/* stdmem.c  -	private memory allocator
 *	Copyright (C) 1998, 2000, 2002 Free Software Foundation, Inc.
 *
 * This file is part of Libgcrypt.
 *
 * Libgcrypt is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser general Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * Libgcrypt is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>

#include "g10lib.h"
#include "stdmem.h"
#include "secmem.h"


#define MAGIC_NOR_BYTE 0x55
#define MAGIC_SEC_BYTE 0xcc
#define MAGIC_END_BYTE 0xaa

#if SIZEOF_UNSIGNED_LONG == 8
  #define EXTRA_ALIGN 4
#else
  #define EXTRA_ALIGN 0
#endif


static int use_m_guard = 1;

/****************
 * Warning: Never use this function after any of the functions
 * here have been used.
 */
void
_gcry_private_enable_m_guard(void)
{
    use_m_guard = 1;
}

/****************
 * Allocate memory of size n.
 * Return NULL if we are out of memory.
 */
void *
_gcry_private_malloc( size_t n)
{
    if(!n) 
      return NULL; /* allocating 0 bytes is undefined - better return
                      an error */
    if( use_m_guard ) {
	char *p;

	if( !(p = malloc( n + EXTRA_ALIGN+5 )) )
	    return NULL;
	((byte*)p)[EXTRA_ALIGN+0] = n;
	((byte*)p)[EXTRA_ALIGN+1] = n >> 8 ;
	((byte*)p)[EXTRA_ALIGN+2] = n >> 16 ;
	((byte*)p)[EXTRA_ALIGN+3] = MAGIC_NOR_BYTE;
	p[4+EXTRA_ALIGN+n] = MAGIC_END_BYTE;
	return p+EXTRA_ALIGN+4;
    }
    else {
	return malloc( n );
    }
}

/****************
 * Allocate memory of size n from the secure memory pool.
 * Return NULL if we are out of memory.
 */
void *
_gcry_private_malloc_secure( size_t n)
{
    if(!n) 
      return NULL; /* allocating 0 bytes is undefined - better return
                      an error */
    if( use_m_guard ) {
	char *p;

	if( !(p = _gcry_secmem_malloc( n +EXTRA_ALIGN+ 5 )) )
	    return NULL;
	((byte*)p)[EXTRA_ALIGN+0] = n;
	((byte*)p)[EXTRA_ALIGN+1] = n >> 8 ;
	((byte*)p)[EXTRA_ALIGN+2] = n >> 16 ;
	((byte*)p)[EXTRA_ALIGN+3] = MAGIC_SEC_BYTE;
	p[4+EXTRA_ALIGN+n] = MAGIC_END_BYTE;
	return p+EXTRA_ALIGN+4;
    }
    else {
	return _gcry_secmem_malloc( n );
    }
}


/****************
 * realloc and clear the old space
 * Return NULL if there is not enoug memory.
 */
void *
_gcry_private_realloc( void *a, size_t n )
{
    if( use_m_guard ) {
	unsigned char *p = a;
	char *b;
	size_t len;

        if (!a)
          return _gcry_private_malloc(n);
        
	_gcry_private_check_heap(p);
	len  = p[-4];
	len |= p[-3] << 8;
	len |= p[-2] << 16;
	if( len >= n ) /* we don't shrink for now */
	    return a;
	if( p[-1] == MAGIC_SEC_BYTE )
	    b = _gcry_private_malloc_secure(n);
	else
	    b = _gcry_private_malloc(n);
	if( !b )
	    return NULL;
	memcpy(b, a, len );
	memset(b+len, 0, n-len );
	_gcry_private_free( p );
	return b;
    }
    else if( _gcry_private_is_secure(a) ) {
	return _gcry_secmem_realloc( a, n );
    }
    else {
	return realloc( a, n );
    }
}


void
_gcry_private_check_heap( const void *a )
{
    if( use_m_guard ) {
	const byte *p = a;
	size_t len;

	if( !p )
	    return;

	if( !(p[-1] == MAGIC_NOR_BYTE || p[-1] == MAGIC_SEC_BYTE) )
	    _gcry_log_fatal("memory at %p corrupted (underflow=%02x)\n", p, p[-1] );
	len  = p[-4];
	len |= p[-3] << 8;
	len |= p[-2] << 16;
	if( p[len] != MAGIC_END_BYTE )
	    _gcry_log_fatal("memory at %p corrupted (overflow=%02x)\n", p, p[-1] );
    }
}

/****************
 * Free a memory block allocated by this opr the secmem module
 */
void
_gcry_private_free( void *a )
{
    byte *p = a;

    if( !p )
	return;
    if( use_m_guard ) {
	_gcry_private_check_heap(p);
	if( _gcry_private_is_secure(a) )
	    _gcry_secmem_free(p-EXTRA_ALIGN-4);
	else {
	    free(p-EXTRA_ALIGN-4);
	}
    }
    else if( _gcry_private_is_secure(a) )
	_gcry_secmem_free(p);
    else
	free(p);
}