Python Embracing Windows Azure

Sriram Krishnan, a Microsoft Program Manager, recently posted on using Python to access Azure's storage service. Azure, you may recall, is Microsoft's latest try to break into cloud computing. In a recent entry on his blog, Krishnan features a Python wrapper that shows how to automate your session's authentication with Azure. First, you make the connection:

conn = WAStorageConnection(DEVSTORE_HOST, DEVSTORE_ACCOUNT, DEVSTORE_SECRET_KEY)
     for (container_name,etag, last_modified ) in conn.list_containers():
     print container_name
     print etag
     print last_modified


     conn.create_container("testcontainer", False)
     conn.put_blob("testcontainer","test","Hello World!" )
     print conn.get_blob("testcontainer", "test")


Then you get the security headers:

def _get_auth_header(self, http_method, path, data, headers):
     # As documented at http://msdn.microsoft.com/en-us/library/dd179428.aspx
     string_to_sign =""


     #First element is the method
     string_to_sign += http_method + NEW_LINE


     #Second is the optional content MD5
     string_to_sign += NEW_LINE


     #content type - this should have been initialized atleast to a blank value
     if headers.has_key("content-type"):
         string_to_sign += headers["content-type"]
     string_to_sign += NEW_LINE


     # date - we don't need to add header here since the special date storage header
     # always exists in our implementation
     string_to_sign += NEW_LINE


     # Construct canonicalized storage headers.
     # TODO: Note that this doesn't implement parts of the spec - combining header fields with same name,
     # unfolding long lines and trimming white spaces around the colon


     ms_headers =[header_key for header_key in headers.keys() if header_key.startswith(PREFIX_STORAGE_HEADER)]
     ms_headers.sort()
     for header_key in ms_headers:
         string_to_sign += "%s:%s%s" % (header_key, headers[header_key], NEW_LINE)


     # Add canonicalized resource
     string_to_sign += "/" + self.account_name + path
     utf8_string_to_sign = unicode(string_to_sign).encode("utf-8")
     hmac_digest = hmac.new(self.secret_key, utf8_string_to_sign, hashlib.sha256).digest()
     return base64.encodestring(hmac_digest).strip()


As noted by Krishnan, this is his draft code and not production quality. You can get updates at his GitHub spot.

Kudos to Abel Avram for his discussion on this.