Download Azure blob from bash

get_blob.sh

#!/bin/sh

usage() {
  echo "usage: ${0##*/} <azure storage key> <azure storage account> <container-name> <blob-name>"
}

if [ -z "$1" ] || [ -z "$2" ] || [ -z "$3" ] || [ -z "$4" ]; then
  usage
  exit 1
fi

access_key="$1"
storage_account="$2"
container_name="$3"

blob_store_url="blob.core.windows.net"
authorization="SharedKey"

request_method="GET"
request_date=$(TZ=GMT LC_ALL=en_US.utf8 date "+%a, %d %h %Y %H:%M:%S %Z")
storage_service_version="2011-08-18"

# HTTP Request headers
x_ms_date_h="x-ms-date:$request_date"
x_ms_version_h="x-ms-version:$storage_service_version"

# Build the signature string
canonicalized_headers="${x_ms_date_h}\n${x_ms_version_h}"
canonicalized_resource="/${storage_account}/${container_name}/$4"

string_to_sign="${request_method}\n\n\n\n\n\n\n\n\n\n\n\n${canonicalized_headers}\n${canonicalized_resource}"

# Decode the Base64 encoded access key, convert to Hex.
decoded_hex_key="$(echo -n $access_key | base64 -d -w0 | xxd -p -c256)"

# Create the HMAC signature for the Authorization header
signature=$(printf "$string_to_sign" | openssl dgst -sha256 -mac HMAC -macopt "hexkey:$decoded_hex_key" -binary | base64 -w0)

authorization_header="Authorization: $authorization $storage_account:$signature"

URL="https://${storage_account}.${blob_store_url}/${container_name}/$4"

curl -s \
  -H "$x_ms_date_h" \
  -H "$x_ms_version_h" \
  -H "$authorization_header" \
  "$URL" -o "$4"