jacobjohansen/policyuniverse

Parse and Process AWS IAM Policies, Statements, ARNs, and wildcards.

PolicyUniverse

This package provides classes to parse AWS IAM and Resource Policies.

Additionally, this package can expand wildcards in AWS Policies using permissions obtained from the AWS Policy Generator.

See the Service and Permissions data.

This package can also minify an AWS policy to help you stay under policy size limits. Avoid doing this if possible, as it creates ugly policies. 💩

Install:

pip install policyuniverse

Usage:

• ARN class
• Policy class
• Statement class
• Action Categories
• Expanding and Minification

Reading ARNs

from policyuniverse.arn import ARN
arn = ARN('arn:aws:iam::012345678910:role/SomeTestRoleForTesting')
assert arn.error == False
assert arn.tech == 'iam'
assert arn.region == ''  # IAM is universal/global
assert arn.account_number == '012345678910'
assert arn.name == 'role/SomeTestRoleForTesting'
assert arn.partition == 'aws'
assert arn.root == False  # Not the root ARN
assert arn.service == False  # Not an AWS service like lambda.amazonaws.com

arn = ARN('012345678910')
assert arn.account_number == '012345678910'

arn = ARN('lambda.amazonaws.com')
assert arn.service == True
assert arn.tech == 'lambda'

IAM and Resource Policies

Policy with multiple statements

# Two statements, both with conditions
policy05 = dict(
    Version='2010-08-14',
    Statement=[
        dict(
            Effect='Allow',
            Principal='arn:aws:iam::012345678910:root',
            Action=['s3:*'],
            Resource='*',
            Condition={
                'IpAddress': {
                    'AWS:SourceIP': ['0.0.0.0/0']
                }}),
        dict(
            Effect='Allow',
            Principal='arn:aws:iam::*:role/Hello',
            Action=['ec2:*'],
            Resource='*',
            Condition={
                'StringLike': {
                    'AWS:SourceOwner': '012345678910'
                }})
        ])

from policyuniverse.policy import Policy
from policyuniverse.statement import ConditionTuple, PrincipalTuple

policy = Policy(policy05)
assert policy.whos_allowed() == set([
    PrincipalTuple(category='principal', value='arn:aws:iam::*:role/Hello'),
    PrincipalTuple(category='principal', value='arn:aws:iam::012345678910:root'),
    ConditionTuple(category='cidr', value='0.0.0.0/0'),
    ConditionTuple(category='account', value='012345678910')
])

# The given policy is not internet accessible.
# The first statement is limited by the principal, and the condition is basically a no-op.
# The second statement has a wildcard principal, but uses the condition to lock it down.
assert policy.is_internet_accessible() == False

Internet Accessible Policy:

# An internet accessible policy:
policy01 = dict(
    Version='2012-10-08',
    Statement=dict(
        Effect='Allow',
        Principal='*',
        Action=['rds:*'],
        Resource='*',
        Condition={
            'IpAddress': {
                'AWS:SourceIP': ['0.0.0.0/0']
            }
        }))

policy = Policy(policy01)
assert policy.is_internet_accessible() == True
assert policy.internet_accessible_actions() == set(['rds:*'])

Statements

A policy is simply a collection of statements.

statement12 = dict(
    Effect='Allow',
    Principal='*',
    Action=['rds:*'],
    Resource='*',
    Condition={
        'StringEquals': {
            'AWS:SourceVPC': 'vpc-111111',
            'AWS:Sourcevpce': 'vpce-111111',
            'AWS:SourceOwner': '012345678910',
            'AWS:SourceAccount': '012345678910'
        },
        'StringLike': {
            'AWS:userid': 'AROAI1111111111111111:*'
        },
        'ARNLike': {
            'AWS:SourceArn': 'arn:aws:iam::012345678910:role/Admin'
        },
        'IpAddressIfExists': {
            'AWS:SourceIP': [
                '123.45.67.89',
                '10.0.7.0/24',
                '172.16.0.0/16']
        }
    })

from policyuniverse.statement import Statement
from policyuniverse.statement import ConditionTuple, PrincipalTuple

statement = Statement(statement12)
assert statement.effect == 'Allow'
assert statement.actions == set(['rds:*'])

# rds:* expands out to ~88 individual permissions
assert len(statement.actions_expanded) == 88

assert statement.uses_not_principal() == False
assert statement.principals == set(['*'])
assert statement.condition_arns == set(['arn:aws:iam::012345678910:role/Admin'])
assert statement.condition_accounts == set(['012345678910'])
assert statement.condition_userids == set(['AROAI1111111111111111:*'])
assert statement.condition_cidrs == set(['10.0.7.0/24', '172.16.0.0/16', '123.45.67.89'])
assert statement.condition_vpcs == set(['vpc-111111'])
assert statement.condition_vpces == set(['vpce-111111'])
assert statement.is_internet_accessible() == False
assert statement.whos_allowed() == set([
    PrincipalTuple(category='principal', value='*'),
    ConditionTuple(category='cidr', value='123.45.67.89'),
    ConditionTuple(category='account', value='012345678910'),
    ConditionTuple(category='userid', value='AROAI1111111111111111:*'),
    ConditionTuple(category='vpc', value='vpc-111111'),
    ConditionTuple(category='arn', value='arn:aws:iam::012345678910:role/Admin'),
    ConditionTuple(category='cidr', value='172.16.0.0/16'),
    ConditionTuple(category='vpce', value='vpce-111111'),
    ConditionTuple(category='cidr', value='10.0.7.0/24')])

Action Categories

policy = {
        "Statement": [{
            "Action": ["s3:put*", "sqs:get*", "sns:*"],
            "Resource": "*",
            "Effect": "Allow"
          }]
      }

from policyuniverse.policy import Policy
p = Policy(policy)
for k, v in p.action_summary().items():
    print(k,v)
>>> ('s3', set([u'Write', u'Permissions', u'Tagging']))
>>> ('sqs', set([u'List']))
>>> ('sns', set([u'List', u'Read', u'Write', u'Permissions']))

Possible categories are Permissions, Write, Read, Tagging, and List. This data can be used to summarize statements and policies and to look for sensitive permissions.

Expanding and Minification

from policyuniverse.expander_minimizer import expand_policy
from policyuniverse.expander_minimizer import minimize_policy

policy = {
        "Statement": [{
            "Action": ["swf:res*"],
            "Resource": "*",
            "Effect": "Allow"
          }]
      }
      
expanded_policy = expand_policy(policy=policy)
>>> Start size: 131. End size: 286
print(expanded_policy == {
        "Statement": [{
            "Action": [
              "swf:respondactivitytaskcanceled",
              "swf:respondactivitytaskcompleted",
              "swf:respondactivitytaskfailed",
              "swf:responddecisiontaskcompleted"
            ],
            "Resource": "*",
            "Effect": "Allow"
          }]
      })
>>> True

minimized_policy = minimize_policy(policy=expanded_policy, minchars=3)
>>> Skipping prefix r because length of 1
>>> Skipping prefix re because length of 2
>>> Skipping prefix r because length of 1
>>> Skipping prefix re because length of 2
>>> Skipping prefix r because length of 1
>>> Skipping prefix re because length of 2
>>> Skipping prefix r because length of 1
>>> Skipping prefix re because length of 2
>>> Start size: 286. End size: 131

print(minimized_policy == policy)
>>> True