Code:   Load_SBit_Png( FT_GlyphSlot     slot,
                 FT_Int           x_offset,
                 FT_Int           y_offset,
                 FT_Int           pix_bits,
                 TT_SBit_Metrics  metrics,
                 FT_Memory        memory,
                 FT_Byte*         data,
                 FT_UInt          png_len,
                 FT_Bool          populate_map_and_metrics )
  {
    FT_Bitmap    *map   = &slot->bitmap;
    FT_Error      error = FT_Err_Ok;
    FT_StreamRec  stream;

    png_structp  png;
    png_infop    info;
    png_uint_32  imgWidth, imgHeight;

    int         bitdepth, color_type, interlace;
    FT_Int      i;
    png_byte*  *rows = NULL; /* pacify compiler */


    if ( x_offset < 0 ||
         y_offset < 0 )
    {
      error = FT_THROW( Invalid_Argument );
       goto Exit;
     }
 
    if ( !populate_map_and_metrics                   &&
         ( x_offset + metrics->width  > map->width ||
           y_offset + metrics->height > map->rows  ||
           pix_bits != 32                          ||
           map->pixel_mode != FT_PIXEL_MODE_BGRA   ) )
     {
       error = FT_THROW( Invalid_Argument );
       goto Exit;
    }

    FT_Stream_OpenMemory( &stream, data, png_len );

    png = png_create_read_struct( PNG_LIBPNG_VER_STRING,
                                  &error,
                                  error_callback,
                                  warning_callback );
    if ( !png )
    {
      error = FT_THROW( Out_Of_Memory );
      goto Exit;
    }

    info = png_create_info_struct( png );
    if ( !info )
    {
      error = FT_THROW( Out_Of_Memory );
      png_destroy_read_struct( &png, NULL, NULL );
      goto Exit;
    }

    if ( ft_setjmp( png_jmpbuf( png ) ) )
    {
      error = FT_THROW( Invalid_File_Format );
      goto DestroyExit;
    }

    png_set_read_fn( png, &stream, read_data_from_FT_Stream );

    png_read_info( png, info );
    png_get_IHDR( png, info,
                  &imgWidth, &imgHeight,
                  &bitdepth, &color_type, &interlace,
                  NULL, NULL );

    if ( error                                        ||
         ( !populate_map_and_metrics                &&
           ( (FT_Int)imgWidth  != metrics->width  ||
             (FT_Int)imgHeight != metrics->height ) ) )
      goto DestroyExit;

    if ( populate_map_and_metrics )
    {
      FT_Long  size;


      metrics->width  = (FT_Int)imgWidth;
      metrics->height = (FT_Int)imgHeight;

      map->width      = metrics->width;
      map->rows       = metrics->height;
      map->pixel_mode = FT_PIXEL_MODE_BGRA;
      map->pitch      = map->width * 4;
      map->num_grays  = 256;

      /* reject too large bitmaps similarly to the rasterizer */
      if ( map->rows > 0x7FFF || map->width > 0x7FFF )
      {
        error = FT_THROW( Array_Too_Large );
        goto DestroyExit;
      }

      size = map->rows * map->pitch;

      error = ft_glyphslot_alloc_bitmap( slot, size );
      if ( error )
        goto DestroyExit;
    }

    /* convert palette/gray image to rgb */
    if ( color_type == PNG_COLOR_TYPE_PALETTE )
      png_set_palette_to_rgb( png );

    /* expand gray bit depth if needed */
    if ( color_type == PNG_COLOR_TYPE_GRAY )
    {
#if PNG_LIBPNG_VER >= 10209
      png_set_expand_gray_1_2_4_to_8( png );
#else
      png_set_gray_1_2_4_to_8( png );
#endif
    }

    /* transform transparency to alpha */
    if ( png_get_valid(png, info, PNG_INFO_tRNS ) )
      png_set_tRNS_to_alpha( png );

    if ( bitdepth == 16 )
      png_set_strip_16( png );

    if ( bitdepth < 8 )
      png_set_packing( png );

    /* convert grayscale to RGB */
    if ( color_type == PNG_COLOR_TYPE_GRAY       ||
         color_type == PNG_COLOR_TYPE_GRAY_ALPHA )
      png_set_gray_to_rgb( png );

    if ( interlace != PNG_INTERLACE_NONE )
      png_set_interlace_handling( png );

    png_set_filler( png, 0xFF, PNG_FILLER_AFTER );

    /* recheck header after setting EXPAND options */
    png_read_update_info(png, info );
    png_get_IHDR( png, info,
                  &imgWidth, &imgHeight,
                  &bitdepth, &color_type, &interlace,
                  NULL, NULL );

    if ( bitdepth != 8                              ||
        !( color_type == PNG_COLOR_TYPE_RGB       ||
           color_type == PNG_COLOR_TYPE_RGB_ALPHA ) )
    {
      error = FT_THROW( Invalid_File_Format );
      goto DestroyExit;
    }

    switch ( color_type )
    {
    default:
      /* Shouldn't happen, but fall through. */

    case PNG_COLOR_TYPE_RGB_ALPHA:
      png_set_read_user_transform_fn( png, premultiply_data );
      break;

    case PNG_COLOR_TYPE_RGB:
      /* Humm, this smells.  Carry on though. */
      png_set_read_user_transform_fn( png, convert_bytes_to_data );
      break;
    }

    if ( FT_NEW_ARRAY( rows, imgHeight ) )
    {
      error = FT_THROW( Out_Of_Memory );
      goto DestroyExit;
    }

    for ( i = 0; i < (FT_Int)imgHeight; i++ )
      rows[i] = map->buffer + ( y_offset + i ) * map->pitch + x_offset * 4;

    png_read_image( png, rows );

    FT_FREE( rows );

    png_read_end( png, info );

  DestroyExit:
    png_destroy_read_struct( &png, &info, NULL );
    FT_Stream_Close( &stream );

  Exit:
    return error;
  }

Vulnerability Type: DoS Overflow
CWE ID: CWE-119
Summary: The Load_SBit_Png function in sfnt/pngshim.c in FreeType before 2.5.4 does not restrict the rows and pitch values of PNG data, which allows remote attackers to cause a denial of service (integer overflow and heap-based buffer overflow) or possibly have unspecified other impact by embedding a PNG file in a .ttf font file.
Commit Message: 