Glen Knight

Easily Manage Security Group Rules with the New Security Group Rule ID

July 7, 2021 by knightglen_sruobz

At AWS, we tirelessly innovate to allow you to focus on your business, not its underlying IT infrastructure. Sometimes we launch a new service or a major capability. Sometimes we focus on details that make your professional life easier.

Today, I’m happy to announce one of these small details that makes a difference: VPC security group rule IDs.

A security group acts as a virtual firewall for your cloud resources, such as an Amazon Elastic Compute Cloud (Amazon EC2) instance or a Amazon Relational Database Service (RDS) database. It controls ingress and egress network traffic. Security groups are made up of security group rules, a combination of protocol, source or destination IP address and port number, and an optional description.

When you use the AWS Command Line Interface (CLI) or API to modify a security group rule, you must specify all these elements to identify the rule. This produces long CLI commands that are cumbersome to type or read and error-prone. For example:

aws ec2 revoke-security-group-egress 
         --group-id sg-0xxx6          
         --ip-permissions IpProtocol=tcp, FromPort=22, ToPort=22, IpRanges='[{CidrIp=192.168.0.0/0}, {84.156.0.0/0}]'

What’s New?
A security group rule ID is an unique identifier for a security group rule. When you add a rule to a security group, these identifiers are created and added to security group rules automatically. Security group IDs are unique in an AWS Region. Here is the Edit inbound rules page of the Amazon VPC console:

As mentioned already, when you create a rule, the identifier is added automatically. For example, when I’m using the CLI:

aws ec2 authorize-security-group-egress                                  
        --group-id sg-0xxx6                                              
        --ip-permissions IpProtocol=tcp,FromPort=22,ToPort=22,           
                         IpRanges=[{CidrIp=1.2.3.4/32}]
        --tag-specifications                                             
                         ResourceType='security-group-rule',             
                         "Tags": [{                                      
                           "Key": "usage", "Value": "bastion"            
                         }]

The updated AuthorizeSecurityGroupEgress API action now returns details about the security group rule, including the security group rule ID:

"SecurityGroupRules": [
    {
        "SecurityGroupRuleId": "sgr-abcdefghi01234561",
        "GroupId": "sg-0xxx6",
        "GroupOwnerId": "6800000000003",
        "IsEgress": false,
        "IpProtocol": "tcp",
        "FromPort": 22,
        "ToPort": 22,
        "CidrIpv4": "1.2.3.4/32",
        "Tags": [
            {
                "Key": "usage",
                "Value": "bastion"
            }
        ]
    }
]

We’re also adding two API actions: DescribeSecurityGroupRules and ModifySecurityGroupRules to the VPC APIs. You can use these to list or modify security group rules respectively.

What are the benefits ?
The first benefit of a security group rule ID is simplifying your CLI commands. For example, the RevokeSecurityGroupEgress command used earlier can be now be expressed as:

aws ec2 revoke-security-group-egress 
         --group-id sg-0xxx6         
         --security-group-rule-ids "sgr-abcdefghi01234561"

Shorter and easier, isn’t it?

The second benefit is that security group rules can now be tagged, just like many other AWS resources. You can use tags to quickly list or identify a set of security group rules, across multiple security groups.

In the previous example, I used the tag-on-create technique to add tags with --tag-specifications at the time I created the security group rule. I can also add tags at a later stage, on an existing security group rule, using its ID:

aws ec2 create-tags                         
        --resources sgr-abcdefghi01234561   
        --tags "Key=usage,Value=bastion"

Let’s say my company authorizes access to a set of EC2 instances, but only when the network connection is initiated from an on-premises bastion host. The security group rule would be IpProtocol=tcp, FromPort=22, ToPort=22, IpRanges='[{1.2.3.4/32}]' where 1.2.3.4 is the IP address of the on-premises bastion host. This rule can be replicated in many security groups.

What if the on-premises bastion host IP address changes? I need to change the IpRanges parameter in all the affected rules. By tagging the security group rules with usage : bastion, I can now use the DescribeSecurityGroupRules API action to list the security group rules used in my AWS account’s security groups, and then filter the results on the usage : bastion tag. By doing so, I was able to quickly identify the security group rules I want to update.

aws ec2 describe-security-group-rules 
        --max-results 100 
        --filters "Name=tag-key,Values=usage" --filters "Name=tag-value,Values=bastion" 

This gives me the following output:

{
    "SecurityGroupRules": [
        {
            "SecurityGroupRuleId": "sgr-abcdefghi01234561",
            "GroupId": "sg-0xxx6",
            "GroupOwnerId": "40000000003",
            "IsEgress": false,
            "IpProtocol": "tcp",
            "FromPort": 22,
            "ToPort": 22,
            "CidrIpv4": "1.2.3.4/32",
            "Tags": [
                {
                    "Key": "usage",
                    "Value": "bastion"
                }
            ]
        }
    ],
    "NextToken": "ey...J9"
}

As usual, you can manage results pagination by issuing the same API call again passing the value of NextToken with --next-token.

Availability
Security group rule IDs are available for VPC security groups rules, in all commercial AWS Regions, at no cost.

It might look like a small, incremental change, but this actually creates the foundation for future additional capabilities to manage security groups and security group rules. Stay tuned!

— seb

Source: AWS News