HMAC SRS Auth

example.py

from auth import HMACAuthSRS
import requests

key_id = "..." # 
secret_key = "..." #
url = "http://somewhere.slac.stanford.edu/SomeApplication"
auth = HMACAuthSRS(key_id, secret_key, url)

# See http://docs.python-requests.org/en/latest/user/quickstart/
resp = requests.get("http://somewhere.slac.stanford.edu/SomeApplication/someResource", auth=auth)
if resp.status_code == 200:
  data = resp.json()
  print data["key"]

resp = requests.post("http://somewhere.slac.stanford.edu/SomeApplication/someResource", data = {"key":"value"}, auth=auth)

if resp.status_code == 201:
  print "Successful!"

hmac_auth.py

import base64
from email.utils import formatdate
import hashlib
import hmac
from requests.auth import AuthBase
from urlparse import urlparse

__author__ = 'bvan'


class HMACAuth(AuthBase):
    def __init__(self, key_id, secret_key, header_name, signature_format, url=None):
        """key_id must be base64"""
        if url:
            self.resource_base_url = url
        self.key_id = str(key_id)
        self.secret_key = base64.b64decode(str(secret_key))
        self.header_name = header_name
        self.sig_fmt = signature_format

    def __call__(self, request):
        # Create date header if it is not created yet.
        if 'date' not in request.headers:
            request.headers['date'] = formatdate(timeval=None, localtime=False, usegmt=True)
        request.headers[self.header_name] = self.sig_fmt.format(self.key_id, self.get_signature(request))
        return request

    def get_signature(self, r):
        canonical_string = self.get_canonical_string(r.url, r.headers, r.method)
        h = hmac.new(self.secret_key, canonical_string, digestmod=hashlib.sha1)
        return base64.encodestring(h.digest()).strip()

    def get_canonical_string(self, url, headers, method):
        parsedurl = urlparse(url)
        d_headers = {}
        for key in headers:
            lk = key.lower()
            d_headers[lk] = headers[key]
        # hacky way of doing this...
        if self.resource_base_url:
            rpath = parsedurl.path.replace(urlparse(self.resource_base_url).path, "")
        else:
            rpath = "/" + "".join(parsedurl.path.split("/r/")[1:])
        if parsedurl.params and len(parsedurl.params):
            rpath = rpath + ";" + parsedurl.params
        content_md5 = d_headers['content-md5'] if 'content-md5' in d_headers else ""
        content_type = d_headers['content-type'] if 'content-type' in d_headers else ""
        date = d_headers['date']
        hash_buf = "%s\n%s\n%s\n%s\n%s\n" % (method, rpath, content_md5, content_type, date)
        return hash_buf


# noinspection PyAbstractClass
class HMACAuthSRS(HMACAuth):
    def __init__(self, key_id, secret_key, url=None):
        super(HMACAuthSRS, self).__init__(key_id, secret_key, u"Authorization", u"SRS:{0}:{1}", url)