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security groups

AWS EC2 List Firewall Rules

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AWS EC2 Firewall rules are defined within security groups. Security groups are attached to an instance. An instance can have up to 5 security groups. Essentially, this script gathers all the security groups associated with an instance, loops through them, and then outputs the ingress and egress rules of each security group to a file in a text format.

#!/bin/bash
# set variables
instanceid='i-xxxxxxxxxxxxxxxx'
region='us-east-1'
profile='sample'
# log and temp files
output="ec2-sg.log"
tmpfil="ec2-sg.tmp"
# empty log at start
> $output
# get sg ids
aws ec2 describe-instances \
--instance-ids $instanceid \
--region $region \
--profile $profile \
--query 'Reservations[*].Instances[*].SecurityGroups[*].[GroupId]' --output text > $tmpfil
while read -r id; do
  echo '============================================' >> $output
  echo $id >> $output
  echo '============================================' >> $output
  echo '---------------- INGRESS -------------------' >> $output
  aws ec2 describe-security-groups \
  --group-ids $id \
  --profile $profile \
  --region $region \
  --output text \
  --query 'SecurityGroups[].IpPermissions[].[FromPort,ToPort,IpProtocol,IpRanges[].CidrIp[]|[0]]' >> $output
  echo '---------------- EGRESS --------------------' >> $output
  aws ec2 describe-security-groups \
  --group-ids $id \
  --profile $profile \
  --region $region \
  --output text \
  --query 'SecurityGroups[].IpPermissionsEgress[].[FromPort,ToPort,IpProtocol,IpRanges[].CidrIp[]|[0]]' >> $output
done < $tmpfil

Here’s a sample output.

============================================
sg-xxxxxxxxxxxxxxx
============================================
---------------- INGRESS -------------------
5985    5985    tcp     10.0.0.220/32
10005   10005   tcp     10.0.0.164/32
---------------- EGRESS --------------------
80      80      tcp     10.0.0.14/32
40000   65535   udp     10.0.0.0/8
3389    3389    tcp     10.0.0.96/32
9389    9389    tcp     10.0.0.0/8
5985    5986    tcp     10.0.0.96/32

AWS Security Groups IP Cidr

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Here’s how to search for AWS Security Groups containing this IP Cidr.

aws ec2 describe-security-groups \
--filter Name=egress.ip-permission.cidr,Values='10.8.8.8/32' \
--query "SecurityGroups[*].{Name:GroupName}" \
--output text \
--profile default \
--region us-east-1

Search with ports.

aws ec2 describe-security-groups \
--filter Name=egress.ip-permission.cidr,Values='10.8.8.8/32' \
         Name=egress.ip-permission.from-port,Values='22' \
         Name=egress.ip-permission.to-port,Values='22' \
--query "SecurityGroups[*].{Name:GroupName}" \
--output text \
--profile default \
--region us-east-1

Query will only display the Security Group name.

Deleting AWS Security Groups

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Every once in a while, you may need to do some cleanup and perform maintenance in AWS. One area where you can do some cleanup is the security groups. To check if security groups are in-used, is by way of the AWS Console. You can filter the security group via Instances. But that is not going to be enough. Security groups are also used in RDS as well as in load balancers. Overall, you have to be extra careful not to delete a security group that’s in-use. Fortunately, AWS will prompt you if you try to delete a security group that is still in-use. It’s a safety feature that can potentially save you from headaches.