Fix: sessiond: instance uuid is not sufficiently unique

[lttng-tools.git] / src / common / uuid.c

/*
 * Copyright (C) 2018 Jérémie Galarneau <jeremie.galarneau@efficios.com>
 * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com>
 *
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 */

#include <common/compat/string.h>
#include <common/random.h>
#include <common/error.h>

#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include "uuid.h"

static const lttng_uuid nil_uuid;
static bool lttng_uuid_is_init;

void lttng_uuid_to_str(const lttng_uuid uuid, char *uuid_str)
{
	sprintf(uuid_str, LTTNG_UUID_FMT, LTTNG_UUID_FMT_VALUES(uuid));
}

int lttng_uuid_from_str(const char *str_in, lttng_uuid uuid_out)
{
	int ret = 0;
	lttng_uuid uuid_scan;

	if ((str_in == NULL) || (uuid_out == NULL)) {
		ret = -1;
		goto end;
	}

	if (lttng_strnlen(str_in, LTTNG_UUID_STR_LEN) != LTTNG_UUID_STR_LEN - 1) {
		ret = -1;
		goto end;
	}

	/* Scan to a temporary location in case of a partial match. */
	if (sscanf(str_in, LTTNG_UUID_FMT, LTTNG_UUID_SCAN_VALUES(uuid_scan)) !=
			LTTNG_UUID_LEN) {
		ret = -1;
	}

	lttng_uuid_copy(uuid_out, uuid_scan);
end:
	return ret;
}

bool lttng_uuid_is_equal(const lttng_uuid a, const lttng_uuid b)
{
	return memcmp(a, b, LTTNG_UUID_LEN) == 0;
}

bool lttng_uuid_is_nil(const lttng_uuid uuid)
{
	return memcmp(nil_uuid, uuid, sizeof(lttng_uuid)) == 0;
}

void lttng_uuid_copy(lttng_uuid dst, const lttng_uuid src)
{
	memcpy(dst, src, LTTNG_UUID_LEN);
}

/*
 * Generate a random UUID according to RFC4122, section 4.4.
 */
int lttng_uuid_generate(lttng_uuid uuid_out)
{
	int i, ret = 0;

	if (uuid_out == NULL) {
		ret = -1;
		goto end;
	}

	if (!lttng_uuid_is_init) {
		seed_t new_seed;

		ret = lttng_produce_best_effort_random_seed(&new_seed);
		if (ret) {
			ERR("Failed to initialize random seed while generating UUID");
			goto end;
		}

		srand(new_seed);
		lttng_uuid_is_init = true;
	}

	/*
	 * Generate 16 bytes of random bits.
	 */
	for (i = 0; i < LTTNG_UUID_LEN; i++) {
		uuid_out[i] = (uint8_t) rand();
	}

	/*
	 * Set the two most significant bits (bits 6 and 7) of the
	 * clock_seq_hi_and_reserved to zero and one, respectively.
	 */
	uuid_out[8] &= ~(1 << 6);
	uuid_out[8] |= (1 << 7);

	/*
	 * Set the four most significant bits (bits 12 through 15) of the
	 * time_hi_and_version field to the 4-bit version number from
	 * Section 4.1.3.
	 */
	uuid_out[6] &= 0x0f;
	uuid_out[6] |= (LTTNG_UUID_VER << 4);

end:
	return ret;
}