I have an Aurora cluster in RDS and a Lambda Function.
Both are assigned the same VPC.
Both have the same subnets (us-east-1 a-f)
Both have the same security group assigned
Lambda is assigned a role with AmazonRDSFullAccess, AmazonVPCFullAccess,
AWSLambdaVPCAccessExecutionRole
When I run the lambda instance, I get connection timeout when trying to connect to Aurora. I'm able to access Aurora locally (with access key added to aws configure).
Any ideas what else I can check for why lambda wouldn't have access to the instance? Thank you
Update: The subnets each have the following configuration:
Both have the same security group assigned
It's a common misconception that members of the same security group can communicate with each other by virtue of being members of the same group. This is not the case. Being members of the same group only means they follow the same set of rules.
Members of a security group can only access other members of the group if the group allows access to itself.
Instances associated with a security group can't talk to each other unless you add rules allowing it (exception: the default security group has these rules by default).
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_SecurityGroups.html
Add a rule to this group for "MySQL/Aurora" traffic, but instead of entering an IP address, enter the sg-xxxxxxxx identifier of the security group.
I had a similar problem until I realized the VPC I was using did not have dns resolution enabled for hosts within the VPC.
The enableDnsSupport option needs to be set for the VPC.
See http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-dns.html
Related
RDS Database details:
I have an publicly accessible RDS database which is restricted to be accessible to only specific IP address.
The RDS have 2 security groups attached to the RDS:
1st security group allows a specific IP address to access it.
2nd security group allows multiple specific IP addresses to access
it.
Note: I know I can just keep a single security group for this purpose.
This RDS database have the default VPC and 3 public subnets. All these subnets have 2 routes in route tables:
Destination: default vpc's cidr range and Target: local
Destination: 0.0.0.0/0 and Target: internet gateway
Lambda function details:
I have a lambda function, which does not have any vpc configured.
I am trying to access the RDS database from code in the lambda function. Since lambda doesn't have any specific IP address, I couldn't add inbound rule in RDS's security group to allow it. When I simply add inbound rule in RDS's security group to allow access from all IPs then my lambda function code is able to connect to RDS database and work with it.
I wouldn't want my RDS database to be allowed access from anywhere on the internet, what configuration/settings do I need to make to be able to access RDS from lambda.
I also tried configuring the lambda function to be in same vpc and same subnets as that of for RDS instance; but I haven't been successful in making a connection to the RDS database.
Best in this case is to use the same VPC for your lambda as the RDS instance. This is cheaper and is more secure. You don't have to setup a internet gateway and elastic IP. And you can only access your RDS instance from within the VPC.
You can enable this using Lambda management console. Select Lambda function which need access to RDS instance and then go to Configuration -> Advanced settings and select the VPC (which is your RDS instance is in) you need it to access.
For instances attached to the same security group—make the security group the source for the inbound rule and the destination for the outbound rule.
For instances in different security groups—make sure that both security groups allow access to one another.
If this is still not working check the error message that is returned when setting up the connection with RDS. Timeout means issue with network.
find out more here https://aws.amazon.com/premiumsupport/knowledge-center/connect-lambda-to-an-rds-instance/
I saw this today and it seemed odd. In one region I have no VPC, but I apparently have a default security group that can't be deleted because "This is a default security group. Default security groups cannot be deleted."
How did this default security group come to exist without a VPC?
At one point there must have been a VPC, which came with this default security group, but I thought if the VPC is deleted the corresponding default security group would be deleted along with it.
All modern AWS accounts are provisioned with a VPC. VPCs can be deleted but the default security group can not.
I believe this dates back to the beginning of the EC2 service (i.e. EC2 Classic). In 2013 and earlier, users were able to create instances on a flat network that was shared with other customers and there was no concept of VPCs. AWS required EC2 instances to be associated with a security group but if none were created/selected by the user, AWS could rely on the default security group being available.
So the reason that we can have a default security group without a VPC is that security groups were actually a concept before VPCs and AWS still keeps this default security group requirement as a side effect of some of those earlier infrastructure requirements.
Ran into this yesterday.
Was using EC2 Classic Resource Finder and came across this resource along with some Security Groups(including the default) and an EIP. Deleted the non-default SG's and released the EIP without issue. Was unable to delete the default SG with the error "The following security groups can't be deleted. They are either default security groups, referenced by other security groups or they are associated with instances or network interfaces".
Ensuring this was not associated with a VPC or any other resources were referencing it, we reached out to support. Support confirmed that this resource will be sunset with EC2 Classic in 2023.
I think that must be it. I remembered deleting a default VPC for security reasons, but the default security group persisted.
Security is one of the key aspects in this term.
It is useful to note that security is always considered a top priority job at AWS. Therefore, Default Security Group cannot be deleted partially because they it is the last line of defense for potentially malicious attack on your Amazon EC2 instances. Amazon relies on Security Groups as virtual firewalls that your instances will be paired-up with exclusively for safety reasons. That is also why default SGs by default block any incoming traffic.
On the hand, protective NACL (Network Access Control Lists) feature is only one aspect of the VPC setup. VPCs are primarily logical networking compartments in your cloud infrastructure and you have absolute freedom to define them in any way you see fit. One use case is that you can have complex routing solutions that define many of the aspects of your cloud infrastructure, and accidentally adding Amazon EC2 instances to a default VPC by your developers can lead to hours of debugging why your resource is not behaving as expected.
In summary, security and the mentioned legacy aspects of the Amazon EC2 Classic instances related to the VPC concept (EC2-Classic and a VPC ) are one of the key reasons why default SGs can not be deleted compared to the default VPCs. Still, if you delete the default VPC, you will not be able to restore it or to provision new Amazon EC2 instances until you create at least one custom VPC in the respective region.
If you delete the default VPC, any running EC2 instances, network interfaces, it will automatically delete the default security group as well.
Can you delete a default VPC for a region?
You can delete a default subnet or default VPC just as you can delete
any other subnet or VPC.
However, if you delete your default subnets or default VPC, you must
explicitly specify a subnet in another VPC in which to launch your
instance, because you can't launch instances into EC2-Classic. If you
do not have another VPC, you must create a nondefault VPC and
nondefault subnet. For more information, see Create a VPC.
Reference: https://docs.aws.amazon.com/vpc/latest/userguide/default-vpc.html
I want to allow a lambda to access a RDS database.
What I've done:
put the lambda in the database's VPC, i.e. in the same security group and subnets as the database
add an inbound rule to the security group: allow connections from itself
That avoids creating a separate security group for the lambda and allowing the lambda's group to access the MySQL one.
That works, but is that OK? Why should I create a separate group for the lambda?
Yes, that would work, but it doesn't make logical sense unless you are desperately trying to reduce the number of security groups being used.
The preferred configuration would be:
A security group on the Lambda function (Lambda-SG)
A security group on the RDS instance (RDS-SG) allowing an inbound connection from Lambda-SG
This is easier to understand and avoids situations where you wish to grant access to RDS but not Lambda.
My goal is simple:
Allow any instance inside a VPC to connect to a specific security group.
The field for allowed sources suggests: "CIDR, IP or Security group".
Is there a way for me to specify a VPC?
The reason beeing that I have multiple instances inside a VPC with different security groups but all need access to the security group I am creating.
Your VPC has a CIDR group range, so just specify the CIDR group that is being used by your VPC and it will allow access from anything in the VPC.
What you are asking is the primary functionality of a security group. For example, if the CIDR of the VPC you want to allow is 10.4.0.0/16,
Set the Inbound route to the required CIDR group. The Outbound will automatically be set as per AWS VPC design.
I run a service on my EC2 instance and I want to setup an inbound rule that only allows my lambda function to access it. The security group allows me to restrict access by a specific IP, but I don't think that lambda functions have a specific IP assigned. Is there a way to do what I want?
If you are enabling VPC access for your Lambda function, as per this blog post, then you will create a security group for your Lambda functions to use within your VPC. All you need to do at that point is go into the security group your EC2 instance is using and grant access to the security group the Lambda function is using. This is the method I recommend.
If you are not using VPC access then your EC2 instance would need to be publicly accessible and you would basically be going over the internet to access the EC2 instance from the Lambda function. If that's the case then there is no good way to restrict that in the security group. You could (with difficulty) open it up to only requests that originate within AWS, but that still leaves it open to all other users of AWS. If you must go over the internet to access your EC2 instance from Lambda then it would be best to send some sort of security token with each request Lambda sends, and ignore any requests on the EC2 server that don't contain that security token.
What happens if we want our Lambda function to access resources in our VPC? This is a bit of a puzzlement because the Lambda function does not have a stable IP address that we can use as a source in our VPC security groups or in our subnet ACLs.
AWS has overcome these limitations by allowing you to specify a subnet and security group to associate with the Lambda function. You would think that this security group and subnet ACL would control traffic in and out of the Lambda function, but this is wrong. Firstly, Lambda functions do not listen for traffic on any port and so the concept of inbound traffic to a Lambda function is not applicable. Secondly, outbound connections from the Lambda function to VPC resources are not restricted in any way by the Lambda function’s security group. So, what is this mysterious Lambda function security group good for and how does it work?
It turns out that the Lambda function’s security group is just a naming placeholder that we can use in our other EC2 security groups. For example, a Lambda function can make a GET request to an EC2 instance on a private subnet in your VPC. We start out with two security groups. The first one is a normal security group that controls traffic to and from our EC2 instance that will be serving up the files on port 8080. It has a single inbound rule that allows port 8080 traffic with a source being the Lambda function’s security group. Recall that security group rules can specify source or destination as another security group which is a placeholder for all the hosts that are members of that source or destination security group.
The Lambda function’s security group has no rules whatsoever. None are required. It is merely a placeholder for the Lambda function that allows us to specify the Lambda function as source in our other EC2 security groups. Remember that the Lambda function has a random IP address that changes from day to day and hour to hour, so it is not possible to specify it as source for the inbound traffic to the EC2 instance.
Security groups normally control traffic in and out of a network interface but in the case of an AWS Lambda function security group, there is no interface and no rules – it is merely a placeholder.
A Lambda with no VPC association will be on the Internet and assigned with an arbitrary Public IP (obviously from Amazon Registered IPs) which will not be a fix address. So it is almost impossible to whitelist that IP in your EC2's SG since next time that Lambda spins up the IP could change and is not predictable.
However there is a way to Partially limit the Network Access only to the Resources Located in the VPC including Lambda's(since components will be assigned with Internal-IPs). Let's say you want that EC2 server only be accessible from Internal vpc network, therefor you place it in your Internal Subnet with no Public IP assigned to it. Now You can set SG on your EC2 to only accept IP from the Internal subnet CIDR range of your VPC. By Associating Lambda to that VPC and Placing it in the Private Subnet, Lambda will get arbitrary IP from Internal CIDR Range of your VPC which obviously falls in the SG range already configured for your EC2 (If you are going to have lots of Lambda in parallel just make sure you have enough amount of IPs within your defined CIDR range).
If you want your components to Communicate Internally meanwhile be able to access the Internet as well you can add a NAT Gateway Routable to IGW and then you will add Routing rule to the Internal Subnets to point to your NAT Gateway. Therefore all your component within the Internal subnet will be assigned with a Routing Tables pointing to NAT and subsequently the Internet.
Your Lambda will have a temporary IP assigned to it when it runs.
If you configure the IAM role attached to it so it can Allow/Revoke Security Group Ingress, you can make it "let himself in" to your sec group.
Check out this article for an example on adding an IP or CIDR block to your inbound list.
I would clean it up straight away when the function is done.
You can refer below articles to do the same,
1. https://medium.com/#justanotherspyy/how-to-connect-your-lambda-function-securely-to-your-private-rds-instances-in-your-vpc-29789220a33
2. https://medium.com/orchestrated/steps-to-secure-aws-serverless-lambda-part-1-a6e5d1b05f45
The summary would be,
1. Create a role for Lambda using below two policies,
AWSLambdaBasicExecutionRole — provides CloudWatch logging.
AWSLambdaENIManagementAccess — provides ENI description, creation, and deletion.
2. Put lambda in the same VPC of EC2 and create a security group for the lambda function.
3. Put this security group in EC2's security group's inbound rules.