Add Example URI Signer Python Script

plugins/experimental/uri_signing/python_signer/README.md

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+Python URI Signer
+==================
+
+Given a configuration file and a URI, this python script will generate a signed URI according to the URI signing protocol outlined [here](https://tools.ietf.org/html/draft-ietf-cdni-uri-signing-16): 
+
+The script takes a config file and a uri as command line arguments. It picks one of the keys located in the json file at random
+and embeds a valid JWT as a query string parameter into the uri and prints this new signed URI to standard out. 
+
+** Disclaimer ** 
+Please note that this script is provided as a very simple example of how to implement a signer should not be considered production ready. 
+
+Requirements
+------ 
+
+[python-jose](https://pypi.org/project/python-jose/) library must be installed (pip install python-jose).
+
+Config
+------ 
+
+The config file should be a JSON object that contains the following:
+
+  - `iss`: A string representing the issuer of the token
+  - `token_lifetime`: The lifetime of the token in seconds. Expiry of the token is calculated as now + token_lifetime
+  - `aud`: A string representing the intended audience of the token.
+  - `cdnistt`: Boolean value which if set to true uses cookie signed token transport, allowing the validator of the token to 
+    to issue subsequent tokens via set cookie headers.
+  - `cdniets`: Must be set if using cdnistt. Provides means of setting Expiry Times when generating subsequent tokens. It denotes 
+    the number of seconds to be added to the time at which the JWT is verified that gives the value of the Expiry Time claim of the 
+    next signed JWT.
+  - `keys`: A list of json objects, each one representing a key. Each key should have the following attributes:
+      - `alg`: The Cryptographic algorithm to be used with the key.
+      - `kid`: The key identifier
+      - `kty`: The key type
+      - `k`: The key itself
+
+example_config.json can be used as a template for the configuration file.

plugins/experimental/uri_signing/python_signer/example_config.json

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+{
+	"iss": "Example Issuer",
+	"token_lifetime": 90,
+	"aud": "Caching Software",
+    "cdnistt": true,
+    "cdniets": 30,
+	"keys": [
+		{
+			"alg": "HS256",
+			"kid": 0,
+			"kty": "oct",
+			"k": "SECRET1"
+		},
+		{
+			"alg": "HS256",
+			"kid": 1,
+			"kty": "oct",
+			"k": "SECRET2"
+		},
+		{
+			"alg": "HS256",
+			"kid": 2,
+			"kty": "oct",
+			"k": "SECRET3"
+		},
+		{
+			"alg": "HS256",
+			"kid": 3,
+			"kty": "oct",
+			"k": "SECRET4"
+		}
+	]
+}

plugins/experimental/uri_signing/python_signer/uri_signer.py

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+#!/usr/bin/env python3
+
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import json
+import argparse
+import random
+import time
+import os
+
+# https://github.com/mpdavis/python-jose
+from jose import jwk, jwt
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('-c', '--config',
+                        help="Configuration File",
+                        required=True)
+    parser.add_argument('-u', '--uri',
+                        help="URI to sign",
+                        required=True)
+    args = parser.parse_args()
+
+    with open(args.config, 'r') as f:
+        config = json.load(f)
+
+    keys = config["keys"]
+
+    # Randomly select a key
+    key_index = random.randint(0,len(keys)-1)
+    print("Using Key: " + str(keys[key_index]["kid"]) + " to sign URI.")
+    key = keys[key_index]
+
+    # Build Out claimset
+    claimset = {}
+    if ("iss" in config.keys()):
+        claimset["iss"] = config["iss"]
+
+    if ("token_lifetime" in config.keys()):
+        claimset["exp"] = int(time.time()) + config["token_lifetime"]
+    else:
+        claimset["exp"] = int(time.time()) + 30
+
+    if("aud" in config.keys()):
+        claimset["aud"] = config["aud"]
+
+    if("cdnistt"  in config.keys()):
+        if config["cdnistt"]:
+            claimset["cdnistt"] = 1
+            if("cdniets" in config.keys()):
+                claimset["cdniets"] = config["cdniets"]
+            else:
+                claimset["cdniets"] = 30
+
+    Token = jwt.encode(claimset,key,algorithm=key["alg"])
+
+    print("Signed URL: " + args.uri + "?urisigning=" + Token)
+
+if __name__ == "__main__":
+     main()