-
Notifications
You must be signed in to change notification settings - Fork 363
/
authmodule.py
218 lines (175 loc) · 9.04 KB
/
authmodule.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
"""
Copyright 2015-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance with the License. A copy of the License is located at
http://aws.amazon.com/apache2.0/
or in the "license" file accompanying this file. This file 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 pprint
import re
import time
def lambda_handler(event, context):
print("Client token: " + event["authorizationToken"])
print("Method ARN: " + event["methodArn"])
"""validate the incoming token"""
"""and produce the principal user identifier associated with the token"""
"""this could be accomplished in a number of ways:"""
"""1. Call out to OAuth provider"""
"""2. Decode a JWT token inline"""
"""3. Lookup in a self-managed DB"""
principalId = "user|a1b2c3d4"
"""you can send a 401 Unauthorized response to the client by failing like so:"""
"""raise Exception('Unauthorized')"""
"""if the token is valid, a policy must be generated which will allow or deny access to the client"""
"""if access is denied, the client will receive a 403 Access Denied response"""
"""if access is allowed, API Gateway will proceed with the backend integration configured on the method that was called"""
"""this function must generate a policy that is associated with the recognized principal user identifier."""
"""depending on your use case, you might store policies in a DB, or generate them on the fly"""
"""keep in mind, the policy is cached for 5 minutes by default (TTL is configurable in the authorizer)"""
"""and will apply to subsequent calls to any method/resource in the RestApi"""
"""made with the same token"""
"""the example policy below denies access to all resources in the RestApi"""
tmp = event["methodArn"].split(":")
apiGatewayArnTmp = tmp[5].split("/")
awsAccountId = tmp[4]
policy = AuthPolicy(principalId, awsAccountId)
policy.restApiId = apiGatewayArnTmp[0]
policy.region = tmp[3]
policy.stage = apiGatewayArnTmp[1]
# Blueprint denies all methods by default
# policy.denyAllMethods()
# Example allows all methods
policy.allowAllMethods()
"""policy.allowMethod(HttpVerb.GET, "/pets/*")"""
"""finally, build the policy and exit the function using return"""
return policy.build()
class HttpVerb:
GET = "GET"
POST = "POST"
PUT = "PUT"
PATCH = "PATCH"
HEAD = "HEAD"
DELETE = "DELETE"
OPTIONS = "OPTIONS"
ALL = "*"
class AuthPolicy:
awsAccountId = ""
"""The AWS account id the policy will be generated for. This is used to create the method ARNs."""
principalId = ""
"""The principal used for the policy, this should be a unique identifier for the end user."""
version = "2012-10-17"
"""The policy version used for the evaluation. This should always be '2012-10-17'"""
pathRegex = r"^[/.a-zA-Z0-9-\*]+$"
"""The regular expression used to validate resource paths for the policy"""
"""these are the internal lists of allowed and denied methods. These are lists
of objects and each object has 2 properties: A resource ARN and a nullable
conditions statement.
the build method processes these lists and generates the appropriate
statements for the final policy"""
allowMethods = []
denyMethods = []
restApiId = "*"
"""The API Gateway API id. By default this is set to '*'"""
region = "*"
"""The region where the API is deployed. By default this is set to '*'"""
stage = "*"
"""The name of the stage used in the policy. By default this is set to '*'"""
def __init__(self, principal, awsAccountId):
self.awsAccountId = awsAccountId
self.principalId = principal
self.allowMethods = []
self.denyMethods = []
def _addMethod(self, effect, verb, resource, conditions):
"""Adds a method to the internal lists of allowed or denied methods. Each object in
the internal list contains a resource ARN and a condition statement. The condition
statement can be null."""
if verb != "*" and not hasattr(HttpVerb, verb):
raise NameError("Invalid HTTP verb " + verb + ". Allowed verbs in HttpVerb class")
resourcePattern = re.compile(self.pathRegex)
if not resourcePattern.match(resource):
raise NameError("Invalid resource path: " + resource + ". Path should match " + self.pathRegex)
if resource[:1] == "/":
resource = resource[1:]
resourceArn = (
"arn:aws:execute-api:"
+ self.region
+ ":"
+ self.awsAccountId
+ ":"
+ self.restApiId
+ "/"
+ self.stage
+ "/"
+ verb
+ "/"
+ resource
)
if effect.lower() == "allow":
self.allowMethods.append({"resourceArn": resourceArn, "conditions": conditions})
elif effect.lower() == "deny":
self.denyMethods.append({"resourceArn": resourceArn, "conditions": conditions})
def _getEmptyStatement(self, effect):
"""Returns an empty statement object prepopulated with the correct action and the
desired effect."""
statement = {
"Action": "execute-api:Invoke",
"Effect": effect[:1].upper() + effect[1:].lower(),
"Resource": [],
}
return statement
def _getStatementForEffect(self, effect, methods):
"""This function loops over an array of objects containing a resourceArn and
conditions statement and generates the array of statements for the policy."""
statements = []
if len(methods) > 0:
statement = self._getEmptyStatement(effect)
for curMethod in methods:
if curMethod["conditions"] is None or len(curMethod["conditions"]) == 0:
statement["Resource"].append(curMethod["resourceArn"])
else:
conditionalStatement = self._getEmptyStatement(effect)
conditionalStatement["Resource"].append(curMethod["resourceArn"])
conditionalStatement["Condition"] = curMethod["conditions"]
statements.append(conditionalStatement)
statements.append(statement)
return statements
def allowAllMethods(self):
"""Adds a '*' allow to the policy to authorize access to all methods of an API"""
self._addMethod("Allow", HttpVerb.ALL, "*", [])
def denyAllMethods(self):
"""Adds a '*' allow to the policy to deny access to all methods of an API"""
self._addMethod("Deny", HttpVerb.ALL, "*", [])
def allowMethod(self, verb, resource):
"""Adds an API Gateway method (Http verb + Resource path) to the list of allowed
methods for the policy"""
self._addMethod("Allow", verb, resource, [])
def denyMethod(self, verb, resource):
"""Adds an API Gateway method (Http verb + Resource path) to the list of denied
methods for the policy"""
self._addMethod("Deny", verb, resource, [])
def allowMethodWithConditions(self, verb, resource, conditions):
"""Adds an API Gateway method (Http verb + Resource path) to the list of allowed
methods and includes a condition for the policy statement. More on AWS policy
conditions here: http://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements.html#Condition"""
self._addMethod("Allow", verb, resource, conditions)
def denyMethodWithConditions(self, verb, resource, conditions):
"""Adds an API Gateway method (Http verb + Resource path) to the list of denied
methods and includes a condition for the policy statement. More on AWS policy
conditions here: http://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements.html#Condition"""
self._addMethod("Deny", verb, resource, conditions)
def build(self):
"""Generates the policy document based on the internal lists of allowed and denied
conditions. This will generate a policy with two main statements for the effect:
one statement for Allow and one statement for Deny.
Methods that includes conditions will have their own statement in the policy."""
if (self.allowMethods is None or len(self.allowMethods) == 0) and (
self.denyMethods is None or len(self.denyMethods) == 0
):
raise NameError("No statements defined for the policy")
policy = {
"principalId": self.principalId,
"policyDocument": {"Version": self.version, "Statement": []},
}
policy["policyDocument"]["Statement"].extend(self._getStatementForEffect("Allow", self.allowMethods))
policy["policyDocument"]["Statement"].extend(self._getStatementForEffect("Deny", self.denyMethods))
return policy