I have a license server that has a static IP set up inside the same security group and VPC as the EC2s I’m spinning up using terraform. Basically I want the license server and these EC2s to be able to communicate. At the moment they can’t because the security doesn’t add the EC2s as an inbound rule so that the license server also gets it as an inbound rule (same security group). I’m wondering how to add the IP of the EC2 I’m spinning up in terraform to the inbound of its security group so that it can talk to the license server?
There is no such concept as being "inside the same security group". Security Groups rules apply to each instance individually.
The correct configuration is:
Create a Security Group for the EC2 instances (EC2-SG) that permits appropriate Inbound access to use the instance, and
Create a Security Group for the licensing server (License-SG) that permits Inbound access on the licensing port from EC2-SG
That is, you need TWO security groups. License-SG will permit inbound access from any EC2 instance that has is associated with EC2-SG. You can have more security group as necessary for your instances -- simply add them as sources in License-SG.
Security Groups can also refer to themselves. In your current situation, where the instances and the licensing server are all associated with the same security group, you could add a rule that permits inbound connections from itself. However, this is also saying that the instances are permitting inbound connections from the licensing server, which would not be a correct configuration.
Please note that all communication within the VPC should take place via private IP addresses, otherwise the traffic exits the VPC and then comes in again, which does not allow Security Groups to operate correctly (and also costs you more money!).
Related
I had a very specific question regarding SGs speficcally around Inbound and Outbound rules.
Situation
Lets say we have an EC2 instance with SG-12345 which is trying to talk to a MYSQL database on SG-98765 and I want an Ec2 to talk to the database.
I read the AWS documentation that Security Groups are stateful. Given this the question I had was:-
Is there any difference between
adding the DATABASE SG (SG-98765) to the OUTBOUND RULES of the EC2 (SG-12345)
vs
adding the EC2 SG (SG-12345) to the INBOUND RULES of the DATABASE SB (SG-98765)?
Is there any difference between adding the DATABASE SG (SG-98765) to
the OUTBOUND RULES of the EC2 (SG-12345) vs adding the EC2 SG
(SG-12345) to the INBOUND RULES of the DATABASE SB (SG-98765)?
Yes. If you don't add both rules, the connection will be denied.
The statefulness of security groups does not apply across multiple security groups. It simply allows responses to requests that were permitted by the security group to also be permitted by the security group. Both security groups still have to allow the initial network request.
Often you will see security groups on an EC2 instance allow all outbound traffic by default, or allow all outbound traffic to the VPC CIDR perhaps. And then the inbound rules on the database would control what can actually connect to the database.
I am trying to understand this statement:
"You can reference AWS Security Groups from other Security Groups."
What exactly does this mean?
This is how I understood this. I created a security group and call it "SG-10" and attached it to an instance "EC2-10". The SG "SG-10" has allow port 443 defined inside it.
Now, I create a security group and call it "SG-20" and attached this to an instance "EC2-20". This also has port 443 allowed. Now, if I call "SG-10" inside "SG-20" does this mean that "EC2-10" will be able to connect to "EC2-20" on port 443.?
Regards,
Nik.
if I call "SG-10" inside "SG-20"
No, you can not call a security group, this does not make any sense.
If a security group A references security group B, it does mean that the instance to which the security group A is attached allows inbound or outbound traffic to another instance to which security group B is attached. But if you want to send traffic form instance with security group A to the instance with security group B, you have to use the IP or the DNS of the instance B.
Usually the reason why we would want to reference a security group instead of an IP, is that the IP might change over time or it is not exposed at all. A fairly common example is having an application load balancer (ALB) and a group of EC2 instances which allow traffic only from the ALB. The IP address of the ALB changes over time, so in order to be able to receive traffic from the ALB, we can reference the security group attached to it.
In we want to reference a security group from another security group, we have to edit the rules of the initial security group:
As an example of referencing security groups, imagine a 3-tier architecture:
A Load Balancer receiving traffic from the Internet and sending requests to an Amazon EC2 instance
An Amazon EC2 instance receiving requests from the Load Balancer and sending queries to an Amazon RDS database
An Amazon RDS database receiving requests from the EC2 instance
This would involve 3 security groups:
A security group on the Load Balancer (LB-SG) that allows incoming traffic on port 80/443.
A security group on the EC2 instance (App-SG) that allows incoming traffic on port 80 only from the load balancer. It does this by setting the source to LB-SG.
A security group on the RDS database (DB-SG) that allows incoming traffic on the relevant port (eg 3306) only from the EC2 instance. It does this by setting the source to App-SG.
All security groups allow All Outbound Traffic.
By referencing other security groups, resources can be added/removed without having to change the security groups. For example, another EC2 instance could be launched and assigned the App-SG security group. This new instance would then be able to communicate with the database since DB-SG allows incoming traffic from App-SG, without being tied to any specific IP addresses.
If a resource is associated with multiple security groups, then all rules apply to the resource. Security Groups only say what is 'Allowed'. They do not include 'Deny' rules.
In your SG-10/SG-20 example, you do not mention the source of the traffic, so it is not possible to answer your question. If you want EC2-20 to accept connections from EC2-10, then the SG-20 security group should allow connections with the Source set to SG-10.
As an aside, I should mention that Network ACLs should normally be left at their default "Allow All" settings unless there is a specific networking requirement (eg creating a DMZ).
I've been burned on this before by trying to connect to an EC2 instance's public address... sounds very similar to your setup. Please check this question: Source Security group isnt working as expected in aws. Actually. When you wire up the inbound rule so that the source is a security group, you must communicate through the source instance's private address.
So i am trying to build a private vpc having a private and a public subnet. I want to communicate 2 linux ec2 machines with each other within same vpc. Also please explain inbound and outbound rules with ACLs in simplest way.
If both Amazon EC2 instances serve the same function (are operationally the 'same'), then:
Create a Security Group
Add in Inbound Rule on the security group permitting access from the Security Group (itself) on the desired port number
Attach the Security Group to both instances
This will allow both instances to communicate with each other because security groups are applied to each instance individually, so the Inbound Rules must permit access from 'itself'.
If the EC2 instances serve different purposes, (eg one is an app server, one is a database server):
Create a Security Group on the App server (App-SG) with desired inbound permissions from the Internet
Create a Security Group on the Database server (DB-SG) with inbound permissions on the desired port from App-SG
That is, DB-SG specifically refers to App-SG when defining inbound permissions.
Do not modify ACLs in the VPC unless you have a very specific reason for limiting network access (eg creating a DMZ).
i have a jupyter notebook on one ec2 instance that want to get the data from data service that is deployed on other ec2 instance. should i put ingress and egress rules for each other on both instances? I'm quite new on the field, so any explanations are appreciated! :)
Yes, you can create 2 different security groups and attach to each one.
You can allow inbound traffic from a particular security group, all instances that have the security group attached can send traffic to the instance on the port you specify.
Another important thing no notice is that security groups are stateful, when you set outbound rules the response traffic is allowed regardless of the inbound rules.
Security Group Outbound rules allow all traffic by default. Typically, you should not modify these settings.
The best way to configure you setup is:
Create a Jupyter-SG security group and associate it with your Jupyter EC2 instance. Add whatever rules you use to connect with the instance (eg SSH).
Create a Data-SG security group and associate it with your "Data Service" EC2 instance. Add a rule permitting inbound access on the desired port, with Source set to the Security Group ID of Jupyter-SG.
This tells the Data-SG security group to permit inbound access from the Jupyter instance (or, more accurately, from any instance that is associated with the Jupyter-SG security group).
I am setting up EMR clusters on demand, and have a windows EC2 server as a workstation, and a linux EC2 server as a secondary server. All in the same VPC. I would like to avoid having to set security group rules each time an instances comes up with a new IP.
How would I simply allow any traffic to flow freely between all servers in the same VPC?
Thanks!
EDIT- Thanks for the replies, I know this is not good practice in production, but we are dealing with some issues tracking down functionality which we believe is caused by ports, this is just a exploration phase, and this will help us. Thanks!
In the security groups, assign incoming access to other security groups by specifying a security group ID instead of IP addresses. In the web console, if you start typing "sg" in the source field it will pop up a list of your security groups to choose from. Using a security group ID as the source allows all resources that belong to that security group to have access.
Alternatively, if you just want one rule that allows access to every resource in your VPC you would specify your VPC's IP range.
to Allow any traffic between ALL servers in the VPC is not a good practice.
you should rethink in your VPC purpose.
Any way, if you want a group of servers to communicate with each other you can create a Security Group
And Assign it for all servers that you want.
and in inbound rules you add one rule from type "All TCP" and the source of this rule will be the same Security Group.
if your Security Group ID is 'sg-xxxxxxxx'
then the rule will be like this:
All TPC | TCP | 0-65535 | custom | sg-xxxxxxxx
To add to the other answers here, if you really want this, you can set it up via the Subnet or VPC IP CIDR Block
For example, if your VPC is 10.0.0.0/16, then add that to your security groups and all VPC traffic should be able to flow to each other.