Use Gin framework to implement API gateway and authentication and authorization functions-Golang-php.cn

In the modern Internet architecture, API gateway has become an important component and is widely used in enterprise and cloud computing scenarios. The main function of the API gateway is to uniformly manage and distribute the API interfaces of multiple microservice systems, provide access control and security protection, and can also perform API document management, monitoring and logging.

In order to better ensure the security and scalability of the API gateway, some access control and authentication and authorization mechanisms have also been added to the API gateway. Such a mechanism can ensure the legitimacy between users and services and prevent attacks and illegal operations.

In this article, we will introduce how to use the Gin framework to implement API gateway and authentication and authorization functions.

1. Introduction to Gin framework

Gin is a lightweight Web framework developed based on Go language. Its design goal is to provide a high-performance web framework while maintaining simplicity and ease of use. The Gin framework provides common web functions such as routing, middleware, templates, and rendering. It also supports custom middleware and HTTP error handling methods, allowing you to quickly create web applications that meet your requirements.

2. Build the basic framework of API gateway

First, we need to install and import the Gin framework to create a basic web application. Before this, we need to install the Go language in the local environment, and then execute the following command to install the Gin framework.

go get -u github.com/gin-gonic/gin

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Next, we create a main.go file as the entry file of the program.

package main

import "github.com/gin-gonic/gin"

func main() {
    router := gin.Default()
    router.Any("/", func(c *gin.Context) {
        c.JSON(200, gin.H{
            "message": "Hello, Gin!",
        })
    })
    router.Run(":8080")
}

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In the above code, we imported the Gin framework library and created a default route. The root path of the route ("/") can return a JSON format response information for any request method (Any). Finally, we started the HTTP service through the Run method and listened to the local port 8080.

Now, we can enter the following command in the terminal to start the program and verify whether it can serve normally.

go run main.go

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If everything goes well, you should be able to access http://localhost:8080/ in a browser or other client and see the following response in JSON format.

{ "message": "Hello, Gin!" }

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3. Implementation of API Gateway

Next, we will implement the API gateway. Before implementing the API gateway, we need to determine which services will be included in the API gateway. Here, we assume that we have a user management system, a product management system and an order management system, and these three systems have their own API interfaces.

In order to incorporate the API interfaces of these three systems into the API gateway, we need to group and forward routes. A simpler way is to group different microservices according to their functions. For example, routing can be defined like this.

package main

import (
    "github.com/gin-gonic/gin"
    "net/http"
)

func main() {
    router := gin.Default()

    userService := router.Group("/user-service")
    {
        userService.GET("/", func(c *gin.Context) {
            c.JSON(http.StatusOK, gin.H{"data": "User Service API"})
        })
    }

    productService := router.Group("/product-service")
    {
        productService.GET("/", func(c *gin.Context) {
            c.JSON(http.StatusOK, gin.H{"data": "Product Service API"})
        })
    }

    orderService := router.Group("/order-service")
    {
        orderService.GET("/", func(c *gin.Context) {
            c.JSON(http.StatusOK, gin.H{"data": "Order Service API"})
        })
    }

    router.Run(":8080")
}

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In the above code example, we used the Group method of the Gin framework to group the routes of different services and placed them in /user-service, /product-service and /order-service. under a path. Then, we add routes for different services and specify different response information respectively. Here, only simple strings are returned.

If you start the program now and access each service, you should see the following information.

http://localhost:8080/user-service/ returns {"data": "User Service API"}
http://localhost:8080/product-service/ returns {"data" : "Product Service API"}
http://localhost:8080/order-service/ returns {"data": "Order Service API"}

4. Implementation of authentication and authorization

In order to ensure the security and scalability of the API gateway, we also need to add an authentication and authorization mechanism. Here, we can use JWT (JSON Web Token) to implement authentication and authorization functions. JWT is a lightweight authentication and authorization method based on web standards. The JWT authentication process is as follows.

The user requests the API gateway, carrying identity information (such as user name and password, etc.).
The API gateway uses the identity information to send a request to the authentication server and obtain the JWT token.
The API gateway attaches the JWT token to the request header or other locations and forwards it to the server for interface access.
The server performs interface access based on the JWT token and automatically completes authentication and authorization operations.

We also need to install the following libraries to support the use of JWT.

go get -u github.com/dgrijalva/jwt-go

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Next, we need to define a JWT Claims structure and add some necessary parameters, such as UserID and Expiry information. Here UserID is used to record the user's unique identity, and Expiry is used to record the validity period of the token.

type CustomClaims struct {
    UserID string `json:"userID,omitempty"`
    jwt.StandardClaims
}

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Next, we will implement three functions, generateToken, verifyToken and authMiddleware. The generateToken function is used to generate JWT tokens. The specific implementation is as follows.

func generateToken(userID string) (string, error) {
    claims := CustomClaims{
        userID,
        jwt.StandardClaims{
            ExpiresAt: time.Now().Add(time.Hour * 24).Unix(),
            Issuer:    "my-api-gateway",
        },
    }
    token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
    jwtSecret := []byte("my-secret-key")
    return token.SignedString(jwtSecret)
}

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In the above code, we create an instance of the CustomClaims structure, use userID as a parameter of Claims, and specify the expiration time and publisher information Issuer. Then, we use the HS256 algorithm to sign the Claims, call the SignedString method to generate the JWT token, and return it to the client.

Next, we will implement the verifyToken function to verify the token.

func verifyToken(tokenString string) (*CustomClaims, error) {
    jwtSecret := []byte("my-secret-key")
    token, err := jwt.ParseWithClaims(tokenString, &CustomClaims{}, func(token *jwt.Token) (interface{}, error) {
        return jwtSecret, nil
    })
    if err != nil {
        return nil, err
    }
    if claims, ok := token.Claims.(*CustomClaims); ok && token.Valid {
        return claims, nil
    }
    return nil, errors.New("invalid token")
}

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在上面的代码中，我们首先定义了一个JWT Secret（这里我们使用字符串"my-secret-key"作为密钥），然后使用ParseWithClaims方法解析令牌，并将Claims参数设置为CustomClaims类型。然后，我们使用定义的JWT Secret对令牌进行验证，如果验证通过，我们将返回Claims结构体的实例。

最后一个函数是authMiddleware，用于检查请求头中是否携带有效的JWT令牌。如果没有携带或验证失败，中间件将会返回401错误给客户端。

func authMiddleware() gin.HandlerFunc {
    return func(c *gin.Context) {
        authHeader := c.GetHeader("Authorization")

        if authHeader == "" {
            c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "Unauthorized"})
            return
        }

        tokenString := strings.Replace(authHeader, "Bearer ", "", 1)
        claims, err := verifyToken(tokenString)

        if err != nil {
            c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "Unauthorized"})
            return
        }

        c.Set("userID", claims.UserID)
        c.Next()
    }
}

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在上面的代码中，我们首先从请求头中获取Authorization信息，并判断是否为空。如果为空，返回401错误。然后，我们使用strings.Replace方法将Token中的Bearer前缀进行删除，获取真正的JWT令牌。接着，我们调用verifyToken函数对JWT令牌进行验证，如果验证不通过，返回401错误。最后，我们将userID存储在Context中，以备其他中间件和路由使用。

为了演示JWT认证的功能，我们在/user-service服务中添加一个需要身份验证的路由，例如/user-service/profile，它返回用户的详细信息。修改后的main.go代码示例如下。

func main() {
    router := gin.Default()

    userService := router.Group("/user-service")
    {
        userService.GET("/", func(c *gin.Context) {
            c.JSON(http.StatusOK, gin.H{"data": "User Service API"})
        })
        userService.GET("/profile", authMiddleware(), func(c *gin.Context) {
            userID := c.MustGet("userID").(string)
            c.JSON(http.StatusOK, gin.H{"data": "User ID: " + userID})
        })
    }

    productService := router.Group("/product-service")
    {
        productService.GET("/", func(c *gin.Context) {
            c.JSON(http.StatusOK, gin.H{"data": "Product Service API"})
        })
    }

    orderService := router.Group("/order-service")
    {
        orderService.GET("/", func(c *gin.Context) {
            c.JSON(http.StatusOK, gin.H{"data": "Order Service API"})
        })
    }

    router.Run(":8080")
}

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以上代码中，我们在/user-service/profile路由中使用了authMiddleware中间件，来对身份进行验证。例如，如果你想要访问/user-service/profile接口，你需要在请求头中附带有效的JWT令牌，例如：

Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VySURfaWQiOiIxMjM0NTY3ODkwIiwiZXhwIjoxNjMyMzMzNjE0LCJpc3MiOiJteS1hcGktZ2F0ZXdheSJ9OfXlna_Qb2giRByaev2x7w5zz0S2CJZnMMgZ6sVA

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如果你尝试访问此路由，但请求头中没有附带有效的JWT令牌，或者令牌验证失败，你将会得到以下JSON格式的响应。

{ "error": "Unauthorized" }

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如果你携带了有效的JWT令牌，你应该可以看到以下格式的响应。

{ "data": "User ID: 1234567890" }

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五、总结

在本文中，我们介绍了如何使用Gin框架来实现API网关和认证授权功能。我们创建了一个基本的Web应用程序，并将多个微服务系统的API接口纳入到API网关当中。为了提高API网关的安全性和可扩展性，我们使用了JWT认证和授权的机制，通过设置Claims结构体参数来生成和验证JWT令牌，最后使用了AuthMiddleware来检查请求头中的JWT令牌。

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