I have a lambda function that needs to access RDS and the internet. Everything out there points to having to set up a NAT gateway; the RDS in question is publicly accessible, the lambda is able to connect to it if I allow connections to the RDS from all IPs; however, I would like to avoid that. Is there a way to determine the possible range of IPs to be assigned to a lambda function and whitelist that range in the security group>?
Locate your Lambda into your VPC, private subnet and set the security group for Lambda. After that, add the Lambda security group to the inbound source of the RDS security group. Then, the Lambda will communicate with the RDS privately.
The private subnet should route the target 0.0.0.0/0 to the internet through a NAT gateway where the NAT should locate in the public subnet. Then, the private subnet can connect to the internet safely.
Related
Is there anyone who can explain me that situation below ?
I connected to Ec2 intance in private subnet via Bastion Host.Then I created a vpc gateway endpoint to reach s3. I assigned the required role to ec2 and the connection to s3 is done. My question is, how can Ec2 instance in private subnet download something from the internet?
A VPC endpoint is used to access a certain service, in this case S3, over the AWS network instead of over the internet.
If you want your instance to be able to talk to the internet, you'll need to configure a NAT gateway in a public subnet, and you'll need to configure the route table of the private subnet to forward traffic to the NAT gateway.
A simple solution would be:
Put everything in a Public Subnet
Assign a Public IP address to the Amazon EC2 instance
Use Security Groups to secure access on the Amazon EC2 instance (that is, only allow Inbound connections from the Bastion)
The effective result is the same as using a Private Subnet, but the EC2 instance will be able to establish Outbound connections to the Internet (but not Inbound, so it remains secure).
I've created a VPC (due to the RDS connectivity needs inside the lambdas) in AWS which has internet access most of the time, but some times my outside requests timeout (mostly these happen with SES as they're the majority of outside requests). I've configured my VPC the following way (sorry, not in the created order, just reading them off AWS):
VPC with 172.30.0.0/16 CIDR
3 private subnets with 172.30.0.0/24, 172.30.1.0/24, 172.30.2.0/24 and a different availability zone for each (1a, 1b, 1c) with 0.0.0.0/0 route targeting my NAT
1 public subnet with 172.30.3.0/24 to 1a availability zone with a 0.0.0.0/0 route targeting my IGW
2 route tables (private and public) with the 3 private subnets in the private route table and the public one in it's own
Security groups for lambdas directing all outbound traffic to 0.0.0.0/0
Lambdas are configured to use these subnets and the given security group.
I'm not understanding why my internet requests some times fail from inside the VPC, it's almost as if the lambda gets started at some availability zone and that specific one does not have access to the internet inside the vpc.
EDIT: Resolved! I had the public subnet listed in my lambda function which caused the timeouts
AWS Lambda functions that are connected to a VPC should always be configured to use private subnets.
If those Lambda functions also require Internet access, they can use a NAT Gateway or NAT Instance to reach the Internet. These NAT services should be configured to use the public subnet(s).
When the Lambda function is connected to a private subnet, then traffic destined for the Internet will be routed from the private subnet, through the NAT Gateway/NAT Instance, and out to the Internet. This will not work if the Lambda function is connected to a public subnet. (And a Lambda function cannot connect directly from a VPC to the Internet.)
As the title suggests, I placed my Lambda function in a private subnet and now It cannot access or timeout when scanning the DB. Prior to this, it could access and scan the DB. What should I do?
Your DynamoDB resources are not in your VPC. Since you've configured your Lambda functions to connect to your VPC, you need to setup a NAT Gateway or NAT Instance to allow your private resources to access the internet. As the docs state:
AWS Lambda uses the VPC information you provide to set up ENIs that
allow your Lambda function to access VPC resources. Each ENI is
assigned a private IP address from the IP address range within the
Subnets you specify, but is not assigned any public IP addresses.
Therefore, if your Lambda function requires Internet access (for
example, to access AWS services that don't have VPC endpoints), you
can configure a NAT instance inside your VPC or you can use the Amazon
VPC NAT gateway. You cannot use an Internet gateway attached to your
VPC, since that requires the ENI to have public IP addresses.
AWS Lambda Doc
Validate the following:
The route table for the Lambda has a NAT Gateway for internet traffic that resides in public subnet.
DynamoDB Gateway endpoint exists? Check its policy to ensure that it is not limited to specific sources
Outbound access is allowed via the security group and NACL
How can I create this scenario:
- A private subnet-1
- Lambda in subnet-1
- RDS in subnet-1(same subnet with Lambda)
- Both inside the same VPC.
is the above feasible and is it a good architecture ?
I have tried implementing it only issue is, it's timing out. But, when the Lambda is out of the subnet-1 it's working fine.
My understanding is since both RDS and Lambda are in the same subnet they should easily communicate.
It is perfectly okay to have Amazon RDS and the AWS Lambda function connected to the same private subnet.
Some things to note:
If the Lambda function also requires access to the Internet (eg to make calls to Amazon S3), then the VPC will also require a NAT Gateway in a public subnet.
The Lambda function should refer to the RDS instance by DNS Name. This should resolve to a private IP address local to the VPC.
The Lambda function should be assigned a Security Group (eg Lambda-SG)
The security group associated with the RDS instance (RDS-SG) should permit inbound access on the appropriate port (eg 3306 for MySQL) from Lambda-SG.
That is, RDS-SG should permit inbound connections from Lambda-SG.
I am trying to setup a nice and secure VPC for my lambda and RDS work. Essentially, I want my lambda to hit a site, get some data, and shove it into a database.
In isolation the parts all work. However the second I go to harden everything it all falls apart. Here is what I do:
Disable "Publically Available" from the RDS instance
Change the RDS instance to only accept connections from inside the VPC using the security group
Associate the lambda with a VPC (this kills the internet access)
Following this tutorial I created a NAT gateway, deleted the internet gateway from the VPC subnet, and replaced it with the NAT. Now, as expected, nothing can talk inbound, but things can talk outbound.
At this point I knew I needed a bastion instance, so I fired up an EC2 instance.
The EC2 instance is set to the same subnet the RDS and Lambda are on, and unfortunately this means that I have a problem - the NAT gateway is currently soaking up all the traffic via 0.0.0.0/0, which means there's no room for the internet gateway. Without the internet gateway I (obviously) can't SSH into my bastion instance so I can jump to access my RDS database.
How can I configure this all correctly? My guess is that I need to split the subnet up somehow and make a private and public subnet, the public having the bastion and internet gateway in it. However, I'm not sure how this will all work so the bastion instance can still properly jump to the RDS.
I'm really quite new to setting up AWS services so I'm hoping I didn't mess anything up long the way.
Following this tutorial I created a NAT gateway, deleted the internet
gateway from the VPC subnet, and replaced it with the NAT. Now, as
expected, nothing can talk inbound, but things can talk outbound.
Short Answer
The short answer is you shouldn't have "Killed the Internet Gateway"; thats not a step in the link you provided :) Leave the internet gateway as is in your current subnet. You're going to need a public subnet and the one that was routing 0.0.0.0/0 to IGW is an example of one you can could use.
The work involved is placing your NAT gateway in the Public Subnet, placing your bastion host in the public subnet, placing your lambda function in the private subnet, routing traffic in the private subnet to the NAT gateway in the public subnet, and providing your lambda function with access to your security group by putting it in its own lambda security group and "white listing" the lambda security group in the inbound rules for the security group protecting your database.
Background
Below I have an expanded answer providing background as to public/private subnets, granting internet access to private subnets, and allowing lambda access through security groups. If you don't feel like reading the background then jump to very end where I give a bullet point summary of the steps you'll need.
Public Subnet
A public subnet is one in which traffic originating outside your VPC, or destined for a target outside your VPC (internet), is routed through an internet gateway (IGW). AWS gives you initial default public subnets configured this way; you can identify them in the console by looking at their route table and seeing that under "destination" you find "0.0.0.0/0" targeting an IGW. This means a public subnet is more of a design pattern for "internet accessible" subnet made possible by simply configuring its default route to point to an IGW. If you wish to create a new public subnet you can create a new route table as well that point internet traffic at an IGW and link that route table to your new subnet. This is fairly easy in the console.
Private Subnet
A private subnet is a subnet with no IGW and not directly reachable from the internet, meaning you cannot connect to a public IP address of a system on a private subnet. With the exception of the AWS pre-configured default subnets, this is how new subnets your manually create are setup, as black boxes till you specify otherwise.
Granting Internet Access to Private Subnet
When you want things in your private subnet to be able to reach out to external internet services you can do this by using an intermediary known as a NAT gateway. Configure a route table the same as in the public subnet with the only difference being traffic destined for 0.0.0.0/0(Internet) you target for a NAT gateway sitting inside the public subnet. That last part is critical. Your NAT gateway needs to be in the public subnet but your private subnet is using it as the target for external traffic.
Security Group Access for Lambda
One simple way to allow your lambda function through your security group/firewall is to create a security group just for your lambda function and configure the security group protecting your RDS so that it allows traffic from the lambda security group.
In other words, in security group settings you don't have to specify just IP addresses as sources, you can specify other security groups and this is a pretty neat way of grouping items without having to know their IP address. Your lambda functions can run in the "Lambda Security Group" and anything protected by a security group that you want them to access can be configured to accept traffic from the "Lambda Security Group". Just make sure you actually associate your lambda function with the lambda security group as well as place it in the private subnet.
Lambda VPC Steps in a Nutshetll
Create a new NAT gateway and place it in the public subnet. This
point is important, the NAT gateway goes in the public subnet ( a
subnet whose route table routes 0.0.0.0/0 to an IGW)
Create a new subnet, you can call it Private-Lambda-Subnet. Unlike
the
default pre-configured subnets AWS gives you, this new subnet is
immediately private out of the box.
Create a new route table and link it to your Private-Lambda-Subnet
In the new route table for your private subnet add an entry that
routes 0.0.0.0/0 to a target of the NAT gateway. This is how your
private subnet will indirectly access the internet, by forwarding
traffic to the NAT which will then forward it to the IGW.
Your bastion host and anything else you want to be be publicly
accessible will need to be in the public subnet. This is probably
where you already have your RDS instances, which is fine if they are
firewalled/security group protected.
Create a new security group for your lambda function(s). You can
call it LambdaSecurityGroup.
Configure the inbound rules of your RDS guarding security group to
allow traffic from the LambdaSecurityGroup. This is possible because
you can use other security groups as sources in the firewall
settings, not just ip addresses.
You need a public subnet (default route is the Internet Gateway) and a private subnet (default route is the NAT Gateway). The NAT Gateway, itself, goes on the public subnet, so that it can access the Internet on behalf of the other subnets for which it is providing services. The bastion also goes on the public subnet, but Lambda and RDS go on the private subnet.
Anything can talk to anything on any subnet within a VPC as long as security groups allow it (and Network ACLs, but don't change these unless you have a specific reason to -- if you aren't sure, then the default settings are sufficient).