Securing Flask APIs using JWT
About Me
Md. Shahbaz Alam
Full Stack Developer
Auth0 Ambassador
Mozilla Reps Mentor
GDG Ranchi Organizer
@mdsbzalam
Agenda
1. JSON Web Tokens ( JWT )
2. Python Frameworks
3. Flask
4. Demo
JWT
What is JSON Web Tokens?
- Based on Web Standard ( RFC 7519 )
- securely communicate JSON Objects
- A way to encode information
- Allow shared parties to verify information is legit
- Secret-based Verification
- When secret changes then information is no more legit
- Consists of a header, payload and signature
- Self-contained
JWT
JSON Web Token
JWT
The JWT Header
The header is a JSON Object usually consisting of the type( typ ) , which is JWT, and the algorithm used for encrypting the JWT (alg ):
{
"alg": "HS256",
"typ": "JWT"
}JWT
The JWT Payload
The Payload is a JSON object that consists of user defined attributes ( called public claims ) . Some attributes are defined in the standard ( these are called reserved claims ).
{
// reserved claim
"iss": "https://myapi.com",
// public claim
"user": "mdsbzalam"
}JWT
The JWT Signature
The Signature is the encoded header and payload, signed with a secret.
HMACSHA256(
base64UrlEncode(header) + "." +
base64UrlEncode(payload),
secret
)
This accomplishes several tasks at once, including:
- Proves the identity of the sender
- Ensures the message has not changed
JWT
The JWT Token
A finished token looks like [encoded header].[encoded payload].[signature] :
JWT
The JWT Token
JWT
Advantages:
Easy to parse
Easy to Sign
Compact
compared to XML
compared to XML
compared to ...
You get it.
JWT
Implementing JWT in Python
$ pip install jwt
$ python
>>> import jwt
>>> jwt.encode({'jwt':'JSON Web Token'},'secret')
JWT
decoding JWT in Python
$
......
>>> token = jwt.encode({'py':'Python'},'secret')
>>> jwt.decode(token , 'secret')
{'py':'Python'}Python Frameworks
Why Python?
- Fastest growing programming language
- Huge Community base is improving every aspect of the language
- More & more open source libraries are being released to address AI, ML, and Web Development.
- https://docs.python.org/3/ for new adopters to learn its essence fast
Python Frameworks
Full-stack frameworks:
Python Frameworks
Microframeworks:
Python Frameworks
Asynchronous frameworks:
other:
Flask App
Dependencies:
- Python 2 or 3
- Flask
- jsonify
- request
- make_response
- jwt
- datetime
- wraps
Flask App
Basic Flask App
from flask import Flask
app = Flask(__name__)
if __name__ == "__main__":
app.run(debug=True)Flask App
Lets modify few things..
from flask import Flask
from flask import jsonify
from flask import request
from flask import make_response
...
...Flask App
Now add Authentication to it
...
@app.route('/login')
def login():
auth = request.authorization
if auth and auth.password == 'pyconid':
return jsonify({'message' : 'logged in})
return make_response('Could not verify!', 401,
{'WWW-Authenticate' :
'Basic realm:"Login Required"'})
...Flask App
Lets add two more Routes
...
@app.route('/unprotected')
def unprotected():
return jsonify({'message' :
'Anyone can view this.'})
@app.route('/protected')
def protected():
return jsonify({'message' :
'Only available to people
with valid tokens.'})
...Flask App
It's time to import JWT
...
import jwt
import datetime
...
...Flask App
Modifying Login method to set token
...
app.config['SECRET_KEY'] = 'indonesia'
...
if auth and auth.password == 'pyconid':
token = jwt.encode({'user': auth.username,
'exp': datetime.datetime.utcnow()
+ datetime.timedelta(seconds=50)},
app.config['SECRET_KEY'])
return jsonify({'message' : 'logged in})
...
...Flask App
Creating decorator for protected route
...
def token_required(f):
@wraps(f)
def decorated(*args, **kwargs):
token = request.args.get('token')
# http://127.0.0.1:5000/protected?token=sqibsq12egvdyw
if not token:
return jsonify({'message' : 'Token is missing'}), 403
try:
data = jwt.decode(token, app.config['SECRET_KEY'])
except:
return jsonify({'message' : 'Token is invalid!'}), 403
return f(*args, **kwargs)
return decorated
...Flask App
Adding decorator to protected route
...
@app.route('/protected')
def protected():
return jsonify({'message' :
'Only available to people
with valid tokens.'})
...Flask App
Adding decorator to protected route
...
@app.route('/protected')
@token_required
def protected():
return jsonify({'message' :
'Only available to people
with valid tokens.'})
...Flask App : complete
from flask import Flask, jsonify, request, make_response
import jwt
import datetime
from functools import wraps
app = Flask(__name__)
app.config['SECRET_KEY'] = 'indonesia'
# Token Decorator
def token_required(f):
@wraps(f)
def decorated(*args, **kwargs):
token = request.args.get('token')
if not token:
return jsonify({'message' : 'Token is missing'}), 403
try:
data = jwt.decode(token, app.config['SECRET_KEY'])
except:
return jsonify({'message' : 'Token is invalid!'}), 403
return f(*args, **kwargs)
return decorated
# Unprotected Route and function
@app.route('/unprotected')
def unprotected():
return jsonify({'message' : 'Anyone can view this.'})
# Protected Route and function
@app.route('/protected')
@token_required
def protected():
return jsonify({'message' : 'Only available to people with valid tokens.'})
# Login Route and function
@app.route('/login')
def login():
auth = request.authorization
if auth and auth.password == 'pyconid':
token = jwt.encode({'user': auth.username, 'exp': datetime.datetime.utcnow() + datetime.timedelta(seconds=40)}, app.config['SECRET_KEY'])
return jsonify({'token' : token})
return make_response('Could not verify!', 401, {'WWW-Authenticate' : 'Basic realm:"Login Required"'})
if __name__ == "__main__":
app.run(debug=True)Flask App
Try it yourself
[~]$ python flaskdemo.py
Flask App
Auth0 way
Resources
General JWT Resources
jwt.io
Overview of JWT Signing Algorithms
http://bit.ly/jwt-alg
JWT Handbook
http://bit.ly/jwt-book
Connect with me
facebook.com/mdsbzalam
@mdsbzalam
@mdsbzalam
https://in.linkedin.com/in/mdsbzalam
mdsbzalam@gmail.com
Slide
http://bit.ly/pyconid-slide
Thank you
@mdsbzalam