/* $NetBSD: random.c,v 1.1.2.2 2024/02/24 13:07:21 martin Exp $ */ /* * Copyright (C) Internet Systems Consortium, Inc. ("ISC") * * SPDX-License-Identifier: MPL-2.0 * * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, you can obtain one at https://mozilla.org/MPL/2.0/. * * See the COPYRIGHT file distributed with this work for additional * information regarding copyright ownership. */ /* * Portions of isc_random_uniform(): * * Copyright (c) 1996, David Mazieres * Copyright (c) 2008, Damien Miller * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #include #include #include #include #include #include #include #include #include #include #include #include "entropy_private.h" /* * The specific implementation for PRNG is included as a C file * that has to provide a static variable named seed, and a function * uint32_t next(void) that provides next random number. * * The implementation must be thread-safe. */ /* * Two contestants have been considered: the xoroshiro family of the * functions by Villa&Blackman, and PCG by O'Neill. After * consideration, the xoshiro128starstar function has been chosen as * the uint32_t random number provider because it is very fast and has * good enough properties for our usage pattern. */ #include "xoshiro128starstar.c" ISC_THREAD_LOCAL isc_once_t isc_random_once = ISC_ONCE_INIT; static void isc_random_initialize(void) { int useed[4] = { 0, 0, 0, 1 }; #if FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION /* * Set a constant seed to help in problem reproduction should fuzzing * find a crash or a hang. The seed array must be non-zero else * xoshiro128starstar will generate an infinite series of zeroes. */ #else /* if FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION */ isc_entropy_get(useed, sizeof(useed)); #endif /* if FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION */ memmove(seed, useed, sizeof(seed)); } uint8_t isc_random8(void) { RUNTIME_CHECK(isc_once_do(&isc_random_once, isc_random_initialize) == ISC_R_SUCCESS); return (next() & 0xff); } uint16_t isc_random16(void) { RUNTIME_CHECK(isc_once_do(&isc_random_once, isc_random_initialize) == ISC_R_SUCCESS); return (next() & 0xffff); } uint32_t isc_random32(void) { RUNTIME_CHECK(isc_once_do(&isc_random_once, isc_random_initialize) == ISC_R_SUCCESS); return (next()); } void isc_random_buf(void *buf, size_t buflen) { int i; uint32_t r; REQUIRE(buf != NULL); REQUIRE(buflen > 0); RUNTIME_CHECK(isc_once_do(&isc_random_once, isc_random_initialize) == ISC_R_SUCCESS); for (i = 0; i + sizeof(r) <= buflen; i += sizeof(r)) { r = next(); memmove((uint8_t *)buf + i, &r, sizeof(r)); } r = next(); memmove((uint8_t *)buf + i, &r, buflen % sizeof(r)); return; } uint32_t isc_random_uniform(uint32_t upper_bound) { /* Copy of arc4random_uniform from OpenBSD */ uint32_t r, min; RUNTIME_CHECK(isc_once_do(&isc_random_once, isc_random_initialize) == ISC_R_SUCCESS); if (upper_bound < 2) { return (0); } #if (ULONG_MAX > 0xffffffffUL) min = 0x100000000UL % upper_bound; #else /* if (ULONG_MAX > 0xffffffffUL) */ /* Calculate (2**32 % upper_bound) avoiding 64-bit math */ if (upper_bound > 0x80000000) { min = 1 + ~upper_bound; /* 2**32 - upper_bound */ } else { /* (2**32 - (x * 2)) % x == 2**32 % x when x <= 2**31 */ min = ((0xffffffff - (upper_bound * 2)) + 1) % upper_bound; } #endif /* if (ULONG_MAX > 0xffffffffUL) */ /* * This could theoretically loop forever but each retry has * p > 0.5 (worst case, usually far better) of selecting a * number inside the range we need, so it should rarely need * to re-roll. */ for (;;) { r = next(); if (r >= min) { break; } } return (r % upper_bound); }