Google Map API Signature Generation in Python

Question

I'm basically doing the following: https://developers.google.com/maps/documentation/business/webservices/auth

In Python 2.7.3 on my MacBook and on 2.7.5 on a Windows 64bit Server environment I fail to reproduce the correct signature, while I follow the original example exactly. I make a function like this:

import sys
import hashlib
import urllib
import hmac
import base64
import urlparse

def process_url(input_url, private_key):
    print("URL To Sign: " + input_url)
    url = urlparse.urlparse(input_url)
    print("Private Key: " + private_key)
    url_to_sign = url.path + "?" + url.query
    print("Original Path + Query: " + url_to_sign)
    decoded_key = base64.urlsafe_b64decode(private_key)
    signature = hmac.new(decoded_key, url_to_sign, hashlib.sha1)
    encodedSignature = base64.urlsafe_b64encode(signature.digest())
    print("B64 Signature: " + encodedSignature)
    original_url = url.scheme + "://" + url.netloc + url.path + "?" + url.query
    full_url = original_url + "&signature=" + encodedSignature
    print "Full URL: " + full_url
    return full_url

Now this should give the following according to google:

URL: http://maps.googleapis.com/maps/api/geocode/json?address=New+York&sensor=false&client={clientID}
Private Key: vNIXE0xscrmjlyV-12Nj_BvUPaw=
URL Portion to Sign: /maps/api/geocode/json?address=New+York&sensor=false&client={clientID}
Signature: KrU1TzVQM7Ur0i8i7K3huiw3MsA=
Full Signed URL: http://maps.googleapis.com/maps/api/geocode/json?address=New+York&sensor=false&client={clientID}&signature=KrU1TzVQM7Ur0i8i7K3huiw3MsA=

However, when I do the following:

process_url('http://maps.googleapis.com/maps/api/geocode/json?address=New+York&sensor=false&client={clientID}', 'vNIXE0xscrmjlyV-12Nj_BvUPaw=')

I get:

URL To Sign: http://maps.googleapis.com/maps/api/geocode/json?address=New+York&sensor=false&client={clientID}
Private Key: vNIXE0xscrmjlyV-12Nj_BvUPaw=
Original Path + Query: /maps/api/geocode/json?address=New+York&sensor=false&client={clientID}
B64 Signature: WlcBIkr9WMB9uPhXWmAGcjG_2M4=
Full URL: http://maps.googleapis.com/maps/api/geocode/json?address=New+York&sensor=false&client={clientID}&signature=WlcBIkr9WMB9uPhXWmAGcjG_2M4=

So I get "WlcBIkr9WMB9uPhXWmAGcjG_2M4=" and not "KrU1TzVQM7Ur0i8i7K3huiw3MsA=". I swear this used to work, but I get this new W-value consistently over different systems.

Does anyone have any clue what I'm doing wrong? Is the page incorrect or am I doing something basic incorrect??

fortran · Accepted Answer · 2013-11-13 01:10:09Z

1

You are not doing anything wrong, you are signing different data thus getting a different signature.

In the Google example, if you copy and paste you'll notice that the braces are omitted in the clipboard; so it's signing the following URL:

http://maps.googleapis.com/maps/api/geocode/json?address=New+York&sensor=false&client=clientID

But when you tried it, you copied it verbatim, including the curly braces:

http://maps.googleapis.com/maps/api/geocode/json?address=New+York&sensor=false&client={clientID}

So rejoice yourself, your code is right, the only problem is in the sample data!

answered Nov 13, 2013 at 1:10

fortran

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1 Comment

Carst Over a year ago

I have this great eureka/argh mix at the moment haha, thank you so much! :)

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