增加跨域处理的中间件

middleware/request_cors/config.go

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+// Package request_cors ...
+//
+// Description : request_cors ...
+//
+// Author : go_developer@163.com<白茶清欢>
+//
+// Date : 2022-07-13 16:27
+package request_cors
+
+import "net/http"
+
+type cors struct {
+	allowAllOrigins  bool
+	allowCredentials bool
+	allowOriginFunc  func(string) bool
+	allowOrigins     []string
+	normalHeaders    http.Header
+	preflightHeaders http.Header
+	wildcardOrigins  [][]string
+}
+
+var (
+	DefaultSchemas = []string{
+		"http://",
+		"https://",
+	}
+	ExtensionSchemas = []string{
+		"chrome-extension://",
+		"safari-extension://",
+		"moz-extension://",
+		"ms-browser-extension://",
+	}
+	FileSchemas = []string{
+		"file://",
+	}
+	WebSocketSchemas = []string{
+		"ws://",
+		"wss://",
+	}
+)

middleware/request_cors/cros.go

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+// Package request_cors ...
+//
+// Description : 支持跨域的中间件
+//
+// Author : go_developer@163.com<白茶清欢>
+//
+// Date : 2022-07-13 16:25
+package request_cors
+
+import (
+	"errors"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/gin-gonic/gin"
+)
+
+func newCors(config Config) *cors {
+	if err := config.Validate(); err != nil {
+		panic(err.Error())
+	}
+
+	for _, origin := range config.AllowOrigins {
+		if origin == "*" {
+			config.AllowAllOrigins = true
+		}
+	}
+
+	return &cors{
+		allowOriginFunc:  config.AllowOriginFunc,
+		allowAllOrigins:  config.AllowAllOrigins,
+		allowCredentials: config.AllowCredentials,
+		allowOrigins:     normalize(config.AllowOrigins),
+		normalHeaders:    generateNormalHeaders(config),
+		preflightHeaders: generatePreflightHeaders(config),
+		wildcardOrigins:  config.parseWildcardRules(),
+	}
+}
+
+func (cors *cors) applyCors(c *gin.Context) {
+	origin := c.Request.Header.Get("Origin")
+	if len(origin) == 0 {
+		// request is not a CORS request
+		return
+	}
+	host := c.Request.Host
+
+	if origin == "http://"+host || origin == "https://"+host {
+		// request is not a CORS request but have origin header.
+		// for example, use fetch api
+		return
+	}
+
+	if !cors.validateOrigin(origin) {
+		c.AbortWithStatus(http.StatusForbidden)
+		return
+	}
+
+	if c.Request.Method == "OPTIONS" {
+		cors.handlePreflight(c)
+		defer c.AbortWithStatus(http.StatusNoContent) // Using 204 is better than 200 when the request status is OPTIONS
+	} else {
+		cors.handleNormal(c)
+	}
+
+	if !cors.allowAllOrigins {
+		c.Header("Access-Control-Allow-Origin", origin)
+	}
+}
+
+func (cors *cors) validateWildcardOrigin(origin string) bool {
+	for _, w := range cors.wildcardOrigins {
+		if w[0] == "*" && strings.HasSuffix(origin, w[1]) {
+			return true
+		}
+		if w[1] == "*" && strings.HasPrefix(origin, w[0]) {
+			return true
+		}
+		if strings.HasPrefix(origin, w[0]) && strings.HasSuffix(origin, w[1]) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func (cors *cors) validateOrigin(origin string) bool {
+	if cors.allowAllOrigins {
+		return true
+	}
+	for _, value := range cors.allowOrigins {
+		if value == origin {
+			return true
+		}
+	}
+	if len(cors.wildcardOrigins) > 0 && cors.validateWildcardOrigin(origin) {
+		return true
+	}
+	if cors.allowOriginFunc != nil {
+		return cors.allowOriginFunc(origin)
+	}
+	return false
+}
+
+func (cors *cors) handlePreflight(c *gin.Context) {
+	header := c.Writer.Header()
+	for key, value := range cors.preflightHeaders {
+		header[key] = value
+	}
+}
+
+func (cors *cors) handleNormal(c *gin.Context) {
+	header := c.Writer.Header()
+	for key, value := range cors.normalHeaders {
+		header[key] = value
+	}
+}
+
+// Config represents all available options for the middleware.
+type Config struct {
+	AllowAllOrigins bool
+
+	// AllowOrigins is a list of origins a cross-domain request can be executed from.
+	// If the special "*" value is present in the list, all origins will be allowed.
+	// Default value is []
+	AllowOrigins []string
+
+	// AllowOriginFunc is a custom function to validate the origin. It take the origin
+	// as argument and returns true if allowed or false otherwise. If this option is
+	// set, the content of AllowOrigins is ignored.
+	AllowOriginFunc func(origin string) bool
+
+	// AllowMethods is a list of methods the client is allowed to use with
+	// cross-domain requests. Default value is simple methods (GET, POST, PUT, PATCH, DELETE, HEAD, and OPTIONS)
+	AllowMethods []string
+
+	// AllowHeaders is list of non simple headers the client is allowed to use with
+	// cross-domain requests.
+	AllowHeaders []string
+
+	// AllowCredentials indicates whether the request can include user credentials like
+	// cookies, HTTP authentication or client side SSL certificates.
+	AllowCredentials bool
+
+	// ExposeHeaders indicates which headers are safe to expose to the API of a CORS
+	// API specification
+	ExposeHeaders []string
+
+	// MaxAge indicates how long (with second-precision) the results of a preflight request
+	// can be cached
+	MaxAge time.Duration
+
+	// Allows to add origins like http://some-domain/*, https://api.* or http://some.*.subdomain.com
+	AllowWildcard bool
+
+	// Allows usage of popular browser extensions schemas
+	AllowBrowserExtensions bool
+
+	// Allows usage of WebSocket protocol
+	AllowWebSockets bool
+
+	// Allows usage of file:// schema (dangerous!) use it only when you 100% sure it's needed
+	AllowFiles bool
+}
+
+// AddAllowMethods is allowed to add custom methods
+func (c *Config) AddAllowMethods(methods ...string) {
+	c.AllowMethods = append(c.AllowMethods, methods...)
+}
+
+// AddAllowHeaders is allowed to add custom headers
+func (c *Config) AddAllowHeaders(headers ...string) {
+	c.AllowHeaders = append(c.AllowHeaders, headers...)
+}
+
+// AddExposeHeaders is allowed to add custom expose headers
+func (c *Config) AddExposeHeaders(headers ...string) {
+	c.ExposeHeaders = append(c.ExposeHeaders, headers...)
+}
+
+func (c Config) getAllowedSchemas() []string {
+	allowedSchemas := DefaultSchemas
+	if c.AllowBrowserExtensions {
+		allowedSchemas = append(allowedSchemas, ExtensionSchemas...)
+	}
+	if c.AllowWebSockets {
+		allowedSchemas = append(allowedSchemas, WebSocketSchemas...)
+	}
+	if c.AllowFiles {
+		allowedSchemas = append(allowedSchemas, FileSchemas...)
+	}
+	return allowedSchemas
+}
+
+func (c Config) validateAllowedSchemas(origin string) bool {
+	allowedSchemas := c.getAllowedSchemas()
+	for _, schema := range allowedSchemas {
+		if strings.HasPrefix(origin, schema) {
+			return true
+		}
+	}
+	return false
+}
+
+// Validate is check configuration of user defined.
+func (c Config) Validate() error {
+	if c.AllowAllOrigins && (c.AllowOriginFunc != nil || len(c.AllowOrigins) > 0) {
+		return errors.New("conflict settings: all origins are allowed. AllowOriginFunc or AllowOrigins is not needed")
+	}
+	if !c.AllowAllOrigins && c.AllowOriginFunc == nil && len(c.AllowOrigins) == 0 {
+		return errors.New("conflict settings: all origins disabled")
+	}
+	for _, origin := range c.AllowOrigins {
+		if !strings.Contains(origin, "*") && !c.validateAllowedSchemas(origin) {
+			return errors.New("bad origin: origins must contain '*' or include " + strings.Join(c.getAllowedSchemas(), ","))
+		}
+	}
+	return nil
+}
+
+func (c Config) parseWildcardRules() [][]string {
+	var wRules [][]string
+
+	if !c.AllowWildcard {
+		return wRules
+	}
+
+	for _, o := range c.AllowOrigins {
+		if !strings.Contains(o, "*") {
+			continue
+		}
+
+		if c := strings.Count(o, "*"); c > 1 {
+			panic(errors.New("only one * is allowed").Error())
+		}
+
+		i := strings.Index(o, "*")
+		if i == 0 {
+			wRules = append(wRules, []string{"*", o[1:]})
+			continue
+		}
+		if i == (len(o) - 1) {
+			wRules = append(wRules, []string{o[:i-1], "*"})
+			continue
+		}
+
+		wRules = append(wRules, []string{o[:i], o[i+1:]})
+	}
+
+	return wRules
+}
+
+// DefaultConfig returns a generic default configuration mapped to localhost.
+func DefaultConfig() Config {
+	return Config{
+		AllowMethods:     []string{"GET", "POST", "PUT", "PATCH", "DELETE", "HEAD", "OPTIONS"},
+		AllowHeaders:     []string{"Origin", "Content-Length", "Content-Type"},
+		AllowCredentials: false,
+		MaxAge:           12 * time.Hour,
+	}
+}
+
+// Default returns the location middleware with default configuration.
+func Default() gin.HandlerFunc {
+	config := DefaultConfig()
+	config.AllowAllOrigins = true
+	return New(config)
+}
+
+// New returns the location middleware with user-defined custom configuration.
+func New(config Config) gin.HandlerFunc {
+	cors := newCors(config)
+	return func(c *gin.Context) {
+		cors.applyCors(c)
+	}
+}

middleware/request_cors/util.go

@@ -0,0 +1,92 @@
+// Package request_cors ...
+//
+// Description : request_cors ...
+//
+// Author : go_developer@163.com<白茶清欢>
+//
+// Date : 2022-07-13 16:28
+package request_cors
+
+import (
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type converter func(string) string
+
+func generateNormalHeaders(c Config) http.Header {
+	headers := make(http.Header)
+	if c.AllowCredentials {
+		headers.Set("Access-Control-Allow-Credentials", "true")
+	}
+	if len(c.ExposeHeaders) > 0 {
+		exposeHeaders := convert(normalize(c.ExposeHeaders), http.CanonicalHeaderKey)
+		headers.Set("Access-Control-Expose-Headers", strings.Join(exposeHeaders, ","))
+	}
+	if c.AllowAllOrigins {
+		headers.Set("Access-Control-Allow-Origin", "*")
+	} else {
+		headers.Set("Vary", "Origin")
+	}
+	return headers
+}
+
+func generatePreflightHeaders(c Config) http.Header {
+	headers := make(http.Header)
+	if c.AllowCredentials {
+		headers.Set("Access-Control-Allow-Credentials", "true")
+	}
+	if len(c.AllowMethods) > 0 {
+		allowMethods := convert(normalize(c.AllowMethods), strings.ToUpper)
+		value := strings.Join(allowMethods, ",")
+		headers.Set("Access-Control-Allow-Methods", value)
+	}
+	if len(c.AllowHeaders) > 0 {
+		allowHeaders := convert(normalize(c.AllowHeaders), http.CanonicalHeaderKey)
+		value := strings.Join(allowHeaders, ",")
+		headers.Set("Access-Control-Allow-Headers", value)
+	}
+	if c.MaxAge > time.Duration(0) {
+		value := strconv.FormatInt(int64(c.MaxAge/time.Second), 10)
+		headers.Set("Access-Control-Max-Age", value)
+	}
+	if c.AllowAllOrigins {
+		headers.Set("Access-Control-Allow-Origin", "*")
+	} else {
+		// Always set Vary headers
+		// see https://github.com/rs/cors/issues/10,
+		// https://github.com/rs/cors/commit/dbdca4d95feaa7511a46e6f1efb3b3aa505bc43f#commitcomment-12352001
+
+		headers.Add("Vary", "Origin")
+		headers.Add("Vary", "Access-Control-Request-Method")
+		headers.Add("Vary", "Access-Control-Request-Headers")
+	}
+	return headers
+}
+
+func normalize(values []string) []string {
+	if values == nil {
+		return nil
+	}
+	distinctMap := make(map[string]bool, len(values))
+	normalized := make([]string, 0, len(values))
+	for _, value := range values {
+		value = strings.TrimSpace(value)
+		value = strings.ToLower(value)
+		if _, seen := distinctMap[value]; !seen {
+			normalized = append(normalized, value)
+			distinctMap[value] = true
+		}
+	}
+	return normalized
+}
+
+func convert(s []string, c converter) []string {
+	var out []string
+	for _, i := range s {
+		out = append(out, c(i))
+	}
+	return out
+}