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rest api prototyping

the problem

lately i've been working on a lot of web API glue projects. these are usually simple things like "service1 needs to send messages to service2 in a particular format, with a particular set of priviledges." Sometimes its more complicated, but that's usually what it breaks down to.

at first I was writing python code the whole time, exploring the API through python (ugh) and kept getting frustrated; it felt like I wasn't able to go as fast as I would like, I kept making silly mistakes that I wouldn't catch until much later, etc. To fix this, i've moved to prototyping in restclient.el - this is a featureful rest client that you interact with through plain text (i.e., you can version control it!) within emacs.

this has worked great for a lot of things, but falls short when you have to generate an auth token programmatically (instead of using a static key) for each request. this problem is solvable using: a different kind of glue lol. i use python to create the auth token, org-babel to register the result and then pass it to `restclient` which will continue to be my prototyping tool of choice. this write up will go over how i stitch each part together; i'll use Cylance as an example service for api requests.

Authentication and Authorization in Cylance

Cylance relies on something called JWT (JSON Web Token). There's an RFC for this here: https://tools.ietf.org/html/rfc7519. This is not possible to generate within `restclient`, so we do it in python.

To generate the JWT, in Cylance's case, we care about:

TID_VAL, which is the tenant ID. You can find this by logging into the console > settings > integrations. APP_ID and APP_SECRET, which is under the same place, but you'll have to expand the custom application.

We'll add a #+name: argument to the top of the org-mode src block so that the output from the block can be registered for later use.

python code

import uuid
import json
import requests
import jwt
import pdb
from datetime import datetime, timedelta

# initial auth test setup
JTI_VAL = str(uuid.uuid4())
TID_VAL = ""     # The tenant's unique identifier.
APP_ID = ""      # The application's unique identifier.
APP_SECRET = ""  # application's secret to sign the auth token with.

# 30 minutes from now
TIMEOUT = 1800
NOW = datetime.utcnow()
TIMEOUT_DATETIME = NOW + timedelta(seconds=TIMEOUT)
EPOCH_TIME = int((NOW - datetime(1970, 1, 1)).total_seconds())
EPOCH_TIMEOUT = int((TIMEOUT_DATETIME - datetime(1970, 1, 1)).total_seconds())

AUTH_URL = "https://protectapi.cylance.com/auth/v2/token"

CLAIMS = {
    "exp": EPOCH_TIMEOUT,
    "iat": EPOCH_TIME,
    "iss": "http://cylance.com",
    "sub": APP_ID,
    "tid": TID_VAL,
    "jti": JTI_VAL
}

ENCODED = jwt.encode(CLAIMS, APP_SECRET, algorithm='HS256')
# lol you have to decode from a bytes object to a string because
# bytes aren't fucking json serializable
# you never seem to need to re-encode them? python is so fucking weird.
ENCODED = ENCODED.decode()

PAYLOAD = {"auth_token": ENCODED}
HEADERS = {"Content-Type": "application/json; charset=utf-8"}
RESP = requests.post(AUTH_URL, headers=HEADERS, data=json.dumps(PAYLOAD))
print(json.loads(RESP.text)['access_token'])

this will generate a token and attach it to the name space jwt_token as defined previously.

restclient example

once the previous block has run to generate the json web token we can pass it on to this restclient block and use it to query Cylance's API through restclient.el going forward! in order to pass the output from the registered name we used before, jwt_token, we add an argument to the BEGIN_SRC header, like :var x=jwt_token. Then, we can set a restclient local variable equal to the org-babel super-variable and use it within the rest of the src block, as seen below:

# auth.test
:cylance_jwt_token = :x
GET https://protectapi.cylance.com/users/v2?page=1&page_size=1
Authorization: Bearer :cylance_jwt_token
Content-Type: application/json
User-Agent: Emacs Restclient

this will return my user (again, i've disturbed the output but it is roughly what's returned):

{
  "page_number": 1,
  "page_size": 1,
  "total_pages": 6,
  "total_number_of_items": 6,
  "page_items": [
    {
      "id": "",
      "tenant_id": "",
      "first_name": "",
      "last_name": "",
      "email": "me@thiscompanyyo.isit",
      "has_logged_in": true,
      "role_type": "",
      "role_name": "i am the boss",
      "default_zone_role_type": "",
      "default_zone_role_name": "",
      "zones": [],
      "date_last_login": "2019-11-22T14:52:13",
      "date_email_confirmed": null,
      "date_created": "2019-05-17T17:16:52",
      "date_modified": "2019-05-17T17:16:52"
    }
  ]
}
// GET https://protectapi.cylance.com/users/v2?page=1&page_size=1
// HTTP/1.1 200 OK
// Content-Encoding: gzip
// Content-Type: application/json; charset=utf-8
// Date: Fri, 22 Nov 2019 16:24:13 GMT
// Server: openresty
// Content-Length: 339
// Connection: keep-alive
// Request duration: 0.305690s

Troubleshooting python and org-babel

I had huge issues with python virtual environemtns and org-babel while initially setting up this environment. i once had an issue with emacs, I belive in an older version (25 or below i think) where it couldn't find my python binary on macOS. to fix this i manually set it in my init.el file, which worked for a long time.

however, if you start using venvs within emacs, tools like pvenv and venv will not overwrite the global variable set with the new venv specific python binaries if you've globally set the py binary location. This killed me. below are some blocks i used to troubleshoot what was going on.

This one is pretty straight forward: do i have a virtual env active, and where is the python binary as seen by the shell:

echo $VIRTUAL_ENV
which python

Same deal, only "where is the python binary as seen in the python session". in my case, this was showing me the system python binary even when the shell was showing me the venv binary.

import sys
print('\n'.join(sys.path))

this block just proved that i could in fact import the right modules that were only in the venv.

import jwt

Made with Emacs 27.1 (Org mode 9.3)