Move random number re-seeding out of the hot path

Instead of checking if we need to re-seed for every isc_random call,
seed the random number generator in the libisc global initializer
and the per-thread initializer.

lib/isc/Makefile.am

@@ -180,6 +180,7 @@ libisc_la_SOURCES =		\
 	quota.c			\
 	radix.c			\
 	random.c		\
+	random_p.h		\
 	ratelimiter.c		\
 	regex.c			\
 	region.c		\

lib/isc/random.c

@@ -35,7 +35,6 @@
 #include <string.h>
 #include <unistd.h>
 
-#include <isc/once.h>
 #include <isc/random.h>
 #include <isc/result.h>
 #include <isc/thread.h>
@@ -43,6 +42,7 @@
 #include <isc/util.h>
 
 #include "entropy_private.h"
+#include "random_p.h"
 
 /*
  * Written in 2018 by David Blackman and Sebastiano Vigna (vigna@acm.org)
@@ -88,11 +88,8 @@ next(void) {
 
 	return (result_starstar);
 }
-
-static thread_local isc_once_t isc_random_once = ISC_ONCE_INIT;
-
-static void
-isc_random_initialize(void) {
+void
+isc__random_initialize(void) {
 	int useed[4] = { 0, 0, 0, 1 };
 #if FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
 	/*
@@ -108,22 +105,16 @@ isc_random_initialize(void) {
 
 uint8_t
 isc_random8(void) {
-	RUNTIME_CHECK(isc_once_do(&isc_random_once, isc_random_initialize) ==
-		      ISC_R_SUCCESS);
 	return ((uint8_t)next());
 }
 
 uint16_t
 isc_random16(void) {
-	RUNTIME_CHECK(isc_once_do(&isc_random_once, isc_random_initialize) ==
-		      ISC_R_SUCCESS);
 	return ((uint16_t)next());
 }
 
 uint32_t
 isc_random32(void) {
-	RUNTIME_CHECK(isc_once_do(&isc_random_once, isc_random_initialize) ==
-		      ISC_R_SUCCESS);
 	return (next());
 }
 
@@ -135,9 +126,6 @@ isc_random_buf(void *buf, size_t buflen) {
 	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));
@@ -149,8 +137,6 @@ isc_random_buf(void *buf, size_t buflen) {
 
 uint32_t
 isc_random_uniform(uint32_t limit) {
-	RUNTIME_CHECK(isc_once_do(&isc_random_once, isc_random_initialize) ==
-		      ISC_R_SUCCESS);
 	/*
 	 * Daniel Lemire's nearly-divisionless unbiased bounded random numbers.
 	 *

lib/isc/random_p.h

@@ -0,0 +1,30 @@
+/*
+ * 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.
+ */
+
+#pragma once
+
+#include <isc/lang.h>
+
+/*! \file isc/random_p.h
+ * \brief For automatically seeding and re-seeding when required.
+ */
+
+ISC_LANG_BEGINDECLS
+
+void
+isc__random_initialize(void);
+/*!<
+ * \brief Seed the thread-local random number state with fresh entropy.
+ */
+
+ISC_LANG_ENDDECLS

lib/isc/trampoline.c

@@ -22,6 +22,7 @@
 #include <isc/util.h>
 #include <isc/uv.h>
 
+#include "random_p.h"
 #include "trampoline_p.h"
 
 #define ISC__TRAMPOLINE_UNUSED 0
@@ -87,6 +88,8 @@ isc__trampoline_initialize(void) {
 		trampolines[i] = NULL;
 	}
 	isc__trampoline_min = 1;
+
+	isc__random_initialize();
 }
 
 void
@@ -175,6 +178,12 @@ isc__trampoline_attach(isc__trampoline_t *trampoline) {
 	 * malloc() + free() calls altogether, as it would foil the fix.
 	 */
 	trampoline->jemalloc_enforce_init = malloc(8);
+
+	/*
+	 * Re-seed the random number generator in each thread.
+	 */
+	isc__random_initialize();
+
 	uv_mutex_unlock(&isc__trampoline_lock);
 }
 

tests/isc/random_test.c

@@ -640,6 +640,13 @@ binarymatrixrank(uint16_t *values, size_t length) {
  *** Tests for isc_random32() function
  ***/
 
+/* Ensure the RNG has been automatically seeded. */
+ISC_RUN_TEST_IMPL(isc_random32_initialized) {
+	UNUSED(state);
+
+	assert_int_not_equal(isc_random32(), 0);
+}
+
 /* Monobit test for the RANDOM */
 ISC_RUN_TEST_IMPL(isc_random32_monobit) {
 	UNUSED(state);
@@ -764,6 +771,7 @@ ISC_RUN_TEST_IMPL(isc_nonce_bytes_binarymatrixrank) {
 
 ISC_TEST_LIST_START
 
+ISC_TEST_ENTRY(isc_random32_initialized)
 ISC_TEST_ENTRY(isc_random32_monobit)
 ISC_TEST_ENTRY(isc_random32_runs)
 ISC_TEST_ENTRY(isc_random32_blockfrequency)