Troposphere / boto3 dynamic vpc cloudformation template creation

DynamicPublicVPC.py

import boto3
import time
import os
from troposphere import Base64, FindInMap, GetAtt, Join, Output
from troposphere import Parameter, Ref, Tags, Template
from troposphere.ec2 import PortRange, NetworkAcl, Route, \
    SubnetRouteTableAssociation, Subnet, RouteTable, \
    VPCGatewayAttachment, VPC, NetworkInterfaceProperty, NetworkAclEntry, \
    SubnetNetworkAclAssociation, EIP, Instance, InternetGateway

def region_input():
    while True:
        try:
            choice = input("Enter the Region: ")
            if choice in availableregions:
                break
            else:
                print("Invalid Region...Enter a valid Region")
                print("Valid Regions are {0}".format(', '.join(availableregions)))
                raise Exception('Invalid Choice')
        except:
            continue

    return choice

timestr = time.strftime("%Y%m%d-%H%M%S")

#this call can be made without valid aws credentials configured
availableregions = boto3.session.Session().get_available_regions('ec2')
reg = region_input()

#minimum ec2 describe permissions needed for the following boto calls
ec2c = boto3.client('ec2', region_name=reg)
azresp = ec2c.describe_availability_zones(Filters=[{'Name':'state','Values':['available']}])
availableazs = [i['ZoneName'] for i in azresp['AvailabilityZones']]


t = Template()

t.add_version('2010-09-09')

t.add_resource(VPC(
    "VPC",
    EnableDnsSupport="true",
    CidrBlock="10.100.0.0/16",
    EnableDnsHostnames="true",
    Tags=Tags(
        Application=Ref("AWS::StackName"),
        Network="{0} Spot Instance VPC".format(reg),
        Name="{0} Spot Instance VPC".format(reg),
    )
))

t.add_resource(InternetGateway(
    "InternetGateway",
    Tags=Tags(
        Application=Ref("AWS::StackName"),
        Network="{0} Spot Instance VPC".format(reg),
        Name="{0} Spot Instance VPC IGW".format(reg),
    )   
))

t.add_resource(VPCGatewayAttachment(
    "IGWAttachment",
    VpcId=Ref("VPC"),
    InternetGatewayId=Ref("InternetGateway"),
))

t.add_resource(NetworkAcl(
    "NetworkAcl",
    VpcId=Ref("VPC"),
    Tags=Tags(
        Application=Ref("AWS::StackName"),
        Network="{0} Spot Instance VPC".format(reg),
    )
))

t.add_resource(NetworkAclEntry(
    "InboundNetworkAclEntry",
    NetworkAclId=Ref("NetworkAcl"),
    RuleNumber="100",
    Protocol="-1",
    PortRange=PortRange(To="65535", From="0"),
    Egress="false",
    RuleAction="allow",
    CidrBlock="0.0.0.0/0",
))

t.add_resource(NetworkAclEntry(
    "OutboundNetworkAclEntry",
    NetworkAclId=Ref("NetworkAcl"),
    RuleNumber="100",
    Protocol="-1",
    PortRange=PortRange(To="65535", From="0"),
    Egress="true",
    RuleAction="allow",
    CidrBlock="0.0.0.0/0",
))

t.add_resource(RouteTable(
    "RouteTable",
    VpcId=Ref("VPC"),
    Tags=Tags(
        Application=Ref("AWS::StackName"),
        Network="{0} Spot Instance VPC".format(reg),
        Name="Public IGW Routing Table"
    )
))

t.add_resource(Route(
    "IGWRoute",
    DependsOn='IGWAttachment',
    GatewayId=Ref("InternetGateway"),
    DestinationCidrBlock="0.0.0.0/0",
    RouteTableId=Ref("RouteTable"),
))

#loop through usable availability zones for the aws account and create a subnet for each zone
#in the same loop generate subnet associations for the network acl and the route table
for i, az in list(enumerate(availableazs, start=1)):
    t.add_resource(Subnet(
        "PublicSubnet{0}".format(i),
        VpcId=Ref("VPC"),
        CidrBlock="10.100.{0}.0/24".format(i),
        AvailabilityZone="{0}".format(az),
        MapPublicIpOnLaunch=True,
        Tags=Tags(
            Application=Ref("AWS::StackName"),
            Network="{0} Spot Instance VPC".format(reg),
            Name="Public Subnet {0}".format(i),
        )
    ))
    t.add_resource(
        SubnetNetworkAclAssociation(
            "SubnetNetworkAclAssociation{0}".format(i),
            SubnetId=Ref("PublicSubnet{0}".format(i)),
            NetworkAclId=Ref("NetworkAcl"),
        )
    )
    t.add_resource(SubnetRouteTableAssociation(
        "SubnetRouteTableAssociation{0}".format(i),
        SubnetId=Ref("PublicSubnet{0}".format(i)),
        RouteTableId=Ref("RouteTable"),
    ))

#output the file path
print("Generating VPC template for {0}".format(reg))
print(os.path.join(os.getcwd(), "{0}-dynamic-vpc-{1}.template".format(reg, timestr)))
#generate the cloudformation template as json 
f = open("{0}-dynamic-vpc-{1}.template".format(reg, timestr),"w+")
f.write(t.to_json())
f.close()