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/*
* Phusion Passenger - https://www.phusionpassenger.com/
* Copyright (c) 2010-2017 Phusion Holding B.V.
*
* "Passenger", "Phusion Passenger" and "Union Station" are registered
* trademarks of Phusion Holding B.V.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#ifndef _PASSENGER_MEM_ZERO_GUARD_H_
#define _PASSENGER_MEM_ZERO_GUARD_H_
#include <string>
namespace Passenger {
using namespace std;
/**
* Fills the given memory space or string with zeroes when a MemoryZeroGuard object
* is destroyed. Useful for ensuring that buffers containing password data or
* other sensitive information is cleared when it goes out of scope.
*/
class MemZeroGuard {
private:
void *data;
unsigned int size;
string *str;
static void securelyZeroMemory(volatile void *data, unsigned int size) {
/* We do not use memset() here because the compiler may
* optimize out memset() calls. Instead, the following
* code is guaranteed to zero the memory.
* http://www.dwheeler.com/secure-programs/Secure-Programs-HOWTO/protect-secrets.html
*/
volatile char *p = (volatile char *) data;
while (size--) {
*p++ = 0;
}
}
public:
/**
* Creates a new MemZeroGuard object with a memory region to zero.
*
* @param data The data to zero after destruction.
* @param size The size of the data.
* @pre data != NULL
*/
MemZeroGuard(void *data, unsigned int size) {
this->data = data;
this->size = size;
this->str = NULL;
}
/**
* Creates a new MemoryZeroGuard object with a string to zero.
*
* @param str The string to zero after destruction.
*/
MemZeroGuard(string &str) {
this->data = NULL;
this->size = 0;
this->str = &str;
}
/**
* Zero the data immediately. The data will still be zeroed after
* destruction of this object.
*/
void zeroNow() {
if (str == NULL) {
securelyZeroMemory(data, size);
} else {
securelyZeroMemory((volatile void *) str->c_str(), str->size());
}
}
~MemZeroGuard() {
zeroNow();
}
};
} // namespace Passenger
#endif /* _PASSENGER_MEM_ZERO_GUARD_H_ */
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