Gravity Forms Signature - From PHP to Python - php

Question

I need to translate some existing PHP code to Python. This job connects to gravity forms and queries for certain data. In order to make the query, a signature must be calculated in order to verify the connection.
The Gravity Forms web api gives good PHP directions here.
The PHP method is as follows:
function calculate_signature( $string, $private_key ) {
$hash = hash_hmac( 'sha1', $string, $private_key, true );
$sig = rawurlencode( base64_encode( $hash ) );
return $sig;
}
Based on my understanding of Python and the information about hash-hmac and rawurlencoded from php2python.com, I wrote the following:
import hmac, hashlib, urllib, base64
def calculate_signature(string, private_key):
hash_var = hmac.new(private_key, string, hashlib.sha1).digest()
sig = urllib.quote(base64.b64encode(hash_var))
return sig
However, the two signatures are not equivalent, and thus Gravity Forms returns a HTTP 403: Bad Request response.
Am I missing something within my translation?
Update (11/04/15)
I have now matched my php and python urls. However, I still receive a 403 error.

Answer 1

The reason the php and python signatures did not match had nothing to do with their calculate_signature() methods.
The issue was caused by differing expires variables. Php used strtotime("+60 mins") which resulted in a UTC time 60 minutes from now. Whereas Python used datetime.date.now() + timedelta(minutes=60). This is also 60 minutes from now, but in your current timezone.
I always want to calculate the expire variable in UTC so I replaced my Python calculation with datetime.datetime.utcnow() + timedelta(minutes=60).

Answer 2

You're almost there. urllib.quote does not encode slashes, for example, as PHP's rawurlencode does. You can use urllib.quote_plus to achieve the desired effect:
import hmac, hashlib, urllib, base64
def calculate_signature(string, private_key):
hash_var = hmac.new(private_key, string, hashlib.sha1).digest()
sig = urllib.quote_plus(base64.b64encode(hash_var))
return sig