library/memory_buffer_alloc.c - security/mbedtls - Rivoreo Source Code Repositories

 /*
  *  Buffer-based memory allocator
  *
  *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
  *  SPDX-License-Identifier: Apache-2.0
  *
  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
  *  not use this file except in compliance with the License.
  *  You may obtain a copy of the License at
  *
  *  http://www.apache.org/licenses/LICENSE-2.0
  *
  *  Unless required by applicable law or agreed to in writing, software
  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  *
  *  This file is part of mbed TLS (https://tls.mbed.org)
  */

 #if !defined(MBEDTLS_CONFIG_FILE)
 #include "mbedtls/config.h"
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif

 #if defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
 #include "mbedtls/memory_buffer_alloc.h"

 /* No need for the header guard as MBEDTLS_MEMORY_BUFFER_ALLOC_C
    is dependent upon MBEDTLS_PLATFORM_C */
 #include "mbedtls/platform.h"

 #include <string.h>

 #if defined(MBEDTLS_MEMORY_BACKTRACE)
 #include <execinfo.h>
 #endif

 #if defined(MBEDTLS_THREADING_C)
 #include "mbedtls/threading.h"
 #endif

 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
     volatile unsigned char *p = v; while( n-- ) *p++ = 0;
 }

 #define MAGIC1       0xFF00AA55
 #define MAGIC2       0xEE119966
 #define MAX_BT 20

 typedef struct _memory_header memory_header;
 struct _memory_header
 {
     size_t          magic1;
     size_t          size;
     size_t          alloc;
     memory_header   *prev;
     memory_header   *next;
     memory_header   *prev_free;
     memory_header   *next_free;
 #if defined(MBEDTLS_MEMORY_BACKTRACE)
     char            **trace;
     size_t          trace_count;
 #endif
     size_t          magic2;
 };

 typedef struct
 {
     unsigned char   *buf;
     size_t          len;
     memory_header   *first;
     memory_header   *first_free;
     int             verify;
 #if defined(MBEDTLS_MEMORY_DEBUG)
     size_t          alloc_count;
     size_t          free_count;
     size_t          total_used;
     size_t          maximum_used;
     size_t          header_count;
     size_t          maximum_header_count;
 #endif
 #if defined(MBEDTLS_THREADING_C)
     mbedtls_threading_mutex_t   mutex;
 #endif
 }
 buffer_alloc_ctx;

 static buffer_alloc_ctx heap;

 #if defined(MBEDTLS_MEMORY_DEBUG)
 static void debug_header( memory_header *hdr )
 {
 #if defined(MBEDTLS_MEMORY_BACKTRACE)
     size_t i;
 #endif

     mbedtls_fprintf( stderr, "HDR:  PTR(%10zu), PREV(%10zu), NEXT(%10zu), "
                               "ALLOC(%zu), SIZE(%10zu)\n",
                       (size_t) hdr, (size_t) hdr->prev, (size_t) hdr->next,
                       hdr->alloc, hdr->size );
     mbedtls_fprintf( stderr, "      FPREV(%10zu), FNEXT(%10zu)\n",
                       (size_t) hdr->prev_free, (size_t) hdr->next_free );

 #if defined(MBEDTLS_MEMORY_BACKTRACE)
     mbedtls_fprintf( stderr, "TRACE: \n" );
     for( i = 0; i < hdr->trace_count; i++ )
         mbedtls_fprintf( stderr, "%s\n", hdr->trace[i] );
     mbedtls_fprintf( stderr, "\n" );
 #endif
 }

 static void debug_chain()
 {
     memory_header *cur = heap.first;

     mbedtls_fprintf( stderr, "\nBlock list\n" );
     while( cur != NULL )
     {
         debug_header( cur );
         cur = cur->next;
     }

     mbedtls_fprintf( stderr, "Free list\n" );
     cur = heap.first_free;

     while( cur != NULL )
     {
         debug_header( cur );
         cur = cur->next_free;
     }
 }
 #endif /* MBEDTLS_MEMORY_DEBUG */

 static int verify_header( memory_header *hdr )
 {
     if( hdr->magic1 != MAGIC1 )
     {
 #if defined(MBEDTLS_MEMORY_DEBUG)
         mbedtls_fprintf( stderr, "FATAL: MAGIC1 mismatch\n" );
 #endif
         return( 1 );
     }

     if( hdr->magic2 != MAGIC2 )
     {
 #if defined(MBEDTLS_MEMORY_DEBUG)
         mbedtls_fprintf( stderr, "FATAL: MAGIC2 mismatch\n" );
 #endif
         return( 1 );
     }

     if( hdr->alloc > 1 )
     {
 #if defined(MBEDTLS_MEMORY_DEBUG)
         mbedtls_fprintf( stderr, "FATAL: alloc has illegal value\n" );
 #endif
         return( 1 );
     }

     if( hdr->prev != NULL && hdr->prev == hdr->next )
     {
 #if defined(MBEDTLS_MEMORY_DEBUG)
         mbedtls_fprintf( stderr, "FATAL: prev == next\n" );
 #endif
         return( 1 );
     }

     if( hdr->prev_free != NULL && hdr->prev_free == hdr->next_free )
     {
 #if defined(MBEDTLS_MEMORY_DEBUG)
         mbedtls_fprintf( stderr, "FATAL: prev_free == next_free\n" );
 #endif
         return( 1 );
     }

     return( 0 );
 }

 static int verify_chain()
 {
     memory_header *prv = heap.first, *cur;

     if( prv == NULL || verify_header( prv ) != 0 )
     {
 #if defined(MBEDTLS_MEMORY_DEBUG)
         mbedtls_fprintf( stderr, "FATAL: verification of first header "
                                   "failed\n" );
 #endif
         return( 1 );
     }

     if( heap.first->prev != NULL )
     {
 #if defined(MBEDTLS_MEMORY_DEBUG)
         mbedtls_fprintf( stderr, "FATAL: verification failed: "
                                   "first->prev != NULL\n" );
 #endif
         return( 1 );
     }

     cur = heap.first->next;

     while( cur != NULL )
     {
         if( verify_header( cur ) != 0 )
         {
 #if defined(MBEDTLS_MEMORY_DEBUG)
             mbedtls_fprintf( stderr, "FATAL: verification of header "
                                       "failed\n" );
 #endif
             return( 1 );
         }

         if( cur->prev != prv )
         {
 #if defined(MBEDTLS_MEMORY_DEBUG)
             mbedtls_fprintf( stderr, "FATAL: verification failed: "
                                       "cur->prev != prv\n" );
 #endif
             return( 1 );
         }

         prv = cur;
         cur = cur->next;
     }

     return( 0 );
 }

 static void *buffer_alloc_calloc( size_t n, size_t size )
 {
     memory_header *new, *cur = heap.first_free;
     unsigned char *p;
     void *ret;
     size_t original_len, len;
 #if defined(MBEDTLS_MEMORY_BACKTRACE)
     void *trace_buffer[MAX_BT];
     size_t trace_cnt;
 #endif

     if( heap.buf == NULL || heap.first == NULL )
         return( NULL );

     original_len = len = n * size;

     if( n == 0 || size == 0 || len / n != size )
         return( NULL );
     else if( len > (size_t)-MBEDTLS_MEMORY_ALIGN_MULTIPLE )
         return( NULL );

     if( len % MBEDTLS_MEMORY_ALIGN_MULTIPLE )
     {
         len -= len % MBEDTLS_MEMORY_ALIGN_MULTIPLE;
         len += MBEDTLS_MEMORY_ALIGN_MULTIPLE;
     }

     // Find block that fits
     //
     while( cur != NULL )
     {
         if( cur->size >= len )
             break;

         cur = cur->next_free;
     }

     if( cur == NULL )
         return( NULL );

     if( cur->alloc != 0 )
     {
 #if defined(MBEDTLS_MEMORY_DEBUG)
         mbedtls_fprintf( stderr, "FATAL: block in free_list but allocated "
                                   "data\n" );
 #endif
         mbedtls_exit( 1 );
     }

 #if defined(MBEDTLS_MEMORY_DEBUG)
     heap.alloc_count++;
 #endif

     // Found location, split block if > memory_header + 4 room left
     //
     if( cur->size - len < sizeof(memory_header) +
                           MBEDTLS_MEMORY_ALIGN_MULTIPLE )
     {
         cur->alloc = 1;

         // Remove from free_list
         //
         if( cur->prev_free != NULL )
             cur->prev_free->next_free = cur->next_free;
         else
             heap.first_free = cur->next_free;

         if( cur->next_free != NULL )
             cur->next_free->prev_free = cur->prev_free;

         cur->prev_free = NULL;
         cur->next_free = NULL;

 #if defined(MBEDTLS_MEMORY_DEBUG)
         heap.total_used += cur->size;
         if( heap.total_used > heap.maximum_used )
             heap.maximum_used = heap.total_used;
 #endif
 #if defined(MBEDTLS_MEMORY_BACKTRACE)
         trace_cnt = backtrace( trace_buffer, MAX_BT );
         cur->trace = backtrace_symbols( trace_buffer, trace_cnt );
         cur->trace_count = trace_cnt;
 #endif

         if( ( heap.verify & MBEDTLS_MEMORY_VERIFY_ALLOC ) && verify_chain() != 0 )
             mbedtls_exit( 1 );

         ret = (unsigned char *) cur + sizeof( memory_header );
         memset( ret, 0, original_len );

         return( ret );
     }

     p = ( (unsigned char *) cur ) + sizeof(memory_header) + len;
     new = (memory_header *) p;

     new->size = cur->size - len - sizeof(memory_header);
     new->alloc = 0;
     new->prev = cur;
     new->next = cur->next;
 #if defined(MBEDTLS_MEMORY_BACKTRACE)
     new->trace = NULL;
     new->trace_count = 0;
 #endif
     new->magic1 = MAGIC1;
     new->magic2 = MAGIC2;

     if( new->next != NULL )
         new->next->prev = new;

     // Replace cur with new in free_list
     //
     new->prev_free = cur->prev_free;
     new->next_free = cur->next_free;
     if( new->prev_free != NULL )
         new->prev_free->next_free = new;
     else
         heap.first_free = new;

     if( new->next_free != NULL )
         new->next_free->prev_free = new;

     cur->alloc = 1;
     cur->size = len;
     cur->next = new;
     cur->prev_free = NULL;
     cur->next_free = NULL;

 #if defined(MBEDTLS_MEMORY_DEBUG)
     heap.header_count++;
     if( heap.header_count > heap.maximum_header_count )
         heap.maximum_header_count = heap.header_count;
     heap.total_used += cur->size;
     if( heap.total_used > heap.maximum_used )
         heap.maximum_used = heap.total_used;
 #endif
 #if defined(MBEDTLS_MEMORY_BACKTRACE)
     trace_cnt = backtrace( trace_buffer, MAX_BT );
     cur->trace = backtrace_symbols( trace_buffer, trace_cnt );
     cur->trace_count = trace_cnt;
 #endif

     if( ( heap.verify & MBEDTLS_MEMORY_VERIFY_ALLOC ) && verify_chain() != 0 )
         mbedtls_exit( 1 );

     ret = (unsigned char *) cur + sizeof( memory_header );
     memset( ret, 0, original_len );

     return( ret );
 }

 static void buffer_alloc_free( void *ptr )
 {
     memory_header *hdr, *old = NULL;
     unsigned char *p = (unsigned char *) ptr;

     if( ptr == NULL || heap.buf == NULL || heap.first == NULL )
         return;

     if( p < heap.buf || p >= heap.buf + heap.len )
     {
 #if defined(MBEDTLS_MEMORY_DEBUG)
         mbedtls_fprintf( stderr, "FATAL: mbedtls_free() outside of managed "
                                   "space\n" );
 #endif
         mbedtls_exit( 1 );
     }

     p -= sizeof(memory_header);
     hdr = (memory_header *) p;

     if( verify_header( hdr ) != 0 )
         mbedtls_exit( 1 );

     if( hdr->alloc != 1 )
     {
 #if defined(MBEDTLS_MEMORY_DEBUG)
         mbedtls_fprintf( stderr, "FATAL: mbedtls_free() on unallocated "
                                   "data\n" );
 #endif
         mbedtls_exit( 1 );
     }

     hdr->alloc = 0;

 #if defined(MBEDTLS_MEMORY_DEBUG)
     heap.free_count++;
     heap.total_used -= hdr->size;
 #endif

 #if defined(MBEDTLS_MEMORY_BACKTRACE)
     free( hdr->trace );
     hdr->trace = NULL;
     hdr->trace_count = 0;
 #endif

     // Regroup with block before
     //
     if( hdr->prev != NULL && hdr->prev->alloc == 0 )
     {
 #if defined(MBEDTLS_MEMORY_DEBUG)
         heap.header_count--;
 #endif
         hdr->prev->size += sizeof(memory_header) + hdr->size;
         hdr->prev->next = hdr->next;
         old = hdr;
         hdr = hdr->prev;

         if( hdr->next != NULL )
             hdr->next->prev = hdr;

         memset( old, 0, sizeof(memory_header) );
     }

     // Regroup with block after
     //
     if( hdr->next != NULL && hdr->next->alloc == 0 )
     {
 #if defined(MBEDTLS_MEMORY_DEBUG)
         heap.header_count--;
 #endif
         hdr->size += sizeof(memory_header) + hdr->next->size;
         old = hdr->next;
         hdr->next = hdr->next->next;

         if( hdr->prev_free != NULL || hdr->next_free != NULL )
         {
             if( hdr->prev_free != NULL )
                 hdr->prev_free->next_free = hdr->next_free;
             else
                 heap.first_free = hdr->next_free;

             if( hdr->next_free != NULL )
                 hdr->next_free->prev_free = hdr->prev_free;
         }

         hdr->prev_free = old->prev_free;
         hdr->next_free = old->next_free;

         if( hdr->prev_free != NULL )
             hdr->prev_free->next_free = hdr;
         else
             heap.first_free = hdr;

         if( hdr->next_free != NULL )
             hdr->next_free->prev_free = hdr;

         if( hdr->next != NULL )
             hdr->next->prev = hdr;

         memset( old, 0, sizeof(memory_header) );
     }

     // Prepend to free_list if we have not merged
     // (Does not have to stay in same order as prev / next list)
     //
     if( old == NULL )
     {
         hdr->next_free = heap.first_free;
         if( heap.first_free != NULL )
             heap.first_free->prev_free = hdr;
         heap.first_free = hdr;
     }

     if( ( heap.verify & MBEDTLS_MEMORY_VERIFY_FREE ) && verify_chain() != 0 )
         mbedtls_exit( 1 );
 }

 void mbedtls_memory_buffer_set_verify( int verify )
 {
     heap.verify = verify;
 }

 int mbedtls_memory_buffer_alloc_verify()
 {
     return verify_chain();
 }

 #if defined(MBEDTLS_MEMORY_DEBUG)
 void mbedtls_memory_buffer_alloc_status()
 {
     mbedtls_fprintf( stderr,
                       "Current use: %zu blocks / %zu bytes, max: %zu blocks / "
                       "%zu bytes (total %zu bytes), alloc / free: %zu / %zu\n",
                       heap.header_count, heap.total_used,
                       heap.maximum_header_count, heap.maximum_used,
                       heap.maximum_header_count * sizeof( memory_header )
                       + heap.maximum_used,
                       heap.alloc_count, heap.free_count );

     if( heap.first->next == NULL )
     {
         mbedtls_fprintf( stderr, "All memory de-allocated in stack buffer\n" );
     }
     else
     {
         mbedtls_fprintf( stderr, "Memory currently allocated:\n" );
         debug_chain();
     }
 }

 void mbedtls_memory_buffer_alloc_max_get( size_t *max_used, size_t *max_blocks )
 {
     *max_used   = heap.maximum_used;
     *max_blocks = heap.maximum_header_count;
 }

 void mbedtls_memory_buffer_alloc_max_reset( void )
 {
     heap.maximum_used = 0;
     heap.maximum_header_count = 0;
 }

 void mbedtls_memory_buffer_alloc_cur_get( size_t *cur_used, size_t *cur_blocks )
 {
     *cur_used   = heap.total_used;
     *cur_blocks = heap.header_count;
 }
 #endif /* MBEDTLS_MEMORY_DEBUG */

 #if defined(MBEDTLS_THREADING_C)
 static void *buffer_alloc_calloc_mutexed( size_t n, size_t size )
 {
     void *buf;
     if( mbedtls_mutex_lock( &heap.mutex ) != 0 )
         return( NULL );
     buf = buffer_alloc_calloc( n, size );
     if( mbedtls_mutex_unlock( &heap.mutex ) )
         return( NULL );
     return( buf );
 }

 static void buffer_alloc_free_mutexed( void *ptr )
 {
     /* We have to good option here, but corrupting the heap seems
      * worse than loosing memory. */
     if( mbedtls_mutex_lock( &heap.mutex ) )
         return;
     buffer_alloc_free( ptr );
     (void) mbedtls_mutex_unlock( &heap.mutex );
 }
 #endif /* MBEDTLS_THREADING_C */

 void mbedtls_memory_buffer_alloc_init( unsigned char *buf, size_t len )
 {
     memset( &heap, 0, sizeof( buffer_alloc_ctx ) );

 #if defined(MBEDTLS_THREADING_C)
     mbedtls_mutex_init( &heap.mutex );
     mbedtls_platform_set_calloc_free( buffer_alloc_calloc_mutexed,
                               buffer_alloc_free_mutexed );
 #else
     mbedtls_platform_set_calloc_free( buffer_alloc_calloc, buffer_alloc_free );
 #endif

     if( len < sizeof( memory_header ) + MBEDTLS_MEMORY_ALIGN_MULTIPLE )
         return;
     else if( (size_t)buf % MBEDTLS_MEMORY_ALIGN_MULTIPLE )
     {
         /* Adjust len first since buf is used in the computation */
         len -= MBEDTLS_MEMORY_ALIGN_MULTIPLE
              - (size_t)buf % MBEDTLS_MEMORY_ALIGN_MULTIPLE;
         buf += MBEDTLS_MEMORY_ALIGN_MULTIPLE
              - (size_t)buf % MBEDTLS_MEMORY_ALIGN_MULTIPLE;
     }

     memset( buf, 0, len );

     heap.buf = buf;
     heap.len = len;

     heap.first = (memory_header *)buf;
     heap.first->size = len - sizeof( memory_header );
     heap.first->magic1 = MAGIC1;
     heap.first->magic2 = MAGIC2;
     heap.first_free = heap.first;
 }

 void mbedtls_memory_buffer_alloc_free()
 {
 #if defined(MBEDTLS_THREADING_C)
     mbedtls_mutex_free( &heap.mutex );
 #endif
     mbedtls_zeroize( &heap, sizeof(buffer_alloc_ctx) );
 }

 #if defined(MBEDTLS_SELF_TEST)
 static int check_pointer( void *p )
 {
     if( p == NULL )
         return( -1 );

     if( (size_t) p % MBEDTLS_MEMORY_ALIGN_MULTIPLE != 0 )
         return( -1 );

     return( 0 );
 }

 static int check_all_free( )
 {
     if(
 #if defined(MBEDTLS_MEMORY_DEBUG)
         heap.total_used != 0 ||
 #endif
         heap.first != heap.first_free ||
         (void *) heap.first != (void *) heap.buf )
     {
         return( -1 );
     }

     return( 0 );
 }

 #define TEST_ASSERT( condition )            \
     if( ! (condition) )                     \
     {                                       \
         if( verbose != 0 )                  \
             mbedtls_printf( "failed\n" );  \
                                             \
         ret = 1;                            \
         goto cleanup;                       \
     }

 int mbedtls_memory_buffer_alloc_self_test( int verbose )
 {
     unsigned char buf[1024];
     unsigned char *p, *q, *r, *end;
     int ret = 0;

     if( verbose != 0 )
         mbedtls_printf( "  MBA test #1 (basic alloc-free cycle): " );

     mbedtls_memory_buffer_alloc_init( buf, sizeof( buf ) );

     p = mbedtls_calloc( 1, 1 );
     q = mbedtls_calloc( 1, 128 );
     r = mbedtls_calloc( 1, 16 );

     TEST_ASSERT( check_pointer( p ) == 0 &&
                  check_pointer( q ) == 0 &&
                  check_pointer( r ) == 0 );

     mbedtls_free( r );
     mbedtls_free( q );
     mbedtls_free( p );

     TEST_ASSERT( check_all_free( ) == 0 );

     /* Memorize end to compare with the next test */
     end = heap.buf + heap.len;

     mbedtls_memory_buffer_alloc_free( );

     if( verbose != 0 )
         mbedtls_printf( "passed\n" );

     if( verbose != 0 )
         mbedtls_printf( "  MBA test #2 (buf not aligned): " );

     mbedtls_memory_buffer_alloc_init( buf + 1, sizeof( buf ) - 1 );

     TEST_ASSERT( heap.buf + heap.len == end );

     p = mbedtls_calloc( 1, 1 );
     q = mbedtls_calloc( 1, 128 );
     r = mbedtls_calloc( 1, 16 );

     TEST_ASSERT( check_pointer( p ) == 0 &&
                  check_pointer( q ) == 0 &&
                  check_pointer( r ) == 0 );

     mbedtls_free( r );
     mbedtls_free( q );
     mbedtls_free( p );

     TEST_ASSERT( check_all_free( ) == 0 );

     mbedtls_memory_buffer_alloc_free( );

     if( verbose != 0 )
         mbedtls_printf( "passed\n" );

     if( verbose != 0 )
         mbedtls_printf( "  MBA test #3 (full): " );

     mbedtls_memory_buffer_alloc_init( buf, sizeof( buf ) );

     p = mbedtls_calloc( 1, sizeof( buf ) - sizeof( memory_header ) );

     TEST_ASSERT( check_pointer( p ) == 0 );
     TEST_ASSERT( mbedtls_calloc( 1, 1 ) == NULL );

     mbedtls_free( p );

     p = mbedtls_calloc( 1, sizeof( buf ) - 2 * sizeof( memory_header ) - 16 );
     q = mbedtls_calloc( 1, 16 );

     TEST_ASSERT( check_pointer( p ) == 0 && check_pointer( q ) == 0 );
     TEST_ASSERT( mbedtls_calloc( 1, 1 ) == NULL );

     mbedtls_free( q );

     TEST_ASSERT( mbedtls_calloc( 1, 17 ) == NULL );

     mbedtls_free( p );

     TEST_ASSERT( check_all_free( ) == 0 );

     mbedtls_memory_buffer_alloc_free( );

     if( verbose != 0 )
         mbedtls_printf( "passed\n" );

 cleanup:
     mbedtls_memory_buffer_alloc_free( );

     return( ret );
 }
 #endif /* MBEDTLS_SELF_TEST */

 #endif /* MBEDTLS_MEMORY_BUFFER_ALLOC_C */
	/*
	* Buffer-based memory allocator
	*
	* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
	* SPDX-License-Identifier: Apache-2.0
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may
	* not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*
	* This file is part of mbed TLS (https://tls.mbed.org)
	*/

	#if !defined(MBEDTLS_CONFIG_FILE)
	#include "mbedtls/config.h"
	#else
	#include MBEDTLS_CONFIG_FILE
	#endif

	#if defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
	#include "mbedtls/memory_buffer_alloc.h"

	/* No need for the header guard as MBEDTLS_MEMORY_BUFFER_ALLOC_C
	is dependent upon MBEDTLS_PLATFORM_C */
	#include "mbedtls/platform.h"

	#include <string.h>

	#if defined(MBEDTLS_MEMORY_BACKTRACE)
	#include <execinfo.h>
	#endif

	#if defined(MBEDTLS_THREADING_C)
	#include "mbedtls/threading.h"
	#endif

	/* Implementation that should never be optimized out by the compiler */
	static void mbedtls_zeroize( void *v, size_t n ) {
	volatile unsigned char p = v; while( n-- ) p++ = 0;
	}

	#define MAGIC1 0xFF00AA55
	#define MAGIC2 0xEE119966
	#define MAX_BT 20

	typedef struct _memory_header memory_header;
	struct _memory_header
	{
	size_t magic1;
	size_t size;
	size_t alloc;
	memory_header *prev;
	memory_header *next;
	memory_header *prev_free;
	memory_header *next_free;
	#if defined(MBEDTLS_MEMORY_BACKTRACE)
	char **trace;
	size_t trace_count;
	#endif
	size_t magic2;
	};

	typedef struct
	{
	unsigned char *buf;
	size_t len;
	memory_header *first;
	memory_header *first_free;
	int verify;
	#if defined(MBEDTLS_MEMORY_DEBUG)
	size_t alloc_count;
	size_t free_count;
	size_t total_used;
	size_t maximum_used;
	size_t header_count;
	size_t maximum_header_count;
	#endif
	#if defined(MBEDTLS_THREADING_C)
	mbedtls_threading_mutex_t mutex;
	#endif
	}
	buffer_alloc_ctx;

	static buffer_alloc_ctx heap;

	#if defined(MBEDTLS_MEMORY_DEBUG)
	static void debug_header( memory_header *hdr )
	{
	#if defined(MBEDTLS_MEMORY_BACKTRACE)
	size_t i;
	#endif

	mbedtls_fprintf( stderr, "HDR: PTR(%10zu), PREV(%10zu), NEXT(%10zu), "
	"ALLOC(%zu), SIZE(%10zu)\n",
	(size_t) hdr, (size_t) hdr->prev, (size_t) hdr->next,
	hdr->alloc, hdr->size );
	mbedtls_fprintf( stderr, " FPREV(%10zu), FNEXT(%10zu)\n",
	(size_t) hdr->prev_free, (size_t) hdr->next_free );

	#if defined(MBEDTLS_MEMORY_BACKTRACE)
	mbedtls_fprintf( stderr, "TRACE: \n" );
	for( i = 0; i < hdr->trace_count; i++ )
	mbedtls_fprintf( stderr, "%s\n", hdr->trace[i] );
	mbedtls_fprintf( stderr, "\n" );
	#endif
	}

	static void debug_chain()
	{
	memory_header *cur = heap.first;

	mbedtls_fprintf( stderr, "\nBlock list\n" );
	while( cur != NULL )
	{
	debug_header( cur );
	cur = cur->next;
	}

	mbedtls_fprintf( stderr, "Free list\n" );
	cur = heap.first_free;

	while( cur != NULL )
	{
	debug_header( cur );
	cur = cur->next_free;
	}
	}
	#endif /* MBEDTLS_MEMORY_DEBUG */

	static int verify_header( memory_header *hdr )
	{
	if( hdr->magic1 != MAGIC1 )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	mbedtls_fprintf( stderr, "FATAL: MAGIC1 mismatch\n" );
	#endif
	return( 1 );
	}

	if( hdr->magic2 != MAGIC2 )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	mbedtls_fprintf( stderr, "FATAL: MAGIC2 mismatch\n" );
	#endif
	return( 1 );
	}

	if( hdr->alloc > 1 )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	mbedtls_fprintf( stderr, "FATAL: alloc has illegal value\n" );
	#endif
	return( 1 );
	}

	if( hdr->prev != NULL && hdr->prev == hdr->next )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	mbedtls_fprintf( stderr, "FATAL: prev == next\n" );
	#endif
	return( 1 );
	}

	if( hdr->prev_free != NULL && hdr->prev_free == hdr->next_free )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	mbedtls_fprintf( stderr, "FATAL: prev_free == next_free\n" );
	#endif
	return( 1 );
	}

	return( 0 );
	}

	static int verify_chain()
	{
	memory_header prv = heap.first, cur;

	if( prv == NULL \|\| verify_header( prv ) != 0 )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	mbedtls_fprintf( stderr, "FATAL: verification of first header "
	"failed\n" );
	#endif
	return( 1 );
	}

	if( heap.first->prev != NULL )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	mbedtls_fprintf( stderr, "FATAL: verification failed: "
	"first->prev != NULL\n" );
	#endif
	return( 1 );
	}

	cur = heap.first->next;

	while( cur != NULL )
	{
	if( verify_header( cur ) != 0 )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	mbedtls_fprintf( stderr, "FATAL: verification of header "
	"failed\n" );
	#endif
	return( 1 );
	}

	if( cur->prev != prv )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	mbedtls_fprintf( stderr, "FATAL: verification failed: "
	"cur->prev != prv\n" );
	#endif
	return( 1 );
	}

	prv = cur;
	cur = cur->next;
	}

	return( 0 );
	}

	static void *buffer_alloc_calloc( size_t n, size_t size )
	{
	memory_header new, cur = heap.first_free;
	unsigned char *p;
	void *ret;
	size_t original_len, len;
	#if defined(MBEDTLS_MEMORY_BACKTRACE)
	void *trace_buffer[MAX_BT];
	size_t trace_cnt;
	#endif

	if( heap.buf == NULL \|\| heap.first == NULL )
	return( NULL );

	original_len = len = n * size;

	if( n == 0 \|\| size == 0 \|\| len / n != size )
	return( NULL );
	else if( len > (size_t)-MBEDTLS_MEMORY_ALIGN_MULTIPLE )
	return( NULL );

	if( len % MBEDTLS_MEMORY_ALIGN_MULTIPLE )
	{
	len -= len % MBEDTLS_MEMORY_ALIGN_MULTIPLE;
	len += MBEDTLS_MEMORY_ALIGN_MULTIPLE;
	}

	// Find block that fits
	//
	while( cur != NULL )
	{
	if( cur->size >= len )
	break;

	cur = cur->next_free;
	}

	if( cur == NULL )
	return( NULL );

	if( cur->alloc != 0 )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	mbedtls_fprintf( stderr, "FATAL: block in free_list but allocated "
	"data\n" );
	#endif
	mbedtls_exit( 1 );
	}

	#if defined(MBEDTLS_MEMORY_DEBUG)
	heap.alloc_count++;
	#endif

	// Found location, split block if > memory_header + 4 room left
	//
	if( cur->size - len < sizeof(memory_header) +
	MBEDTLS_MEMORY_ALIGN_MULTIPLE )
	{
	cur->alloc = 1;

	// Remove from free_list
	//
	if( cur->prev_free != NULL )
	cur->prev_free->next_free = cur->next_free;
	else
	heap.first_free = cur->next_free;

	if( cur->next_free != NULL )
	cur->next_free->prev_free = cur->prev_free;

	cur->prev_free = NULL;
	cur->next_free = NULL;

	#if defined(MBEDTLS_MEMORY_DEBUG)
	heap.total_used += cur->size;
	if( heap.total_used > heap.maximum_used )
	heap.maximum_used = heap.total_used;
	#endif
	#if defined(MBEDTLS_MEMORY_BACKTRACE)
	trace_cnt = backtrace( trace_buffer, MAX_BT );
	cur->trace = backtrace_symbols( trace_buffer, trace_cnt );
	cur->trace_count = trace_cnt;
	#endif

	if( ( heap.verify & MBEDTLS_MEMORY_VERIFY_ALLOC ) && verify_chain() != 0 )
	mbedtls_exit( 1 );

	ret = (unsigned char *) cur + sizeof( memory_header );
	memset( ret, 0, original_len );

	return( ret );
	}

	p = ( (unsigned char *) cur ) + sizeof(memory_header) + len;
	new = (memory_header *) p;

	new->size = cur->size - len - sizeof(memory_header);
	new->alloc = 0;
	new->prev = cur;
	new->next = cur->next;
	#if defined(MBEDTLS_MEMORY_BACKTRACE)
	new->trace = NULL;
	new->trace_count = 0;
	#endif
	new->magic1 = MAGIC1;
	new->magic2 = MAGIC2;

	if( new->next != NULL )
	new->next->prev = new;

	// Replace cur with new in free_list
	//
	new->prev_free = cur->prev_free;
	new->next_free = cur->next_free;
	if( new->prev_free != NULL )
	new->prev_free->next_free = new;
	else
	heap.first_free = new;

	if( new->next_free != NULL )
	new->next_free->prev_free = new;

	cur->alloc = 1;
	cur->size = len;
	cur->next = new;
	cur->prev_free = NULL;
	cur->next_free = NULL;

	#if defined(MBEDTLS_MEMORY_DEBUG)
	heap.header_count++;
	if( heap.header_count > heap.maximum_header_count )
	heap.maximum_header_count = heap.header_count;
	heap.total_used += cur->size;
	if( heap.total_used > heap.maximum_used )
	heap.maximum_used = heap.total_used;
	#endif
	#if defined(MBEDTLS_MEMORY_BACKTRACE)
	trace_cnt = backtrace( trace_buffer, MAX_BT );
	cur->trace = backtrace_symbols( trace_buffer, trace_cnt );
	cur->trace_count = trace_cnt;
	#endif

	if( ( heap.verify & MBEDTLS_MEMORY_VERIFY_ALLOC ) && verify_chain() != 0 )
	mbedtls_exit( 1 );

	ret = (unsigned char *) cur + sizeof( memory_header );
	memset( ret, 0, original_len );

	return( ret );
	}

	static void buffer_alloc_free( void *ptr )
	{
	memory_header hdr, old = NULL;
	unsigned char p = (unsigned char ) ptr;

	if( ptr == NULL \|\| heap.buf == NULL \|\| heap.first == NULL )
	return;

	if( p < heap.buf \|\| p >= heap.buf + heap.len )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	mbedtls_fprintf( stderr, "FATAL: mbedtls_free() outside of managed "
	"space\n" );
	#endif
	mbedtls_exit( 1 );
	}

	p -= sizeof(memory_header);
	hdr = (memory_header *) p;

	if( verify_header( hdr ) != 0 )
	mbedtls_exit( 1 );

	if( hdr->alloc != 1 )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	mbedtls_fprintf( stderr, "FATAL: mbedtls_free() on unallocated "
	"data\n" );
	#endif
	mbedtls_exit( 1 );
	}

	hdr->alloc = 0;

	#if defined(MBEDTLS_MEMORY_DEBUG)
	heap.free_count++;
	heap.total_used -= hdr->size;
	#endif

	#if defined(MBEDTLS_MEMORY_BACKTRACE)
	free( hdr->trace );
	hdr->trace = NULL;
	hdr->trace_count = 0;
	#endif

	// Regroup with block before
	//
	if( hdr->prev != NULL && hdr->prev->alloc == 0 )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	heap.header_count--;
	#endif
	hdr->prev->size += sizeof(memory_header) + hdr->size;
	hdr->prev->next = hdr->next;
	old = hdr;
	hdr = hdr->prev;

	if( hdr->next != NULL )
	hdr->next->prev = hdr;

	memset( old, 0, sizeof(memory_header) );
	}

	// Regroup with block after
	//
	if( hdr->next != NULL && hdr->next->alloc == 0 )
	{
	#if defined(MBEDTLS_MEMORY_DEBUG)
	heap.header_count--;
	#endif
	hdr->size += sizeof(memory_header) + hdr->next->size;
	old = hdr->next;
	hdr->next = hdr->next->next;

	if( hdr->prev_free != NULL \|\| hdr->next_free != NULL )
	{
	if( hdr->prev_free != NULL )
	hdr->prev_free->next_free = hdr->next_free;
	else
	heap.first_free = hdr->next_free;

	if( hdr->next_free != NULL )
	hdr->next_free->prev_free = hdr->prev_free;
	}

	hdr->prev_free = old->prev_free;
	hdr->next_free = old->next_free;

	if( hdr->prev_free != NULL )
	hdr->prev_free->next_free = hdr;
	else
	heap.first_free = hdr;

	if( hdr->next_free != NULL )
	hdr->next_free->prev_free = hdr;

	if( hdr->next != NULL )
	hdr->next->prev = hdr;

	memset( old, 0, sizeof(memory_header) );
	}

	// Prepend to free_list if we have not merged
	// (Does not have to stay in same order as prev / next list)
	//
	if( old == NULL )
	{
	hdr->next_free = heap.first_free;
	if( heap.first_free != NULL )
	heap.first_free->prev_free = hdr;
	heap.first_free = hdr;
	}

	if( ( heap.verify & MBEDTLS_MEMORY_VERIFY_FREE ) && verify_chain() != 0 )
	mbedtls_exit( 1 );
	}

	void mbedtls_memory_buffer_set_verify( int verify )
	{
	heap.verify = verify;
	}

	int mbedtls_memory_buffer_alloc_verify()
	{
	return verify_chain();
	}

	#if defined(MBEDTLS_MEMORY_DEBUG)
	void mbedtls_memory_buffer_alloc_status()
	{
	mbedtls_fprintf( stderr,
	"Current use: %zu blocks / %zu bytes, max: %zu blocks / "
	"%zu bytes (total %zu bytes), alloc / free: %zu / %zu\n",
	heap.header_count, heap.total_used,
	heap.maximum_header_count, heap.maximum_used,
	heap.maximum_header_count * sizeof( memory_header )
	+ heap.maximum_used,
	heap.alloc_count, heap.free_count );

	if( heap.first->next == NULL )
	{
	mbedtls_fprintf( stderr, "All memory de-allocated in stack buffer\n" );
	}
	else
	{
	mbedtls_fprintf( stderr, "Memory currently allocated:\n" );
	debug_chain();
	}
	}

	void mbedtls_memory_buffer_alloc_max_get( size_t max_used, size_t max_blocks )
	{
	*max_used = heap.maximum_used;
	*max_blocks = heap.maximum_header_count;
	}

	void mbedtls_memory_buffer_alloc_max_reset( void )
	{
	heap.maximum_used = 0;
	heap.maximum_header_count = 0;
	}

	void mbedtls_memory_buffer_alloc_cur_get( size_t cur_used, size_t cur_blocks )
	{
	*cur_used = heap.total_used;
	*cur_blocks = heap.header_count;
	}
	#endif /* MBEDTLS_MEMORY_DEBUG */

	#if defined(MBEDTLS_THREADING_C)
	static void *buffer_alloc_calloc_mutexed( size_t n, size_t size )
	{
	void *buf;
	if( mbedtls_mutex_lock( &heap.mutex ) != 0 )
	return( NULL );
	buf = buffer_alloc_calloc( n, size );
	if( mbedtls_mutex_unlock( &heap.mutex ) )
	return( NULL );
	return( buf );
	}

	static void buffer_alloc_free_mutexed( void *ptr )
	{
	/* We have to good option here, but corrupting the heap seems
	* worse than loosing memory. */
	if( mbedtls_mutex_lock( &heap.mutex ) )
	return;
	buffer_alloc_free( ptr );
	(void) mbedtls_mutex_unlock( &heap.mutex );
	}
	#endif /* MBEDTLS_THREADING_C */

	void mbedtls_memory_buffer_alloc_init( unsigned char *buf, size_t len )
	{
	memset( &heap, 0, sizeof( buffer_alloc_ctx ) );

	#if defined(MBEDTLS_THREADING_C)
	mbedtls_mutex_init( &heap.mutex );
	mbedtls_platform_set_calloc_free( buffer_alloc_calloc_mutexed,
	buffer_alloc_free_mutexed );
	#else
	mbedtls_platform_set_calloc_free( buffer_alloc_calloc, buffer_alloc_free );
	#endif

	if( len < sizeof( memory_header ) + MBEDTLS_MEMORY_ALIGN_MULTIPLE )
	return;
	else if( (size_t)buf % MBEDTLS_MEMORY_ALIGN_MULTIPLE )
	{
	/* Adjust len first since buf is used in the computation */
	len -= MBEDTLS_MEMORY_ALIGN_MULTIPLE
	- (size_t)buf % MBEDTLS_MEMORY_ALIGN_MULTIPLE;
	buf += MBEDTLS_MEMORY_ALIGN_MULTIPLE
	- (size_t)buf % MBEDTLS_MEMORY_ALIGN_MULTIPLE;
	}

	memset( buf, 0, len );

	heap.buf = buf;
	heap.len = len;

	heap.first = (memory_header *)buf;
	heap.first->size = len - sizeof( memory_header );
	heap.first->magic1 = MAGIC1;
	heap.first->magic2 = MAGIC2;
	heap.first_free = heap.first;
	}

	void mbedtls_memory_buffer_alloc_free()
	{
	#if defined(MBEDTLS_THREADING_C)
	mbedtls_mutex_free( &heap.mutex );
	#endif
	mbedtls_zeroize( &heap, sizeof(buffer_alloc_ctx) );
	}

	#if defined(MBEDTLS_SELF_TEST)
	static int check_pointer( void *p )
	{
	if( p == NULL )
	return( -1 );

	if( (size_t) p % MBEDTLS_MEMORY_ALIGN_MULTIPLE != 0 )
	return( -1 );

	return( 0 );
	}

	static int check_all_free( )
	{
	if(
	#if defined(MBEDTLS_MEMORY_DEBUG)
	heap.total_used != 0 \|\|
	#endif
	heap.first != heap.first_free \|\|
	(void ) heap.first != (void ) heap.buf )
	{
	return( -1 );
	}

	return( 0 );
	}

	#define TEST_ASSERT( condition ) \
	if( ! (condition) ) \
	{ \
	if( verbose != 0 ) \
	mbedtls_printf( "failed\n" ); \
	\
	ret = 1; \
	goto cleanup; \
	}

	int mbedtls_memory_buffer_alloc_self_test( int verbose )
	{
	unsigned char buf[1024];
	unsigned char p, q, r, end;
	int ret = 0;

	if( verbose != 0 )
	mbedtls_printf( " MBA test #1 (basic alloc-free cycle): " );

	mbedtls_memory_buffer_alloc_init( buf, sizeof( buf ) );

	p = mbedtls_calloc( 1, 1 );
	q = mbedtls_calloc( 1, 128 );
	r = mbedtls_calloc( 1, 16 );

	TEST_ASSERT( check_pointer( p ) == 0 &&
	check_pointer( q ) == 0 &&
	check_pointer( r ) == 0 );

	mbedtls_free( r );
	mbedtls_free( q );
	mbedtls_free( p );

	TEST_ASSERT( check_all_free( ) == 0 );

	/* Memorize end to compare with the next test */
	end = heap.buf + heap.len;

	mbedtls_memory_buffer_alloc_free( );

	if( verbose != 0 )
	mbedtls_printf( "passed\n" );

	if( verbose != 0 )
	mbedtls_printf( " MBA test #2 (buf not aligned): " );

	mbedtls_memory_buffer_alloc_init( buf + 1, sizeof( buf ) - 1 );

	TEST_ASSERT( heap.buf + heap.len == end );

	p = mbedtls_calloc( 1, 1 );
	q = mbedtls_calloc( 1, 128 );
	r = mbedtls_calloc( 1, 16 );

	TEST_ASSERT( check_pointer( p ) == 0 &&
	check_pointer( q ) == 0 &&
	check_pointer( r ) == 0 );

	mbedtls_free( r );
	mbedtls_free( q );
	mbedtls_free( p );

	TEST_ASSERT( check_all_free( ) == 0 );

	mbedtls_memory_buffer_alloc_free( );

	if( verbose != 0 )
	mbedtls_printf( "passed\n" );

	if( verbose != 0 )
	mbedtls_printf( " MBA test #3 (full): " );

	mbedtls_memory_buffer_alloc_init( buf, sizeof( buf ) );

	p = mbedtls_calloc( 1, sizeof( buf ) - sizeof( memory_header ) );

	TEST_ASSERT( check_pointer( p ) == 0 );
	TEST_ASSERT( mbedtls_calloc( 1, 1 ) == NULL );

	mbedtls_free( p );

	p = mbedtls_calloc( 1, sizeof( buf ) - 2 * sizeof( memory_header ) - 16 );
	q = mbedtls_calloc( 1, 16 );

	TEST_ASSERT( check_pointer( p ) == 0 && check_pointer( q ) == 0 );
	TEST_ASSERT( mbedtls_calloc( 1, 1 ) == NULL );

	mbedtls_free( q );

	TEST_ASSERT( mbedtls_calloc( 1, 17 ) == NULL );

	mbedtls_free( p );

	TEST_ASSERT( check_all_free( ) == 0 );

	mbedtls_memory_buffer_alloc_free( );

	if( verbose != 0 )
	mbedtls_printf( "passed\n" );

	cleanup:
	mbedtls_memory_buffer_alloc_free( );

	return( ret );
	}
	#endif /* MBEDTLS_SELF_TEST */

	#endif /* MBEDTLS_MEMORY_BUFFER_ALLOC_C */