source: vbox/trunk/include/iprt/memsafer.h@ 52018

/** @file
 * IPRT - Memory Allocate for Sensitive Data.
 */

/*
 * Copyright (C) 2006-2014 Oracle Corporation
 *
 * This file is part of VirtualBox Open Source Edition (OSE), as
 * available from http://www.virtualbox.org. This file is free software;
 * you can redistribute it and/or modify it under the terms of the GNU
 * General Public License (GPL) as published by the Free Software
 * Foundation, in version 2 as it comes in the "COPYING" file of the
 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
 *
 * The contents of this file may alternatively be used under the terms
 * of the Common Development and Distribution License Version 1.0
 * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
 * VirtualBox OSE distribution, in which case the provisions of the
 * CDDL are applicable instead of those of the GPL.
 *
 * You may elect to license modified versions of this file under the
 * terms and conditions of either the GPL or the CDDL or both.
 */

#ifndef ___iprt_memsafer_h
#define ___iprt_memsafer_h

#include <iprt/mem.h> /* RTMEM_TAG */

RT_C_DECLS_BEGIN


/** @defgroup grp_rt_memsafer   RTMemSafer - Memory Allocator for Sensitive Data
 * @ingroup grp_rt
 *
 * This API doesn't provide 100% secure storage, it only provider more secure
 * and safer storage.  Thus the API isn't called RTMemSafe because you cannot
 * assume the data is safe against all kinds of extraction methods.
 *
 * The API guarantee that the memory won't be returned to the system containing
 * any of the information you put there.  It will be repeatedly wiped after use.
 *
 * The API tries to isolate your data from other information stored in the
 * process/system.  How well this is done depends on the implementation.  The
 * more complicated implementations will provide protection against heartbleed
 * like bugs where pieces of the heap is copied onto the wire.
 *
 * The more hardened implementations of the API will also do their best to
 * prevent the memory from ending up in process dumps or being readable by
 * debuggers.
 *
 * Finally, two functions are provided for scrambling the sensitive memory while
 * it's not in use.
 *
 * @{
 */

/** Default memory allocation, non-pageable memory backing, return error
 * if not possible to allocate such memor. */
#define RTMEMSAFER_ALLOC_EX_FLAGS_DEFAULT                   (0)
/** Allow pageable memory backing for cases where the content is not that sensitive
 * and allocating non-pageable memory failes. Use with care! */
#define RTMEMSAFER_ALLOC_EX_ALLOW_PAGEABLE_BACKING RT_BIT_32(1)

/**
 * Scrambles memory allocated by RTMemSaferAllocZEx and associates after use.
 *
 * Call this when the sensitive data isn't actively being used.  It will at a
 * minimum make sure the data is slightly scrambled, how hard it is to unbutton
 * is dependent on which implementation is used and available host support.
 *
 * The user must synchronize calls to RTMemSaferScramble and
 * RTMemSaferUnscramble, this memory allocator provides no help and keeps no
 * state information around.
 *
 * @returns IPRT status code.
 * @param   pv          The pointer returned by the allocation function.
 * @param   cb          The exact size given to the allocation function.
 */
RTDECL(int) RTMemSaferScramble(void *pv, size_t cb);

/**
 * Unscrambles memory allocated by RTMemSaferAllocZEx and associates before use.
 *
 * This undoes the effect of RTMemSaferScramble.
 *
 * @returns IPRT status code.
 * @param   pv          The pointer returned by the allocation function.
 * @param   cb          The exact size given to the allocation function.
 */
RTDECL(int) RTMemSaferUnscramble(void *pv, size_t cb);


/**
 * Allocates memory for sensitive data.
 *
 * Some effort will be taken to isolate the data from other memory allocation.
 * Memory is always zeroed.
 *
 * @returns IPRT status code.
 * @param   ppvNew      Where to return the pointer to the memory.
 * @param   cb          Number of bytes to allocate.
 * @param   fFlags      Flags for controlling the allocation. See RTMEMSAFER_ALLOC_EX_FLAGS_* defines.
 * @param   pszTag      Allocation tag used for statistics and such.
 */
RTDECL(int) RTMemSaferAllocZExTag(void **ppvNew, size_t cb, uint32_t fFlags, const char *pszTag) RT_NO_THROW;

/**
 * Allocates memory for sensitive data.
 *
 * Some effort will be taken to isolate the data from other memory allocation.
 * Memory is always zeroed.
 *
 * @returns IPRT status code.
 * @param   a_ppvNew    Where to return the pointer to the memory.
 * @param   a_cb        Number of bytes to allocate.
 * @param   a_fFlags    Flags for controlling the allocation. See RTMEMSAFER_ALLOC_EX_FLAGS_* defines.
 */
#define RTMemSaferAllocZEx(a_ppvNew, a_cb, a_fFlags) RTMemSaferAllocZExTag(a_ppvNew, a_cb, a_fFlags, RTMEM_TAG)

/**
 * Allocates memory for sensitive data.
 *
 * Some effort will be taken to isolate the data from other memory allocation.
 * Memory is always zeroed.
 *
 * @returns Pointer to the allocated memory.
 * @param   cb          Number of bytes to allocate.
 * @param   pszTag      Allocation tag used for statistics and such.
 */
RTDECL(void *) RTMemSaferAllocZTag(size_t cb, const char *pszTag) RT_NO_THROW;

/**
 * Allocates memory for sensitive data.
 *
 * Some effort will be taken to isolate the data from other memory allocation.
 * Memory is always zeroed.
 *
 * @returns Pointer to the allocated memory.
 * @param   a_cb        Number of bytes to allocate.
 */
#define RTMemSaferAllocZ(a_cb) RTMemSaferAllocZTag(a_cb, RTMEM_TAG)


/**
 * Reallocates memory allocated by RTMemSaferAllocZEx, RTMemSaferAllocZ,
 * RTMemSaferAllocZExTag, or RTMemSaferAllocZTag.
 *
 * When extending the allocation, the new memory will be zeroed.  When shrinking
 * the allocation the left over memory will be wiped clean using
 * RTMemWipeThorougly.
 *
 * The function follows the standard realloc behavior.
 *
 * @returns IPRT status code.
 * @param   cbOld       The current allocation size.
 * @param   pvOld       The current allocation.
 * @param   cbNew       The size of the new allocation.
 * @param   ppvNew      Where to return the pointer to the new memory.
 * @param   fFlags      Flags for controlling the allocation. See RTMEMSAFER_ALLOC_EX_FLAGS_* defines,
 *                      this takes only effect when allocating completely new memory, for extending or
 *                      shrinking existing allocations the flags of the allocation take precedence.
 * @param   pszTag      Allocation tag used for statistics and such.
 */
RTDECL(int) RTMemSaferReallocZExTag(size_t cbOld, void *pvOld, size_t cbNew, void **ppvNew, uint32_t fFlags, const char *pszTag) RT_NO_THROW;

/**
 * Reallocates memory allocated by RTMemSaferAllocZEx, RTMemSaferAllocZ,
 * RTMemSaferAllocZExTag, or RTMemSaferAllocZTag.
 *
 * When extending the allocation, the new memory will be zeroed.  When shrinking
 * the allocation the left over memory will be wiped clean using
 * RTMemWipeThorougly.
 *
 * The function follows the standard realloc behavior.
 *
 * @returns IPRT status code.
 * @param   a_cbOld     The current allocation size.
 * @param   a_pvOld     The current allocation.
 * @param   a_cbNew     The size of the new allocation.
 * @param   a_ppvNew    Where to return the pointer to the new memory.
 * @param   a_fFlags    Flags for controlling the allocation. See RTMEMSAFER_ALLOC_EX_FLAGS_* defines,
 *                      this takes only effect when allocating completely new memory, for extending or
 *                      shrinking existing allocations the flags of the allocation take precedence.
 */
#define RTMemSaferReallocZEx(a_cbOld, a_pvOld, a_cbNew, a_ppvNew, a_fFlags) \
    RTMemSaferReallocZExTag(a_cbOld, a_pvOld, a_cbNew, a_ppvNew, a_fFlags, RTMEM_TAG)

/**
 * Reallocates memory allocated by RTMemSaferAllocZ or RTMemSaferAllocZTag.
 *
 * When extending the allocation, the new memory will be zeroed.  When shrinking
 * the allocation the left over memory will be wiped clean using
 * RTMemWipeThorougly.
 *
 * The function follows the standard realloc behavior.
 *
 * @returns Pointer to the allocated memory.
 * @param   cbOld       The current allocation size.
 * @param   pvOld       The current allocation.
 * @param   cbNew       The size of the new allocation.
 * @param   pszTag      Allocation tag used for statistics and such.
 */
RTDECL(void *) RTMemSaferReallocZTag(size_t cbOld, void *pvOld, size_t cbNew, const char *pszTag) RT_NO_THROW;

/**
 * Reallocates memory allocated by RTMemSaferAllocZ or RTMemSaferAllocZTag.
 *
 * When extending the allocation, the new memory will be zeroed.  When shrinking
 * the allocation the left over memory will be wiped clean using
 * RTMemWipeThorougly.
 *
 * The function follows the standard realloc behavior.
 *
 * @returns Pointer to the allocated memory.
 * @param   a_cbOld     The current allocation size.
 * @param   a_pvOld     The current allocation.
 * @param   a_cbNew     The size of the new allocation.
 */
#define RTMemSaferReallocZ(a_cbOld, a_pvOld, a_cbNew) RTMemSaferReallocZTag(a_cbOld, a_pvOld, a_cbNew, RTMEM_TAG)


/**
 * Frees memory allocated by RTMemSaferAllocZ* or RTMemSaferReallocZ*.
 *
 * Before freeing the allocated memory, it will be wiped clean using
 * RTMemWipeThorougly.
 *
 * @returns Pointer to the allocated memory.
 * @param   pv          The allocation.
 * @param   cb          The allocation size.
 */
RTDECL(void) RTMemSaferFree(void *pv, size_t cb) RT_NO_THROW;

/** @}  */
RT_C_DECLS_END

#endif