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JWT 多网站单点登录,放弃session

多个网站之间的登录信息共享, 基于cookie - session的登录认证方式跨域等比较复杂。采用基于算法的认证方式, JWT(json web token)的方式。

 

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参考:

http://www.tuicool.com/articles/IRJnaa

https://coderwall.com/p/8wrxfw/goodbye-php-sessions-hello-json-web-tokens

在JavaScript前端技术大行其道的今天,我们通常只需在后台构建API提供给前端调用,并且后端仅仅设计为给前端移动App调用。用户认证是Web应用的重要组成部分,基于API的用户认证有两个最佳解决方案 —— OAuth 2.0 和JWT(JSON Web Token)。

1、JWT定义及其组成

JWT(JSON Web Token)是一个非常轻巧的规范。这个规范允许我们使用JWT在用户和服务器之间传递安全可靠的信息。

一个JWT实际上就是一个字符串,它由三部分组成,头部、载荷与签名。

载荷(Payload)

我们先将用户认证的操作描述成一个JSON对象。其中添加了一些其他的信息,帮助今后收到这个JWT的服务器理解这个JWT。

{
    "sub": "1",
    "iss": "http://localhost:8000/auth/login",
    "iat": 1451888119,
    "exp": 1454516119,
    "nbf": 1451888119,
    "jti": "37c107e4609ddbcc9c096ea5ee76c667"
}

这里面的前6个字段都是由JWT的标准所定义的。

  • sub: 该JWT所面向的用户
  • iss: 该JWT的签发者
  • iat(issued at): 在什么时候签发的token
  • exp(expires): token什么时候过期
  • nbf(not before):token在此时间之前不能被接收处理
  • jti:JWT ID为web token提供唯一标识

这些定义都可以在 标准 中找到。

将上面的JSON对象进行base64编码可以得到下面的字符串:

eyJzdWIiOiIxIiwiaXNzIjoiaHR0cDpcL1wvbG9jYWx
ob3N0OjgwMDFcL2F1dGhcL2xvZ2luIiwiaWF0IjoxNDUxODg4MTE5LCJleHAiOjE0NTQ1MTYxMTksIm5iZiI6MTQ1MTg4OD
ExOSwianRpIjoiMzdjMTA3ZTQ2MDlkZGJjYzljMDk2ZWE1ZWU3NmM2NjcifQ

这个字符串我们将它称作JWT的Payload(载荷)。

如果你使用Node.js,可以用Node.js的包base64url来得到这个字符串:

var base64url = require('base64url')
var header = {
    "from_user": "B",
    "target_user": "A"
}
console.log(base64url(JSON.stringify(header)))

注:Base64是一种编码,也就是说,它是可以被翻译回原来的样子来的。它并不是一种加密过程。

头部(Header)

JWT还需要一个头部,头部用于描述关于该JWT的最基本的信息,例如其类型以及签名所用的算法等。这也可以被表示成一个JSON对象:

{
  "typ": "JWT",
  "alg": "HS256"
}

在这里,我们说明了这是一个JWT,并且我们所用的签名算法(后面会提到)是HS256算法。

对它也要进行Base64编码,之后的字符串就成了JWT的Header(头部):

eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9

签名(签名)

将上面的两个编码后的字符串都用句号.连接在一起(头部在前),就形成了:

eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxIiwiaXNzIjoiaHR0cDpcL1wvbG9jYWx
ob3N0OjgwMDFcL2F1dGhcL2xvZ2luIiwiaWF0IjoxNDUxODg4MTE5LCJleHAiOjE0NTQ1MTYxMTksIm5iZiI6MTQ1MTg4OD
ExOSwianRpIjoiMzdjMTA3ZTQ2MDlkZGJjYzljMDk2ZWE1ZWU3NmM2NjcifQ

最后,我们将上面拼接完的字符串用HS256算法进行加密。在加密的时候,我们还需要提供一个密钥(secret):

HMACSHA256(
    base64UrlEncode(header) + "." +
    base64UrlEncode(payload),
    secret
)

这样就可以得到我们加密后的内容:

wyoQ95RjAyQ2FF3aj8EvCSaUmeP0KUqcCJDENNfnaT4

这一部分又叫做签名。

最后将这一部分签名也拼接在被签名的字符串后面,我们就得到了完整的JWT:

eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxIiwiaXNzIjoiaHR0cDpcL1wvbG9jYWx
ob3N0OjgwMDFcL2F1dGhcL2xvZ2luIiwiaWF0IjoxNDUxODg4MTE5LCJleHAiOjE0NTQ1MTYxMTksIm5iZiI6MTQ1MTg4OD
ExOSwianRpIjoiMzdjMTA3ZTQ2MDlkZGJjYzljMDk2ZWE1ZWU3NmM2NjcifQ.wyoQ95RjAyQ2FF3aj8EvCSaUmeP0KUqc

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Goodbye PHP Sessions, Hello JSON Web Tokens

REST API's are meant to be stateless. What that means is that each request from a client should include all the information needed to process the request. In other words, if you are writing a REST API in PHP then you should not be using $_SESSION to store data about the client's session. But then how do we remember if a client is logged in or anything else about their state? The only possibility is that the client must be tasked with keeping track of the state. How could this ever be done securely? The client can't be trusted!

Enter JSON web tokens. A JSON web token is a bit of JSON, perhaps something that looks like this:

{
    "user": "alice",
    "email": "test@nospam.com"
}

Of course, we can't just give this to a client and have them give it back to us without some sort of assurance that it hasn't been tampered with. After all, what if they edit the token as follows:

{
    "user": "administrator",
    "email": "test@nospam.com"
}

The solution to this is that JSON web tokens are signed by the server. If the client tampers with the data then the token's signature will no longer match and an error can be raised.

The JWT PHP class makes this easy to do. For example, to create a token after the client successfully logs in, the following code could be used:

$token = array();
$token['id'] = $id;
echo JWT::encode($token, 'secret_server_key');

And then on later API calls the token can be retrieved and verified by this code:

$token = JWT::decode($_POST['token'], 'secret_server_key');
echo $token->id;

If the token has been tampered with then $token will be empty there will not be an id available. The JWT class makes sure that invalid data is never made available. If the token is tampered with, it will be unusable. Pretty simple stuff!

You can get the PHP JWT class as a single file from: https://github.com/rmcdaniel/angular-codeigniter-seed/blob/master/api/application/helpers/jwt_helper.php

as it is used by the AngularJS CodeIgniter Seed project:

https://github.com/rmcdaniel/angular-codeigniter-seed

or the original code from:

https://github.com/luciferous/jwt

Written by Richard McDaniel

posted @ 2017-01-16 15:45 牛顿的小脑 阅读(...) 评论(...) 编辑 收藏

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