How to generate presigned S3 urls using django-storages?

Question

I have a Django form which saves a file to s3 through the django-storages library and works fine. How can I generate and return a pre-signed url so the user can access the file temporarily after it is uploaded ? Is this abstracted by django-storages or do I have to use the boto3 api?

I have spent hours going through the Django-storages documentation however it is not very clear how to do this ..

form.py

class DocumentForm(forms.Form):
    docfile = forms.FileField(
        label='Select a file',
        help_text='max. 42 megabytes'
    )
   name = models.CharField(max_length=20)
   uploaded_at = models.DateTimeField(auto_now_add=True)

views.py

def upload_file(request):
   if request.method == 'POST':
      form = DocumentForm(request.POST)
      if form.is_valid():
         form.save()
         url = ... # generate pre-signed url of uploaded file here
         return render(request, 'upload_response.html', url)

also see aws boto3 docs for pre-signed urls

djvg
– djvg

2023-12-29 15:51:18 +00:00
Commented Dec 29, 2023 at 15:51 — djvg
– djvg, Commented Dec 29, 2023 at 15:51

Flimm · Accepted Answer · 2023-12-15 19:21:32Z

17

Turns out you do not need to use boto3 to generate a presigned url. Django-storages abstracts the entire process. You can simply access the url attribute on the FileField, like in this example:

document_form = DocumentForm.objects.get(pk=1)
url = document_form.docfile.url

--- Edit ----

For reference, here is the S3 storage class method that generates the pre-signed url for you https://github.com/jschneier/django-storages/blob/770332b598712da27ecdba75c9e202ad6a1a8722/storages/backends/s3boto3.py#L554

edited Dec 15, 2023 at 19:21

Flimm

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answered Feb 18, 2021 at 16:30

Tamdim

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5 Comments

coler-j Over a year ago

Can we get a reference to source on this?

Tamdim Over a year ago

I have just edited the answer with a link to the reference

webjunkie Over a year ago

To actually return a URL with signature, make sure AWS_QUERYSTRING_AUTH = True.

Tamdim Over a year ago

Good point. I believe it is set to True by default if not explicitly set in settings.py

RSK Dec 16, 2024 at 8:53

This is not working - the .url attribute doesn't generate the presigned URL automatically. Has this process changed? I am able to upload to S3 but I am not able to display those files since the bucket is not private.

santosh · Accepted Answer · 2020-10-09 16:56:49Z

3

Here is sample code for generating pre-signed url for object in S3

import boto3

client = boto3.client('s3')
response = client.generate_presigned_url('get_object',Params={'Bucket': bucket_name,
                                                              'Key': objectpath},
                                         HttpMethod="GET", ExpiresIn=expires_in)

answered Oct 9, 2020 at 16:56

santosh

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