PlugHmac

Auth Plug

Installation

The package can be installed by adding plug_hmac to your list of dependencies in mix.exs:

def deps do
  [
    {:plug_hmac, "~> 0.4"}
  ]
end

Usage

Configuration

Add body_reader to your Phoenix's Endpoint

plug Plug.Parsers,
    parsers: [:urlencoded, :multipart, :json],
    pass: ["*/*"],
    body_reader: {PlugHmac.CacheBodyReader, :read_body, []},
    json_decoder: Phoenix.json_library()

For Backend

error_handler: setting error handler module
secret_handler: setting secret handler module
hmac_algo: hmac support algorithem [:md5, :md4, :sha, :sha224, :sha256, :sha384, :sha512, :sha3_224, :sha3_256, :sha3_384, :sha3_512]
client_signature_name: the http header name which use for get authorization data

plug PlugHmac,
  error_handler: __MODULE__,
  secret_handler: __MODULE__,
  hmac_algo: :sha256,
  client_signature_name: "authorization"

@behaviour PlugHmac.ErrorHandler
@behaviour PlugHmac.SecretHandler

## callback for error_handler
def handle(conn, _error) do
  # you can case error here 
  # or update conn here
  # must return conn
  conn
end

## callback for secret_handler
def get_secret(client_id) do
  # get your secret key
  {:ok, your_secret_key}
end

For Client

# make_header(
#         hmac_algo,
#         secret_handler,
#         client_id,
#         method,
#         path,
#         query_string,
#         body,
#         nonce \\ nil
#      )
PlugHmac.make_header(:sha256, __MODULE__, "test_id", "GET", "/api/test_auth", "a1=123&a2=456", "body string")

Principle

客户端在请求时，需要在HTTP的Header增加Authorization:

Authorization: hmac id=test_id,signature=xpSI4lZe5c%2BxlNe%2BUK6MQU8RHZNTjL1CTgQLbFamoYU%3D,nonce=vrlaY%2BzdC2S7cdWEXLiN

PlugHmacplug 会校验 Authorization 值的有效性

参数说明

在开始之前先说明将要用到的参数：

参数名	参数值	说明
Method	GET	请求方法(全大写)
Path	/api/test_auth	请求路径
QueryString	"a1=123&a2=456"	将请求参数用`&`和`=`拼接起来
Body	"body string"	请求的body字符串
ClientID	test_id	由接口提供方提供
SecretKey	qhN8mkCzaxjC1jWD4fDW	由接口提供方提供
Nonce	asd123	随机值字符串

1. Authorization值

在拼接之前先使用 URI-encode，分别对各个参数值进行encode，然后再将其拼接起来，如下：

"hmac " + "id=" + ClientID + ",signature=" + Signature + ",nonce=" + Nonce

2. Signature值

首先按如下顺序拼接各个参数值：

ConcatString = Method+Path+QueryString+Body+Nonce
GET/api/test_autha1=123&a2=456body stringasd123

采用HMAC_SHA256算法使用SecretKey加密ConcatString的值，然后在进行Base64-encode，得到Signature 值，求值公式如下:

hmac.new(SecretKey, ConcatString, hashlib.sha256).digest().encode('base64')
Nop1kEtdf04S8Rr5U409Jmsx8Ic6zeWx2/HJZnLDRuM=