How to use Boto to Audit your AWS EC2 instance security groups
Boto is a Software Development Kit for accessing the AWS API’s using Python.
Recently, I needed to determine how many of my EC2 instances were spawned in a public subnet, that also had security groups with wide open access on any port via any protocol to the instances. Because I have an IGW (Internet Gateway) in my VPC’s and properly setup routing tables, instances launched in the public subnets with wide open security groups (allowing ingress traffic from any source) is a really bad thing 🙂
Here is the code I wrote to identify these naughty instances. It will require slight modifications in your own environment, to match your public subnet IP Ranges, EC2 Tags, and Account names.
#!/usr/bin/env python
__author__ = 'Jason Riedel'
__description__ = 'Find EC2 instances provisioned in a public subnet that have security groups allowing ingress traffic from any source.'
__date__ = 'June 5th 2016'
__version__ = '1.0'
import boto3
def find_public_addresses(ec2):
public_instances = {}
instance_public_ips = {}
instance_private_ips = {}
instance_ident = {}
instances = ec2.instances.filter(Filters=[{'Name': 'instance-state-name', 'Values': ['running'] }])
# Ranges that you define as public subnets in AWS go here.
public_subnet_ranges = ['10.128.0', '192.168.0', '172.16.0']
for instance in instances:
# I only care if the private address falls into a public subnet range
# because if it doesnt Internet ingress cant reach it directly anyway even with a public IP
if any(cidr in instance.private_ip_address for cidr in public_subnet_ranges):
owner_tag = "None"
instance_name = "None"
if instance.tags:
for i in range(len(instance.tags)):
#comment OwnerEmail tag out if you do not tag your instances with it.
if instance.tags[i]['Key'] == "OwnerEmail":
owner_tag = instance.tags[i]['Value']
if instance.tags[i]['Key'] == "Name":
instance_name = instance.tags[i]['Value']
instance_ident[instance.id] = "Name: %s\n\tKeypair: %s\n\tOwner: %s" % (instance_name, instance.key_name, owner_tag)
if instance.public_ip_address is not None:
values=[]
for i in range(len(instance.security_groups)):
values.append(instance.security_groups[i]['GroupId'])
public_instances[instance.id] = values
instance_public_ips[instance.id] = instance.public_ip_address
instance_private_ips[instance.id] = instance.private_ip_address
return (public_instances, instance_public_ips,instance_private_ips, instance_ident)
def inspect_security_group(ec2, sg_id):
sg = ec2.SecurityGroup(sg_id)
open_cidrs = []
for i in range(len(sg.ip_permissions)):
to_port = ''
ip_proto = ''
if 'ToPort' in sg.ip_permissions[i]:
to_port = sg.ip_permissions[i]['ToPort']
if 'IpProtocol' in sg.ip_permissions[i]:
ip_proto = sg.ip_permissions[i]['IpProtocol']
if '-1' in ip_proto:
ip_proto = 'All'
for j in range(len(sg.ip_permissions[i]['IpRanges'])):
cidr_string = "%s %s %s" % (sg.ip_permissions[i]['IpRanges'][j]['CidrIp'], ip_proto, to_port)
if sg.ip_permissions[i]['IpRanges'][j]['CidrIp'] == '0.0.0.0/0':
#preventing an instance being flagged for only ICMP being open
if ip_proto != 'icmp':
open_cidrs.append(cidr_string)
return open_cidrs
if __name__ == "__main__":
#loading profiles from ~/.aws/config & credentials
profile_names = ['de', 'pe', 'pde', 'ppe']
#Translates profile name to a more friendly name i.e. Account Name
translator = {'de': 'Platform Dev', 'pe': 'Platform Prod', 'pde': 'Products Dev', 'ppe': 'Products Prod'}
for profile_name in profile_names:
session = boto3.Session(profile_name=profile_name)
ec2 = session.resource('ec2')
(public_instances, instance_public_ips, instance_private_ips, instance_ident) = find_public_addresses(ec2)
for instance in public_instances:
for sg_id in public_instances[instance]:
open_cidrs = inspect_security_group(ec2, sg_id)
if open_cidrs: #only print if there are open cidrs
print "=================================="
print " %s, %s" % (instance, translator[profile_name])
print "=================================="
print "\tprivate ip: %s\n\tpublic ip: %s\n\t%s" % (instance_private_ips[instance], instance_public_ips[instance], instance_ident[instance])
print "\t=========================="
print "\t open ingress rules"
print "\t=========================="
for cidr in open_cidrs:
print "\t\t" + cidr
To run this you also need to setup your .aws/config and .aws/credentials file.
http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-config-files
Email me tuxninja [at] tuxlabs.com if you have any issues.
Boto is awesome 🙂 Note so is the AWS CLI, but requires some shell scripting as opposed to Python to do cool stuff.
The github for this code here https://github.com/jasonriedel/AWS/blob/master/sg-audit.py
Enjoy !
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