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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>Speacker Description</title>
<style>
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<body>
<textarea id="source">
class: middle, center
#Token Based Authentication system using JWT
By Jaysinh Shukla
---
### Speacker Description
.center[]
* **Role:** Fullstack developer
* **Github:**
1 http://github.com/ultimatecoder
2 http://github.com/jsh-odoo
* **Twitter:** [@jaysinhp](https://twitter.com/jaysinhp)
* **Emai:** [[email protected]](mailto:[email protected])
* **IRC:** thebigj
---
## Types of Authentication
* **Session / Cookie Authentication**
* **Token Authentication**
---
background-image: url(images/session_authentication_multiple_user.svg)
### Session Authentication for Multiple User
---
### Session or Cookie Authentication
* Client sends authentication credentials (username and password) to Server.
* Server verifies authentication credentials
* if valid, assigns **session storage**, creates **session id** and returns
session id to requested client.
* Client stores **session id** probably at **Cookie** storage. This id
is sent by client with every request. And from that **session id** user is
identified further.
* This allows to identified the same user from upcoming request without
reasking user credentials.
---
### Disadvantages of Session Authentication
* Difficult to handle with
[Load balancer][1]
* Required high amount of resource(RAM without mass-storage) for maintaining
huge amount of user session parallaly.
[1]: https://en.wikipedia.org/wiki/Load_balancing_(computing)
* [CORS](https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS)
doesn't work well with cookies
---
### Birth of Token Authentication
* Token based authentication are most popular authentication system for APIs.
* Comparatively puts less load than **Session authentication**.
* Best for
* Scaling
* Load balancer
* No **cookie**, No [CSRF](https://en.wikipedia.org/wiki/Cross-site_request_forgery)
protection.
* Same API, Authentication will be used for Mobile and Front end app.
---
### Algorithm of Token Authentication
* Client sends authentication credentials.
* Authentication credentials are varified by server. If valid **Token** is
crated.
* **Token** is logged to database and the token is sent back as
**authentication token**
* The client sends **Token** with every request to get verified.
* Normally token is generated with random value and hashed with popular
hashing algorithm.
* Revoking access of specific **Token** by deactivating record at token
table.
---
background-image: url(images/Normal_token_authentication.svg)
---
### Example of authentication at Djnago Rest Framework
```python
from rest_framework.authtoken.models import Token
token = Token.objects.create(user=...)
print token.key
```
Above code is used at authentication view where that **token.key** is returned
if credentials are right.
Assuming random output **9944b09199c62bcf9418ad846dd0e4bbdfc6ee4b**
**Example of Client request using [curl](https://curl.haxx.se/)**
```bash
curl -X GET http://127.0.0.1:8000/api/example/ -H 'Authorization: Token 9944b09199c62bcf9418ad846dd0e4bbdfc6ee4b'
```
---
### Example of Token Authentication at Django Rest Framework
```python
@python_2_unicode_compatible
class Token(models.Model):
"""
The default authorization token model.
"""
key = models.CharField(_("Key"), max_length=40, primary_key=True)
user = models.OneToOneField(
settings.AUTH_USER_MODEL, related_name='auth_token',
on_delete=models.CASCADE, verbose_name=_("User")
)
created = models.DateTimeField(_("Created"), auto_now_add=True)
class Meta:
verbose_name = _("Token")
verbose_name_plural = _("Tokens")
def save(self, *args, **kwargs):
if not self.key:
self.key = self.generate_key()
return super(Token, self).save(*args, **kwargs)
def generate_key(self):
return binascii.hexlify(os.urandom(20)).decode()
```
---
### Problems, Problems every where
* Impossible to
* identify user from which client (like Angular App, Android App, etc) is
authenticated with.
* provide way of access control with respect to client.
* judge that the token is valid by time or not.
* predict for how much time **token** is valid for.
* Difficult to
* Scale because of having dependancy on database to authenticate client
with each request
* run authentication logic seperate from API server.
* Quite difficult to
* scale
* identify when client is identified from multiple sources symentically.
---
### Solution is awesome JWT!
* Suggested pronunciation is "jot".
* JSON Web Token is JSON based Web Authentication Token.
* The token is a combination of three parts. Header, Claim set and Signature.
* Each part of authentication token is encoded with
[base64url](https://en.wikipedia.org/wiki/Base64) encoding and seperated with **"."**
---
background-image: url(images/JWT_token_authentication.svg)
---
### Structure Of JSON Web Token
```base
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4
MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ.dBjftJeZ4CVP-mB92K2
7uhbUJU1p1r_wW1gFWFOEjXk
```
* The token is containing three different part seperated with **"."**
* Each part is encoded with [base64url](https://en.wikipedia.org/wiki/Base64) encoding.
* The first part the .red[Red Part] is **JOSE Header**
* The second part the .blue[Blue Part] is **JWT Claim set**
* The third part the .green[Green Part] is **JWT Signature**
* **Base64URL(JOSE Header).Base64URL(JWT Claims).Base64URL(JWT Signatuer)**
---
### JOSE Header
```base
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
```
* Decoded with Base64 encoding:
```json
{
"typ":"JWT",
"alg":"HS256"
}
```
* Here,
* **typ** defines type of the JSON Web Token. It is not optional.
* **alg** represents type of algorithm used for signing the claim set.
---
### JWT Claim-set
```bash
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
```
* Decoding with Base64 encoding:
```json
{
"iss":"joe",
"exp":1300819380,
"is_root":true
}
```
* Here,
* **iss** is registered claim. It represents the name of Issuer of the token
* **exp** is registered claim. It represents expiration time in format of
[Unix time](https://en.wikipedia.org/wiki/Unix_time)
* **is_root** is unregistred claim. User defined claim which can be presumed
that it is considring user as root user.
---
### JWT Signature
```bash
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
```
* Signature is MAC of encoded JOSE Header and encoded JWS Payload
with the HMAC SHA-256 algorithm.
* And then base64url encoding of that HMAC value.
* This signature helps to verify the authenticity of the **Token**.
---
### Generate JWT Token
* Define **secret key**
* Example using [pyjwt](https://github.com/jpadilla/pyjwt)
```python
>>> import jwt
>>> token = jwt.encode({'user_id': 1}, '12345', algorithm='HS256')
>>> token
b'eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJ1c2VyX2lkIjoxfQ.0X_1nSfbSETzHhcoeywtv6zXXlQd13M3d0-su89rfvM'
```
* Here, **12345** is considered as secret key and **HS256** is the algorithm
we are using.
---
### Example of Verifying Token
```python
# Assume token is 'eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJ1c2VyX2lkIjoxfQ.0X_1nSfbSETzHhcoeywtv6zXXlQd13M3d0-su89rfvM'
>>> jwt.decode(token, '12345', algorithms=['HS256'])
{'user_id': 1}
```
* Here, **12345** is secret key.
---
### JWT Authentication at Django
```python
from django.contrib.auth import authenticate
class Login(View):
def post(self, request, *args, **kwargs):
username = request.POST.get('username')
password = request.POST.get('password')
user = authenticate(username=username, password=password)
if user:
payload = {
'id': user.pk,
'username': user.username,
'staff': user.is_staff,
'exp': datetime.utcnow() + EXPIRY_TIME
}
token = {'token': jwt.encode(payload, SECRET)}
return HttpResponse(
json.dumps(token),
content_type="application/json"
)
else:
return HttpResponse(
json.dumps({'Error': "Invalid credentials"}),
status=400,
content_type="application/json"
)
```
---
### JWT Token Verification at Django
```python
class JWT_AuthMiddleware(object):
def _get_token(request=None):
return request.META.get('HTTP_AUTHORIZATION') or request.GET.get('token')
def process_request(self, request):
token = self._get_token(request)
try:
payload = jwt.decode(token, SECRET)
request.user = User.objects.get(
username=payload.get('username'),
pk=payload.get('id'),
is_active=True
)
except jwt.ExpiredSignature, jwt.DecodeError, jwt.InvalidTokenError:
return HttpResponse({'Error': "Token is invalid"}, status="403")
except User.DoesNotExist:
return HttpResponse({'Error': "Internal server error"}, status="500")
```
---
### Still it is not over!
* If user is logged out, then also the token will be accepted until it is
expired by time.
* For Example, We assigned the token to "X" user and assigned the expire time
to next 3 days and user is logged out after 1 day, that token can be
used by attacker for that unused 2 days and API will consider **Token** as
valid.
* As a best practice, set expiry time not longer than **10 minutes**!
* As a good practice keep less values in claim. Adding many claims may
increase size of token which takes time to transfer the token.
* Change your **Secret key** periodically and Black list tokens if possible.
---
### What we are doing with JWT
* Creating JWT token
* Validating **Token** at every request.
* Allowing user to **refresh token** if given **Token** is valid.
* If user is logging out then creating entry of token to **Black list** table
* Advantage:
* Token will not be used further if it is **Black listed** even in the
valid time frame.
---
background-image: url(images/Our_token_authentication.svg)
---
### JWT Claims
* Types of Claims
1 Registered Claim Names
2 Public Claim Names
3 Private Claim Names
---
### JWT Registered Claim names
* **iss:** Dipicting Issuer of the token
* **sub:** Subject of the Token
* **aud:** Audiance for which token is given for
* **exp:** Expiration time in Unix time.
* **nbf:** Token should not be accepted before this value. In Unix time format
* **iat:** Representing age of the token
* **jti:** Dipicting ID of the token
---
### JWT Public Claim names
* It can be defined by fellows using JWT on condition that they have to
register this claim at [IANA "JSON Web Token Claims" registry](http://www.iana.org/assignments/jwt/jwt.xhtml)
---
### JWT Private Claim names
* Custom claims which are not publicly used but represented as claims in JWT.
* This custom claims should be considered as private claims.
---
### Similar Technologies
1 [Simple Web Token](https://msdn.microsoft.com/library/azure/hh781551.aspx)
2 [JSON Simple Singh](https://jsonenc.info/jss/1.0/)
---
### Why not to go with Oauth 2.0?
* Oauth 2.0 uses JWT as token exchange standard.
* But Oauth 2.0 is more focused for three parties. **Resource owner**, **Authorization Server**,
**Resource Server**
* Using JWT is simple and more efficient when focus is only authentication.
* OAuth 2.0 contains many payload values which will increase the size of token.
---
### References
* https://en.wikipedia.org/wiki/Session_(computer_science)
* https://tools.ietf.org/html/rfc7519
* https://auth0.com/blog/2014/01/07/angularjs-authentication-with-cookies-vs-token/
</textarea>
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