Commit message: Added extra check to fix https://github.com/ImageMagick/ImageMagick/issues/93
CVE: CVE-2016-7522
CWE: CWE-125
Vulnerability description: The ReadPSDImage function in MagickCore/locale.c in ImageMagick allows remote attackers to cause a denial of service (out-of-bounds read) via a crafted PSD file.

Project: ImageMagick
File: psd.c

static Image *ReadPSDImage(const ImageInfo *image_info,ExceptionInfo *exception)
{
  Image
    *image;

  MagickBooleanType
    has_merged_image,
    skip_layers;

  MagickOffsetType
    offset;

  MagickSizeType
    length;

  MagickBooleanType
    status;

  PSDInfo
    psd_info;

  register ssize_t
    i;

  ssize_t
    count;

  unsigned char
    *data;

  /*
    Open image file.
  */
  assert(image_info != (const ImageInfo *) NULL);
  assert(image_info->signature == MagickCoreSignature);
  if (image_info->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
      image_info->filename);
  assert(exception != (ExceptionInfo *) NULL);
  assert(exception->signature == MagickCoreSignature);

  image=AcquireImage(image_info,exception);
  status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
  if (status == MagickFalse)
    {
      image=DestroyImageList(image);
      return((Image *) NULL);
    }
  /*
    Read image header.
  */
  image->endian=MSBEndian;
  count=ReadBlob(image,4,(unsigned char *) psd_info.signature);
  psd_info.version=ReadBlobMSBShort(image);
  if ((count == 0) || (LocaleNCompare(psd_info.signature,"8BPS",4) != 0) ||
      ((psd_info.version != 1) && (psd_info.version != 2)))
    ThrowReaderException(CorruptImageError,"ImproperImageHeader");
  (void) ReadBlob(image,6,psd_info.reserved);
  psd_info.channels=ReadBlobMSBShort(image);
  if (psd_info.channels > MaxPSDChannels)
    ThrowReaderException(CorruptImageError,"MaximumChannelsExceeded");
  psd_info.rows=ReadBlobMSBLong(image);
  psd_info.columns=ReadBlobMSBLong(image);
  if ((psd_info.version == 1) && ((psd_info.rows > 30000) ||
      (psd_info.columns > 30000)))
    ThrowReaderException(CorruptImageError,"ImproperImageHeader");
  psd_info.depth=ReadBlobMSBShort(image);
  if ((psd_info.depth != 1) && (psd_info.depth != 8) && (psd_info.depth != 16))
    ThrowReaderException(CorruptImageError,"ImproperImageHeader");
  psd_info.mode=ReadBlobMSBShort(image);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(CoderEvent,GetMagickModule(),
      "  Image is %.20g x %.20g with channels=%.20g, depth=%.20g, mode=%s",
      (double) psd_info.columns,(double) psd_info.rows,(double)
      psd_info.channels,(double) psd_info.depth,ModeToString((PSDImageType)
      psd_info.mode));
  /*
    Initialize image.
  */
  image->depth=psd_info.depth;
  image->columns=psd_info.columns;
  image->rows=psd_info.rows;
  status=SetImageExtent(image,image->columns,image->rows,exception);
  if (status == MagickFalse)
    return(DestroyImageList(image));
  if (SetImageBackgroundColor(image,exception) == MagickFalse)
    {
      image=DestroyImageList(image);
      return((Image *) NULL);
    }
  if (psd_info.mode == LabMode)
    SetImageColorspace(image,LabColorspace,exception);
  if (psd_info.mode == CMYKMode)
    {
      SetImageColorspace(image,CMYKColorspace,exception);
      image->alpha_trait=psd_info.channels > 4 ? BlendPixelTrait :
        UndefinedPixelTrait;
    }
  else if ((psd_info.mode == BitmapMode) || (psd_info.mode == GrayscaleMode) ||
      (psd_info.mode == DuotoneMode))
    {
      status=AcquireImageColormap(image,psd_info.depth != 16 ? 256 : 65536,
        exception);
      if (status == MagickFalse)
        ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
      if (image->debug != MagickFalse)
        (void) LogMagickEvent(CoderEvent,GetMagickModule(),
          "  Image colormap allocated");
      SetImageColorspace(image,GRAYColorspace,exception);
      image->alpha_trait=psd_info.channels > 1 ? BlendPixelTrait :
        UndefinedPixelTrait;
    }
  else
    image->alpha_trait=psd_info.channels > 3 ? BlendPixelTrait :
      UndefinedPixelTrait;
  /*
    Read PSD raster colormap only present for indexed and duotone images.
  */
  length=ReadBlobMSBLong(image);
  if (length != 0)
    {
      if (image->debug != MagickFalse)
        (void) LogMagickEvent(CoderEvent,GetMagickModule(),
          "  reading colormap");
      if (psd_info.mode == DuotoneMode)
        {
          /*
            Duotone image data;  the format of this data is undocumented.
          */
          data=(unsigned char *) AcquireQuantumMemory((size_t) length,
            sizeof(*data));
          if (data == (unsigned char *) NULL)
            ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
          (void) ReadBlob(image,(size_t) length,data);
          data=(unsigned char *) RelinquishMagickMemory(data);
        }
      else
        {
          size_t
            number_colors;

          /*
            Read PSD raster colormap.
          */
          number_colors=length/3;
          if (number_colors > 65536)
            ThrowReaderException(CorruptImageError,"ImproperImageHeader");
          if (AcquireImageColormap(image,number_colors,exception) == MagickFalse)
            ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
          for (i=0; i < (ssize_t) image->colors; i++)
            image->colormap[i].red=ScaleCharToQuantum((unsigned char)
              ReadBlobByte(image));
          for (i=0; i < (ssize_t) image->colors; i++)
            image->colormap[i].green=ScaleCharToQuantum((unsigned char)
              ReadBlobByte(image));
          for (i=0; i < (ssize_t) image->colors; i++)
            image->colormap[i].blue=ScaleCharToQuantum((unsigned char)
              ReadBlobByte(image));
          image->alpha_trait=UndefinedPixelTrait;
        }
    }
  if ((image->depth == 1) && (image->storage_class != PseudoClass))
    ThrowReaderException(CorruptImageError, "ImproperImageHeader");
  has_merged_image=MagickTrue;
  length=ReadBlobMSBLong(image);
  if (length != 0)
    {
      unsigned char
        *blocks;

      /*
        Image resources block.
      */
      if (image->debug != MagickFalse)
        (void) LogMagickEvent(CoderEvent,GetMagickModule(),
          "  reading image resource blocks - %.20g bytes",(double)
          ((MagickOffsetType) length));
      blocks=(unsigned char *) AcquireQuantumMemory((size_t) length,
        sizeof(*blocks));
       if (blocks == (unsigned char *) NULL)
         ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
       count=ReadBlob(image,(size_t) length,blocks);
      if ((count != (ssize_t) length) ||
           (LocaleNCompare((char *) blocks,"8BIM",4) != 0))
         {
           blocks=(unsigned char *) RelinquishMagickMemory(blocks);
          ThrowReaderException(CorruptImageError,"ImproperImageHeader");
        }
      ParseImageResourceBlocks(image,blocks,(size_t) length,&has_merged_image,
        exception);
      blocks=(unsigned char *) RelinquishMagickMemory(blocks);
    }
  /*
    Layer and mask block.
  */
  length=GetPSDSize(&psd_info,image);
  if (length == 8)
    {
      length=ReadBlobMSBLong(image);
      length=ReadBlobMSBLong(image);
    }
  offset=TellBlob(image);
  skip_layers=MagickFalse;
  if ((image_info->number_scenes == 1) && (image_info->scene == 0) &&
      (has_merged_image != MagickFalse))
    {
      if (image->debug != MagickFalse)
        (void) LogMagickEvent(CoderEvent,GetMagickModule(),
          "  read composite only");
      skip_layers=MagickTrue;
    }
  if (length == 0)
    {
      if (image->debug != MagickFalse)
        (void) LogMagickEvent(CoderEvent,GetMagickModule(),
          "  image has no layers");
    }
  else
    {
      if (ReadPSDLayers(image,image_info,&psd_info,skip_layers,exception) !=
          MagickTrue)
        {
          (void) CloseBlob(image);
          image=DestroyImageList(image);
          return((Image *) NULL);
        }

      /*
         Skip the rest of the layer and mask information.
      */
      SeekBlob(image,offset+length,SEEK_SET);
    }
  /*
    If we are only "pinging" the image, then we're done - so return.
  */
  if (image_info->ping != MagickFalse)
    {
      (void) CloseBlob(image);
      return(GetFirstImageInList(image));
    }
  /*
    Read the precombined layer, present for PSD < 4 compatibility.
  */
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(CoderEvent,GetMagickModule(),
      "  reading the precombined layer");
  if ((has_merged_image != MagickFalse) || (GetImageListLength(image) == 1))
    has_merged_image=(MagickBooleanType) ReadPSDMergedImage(image_info,image,
      &psd_info,exception);
  if ((has_merged_image == MagickFalse) && (GetImageListLength(image) == 1) &&
      (length != 0))
    {
      SeekBlob(image,offset,SEEK_SET);
      status=ReadPSDLayers(image,image_info,&psd_info,MagickFalse,exception);
      if (status != MagickTrue)
        {
          (void) CloseBlob(image);
          image=DestroyImageList(image);
          return((Image *) NULL);
        }
    }
  if ((has_merged_image == MagickFalse) && (GetImageListLength(image) > 1))
    {
      Image
        *merged;

      SetImageAlphaChannel(image,TransparentAlphaChannel,exception);
      image->background_color.alpha=TransparentAlpha;
      image->background_color.alpha_trait=BlendPixelTrait;
      merged=MergeImageLayers(image,FlattenLayer,exception);
      ReplaceImageInList(&image,merged);
    }
  (void) CloseBlob(image);
  return(GetFirstImageInList(image));
}