Add jwt library in contrib

kyleconroy · kyleconroy · commit e87ba8f0a36c · 2011-07-22T10:08:20.000-07:00
diff --git a/twilio/contrib/jwt/__init__.py b/twilio/contrib/jwt/__init__.py
@@ -0,0 +1,72 @@
+""" JSON Web Token implementation
+
+Minimum implementation based on this spec:
+http://self-issued.info/docs/draft-jones-json-web-token-01.html
+"""
+import base64
+import hashlib
+import hmac
+
+try:
+    import json
+except ImportError:
+    import simplejson as json
+    
+__all__ = ['encode', 'decode', 'DecodeError']
+
+class DecodeError(Exception): pass
+
+signing_methods = {
+    'HS256': lambda msg, key: hmac.new(key, msg, hashlib.sha256).digest(),
+    'HS384': lambda msg, key: hmac.new(key, msg, hashlib.sha384).digest(),
+    'HS512': lambda msg, key: hmac.new(key, msg, hashlib.sha512).digest(),
+}
+
+def base64url_decode(input):
+    input += '=' * (4 - (len(input) % 4))
+    return base64.urlsafe_b64decode(input)
+
+def base64url_encode(input):
+    return base64.urlsafe_b64encode(input).replace('=', '')
+
+def header(jwt):
+    header_segment = jwt.split('.', 1)[0]
+    try:
+        return json.loads(base64url_decode(header_segment))
+    except (ValueError, TypeError):
+        raise DecodeError("Invalid header encoding")
+
+def encode(payload, key, algorithm='HS256'):
+    segments = []
+    header = {"typ": "JWT", "alg": algorithm}
+    segments.append(base64url_encode(json.dumps(header)))
+    segments.append(base64url_encode(json.dumps(payload)))
+    signing_input = '.'.join(segments)
+    try:
+        ascii_key = unicode(key).encode('utf8')
+        signature = signing_methods[algorithm](signing_input, ascii_key)
+    except KeyError:
+        raise NotImplementedError("Algorithm not supported")
+    segments.append(base64url_encode(signature))
+    return '.'.join(segments)
+
+def decode(jwt, key='', verify=True):
+    try:
+        signing_input, crypto_segment = jwt.rsplit('.', 1)
+        header_segment, payload_segment = signing_input.split('.', 1)
+    except ValueError:
+        raise DecodeError("Not enough segments")
+    try:
+        header = json.loads(base64url_decode(header_segment))
+        payload = json.loads(base64url_decode(payload_segment))
+        signature = base64url_decode(crypto_segment)
+    except (ValueError, TypeError):
+        raise DecodeError("Invalid segment encoding")
+    if verify:
+        try:
+            ascii_key = unicode(key).encode('utf8')
+            if not signature == signing_methods[header['alg']](signing_input, ascii_key):
+                raise DecodeError("Signature verification failed")
+        except KeyError:
+            raise DecodeError("Algorithm not supported")
+    return payload
