mirror of https://github.com/getdnsapi/getdns.git
118 lines
3.5 KiB
C
118 lines
3.5 KiB
C
/* arc4_lock.c - global lock for arc4random
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*
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* Copyright (c) 2014, NLnet Labs. All rights reserved.
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*
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* This software is open source.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* Neither the name of the NLNET LABS nor the names of its contributors may
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* be used to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
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* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "config.h"
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#define LOCKRET(func) func
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#ifdef HAVE_PTHREAD
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#include "pthread.h"
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static pthread_mutex_t arc_lock = PTHREAD_MUTEX_INITIALIZER;
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void _ARC4_LOCK(void)
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{
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pthread_mutex_lock(&arc_lock);
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}
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void _ARC4_UNLOCK(void)
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{
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pthread_mutex_unlock(&arc_lock);
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}
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#elif defined(GETDNS_ON_WINDOWS)
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/*
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* There is no explicit arc4random_init call, and thus
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* the critical section must be allocated on the first call to
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* ARC4_LOCK(). The interlocked test is used to verify that
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* the critical section will be allocated only once.
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*
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* The work around is for the main program to call arc4random()
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* at the beginning of execution, before spinning new threads.
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*
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* There is also no explicit arc4random_close call, and thus
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* the critical section is never deleted. It will remain allocated
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* as long as the program runs.
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*/
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static CRITICAL_SECTION arc_critical_section;
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static volatile long arc_critical_section_initialized = 0;
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void _ARC4_LOCK(void)
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{
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long r = InterlockedCompareExchange(&arc_critical_section_initialized, 1, 0);
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if (r != 2)
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{
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if (r == 0)
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{
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InitializeCriticalSection(&arc_critical_section);
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arc_critical_section_initialized = 2;
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}
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else if (r == 1)
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{
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/*
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* If the critical section is initialized, the first test
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* will return the value 2.
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*
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* If several threads try to initialize the arc4random
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* state "at the same time", the first one will find
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* the "initialized" variable at 0, the other ones at 1.
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*
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* Since this is a fairly rare event, we resolve it with a
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* simple active wait loop.
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*/
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while (arc_critical_section_initialized != 2)
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{
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Sleep(1);
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}
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}
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}
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EnterCriticalSection(&arc_critical_section);
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}
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void _ARC4_UNLOCK(void)
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{
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LeaveCriticalSection(&arc_critical_section);
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}
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#else
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/* XXX - add non pthread specific lock routines here */
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void _ARC4_LOCK(void)
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{
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}
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void _ARC4_UNLOCK(void)
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{
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}
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#endif
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