assume-role

#!/bin/sh
set -eu

# This script runs the AWS assume-role command, captures the output, sets the
# environment variables (AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY and
# AWS_SESSION_TOKEN) and executes the command given.

usage() {
    echo "$(basename "$0"): [-h|--help] ROLE_ARN COMMAND [PARAMETER [PARAMETER ...]]"
}

command -v aws > /dev/null || { echo 'Cannot find the AWS CLI, exiting.' >&2; exit 1; }

if [ "$#" -lt 2 ]
then
    usage
    exit 1
fi

role_arn="$1"
shift

credentials="$(aws sts assume-role \
    --output text \
    --duration-seconds 3600 \
    --role-arn "$role_arn" \
    --role-session-name 'CircleCI_executor')"

AWS_ACCESS_KEY_ID="$(echo "$credentials" | awk 'NR == 2 {print $2}')"
AWS_SECRET_ACCESS_KEY="$(echo "$credentials" | awk 'NR == 2 {print $4}')"
AWS_SESSION_TOKEN="$(echo "$credentials" | awk 'NR == 2 {print $5}')"

export AWS_ACCESS_KEY_ID
export AWS_SECRET_ACCESS_KEY
export AWS_SESSION_TOKEN

unset AWS_SECURITY_TOKEN

eval exec "$@"