Pasting images versus uploading

[Mike Dewhirst]

Users need to include an image of a molecular structure in a project I'm
building. These are small enough that I could limit the size without
restricting functionality. The image needs to be printed out for a report.

What is the best approach?

I have implemented a TinyMCE-lite HTMLField which accepts a pasted image
and in other systems I have used a Django ImageField for uploading.
ImageField is obviously easier on database size but pasting is easier on
the users.

I'm keen to make the UI easier (by pasting) but I worry it is a
vulnerability if abused.

Thanks for any advice

Cheers

Mike

[Ryan Nowakowski]

Maybe you could swap out the default ImageField widget for TinyMCE-lite HTMLField? Security-wise you probably want to sanitize the input from HTMLField in Django to make sure only img tags are allowed.

[Mike Dewhirst]

On 9/10/2020 11:55 am, Ryan Nowakowski wrote:
> Maybe you could swap out the default ImageField widget for
> TinyMCE-lite HTMLField? Security-wise you probably want to sanitize
> the input from HTMLField in Django to make sure only img tags are allowed.

With the image pasted in, viewing the browser page source it is
represented as just a string although it does contain ...

... src="data:image/png;base64,iVBOR ...


Are you saying all I have to do is write a clean() method for the
HTMLField to detect various image types?

Thanks

Mike

>
> On October 7, 2020 7:02:16 PM CDT, Mike Dewhirst
> <mi...@dewhirst.com.au> wrote:
>
> Users need to include an image of a molecular structure in a project I'm
> building. These are small enough that I could limit the size without
> restricting functionality. The image needs to be printed out for a report.
>
> What is the best approach?
>
> I have implemented a TinyMCE-lite HTMLField which accepts a pasted image
> and in other systems I have used a Django ImageField for uploading.
> ImageField is obviously easier on database size but pasting is easier on
> the users.
>
> I'm keen to make the UI easier (by pasting) but I worry it is a
> vulnerability if abused.
>
> Thanks for any advice
>
> Cheers
>
> Mike
>

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[Dvs Khamele]

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[Ryan Nowakowski]

On Fri, Oct 09, 2020 at 06:22:10PM +1100, Mike Dewhirst wrote:
> On 9/10/2020 11:55 am, Ryan Nowakowski wrote:
> > Maybe you could swap out the default ImageField widget for
> > TinyMCE-lite HTMLField? Security-wise you probably want to sanitize
> > the input from HTMLField in Django to make sure only img tags are allowed.
>
> With the image pasted in, viewing the browser page source it is
> represented as just a string although it does contain ...
>
> ... src=&quot;data:image/png;base64,iVBOR ...
>
>
> Are you saying all I have to do is write a clean() method for the
> HTMLField to detect various image types?

In your Django form class I'd write a clean method specifically for that
field[1] that parses the html, perhaps using BeautifulSoup[2]. Then
search for any "img" tags. For each img tag, parse the data URI[3] to
get the image data.

You still have the problem that the HTMLField is meant to be a
replacement for TextField so you'll need to figure out how to back that
with an ImageField instead. Perhaps you should try to go one level
lower and use the TinyMCE form widget[4] instead of using the HTMLField?

[1] https://docs.djangoproject.com/en/3.1/ref/forms/validation/#cleaning-a-specific-field-attribute
[2] https://www.crummy.com/software/BeautifulSoup/bs4/doc/
[3] https://stackoverflow.com/a/33870677/226697
[4] http://romanvm.github.io/django-tinymce4-lite/usage.html#tinymce-widget-for-forms

[Mike Dewhirst]

Ryan

Thank you for that research and advice. I need to follow through and absorb the implications. That means trying both and then deciding. 

I'll report in due course.

Thanks to all

Mike

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