A Python implementation of JSON Web Signatures draft 02
$ git://github.com/brianlovesdata/python-jws.git
$ python setup.py install
The JWS spec reserves several algorithms for cryptographic signing. Out of the 9, this library currently supports 7:
HMAC – native
- HS256 – HMAC using SHA-256 hash algorithm
- HS384 – HMAC using SHA-384 hash algorithm
- HS512 – HMAC using SHA-512 hash algorithm
RSA – requires special version of pycrypto, read below
- RS256 – RSA using SHA-256 hash algorithm
ECDSA – requires ecdsa lib: pip install ecdsa
- ES256 – ECDSA using P-256 curve and SHA-256 hash algorithm
- ES384 – ECDSA using P-384 curve and SHA-384 hash algorithm
- ES512 – ECDSA using P-521 curve and SHA-512 hash algorithm
There is also a mechanism for extending functionality by adding your own algorithms without cracking open the whole codebase. See the advanced usage section for an example.
NOTE: you must use the version of pycrypto submoduled to
vendor/pycrypto to get RSA256 support. However if you don't ever plan on using
RSA, you don't have to worry about it – all crypto libraries are lazily loaded
so you won't even notice it's not there.
If you want to know why RSA support is limited, read this: https://github.com/brianlovesdata/python-jws/blob/master/jws/algos.py#L42
Let's check out some examples.
>>> import jws
>>> header = { 'alg': 'HS256' }
>>> payload = { 'claim': 'JSON is the raddest.', 'iss': 'brianb' }
>>> signature = jws.sign(header, payload, 'secret')
>>> jws.verify(header, payload, signature, 'secret')
True
>>> jws.verify(header, payload, signature, 'badbadbad')
Traceback (most recent call last):
...
jws.exceptions.SignatureError: Could not validate signature
Now with a real key!
>>> import ecdsa
>>> sk256 = ecdsa.SigningKey.generate(curve=ecdsa.NIST256p)
>>> vk = sk256.get_verifying_key()
>>> header = { 'alg': 'ES256' }
>>> sig = jws.sign(header, payload, sk256)
>>> jws.verify(header, payload, sig, vk)
True
Make this file
# file: sillycrypto.py
import jws
from jws.algos import AlgorithmBase, SignatureError
class FXUY(AlgorithmBase):
def __init__(self, x, y):
self.x = int(x)
self.y = int(y)
def sign(self, msg, key):
return 'verysecure' * self.x + key * self.y
def verify(self, msg, sig, key):
if sig != self.sign(msg, key):
raise SignatureError('nope')
return True
jws.algos.CUSTOM += [
# a regular expression with two named matching groups. (x and y)
# named groups will be sent to the class constructor
(r'^F(?P<x>\d)U(?P<y>\d{2})$', FXUY),
]
And in an interpreter:
>>> import jws
>>> header = { 'alg': 'F7U12' }
>>> payload = { 'claim': 'wutt' }
>>> sig = jws.sign(header, payload, '<trollface>')
Traceback (most recent call last):
....
jws.exceptions.AlgorithmNotImplemented: "F7U12" not implemented.
>>>
>>> import sillycrypto
>>> sig = jws.sign(header, payload, '<trollface>')
>>> jws.verify(header, payload, sig, '<trollface>')
True
>>> jws.verify(header, payload, sig, 'y u no verify?')
Traceback (most recent call last):
....
jws.exceptions.SignatureError: nope
Check out https://github.com/brianlovesdata/python-jws/blob/master/examples/minijwt.py for a 14-line implemention of JWT.
See https://github.com/brianlovesdata/python-jws/blob/master/examples/ragecrypto.py for a rage-comic inspired cryptography extension.
- Write about all the rad stuff that can be done around headers (as extensible as crypto algos)
- Pull in JWK support
use nosetests
MIT