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frost/README.md

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pytest-services

Clients and pytest tests for checking that third party services the @foxsec team uses are configured correctly.

We trust third party services to return their status correctly, but want to answer questions whether they are configured properly such as:

  • Are our AWS DB snapshots publicly accessible?
  • Is there a dangling DNS entry in Route53?
  • Will someone get paged when an alert goes off?

Usage

Requirements

Note: other versions may work too these are the versions @g-k used for development

Installing

From the project root run:

make install

This will:

  • create a Python virtualenv to isolate it from other Python packages
  • install Python requirements in the virtualenv

Running

Activate the venv in the project root:

source venv/bin/activate

To fetch RDS resources from the cache or AWS API and check that backups are enabled for DB instances for the configured aws profile named default in the us-west-2 region we can run:

pytest --ignore pagerduty/ --ignore aws/s3 --ignore aws/ec2 -k test_rds_db_instance_backup_enabled -s --aws-profiles default --aws-regions us-west-2 --aws-debug-calls

The options include pytest options:

  • --ignore to skip fetching resources for non-RDS resources
  • -k for selecting tests matching the substring test_rds_db_instance_backup_enabled for the one test we want to run
  • -m not used but the marker filter can be useful for selecting all tests for specific services (e.g. -m rds)
  • -s to disable capturing stdout so we can see the progress fetching AWS resources

and options pytest-services adds:

  • --aws-debug-calls for printing (with -s) API calls we make
  • --aws-profiles for selecting one or more AWS profiles to fetch resources for or the AWS default profile / AWS_PROFILE environment variable
  • --aws-regions for selecting one or more AWS regions to fetch resources from or the default of all regions
  • --aws-require-tag adds Tag names to check on all EC2 instances for the aws.ec2.test_ec2_instance_has_required_tags test
  • --offline a flag to tell HTTP clients to not make requests and return empty params
  • --severity-config path to a config file for marking different tests with different severities

and produces output like the following showing a DB instance with backups disabled:

=========================================================== test session starts ===========================================================
platform darwin -- Python 3.6.2, pytest-3.3.2, py-1.5.2, pluggy-0.6.0
metadata: {'Python': '3.6.2', 'Platform': 'Darwin-15.6.0-x86_64-i386-64bit', 'Packages': {'pytest': '3.3.2', 'py': '1.5.2', 'pluggy': '0.6.
0'}, 'Plugins': {'metadata': '1.5.1', 'json': '0.4.0', 'html': '1.16.1'}}
rootdir: /Users/gguthe/mozilla-services/pytest-services, inifile:
plugins: metadata-1.5.1, json-0.4.0, html-1.16.1
collecting 0 items                                                                                                                        c
alling AWSAPICall(profile='default', region='us-west-2', service='rds', method='describe_db_instances', args=[], kwargs={})
collecting 4 items
...
aws/rds/test_rds_db_instance_backup_enabled.py ...F                                                                                 [100%]

================================================================ FAILURES =================================================================
_______________________________________ test_rds_db_instance_backup_enabled[test-db] ________________________________________

rds_db_instance = {'AllocatedStorage': 50, 'AutoMinorVersionUpgrade': True, 'AvailabilityZone': 'us-west-2c', 'BackupRetentionPeriod': 0, .
..}

    @pytest.mark.rds
    @pytest.mark.parametrize('rds_db_instance',
                             rds_db_instances(),
                             ids=lambda db_instance: db_instance['DBInstanceIdentifier'])
    def test_rds_db_instance_backup_enabled(rds_db_instance):
>       assert rds_db_instance['BackupRetentionPeriod'] > 0, \
            'Backups disabled for {}'.format(rds_db_instance['DBInstanceIdentifier'])
E       AssertionError: Backups disabled for test-db
E       assert 0 > 0

aws/rds/test_rds_db_instance_backup_enabled.py:12: AssertionError
=========================================================== 72 tests deselected ===========================================================
============================================ 1 failed, 3 passed, 72 deselected in 3.12 seconds ============================================

Caching

The AWS client will use AWS API JSON responses when available and save them using AWS profile, region, service name, service method, botocore args and kwargs in the cache key to filenames with the format .cache/v/pytest_aws:<aws profile>:<aws region>:<aws service>:<service method>:<args>:<kwargs>.json e.g.

head .cache/v/pytest_aws:cloudservices-aws-stage:us-west-2:rds:describe_db_instances::.json
{
    "DBInstances": [
        {
            "AllocatedStorage": 5,
            "AutoMinorVersionUpgrade": true,
            "AvailabilityZone": "us-west-2c",
            "BackupRetentionPeriod": 1,
            "CACertificateIdentifier": "rds-ca-2015",
            "CopyTagsToSnapshot": false,
            "DBInstanceArn": "arn:aws:rds:us-west-2:123456678901:db:test-db",

These files can be removed individually or all at once with the pytest --cache-clear option.

Test Severity

pytest-services adds the command line arg --severity-config for adding a severity marker to tests. A severity can be INFO, WARN, or ERROR.

These do not modify pytest results (pass, fail, xfail, skip, etc.).

The config file looks like (available in ./severity.conf.example):

# pytest-sevices example severity conf
test_ec2_instance_has_required_tags	INFO
*  WARN

And results in a severity and severity marker being included in the json metadata:

pytest --ignore pagerduty/ --ignore aws/s3 --ignore aws/rds --ignore aws/iam -s --aws-profiles stage --aws-regions us-east-1 --aws-require-tags Name Type App Stack -k test_ec2_instance_has_required_tags --severity-config severity.conf --json=report.json
...

python -m json.tool report.json
{
    "report": {
        "environment": {
            "Python": "3.6.2",
            "Platform": "Darwin-15.6.0-x86_64-i386-64bit"
        },
        "tests": [
            {
...
                "metadata": [
                    {
...
                    "markers": {
...
                            "severity": {
                                "name": "severity",
                                "args": [
                                    "INFO"
                                ],
                                "kwargs": {}
                            }
                        },
...
                        "severity": "INFO",
                        "unparametrized_name": "test_ec2_instance_has_required_tags"
                    }
...

Development

Goals

  1. replace one-off scripts for each check
  2. share checks with other organizations
  3. consolidate bugs in one place (i.e. one thing to update)
  4. in pytest use a known existing framework for writing checks
  5. be vendor agnostic e.g. support checks across cloud providers or in hybrid environments or competing services
  6. cache and share responses to reduce third party API usage (i.e. lots of tests check AWS security groups so fetch them once)
  7. provide a way to run a single test or subset of tests

Non-Goals

  1. Invent a new DSL for writing expectations (use pytest conventions)
  2. Verify how third party services or their client libraries work (e.g. don't answer "Does GET / on the CRUD1 API return 400 when query param q is $bad_value?")

Design

Currently this is a monolithic pytest package, but should eventually be extracted into a pytest plugin and with separate dependent pytest plugins for each service.

API responses should fit on disk and in memory (i.e. don't use this for log processing or checking binaries for malware), and be safe to cache for minutes, hours, or days (i.e. probably don't use this for monitoring a streaming API) (NB: bug for specifying data freshness).

Additionally we want:

  • data fetching functions in a resources.py
  • data checking and test helpers in a helpers.py
  • prefix test files with test_
  • tests to have pytest markers for any services they depend on for data
  • HTTP clients should be read only and use read only credentials
  • running a test should not modify services

File Layout

pytest-services
...
├── <third party service A>
│   ├── client.py
│   ├── <subservice A (optional)>
│   │   ├── __init__.py
│   │   ├── helpers.py
│   │   ├── resources.py
│   │   ├── ...
│   │   └── test_ec2_security_group_all_ports.py
│   ├── <subservice b (optional)>
│   │   ├── __init__.py
│   │   ├── resources.py
│   │   ├── ...
│   │   └─ test_s3_bucket_web_hosting_disabled.py
└── <third party service B>
    ├── __init__.py
    ├── helpers.py
    ├── resources.py
    └── test_user_has_escalation_policy.py

Adding an example test

Let's write a test to check that http://httpbin.org/ip returns an AWS IP:

  1. create a file httpbin/test_httpbin_ip.py with the contents:
import itertools
import ipaddress
import pytest
import json
import urllib.request


def get_httpbin_ips():
    # IPs we always want to test
    ips = [
        '127.0.0.1',
        '13.58.0.0',
    ]

    req = urllib.request.Request('http://httpbin.org/ip')

    with urllib.request.urlopen(req) as response:
        body = response.read().decode('utf-8')
        ips.append(json.loads(body).get('origin', None))

    return ips


def get_aws_ips():
    req = urllib.request.Request('https://ip-ranges.amazonaws.com/ip-ranges.json')

    with urllib.request.urlopen(req) as response:
        body = response.read().decode('utf-8')
        return json.loads(body)['prefixes']


@pytest.mark.httpbin
@pytest.mark.aws_ip_ranges
@pytest.mark.parametrize(
    ['ip', 'aws_ip_ranges'],
    zip(get_httpbin_ips(), itertools.repeat(get_aws_ips())))
def test_httpbin_ip_in_aws(ip, aws_ip_ranges):
    for aws_ip_range in aws_ip_ranges:
        assert ipaddress.IPv4Address(ip) not in ipaddress.ip_network(aws_ip_range['ip_prefix']), \
          "{0} is in AWS range {1[ip_prefix]} region {1[region]} service {1[service]}".format(ip, aws_ip_range)

Notes:

  • we add two data fetching functions that return lists that we can zip into tuples for the pytest parametrize decorator
  • we add markers for the services we're fetching data from
  1. Running it we see that one of the IPs is an AWS IP:
pytest --ignore pagerduty/ --ignore aws/
platform darwin -- Python 3.6.2, pytest-3.3.2, py-1.5.2, pluggy-0.6.0
metadata: {'Python': '3.6.2', 'Platform': 'Darwin-15.6.0-x86_64-i386-64bit', 'Packages': {'pytest': '3.3.2', 'py': '1.5.2', 'pluggy': '0.6.0'}, 'Plugins': {'metadata': '1.5.1', 'json': '0.4.0', 'html': '1.16.1'}}
rootdir: /Users/gguthe/mozilla-services/pytest-services, inifile:
plugins: metadata-1.5.1, json-0.4.0, html-1.16.1
collected 3 items

httpbin/test_httpbin_ip_in_aws.py .F.                                                                                               [100%]

================================================================ FAILURES =================================================================
____________________________________________ test_httpbin_ip_in_aws[13.58.0.0-aws_ip_ranges1] _____________________________________________

ip = '13.58.0.0'
aws_ip_ranges = [{'ip_prefix': '13.32.0.0/15', 'region': 'GLOBAL', 'service': 'AMAZON'}, {'ip_prefix': '13.35.0.0/16', 'region': 'GLOB...on': 'us-west-1', 'service': 'AMAZON'}, {'ip_prefix': '13.57.0.0/16', 'region': 'us-west-1', 'service': 'AMAZON'}, ...]

    @pytest.mark.httpbin
    @pytest.mark.aws_ip_ranges
    @pytest.mark.parametrize(
        ['ip', 'aws_ip_ranges'],
        zip(get_httpbin_ips(), itertools.repeat(get_aws_ips())),
        # ids=lambda ip: ip
        )
    def test_httpbin_ip_in_aws(ip, aws_ip_ranges):
        for aws_ip_range in aws_ip_ranges:
>           assert ipaddress.IPv4Address(ip) not in ipaddress.ip_network(aws_ip_range['ip_prefix']), \
              "{0} is in AWS range {1[ip_prefix]} region {1[region]} service {1[service]}".format(ip, aws_ip_range)
E           AssertionError: 13.58.0.0 is in AWS range 13.58.0.0/15 region us-east-2 service AMAZON
E           assert IPv4Address('13.58.0.0') not in IPv4Network('13.58.0.0/15')
E            +  where IPv4Address('13.58.0.0') = <class 'ipaddress.IPv4Address'>('13.58.0.0')
E            +    where <class 'ipaddress.IPv4Address'> = ipaddress.IPv4Address
E            +  and   IPv4Network('13.58.0.0/15') = <function ip_network at 0x107cf66a8>('13.58.0.0/15')
E            +    where <function ip_network at 0x107cf66a8> = ipaddress.ip_network

httpbin/test_httpbin_ip_in_aws.py:43: AssertionError
=================================================== 1 failed, 2 passed in 15.69 seconds ===================================================

Note: marking tests as expected failures with @pytest.mark.xfail can hide data fetching errors

To improve this we could:

  1. Add parametrize ids so it's clearer which parametrize caused test failures
  2. Add directions about why it's an issue and how to fix it or what the associated risks are

As we add more tests we can:

  1. Move the JSON fetching functions to <service name>/resources.py files and import them into the test
  2. Move the fetching logic to a shared library <service name>/client.py and save to the pytest cache