I've got two systems that need to talk. The systems are setup likeso:
System A, running Django (Python 2.5) on Google App Engine (GAE)
System B, running Django (Python 2.6) on Ubuntu/Linux over Lighttpd (maybe nginx, later)
System A will periodically make requests ('requisitions') of System B using Url Fetch.
System B has a Django app setup to listen for these requests with a urls.py with something like:
urlpatterns = patterns('producer.views',
url(r'^requisition$', 'requisition', name='requisition'),
)
And a corresponding views.py with something like:
import json
from django.http import HttpResponse
def requisition(request):
" do something "
response = HttpResponse()
response['Content-type'] = 'application/json'
response.write(json.dumps(...))
return response
It would be a valuable addition to security of the system if System B responded to requisitions only from System A.
I'd like to know what options are available for System B to verify that requests have come from System A. I've considered the following:
- Check that the IP address is from GAE (however I don't know the GAE IP addresses, they may change, and they may be spoofed)
- Check that the reverse DNS of the IP is from GAE (however I don't know what GAE's DNS entries are, if they will change, and they may be spoofed)
- Use a TLS client certificate from System A - but I don't know how to do this with GAE
- Do a challenge/response based on something shared, like a salt, with pycrypto
Ideally I want to end up with a views.py with something likeso:
...
from django.http import HttpResponseForbidden
def requisition(request):
" do something "
if not verify_request_origin():
return HttpResponseForbidden("Denied.")
response = HttpResponse()
...
Where verify_request_origin() returns true when the request made to System B was from System A on GAE.
Thank you and I look forward to hearing your thoughts.