
  35         }
  36
  37         if (lttng_strnlen(str_in, LTTNG_UUID_STR_LEN) != LTTNG_UUID_STR_LEN - 1) {
  38                 ret = -1;
  39                 goto end;
  40         }
  41
  42         /* Scan to a temporary location in case of a partial match. */
  43         if (sscanf(str_in, LTTNG_UUID_FMT, LTTNG_UUID_SCAN_VALUES(uuid_scan)) !=
  44                         LTTNG_UUID_LEN) {
  45                 ret = -1;
  46         }
  47
  48         lttng_uuid_copy(uuid_out, uuid_scan);
  49 end:
  50         return ret;
  51 }
  52
  53 bool lttng_uuid_is_equal(const lttng_uuid a, const lttng_uuid b)
  54 {
  55         return memcmp(a, b, LTTNG_UUID_LEN) == 0;
  56 }
  57
  58 bool lttng_uuid_is_nil(const lttng_uuid uuid)
  59 {
  60         return memcmp(nil_uuid, uuid, sizeof(lttng_uuid)) == 0;
  61 }
  62
  63 void lttng_uuid_copy(lttng_uuid dst, const lttng_uuid src)
  64 {
  65         memcpy(dst, src, LTTNG_UUID_LEN);
  66 }
  67
  68 /*
  69  * Generate a random UUID according to RFC4122, section 4.4.
  70  */
  71 int lttng_uuid_generate(lttng_uuid uuid_out)
  72 {
  73         int i, ret = 0;
  74
  75         if (uuid_out == NULL) {
  76                 ret = -1;
  77                 goto end;
  78         }
  79
  80         if (!lttng_uuid_is_init) {
  81                 /*
  82                  * We don't need cryptographic quality randomness to
  83                  * generate UUIDs, seed rand with the epoch.
  84                  */
  85                 const time_t epoch = time(NULL);
  86
  87                 if (epoch == (time_t) -1) {
  88                         ret = -1;
  89                         goto end;
  90                 }
  91                 srand(epoch);
  92
  93                 lttng_uuid_is_init = true;
  94         }
  95
  96         /*
  97          * Generate 16 bytes of random bits.
  98          */
  99         for (i = 0; i < LTTNG_UUID_LEN; i++) {
 100                 uuid_out[i] = (uint8_t) rand();
 101         }
 102
 103         /*
 104          * Set the two most significant bits (bits 6 and 7) of the
 105          * clock_seq_hi_and_reserved to zero and one, respectively.
 106          */
 107         uuid_out[8] &= ~(1 << 6);
 108         uuid_out[8] |= (1 << 7);
 109
 110         /*
 111          * Set the four most significant bits (bits 12 through 15) of the
 112          * time_hi_and_version field to the 4-bit version number from
 113          * Section 4.1.3.
 114          */
 115         uuid_out[6] &= 0x0f;
 116         uuid_out[6] |= (LTTNG_UUID_VER << 4);
 117
 118 end:
 119         return ret;
 120 }