This is how I configured the deploy of my rails apps to AWS Elastic Beanstalk through CircleCI 1.0.
If you are using the Circle CI 2.0, take a look at this article from ryansimms
On Project Settings > Environment Variables add this keys:
- AWS_ACCESS_KEY_ID
 - AWS_SECRET_ACCESS_KEY
The aws user must have the right permissions. This can be hard, maybe, this can help you. 
./setup-eb.sh
set -x
set -e
mkdir /home/ubuntu/.aws
touch /home/ubuntu/.aws/config
chmod 600 /home/ubuntu/.aws/config
echo "[profile eb-cli]" > /home/ubuntu/.aws/config
echo "aws_access_key_id=$AWS_ACCESS_KEY_ID" >> /home/ubuntu/.aws/config
echo "aws_secret_access_key=$AWS_SECRET_ACCESS_KEY" >> /home/ubuntu/.aws/configAdd the awsebcli dependency:
dependencies:
  pre:
    - sudo apt-get update
    - sudo apt-get install python-dev
    - sudo pip install awsebcliAdd the deployment config:
deployment:
  production:
    branch: master
    commands:
      - bash ./setup-eb.sh
      - eb deploy- If your deploy user don't have the 
elasticbeanstalk:DescribeEventspermission, theeb deploywill run for ever. CircleCI will cancel it after 10 minutes and break the build with timeout. 
eb init will create this file for you. However, if you don't want to run it, you can simply create and configure this file manualy:
./elasticbeanstalk/config.yml
branch-defaults:
  master:
    environment: you-environment-name
global:
  application_name: your-application-name
  default_ec2_keyname: ec2-key-pair-name
  default_platform: 64bit Amazon Linux 2015.03 v1.4.3 running Ruby 2.2 (Puma)
  default_region: sa-east-1
  profile: eb-cli
  sc: git
I did, just replace
sudo pip install awsebclibysudo pip install awsebcli --ignore-installed setuptools