A Bash script to retrieve a file stored on S3 via temporary IAM role credentials.

s3-get.sh

#!/bin/bash

if [ $# -ne 3 ]
then
	echo "Usage: s3-get iam-role-name s3-resource output-file"
	exit 1
fi

Role=$1
Resource=$2
Output=$3

AccessKeyId=`curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/${Role} | sed -n '/AccessKeyId/{p;}' | cut -f4 -d'"'`
SecretAccessKey=`curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/${Role} | sed -n '/SecretAccessKey/{p;}' | cut -f4 -d'"'`
Token=`curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/${Role} | sed -n '/Token/{p;}' | cut -f4 -d'"'`
Date="`date +'%a, %d %b %Y %H:%M:%S %z'`"
SignatureString="GET\n\n\n${Date}\nx-amz-security-token:${Token}\n/${Resource}"
Signature=`/bin/echo -en "${SignatureString}" | openssl sha1 -hmac ${SecretAccessKey} -binary | base64`

curl -s -H "Date: ${Date}" -H "X-AMZ-Security-Token: ${Token}" -H "Authorization: AWS ${AccessKeyId}:${Signature}" "https://s3-eu-west-1.amazonaws.com/${Resource}" -o "${Output}"

AWESOME!!! Thank you, don't think you have been given enough credit!!