Conseguindo assinatura do S3 para enviar arquivos via PUT direto do cliente.

signature_upload_to_s3.py

# -*- coding: utf-8 -*-

from django.conf import settings
from django.http import JsonResponse
from hashlib import sha1
import base64
import hmac
import time
import urllib


__all__ = ['sign_s3', ]


def sign_s3(request):
    """

    https://devcenter.heroku.com/articles/s3-upload-python

    """

    AWS_ACCESS_KEY = settings.AWS_ACCESS_KEY_ID
    AWS_SECRET_KEY = settings.AWS_SECRET_ACCESS_KEY
    S3_BUCKET = settings.AWS_STORAGE_BUCKET_NAME
    S3_URL = settings.S3_URL

    mime_type = request.GET.get('file_type', None)
    file_name = request.GET.get('file_name', None)
    object_name = urllib.quote_plus(file_name)

    expires = int(time.time()+60*60*24)
    amz_headers = "x-amz-acl:public-read"

    string_to_sign = 'PUT\n\n{0}\n{1}\n{2}\n/{3}/{4}'.format(
        mime_type, expires, amz_headers, S3_BUCKET, object_name)

    signature = base64.encodestring(
        hmac.new(
            AWS_SECRET_KEY.encode(), string_to_sign.encode('utf8'), sha1
        ).digest()
    )
    signature = urllib.quote_plus(signature.strip())

    url = '{0}tmp-upload/{1}'.format(S3_URL, object_name)

    return JsonResponse({
        'signed_request':
            '{0}?AWSAccessKeyId={1}&Expires={2}&Signature={3}'.format(
                url, AWS_ACCESS_KEY, expires, signature),
        'url': url,
    })