request.environ['HTTP_REFERER'] is None

Question

i want to get HTTP_REFERER in python flask framework. My route is this:

@app.route('/login')

def login():

    if authenticateForPanel():
        return redirect(url_for("panel"))
    else:               
        ref = request.environ['HTTP_REFERER']

        return render_template('login.html',blogOptions = g.blogOptions,ref=ref)

When i execute this,i got KeyError: 'HTTP_REFERER' with the traceback:

Traceback (most recent call last):
  File "/Users/ozcan/flask/flask/app.py", line 1823, in __call__
    return self.wsgi_app(environ, start_response)
  File "/Users/ozcan/flask/flask/app.py", line 1811, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "/Users/ozcan/flask/flask/app.py", line 1809, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/ozcan/flask/flask/app.py", line 1482, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/Users/ozcan/flask/flask/app.py", line 1480, in full_dispatch_request
    rv = self.dispatch_request()
  File "/Users/ozcan/flask/flask/app.py", line 1466, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/Users/ozcan/Documents/python/app.py", line 318, in login
    ref = request.environ['HTTP_REFERER']
KeyError: 'HTTP_REFERER'

When i first wrote this code it was working.I do not directly call this url.I call localhost:5000/panel and it redirects me to the login method.So basically there should be a referer,am i wrong?

When i print the request.environ['HTTP_REFERER'] it prints None

I also tried with the

ref = request.referrer but it is None

Why it can be happen?Thanks a lot.

score 4 · Answer 1 · answered Feb 18 '13 at 16:51

The werkzeug Request wrapper, which flask uses by default, does this work for you: request.referrer

from flask import Flask, request
import unittest

app = Flask(__name__)
@app.route('/')
def index():
    return unicode(request.referrer)

class Test(unittest.TestCase):

    def test(self):
        c = app.test_client()
        resp = c.get('/', headers={'Referer': '/somethingelse'})
        self.assertEqual('/somethingelse', resp.data)

if __name__ == '__main__':
    unittest.main()

But in the more general case, to retrieve the value of a dictionary key specifying a default if the key is not present, use dict.get

score 4 · Answer 2 · edited May 23 '17 at 12:23

4

When i first wrote this code it was working.I do not directly call this url.I call localhost:5000/panel and it redirects me to the login method.So basically there should be a referer,am i wrong?

This is not correct. A redirect does not guarantee a referrer. Whether a browser will provide a referrer is browser-specific. Perhaps you were using a different browser that had this behavior at one point? The code you have now is working as best as it can be expected to.

See Will a 302 redirect maintain the referer string?

edited May 23 '17 at 12:23

Community

1
1

answered Feb 18 '13 at 16:53

Mark Hildreth

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then,how can i set a referer? – saidozcan Feb 18 '13 at 16:56
1

As the answer to the question I linked stated, the most surefire way is to not leave this up to the browsers. Instead, include the URL of the referrer as a parameter in your URL. So, something like `http://example.com/login?referrer=http%3A%2F%2Fexample.com%2Fpanel`. – Mark Hildreth Feb 18 '13 at 17:01

score 1 · Answer 3 · edited Jan 05 '19 at 06:19

1

The only way I could get request.referrer to not be None is to load the page through <a href="/something"></a>. Redirecting and making regular old HTTP requests did not include a referrer attribute.

edited Jan 05 '19 at 06:19

Bhargav Rao

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answered Jan 04 '19 at 20:33

House Targaryen

69
7

score 0 · Answer 4 · answered Feb 18 '13 at 16:47

0

@dm03514 has the right idea, but if you're insistent upon using the environ dictionary, you should be using the get method. Also, how are you testing that it is None, i.e., are you using the interactive interpreter to print the value or are you adding print statements in the body?

An example of how you would do this reasonably:

# snip
else:
    ref = request.environ.get('HTTP_REFERER')
    # You can specify a default return value other than None like so:
    # ref = request.environ.get('HTTP_REFERER', '/')
# snip

answered Feb 18 '13 at 16:47

Ian Stapleton Cordasco

26,944
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to check it i print the ref variable to terminal – saidozcan Feb 18 '13 at 16:48
sorry but nothing has changed – saidozcan Feb 18 '13 at 16:49
You mean you add print statements and run the server. And if you're still getting the above exception, you must not have restarted your server. The `get` method does not raise an exception EVER unless the object has no such method. – Ian Stapleton Cordasco Feb 18 '13 at 16:51
No no i did not meant that.I wrote print ref and run the server.I do not have still above exception but now HTTP_REFERER is None – saidozcan Feb 18 '13 at 16:52

request.environ['HTTP_REFERER'] is None

4 Answers4

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