bash script for signed download from s3 bucket

download.sh

S3_SECRET="secret"

AWS_REGION="ap-southeast-1"
S3_BUCKET="s3-bucket"
S3_FOLDER="s3-folder"
TARGET_FILE="targetFile.txt"
FILE_PATH="/${S3_BUCKET}/${S3_FOLDER}/${TARGET_FILE}"

CONTENT_TYPE="text/plain"
DATE_VALUE=`date -R`
SIGN_STRING="GET\n\n${CONTENT_TYPE}\n${DATE_VALUE}\n${FILE_PATH}"
SIGN_HASH=`echo -en ${SIGN_STRING} | openssl dgst -sha1 -hmac ${S3_SECRET} -binary | base64`

curl \
  -H "Host: ${S3_BUCKET}.s3-${AWS_REGION}.amazonaws.com" \
  -H "Date: ${DATE_VALUE}" \
  -H "Content-Type: ${CONTENT_TYPE}" \
  -H "Authorization: AWS ${S3_KEY}:${SIGN_HASH}" \
  -o ${TARGET_FILE} \
  "https://${S3_BUCKET}.s3-${AWS_REGION}.amazonaws.com/${S3_FOLDER}/${TARGET_FILE}"

# simple handling when curl exit code is not 0
CURL_OUTPUT=$?
if [[ $CURL_OUTPUT -ne 0 ]];
then
  echo "Encountered error when using curl to AWS S3."
  exit 1
fi