Given the name of a CloudFormation stack, upload a local SSH public key and connect to its EC2 instance.

aws-cloudformation-ssh-admin.sh

# Note: requires 'jq' utility, https://stedolan.github.io/jq/
# Download or install it locally with your package manager.

# your cloudformation stack name here
export STACK_NAME="eastern-sky-2020"
# your SSH key name here
export SSH_KEY_NAME="id_rsa_aws_ec2"

# filter by Tag named 'aws:cloudformation:stack-name'
aws ec2 describe-instances --filter Name=tag:aws:cloudformation:stack-name,Values=${STACK_NAME} \
  --query 'Reservations[*].Instances[?State.Name==`running`]' | tee /tmp/ec2i.txt \
 | jq -r '.[][] | { "INSTANCE_ID": (.InstanceId), "PUBLIC_IP": (.PublicIpAddress), "AVAIL_ZONE": (.Placement.AvailabilityZone) } | to_entries | .[] | "export " + .key + "=\"" + .value + "\""' \
  | tee /tmp/set-connect-params.sh

# Output should look something like this:
# export INSTANCE_ID="i-0ff4c959b60693129"
# export PUBLIC_IP="3.231.19.211"
# export AVAIL_ZONE="us-east-1a"

# Add these variables to the environment.
source /tmp/set-connect-params.sh

# Verify the variables are there.
env | grep -E "INSTANCE_ID|PUBLIC_IP|AVAIL_ZONE"

# Use the variables for arguments to temporarily push
#   a custom SSH public key to the EC2 instance.
aws ec2-instance-connect send-ssh-public-key \
    --instance-id ${INSTANCE_ID} \
    --instance-os-user ec2-user \
    --availability-zone ${AVAIL_ZONE} \
    --ssh-public-key file://${HOME}/.ssh/${SSH_KEY_NAME}.pub

# Connect via SSH to the instance.
ssh -i ${HOME}/.ssh/${SSH_KEY_NAME}  ec2-user@${PUBLIC_IP}