very almost Implementing an AWS Elastic IP Tackle | by Teri Radichel | Cloud safety | November 2022
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ACM.100 Utilizing an EIP to get a set IP handle for EC2 cases and community interfaces
This can be a continuation of my sequence of posts on Automating Cybersecurity Metrics.
In a earlier publish, I needed to change my IP handle to an IP handle that was already allowed by way of my native firewall with a view to join.
On this publish, I’ll change that current IP handle with an Elastic IP (EIP) handle. Through the use of an EIP, I’ll have a set IP handle that can stay fixed when my EC2 occasion (VM) on AWS stops and begins. I may also level that IP handle at completely different digital machines.
I’ll implement the EIP with a template from CloudFormation. Then I’ll affiliate that new IP handle with the Developer EC2 occasion that we deployed.
Your organization could have an AWS Direct Join or a VPN to create non-public connections to AWS. For some smaller companies, or for those who’re a single person connecting to your individual cloud account, you should use the straightforward choices I am going to introduce under to enhance the safety of your cloud assets. You may additionally want a static IP in some circumstances, reminiscent of for a penetration take a look at or another connection to a 3rd celebration with community restrictions, as I clarify under.
Default AWS EC2 Occasion IP Tackle
If you deploy EC2 cases on AWS with a public IP handle, you don’t management the IP handle assigned to your occasion by default. AWS controls that. You’ll get an assigned handle from one of many many IP addresses within the AWS handle area. As I wrote earlier than, you will discover them right here:
One of many issues with these random assignments of IP addresses is that it makes it very troublesome to construct firewall guidelines. You do not know which IP handle it’s worthwhile to enable, so you might find yourself simply permitting all AWS IP ranges. So what occurs?
Effectively, in some circumstances, attackers make the most of AWS and different cloud suppliers to hold out their assaults as a result of they know that is what you’ve got completed. One instance was the photo voltaic wind hole. I defined how the attackers used Azure and AWS on this publish:
Firewall guidelines typically require an IP handle or CIDR block. That is dependent upon whether or not the firewall is stateless or stateful, phrases I clarify in my e book on the finish of this publish and in earlier posts on this weblog. Stateless firewalls examine particular person packets that don’t have full utility layer information, reminiscent of totally certified domains (FQDNS). A stateful firewall will reassemble packets for inspection and rule enforcement. There are causes every is helpful in your total community structure.
Even when you should use a website identify in your community guidelines, you’ll nonetheless run into issues with DNS with regards to firewall guidelines and EC2 cases. Your area identify is configured to ship somebody to a specific IP handle. You then resolve that it’s worthwhile to cease and begin your EC2 occasion. You now have a brand new IP handle. Your DNS data now not resolve to the proper host.
Another person begins an EC2 occasion and will get your previous handle. Now your web site guests get one other machine. If that machine was serving as a server on an internet site, your area could be pointing to a different web site!
I used to be extraordinarily involved about this concern when deploying a bastion host on Capital One. Builders have been supposed to make use of a website identify to entry it and log in, presumably with manufacturing credentials. The individual operating the DNS servers could not determine why a TTL of 1 hour was too lengthy.
Elastic IP Tackle
As a substitute of counting on domains, we will use an Elastic IP (EIP) handle in AWS to offer an EC2 occasion or load balancer or another useful resource a set IP handle. You arrange a set AWS IP handle and may then assign it to numerous assets. It’s also possible to disassociate an IP handle and assign it to a brand new IP handle later.
It’s extremely versatile, however you are restricted to five per area for an IPv4 handle.
Additionally, be aware that you’ll not be charged for an EIP in use, however for those who don’t have it assigned to any assets, you may be billed for it. Click on Elastic IP Addresses on this web page to view pricing.
Another choice is to carry your individual IP to AWS. This matter is extra difficult than we will cowl on this sequence, however you’ll be able to examine it right here.
It additionally seems that you could request contiguous mounted IP addresses.
Why does it matter? For example you will have 5 IP addresses. If the addresses are steady, you should use a single entry with a CIDR block to permit entry to your IP vary. In any other case you want a single rule in your community guidelines for every handle. Now to illustrate you are utilizing Energetic Listing and you must open 50 separate ports and protocols (that is what I felt once I was attempting to implement it anyway). 50 x 5 = 250 guidelines.
Suppose you’re in a posh community setting that has been acquired by many firms and has many forests and timber for AD and none of them are contiguous. I’ve had flashbacks. You get the thought. That concern is a part of the explanation now you can add extra guidelines for safety teams in AWS than was doable. It was one other considered one of our function requests whereas at Capital One.
Luckily, AWS has launched a brand new function that may assist with that downside known as Prefix Lists. I’ll write extra about them in some posts. You possibly can add an inventory of IP addresses to an inventory of prefixes and use it in safety teams and firewalls. Nevertheless, it will not work for AWS NACL.
Makes use of of elastic IP addresses to enhance safety
Typically clients need you to offer a set IP handle for a penetration take a look at. I do not favor this method as a result of it’s totally simple to overlook one thing when simply utilizing a set IP that’s someway blocked or processed in a different way than new IPs, but when it is a requirement I can use an EIP.
I began writing about my residence community and the way I’m organising and testing firewall merchandise. Sorry I am not completed with this but, I simply have too many pursuits, however I hope to be again quickly. I want the code for the sequence I am writing for business initiatives, so it comes first. Nevertheless, you’ll be able to configure your private home firewall to solely enable SSH entry to particular hosts for those who assign an EIP. There are different methods, some higher than others. For instance, I do not like to make use of DNS companies that are not actually vetted. A VPN could be one other good possibility.
Moreover, you’ll be able to specify that solely sure IP addresses are allowed entry to sure cloud companies reminiscent of GitHub. If you happen to’re utilizing an EC2 occasion to obtain and entry code on a personal GitHub account, you’ll be able to block it solely on the IP addresses you wish to authorize. I am going to present you in a minute. I favor to solely use cloud companies that enable me to regulate entry through IP addresses in that approach.
Creating an EIP in CloudFormation
These are the properties obtainable to us when creating an EIP in CloudFormation.
The one properties that basically hassle me are the next:
Labels — Label: I wish to use a tag to determine the IP handle with a reputation.
Occasion ID: we will affiliate the EIP with an EC2 occasion.
InstanceId isn’t required, so we will create the EIP and affiliate it at a later time utilizing the EIP Affiliation CloudFormation useful resource. This feature could also be required if an EC2 occasion has a number of interfaces or if you wish to affiliate the IP with a community interface as a substitute of an EC2 occasion.
Separation of duties for EIPs to keep away from community misconfigurations
The EIP ought to most likely be created on the community. Our community directors will management the creation of IP addresses. We would additionally need them to regulate which assets could be allotted to which IP addresses.
For example you will have a rogue person who desires to entry a manufacturing useful resource however cannot. If that individual can affiliate a useful resource that he’s not imagined to entry as a consequence of community guidelines with an EIP that he can entry by way of the firewall, it’s doable that he can entry one thing that he should not.
See my earlier weblog publish for an instance the place I could not get my firewall previous AWS, so I disassociated an IP handle from an current occasion and assigned it to the occasion I wished to hook up with. 😀 Mwa-ha-ha. Do not let customers of your cloud setting like me do these issues if they don’t seem to be imagined to. Additionally, by segregating permission to create EC2 cases from community administration, a community administrator would even be unable to take action. They’ve permission to create the IP handle, however to not run a brand new EC2 occasion that may use it.
EIP CloudFormation dependency concerns
Alright, the community directors will create and assign EIPs so we now have some new dependency concerns. We want the community earlier than we will create the EC2 occasion, however the EC2 occasion earlier than we will create the EIP. We’ll wish to create a separate deployment script for the EIP so we will correctly order all of the stuff in our take a look at and kill script.
Easy EIP Template
Let’s begin with a easy EIP template and see if it really works. I put this in EIP.yaml in my Networking CloudFormation (cfn) listing.
Subsequent, I have to replace the deployment script, however be aware that we have to go two parameters. How am I going to get the ID of the occasion? Do not forget that we had a consequence after we created our developer EC2 occasion:
We are able to reference that in our deployment script. I’ll create a brand new deployment script known as deployment_eip.sh for the explanations talked about above. I am going to want to vary the ID of the occasion to reference that export, so I am going to go within the identify of the export and use the export with an ImportValue perform to get the ID of the occasion in my template:
I then added a perform to network_functions.sh
BTW, I initially used $identify for my variable and bought bizarre outcomes. So I want to maneuver this out of bash, however that is the quickest option to do the preliminary POC. Keep tuned for a greater possibility (hope I’ve time).
Now I can name the perform from my deployment_eips.sh script.
And check out it…it labored. And our output for the EIP stack has the brand new IP handle in case we want it. Be aware that that is NOT my IP within the screenshot under, so do not name it 867–5309. If you happen to’re previous you realize what I am speaking about. 🙂
It’s also possible to check out the record of EIPs on the EC2 dashboard and test your EC2 occasion to confirm that the IP handle was assigned accurately.
Additionally, you will see that public IP handle in your EC2 occasion. Be aware that despite the fact that my occasion is stopped, it nonetheless has the general public IP assigned to it:
Now, which will or is probably not sufficient to assist you to connect with that host in AWS. It is dependent upon your native community. Within the subsequent publish, I’ll present you configure native community firewall guidelines.
Observe for updates.
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