memory_buffer_alloc.c

/*
 *  Buffer-based memory allocator
 *
 *  Copyright The Mbed TLS Contributors
 *  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.
 */

#include "common.h"

#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 "mbedtls/platform_util.h"

#include <string.h>

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

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

#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( void )
{
    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( void )
{
    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( void )
{
    return verify_chain();
}

#if defined(MBEDTLS_MEMORY_DEBUG)
void mbedtls_memory_buffer_alloc_status( void )
{
    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( void )
{
#if defined(MBEDTLS_THREADING_C)
    mbedtls_mutex_free( &heap.mutex );
#endif
    mbedtls_platform_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( void )
{
    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 */